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[PATCH v5 10/10] Additional validation for buffer in the ring
107+ messages / 2 participants
[nested] [flat]

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v5 10/10] Additional validation for buffer in the ring
@ 2025-06-11 12:45 Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Ashutosh Bapat @ 2025-06-11 12:45 UTC (permalink / raw)

If the buffer pool has been shrunk, the buffers in the buffer list may
not be valid anymore. Modify GetBufferFromRing to check if the buffer is
still valid before using it. This makes GetBufferFromRing() a bit more
expensive because of additional boolean condition. That may not be
expensive enough to affect query performance. The alternative to that is
more complex as explained below.

The strategy object is created in CurrentMemoryContext and is not
available in any global structure thus accessible when processing buffer
resizing barriers. We may modify GetAccessStrategy() to register
strategy in a global linked list and then arrange to deregister it once
it's no more in use. Looking at the places which use
GetAccessStrategy(), fixing all those may be some work.

Ashutosh Bapat
---
 src/backend/storage/buffer/freelist.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
index 41641bb3ae6..74d070733a4 100644
--- a/src/backend/storage/buffer/freelist.c
+++ b/src/backend/storage/buffer/freelist.c
@@ -948,12 +948,13 @@ GetBufferFromRing(BufferAccessStrategy strategy, uint32 *buf_state)
 		strategy->current = 0;
 
 	/*
-	 * If the slot hasn't been filled yet, tell the caller to allocate a new
-	 * buffer with the normal allocation strategy.  He will then fill this
-	 * slot by calling AddBufferToRing with the new buffer.
+	 * If the slot hasn't been filled yet or the buffer in the slot has been
+	 * invalidated when buffer pool was shrunk, tell the caller to allocate a new
+	 * buffer with the normal allocation strategy.  He will then fill this slot
+	 * by calling AddBufferToRing with the new buffer.
 	 */
 	bufnum = strategy->buffers[strategy->current];
-	if (bufnum == InvalidBuffer)
+	if (bufnum == InvalidBuffer || bufnum > NBuffers)
 		return NULL;
 
 	/*
-- 
2.49.0


--bwrlgp6w2ubxykjq--





^ permalink  raw  reply  [nested|flat] 107+ messages in thread

* [PATCH v7 1/6] Handle pg_get_ruledef default args in system_functions.sql
@ 2025-12-08 23:41 Mark Wong <markwkm@gmail.com>
  0 siblings, 0 replies; 107+ messages in thread

From: Mark Wong @ 2025-12-08 23:41 UTC (permalink / raw)

Modernize pg_get_ruledef to use proargdefaults for optional pretty
argument.
---
 src/backend/utils/adt/ruleutils.c | 18 ------------------
 src/include/catalog/pg_proc.dat   |  8 +++-----
 2 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 35083fcc733..6a4c7e4822d 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -569,24 +569,6 @@ static void get_json_table_nested_columns(TableFunc *tf, JsonTablePlan *plan,
  */
 Datum
 pg_get_ruledef(PG_FUNCTION_ARGS)
-{
-	Oid			ruleoid = PG_GETARG_OID(0);
-	int			prettyFlags;
-	char	   *res;
-
-	prettyFlags = PRETTYFLAG_INDENT;
-
-	res = pg_get_ruledef_worker(ruleoid, prettyFlags);
-
-	if (res == NULL)
-		PG_RETURN_NULL();
-
-	PG_RETURN_TEXT_P(string_to_text(res));
-}
-
-
-Datum
-pg_get_ruledef_ext(PG_FUNCTION_ARGS)
 {
 	Oid			ruleoid = PG_GETARG_OID(0);
 	bool		pretty = PG_GETARG_BOOL(1);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index fa9ae79082b..954f611de5b 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3981,9 +3981,6 @@
 { oid => '8302', descr => 'source text of a property graph',
   proname => 'pg_get_propgraphdef', provolatile => 's', prorettype => 'text',
   proargtypes => 'oid', prosrc => 'pg_get_propgraphdef' },
-{ oid => '1573', descr => 'source text of a rule',
-  proname => 'pg_get_ruledef', provolatile => 's', prorettype => 'text',
-  proargtypes => 'oid', prosrc => 'pg_get_ruledef' },
 { oid => '1640', descr => 'select statement of a view',
   proname => 'pg_get_viewdef', provolatile => 's', proparallel => 'r',
   prorettype => 'text', proargtypes => 'text',
@@ -8591,9 +8588,10 @@
   prosrc => 'macaddr8_send' },
 
 # System-view support functions with pretty-print option
-{ oid => '2504', descr => 'source text of a rule with pretty-print option',
+{ oid => '2504', descr => 'source text of a rule',
   proname => 'pg_get_ruledef', provolatile => 's', prorettype => 'text',
-  proargtypes => 'oid bool', prosrc => 'pg_get_ruledef_ext' },
+  proargtypes => 'oid bool', proargnames => '{rule,pretty}',
+  proargdefaults => '{false}',prosrc => 'pg_get_ruledef' },
 { oid => '2505',
   descr => 'select statement of a view with pretty-print option',
   proname => 'pg_get_viewdef', provolatile => 's', proparallel => 'r',
-- 
2.52.0


--GzYugJnip6WHHvTk
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename=v7-0002-Handle-pg_get_viewdef-default-args-in-system_func.patch



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2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-06-11 12:45 [PATCH v5 10/10] Additional validation for buffer in the ring Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
2025-12-08 23:41 [PATCH v7 1/6] Handle pg_get_ruledef default args in system_functions.sql Mark Wong <markwkm@gmail.com>

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