postgres.git / summary / log / commit / refs

commit    f6ff75f79689d2d0c5bb241435d7fc6a63273223
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Jan 29 18:23:31 2025 +0000

    Make BufferIsExclusiveLocked and BufferIsDirty work for local buffers.
    
    These functions tried to check the state of the buffer's content lock
    even for local buffers.  Since we don't use the content lock for a
    local buffer, that would lead to a "false" result from
    LWLockHeldByMeInMode, which would mean a misleading "false" answer
    from BufferIsExclusiveLocked (we'd rather that case always return
    "true") or an assertion failure in BufferIsDirty.
    
    The core code never applies these two functions to local buffers,
    and apparently no extensions do either, since we've not heard
    complaints.  Still, in the name of future-proofing, let's fix
    them to act as though a pinned local buffer is content-locked.
    
    Author: Srinath Reddy <srinath2133@gmail.com>
    Discussion: https://postgr.es/m/19396ef77f8.1098c4a1810508.2255483659262451647@zohocorp.com


 src/backend/storage/buffer/bufmgr.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 0d8849bf894..ee83669992b 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2472,20 +2472,19 @@ BufferIsExclusiveLocked(Buffer buffer)
 {
 	BufferDesc *bufHdr;
 
+	Assert(BufferIsPinned(buffer));
+
 	if (BufferIsLocal(buffer))
 	{
-		int			bufid = -buffer - 1;
-
-		bufHdr = GetLocalBufferDescriptor(bufid);
+		/* Content locks are not maintained for local buffers. */
+		return true;
 	}
 	else
 	{
 		bufHdr = GetBufferDescriptor(buffer - 1);
+		return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
+									LW_EXCLUSIVE);
 	}
-
-	Assert(BufferIsPinned(buffer));
-	return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
-								LW_EXCLUSIVE);
 }
 
 /*
@@ -2501,21 +2500,22 @@ BufferIsDirty(Buffer buffer)
 {
 	BufferDesc *bufHdr;
 
+	Assert(BufferIsPinned(buffer));
+
 	if (BufferIsLocal(buffer))
 	{
 		int			bufid = -buffer - 1;
 
 		bufHdr = GetLocalBufferDescriptor(bufid);
+		/* Content locks are not maintained for local buffers. */
 	}
 	else
 	{
 		bufHdr = GetBufferDescriptor(buffer - 1);
+		Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
+									LW_EXCLUSIVE));
 	}
 
-	Assert(BufferIsPinned(buffer));
-	Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
-								LW_EXCLUSIVE));
-
 	return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
 }
 


[parent: 128897b101e0]