From: Julien Rouhaud <rjuju123@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>
Subject: Re: Online checksums verification in the backend
Date: Wed, 18 Mar 2020 11:10:55 +0100
Message-ID: <20200318101055.GA36918@nol> (raw)
In-Reply-To: <20200318060610.GA58497@nol>
References: <CAOBaU_aVvMjQn=ge5qPiJOPMmOj5=ii3st5Q0Y+WuLML5sR17w@mail.gmail.com>
<CA+TgmoavHnO20Stahs6MPe53qBqeiaCTwsktSVd7LDW+Z9pNtw@mail.gmail.com>
<CAOBaU_aiAaas1SLS6erWa0cJStxSt+QBRPah16CqXZY4mATbTQ@mail.gmail.com>
<20191210022633.GD72921@paquier.xyz>
<CAOBaU_YOmFfO8Ow=EScWULku7CvUiNYdx_2QS8hfi92D=tv=OQ@mail.gmail.com>
<20200311071823.GA4643@nol>
<20200316030638.GA2331@paquier.xyz>
<20200316082122.3wr4swqvpe7j5cg5@nol>
<20200318042047.GH214947@paquier.xyz>
<20200318060610.GA58497@nol>
On Wed, Mar 18, 2020 at 07:06:19AM +0100, Julien Rouhaud wrote:
> On Wed, Mar 18, 2020 at 01:20:47PM +0900, Michael Paquier wrote:
> > On Mon, Mar 16, 2020 at 09:21:22AM +0100, Julien Rouhaud wrote:
> > > On Mon, Mar 16, 2020 at 12:29:28PM +0900, Michael Paquier wrote:
> > >> With a large amount of
> > >> shared buffer eviction you actually increase the risk of torn page
> > >> reads. Instead of a logic relying on partition mapping locks, which
> > >> could be unwise on performance grounds, did you consider different
> > >> approaches? For example a kind of pre-emptive lock on the page in
> > >> storage to prevent any shared buffer operation to happen while the
> > >> block is read from storage, that would act like a barrier.
> > >
> > > Even with a workload having a large shared_buffers eviction pattern, I don't
> > > think that there's a high probability of hitting a torn page. Unless I'm
> > > mistaken it can only happen if all those steps happen concurrently to doing the
> > > block read just after releasing the LWLock:
> > >
> > > - postgres read the same block in shared_buffers (including all the locking)
> > > - dirties it
> > > - writes part of the page
> > >
> > > It's certainly possible, but it seems so unlikely that the optimistic lock-less
> > > approach seems like a very good tradeoff.
> >
> > Having false reports in this area could be very confusing for the
> > user. That's for example possible now with checksum verification and
> > base backups.
>
>
> I agree, however this shouldn't be the case here, as the block will be
> rechecked while holding proper lock the 2nd time in case of possible false
> positive before being reported as corrupted. So the only downside is to check
> twice a corrupted block that's not found in shared buffers (or concurrently
> loaded/modified/half flushed). As the number of corrupted or concurrently
> loaded/modified/half flushed blocks should usually be close to zero, it seems
> worthwhile to have a lockless check first for performance reason.
I just noticed some dumb mistakes while adding the new GUCs. v5 attached to
fix that, no other changes.
Attachments:v5-0001-Add-a-pg_check_relation-function.patch (text/plain, 38.0K) download
From 6bea507c5dbd7bff862c75b93fc023f0f33aba99 Mon Sep 17 00:00:00 2001
From: Julien Rouhaud <jrouhaud@vmware.com>
Date: Mon, 4 Nov 2019 08:40:23 +0100
Subject: [PATCH v5] Add a pg_check_relation() function.
This functions checks the validity of the checksums for all non-dirty blocks of
a given relation, and optionally a given fork, and returns the list of all
blocks that don't match, along with the expected and found checksums.
Author: Julien Rouhaud
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/CAOBaU_aVvMjQn%3Dge5qPiJOPMmOj5%3Dii3st5Q0Y%2BWuLML5sR17w%40mail.gmail.com
---
doc/src/sgml/func.sgml | 44 ++
src/backend/catalog/system_views.sql | 7 +
src/backend/storage/page/checksum.c | 427 +++++++++++++++++-
src/backend/utils/adt/Makefile | 1 +
src/backend/utils/adt/checksumfuncs.c | 96 ++++
src/backend/utils/init/globals.c | 8 +
src/backend/utils/misc/guc.c | 43 ++
src/include/catalog/pg_proc.dat | 8 +
src/include/miscadmin.h | 8 +
src/include/storage/checksum.h | 7 +
src/include/utils/guc_tables.h | 1 +
src/test/Makefile | 3 +-
src/test/check_relation/.gitignore | 2 +
src/test/check_relation/Makefile | 23 +
src/test/check_relation/README | 23 +
.../check_relation/t/01_checksums_check.pl | 276 +++++++++++
16 files changed, 973 insertions(+), 4 deletions(-)
create mode 100644 src/backend/utils/adt/checksumfuncs.c
create mode 100644 src/test/check_relation/.gitignore
create mode 100644 src/test/check_relation/Makefile
create mode 100644 src/test/check_relation/README
create mode 100644 src/test/check_relation/t/01_checksums_check.pl
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgmlindex fc4d7f0f78..4baa2bb5e9 100644--- a/doc/src/sgml/func.sgml+++ b/doc/src/sgml/func.sgml@@ -21819,6 +21819,50 @@ SELECT (pg_stat_file('filename')).modification;
</sect2>
+ <sect2 id="functions-data-sanity">+ <title>Data Sanity Functions</title>++ <para>+ The functions shown in <xref linkend="functions-data-sanity-table"/>+ provide means to check for health of data file in a cluster.+ </para>++ <table id="functions-data-sanity-table">+ <title>Data Sanity Functions</title>+ <tgroup cols="3">+ <thead>+ <row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry>+ </row>+ </thead>++ <tbody>+ <row>+ <entry>+ <literal><function>pg_check_relation(<parameter>relation</parameter> <type>oid</type>, <parameter>fork</parameter> <type>text</type>)</function></literal>+ </entry>+ <entry><type>setof record</type></entry>+ <entry>Validate the checksums for all blocks of a given relation, and+ optionally the given fork.</entry>+ </row>+ </tbody>+ </tgroup>+ </table>++ <indexterm>+ <primary>pg_check_relation</primary>+ </indexterm>+ <para>+ <function>pg_check_relation</function> iterates over all the blocks of all+ or the specified fork of a given relation and verify their checksum. It+ returns the list of blocks for which the found checksum doesn't match the+ expected one. You must be a member of the+ <literal>pg_read_all_stats</literal> role to use this function. It can+ only be used if data checksums are enabled. See <xref+ linkend="app-initdb-data-checksums"/> for more information.+ </para>++ </sect2>+
</sect1>
<sect1 id="functions-trigger">
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sqlindex b8a3f46912..e266292b03 100644--- a/src/backend/catalog/system_views.sql+++ b/src/backend/catalog/system_views.sql@@ -1386,6 +1386,13 @@ LANGUAGE INTERNAL
STRICT STABLE PARALLEL SAFE
AS 'jsonb_path_query_first_tz';
+CREATE OR REPLACE FUNCTION pg_check_relation(+ IN relation regclass DEFAULT NULL::regclass, IN fork text DEFAULT NULL::text,+ OUT relid oid, OUT forknum integer, OUT failed_blocknum bigint,+ OUT expected_checksum integer, OUT found_checksum integer)+ RETURNS SETOF record VOLATILE LANGUAGE internal AS 'pg_check_relation'+ PARALLEL RESTRICTED;+
--
-- The default permissions for functions mean that anyone can execute them.
-- A number of functions shouldn't be executable by just anyone, but rather
diff --git a/src/backend/storage/page/checksum.c b/src/backend/storage/page/checksum.cindex e010691c9f..aec5e2ad2d 100644--- a/src/backend/storage/page/checksum.c+++ b/src/backend/storage/page/checksum.c@@ -15,8 +15,429 @@
#include "storage/checksum.h"
/*
- * The actual code is in storage/checksum_impl.h. This is done so that- * external programs can incorporate the checksum code by #include'ing- * that file from the exported Postgres headers. (Compare our CRC code.)+ * The actual checksum computation code is in storage/checksum_impl.h. This+ * is done so that external programs can incorporate the checksum code by+ * #include'ing that file from the exported Postgres headers. (Compare our+ * CRC code.)
*/
#include "storage/checksum_impl.h"
++#include "access/heapam.h"+#include "access/htup_details.h"+#include "catalog/pg_authid_d.h"+#include "commands/dbcommands.h"+#include "funcapi.h"+#include "miscadmin.h"+#include "pgstat.h"+#include "storage/buf_internals.h"+#include "storage/checksum.h"+#include "storage/lockdefs.h"+#include "utils/acl.h"+#include "utils/builtins.h"+#include "utils/guc.h"+#include "utils/lsyscache.h"+#include "utils/rel.h"+#include "utils/syscache.h"++/*+ * A zero checksum can never be computed, see pg_checksum_page() */+#define NoComputedChecksum 0++/* ----------------+ * The rest of this module provides a set of functions that can be used to+ * safely check all checksums on a running cluster.+ *+ * Please note that those only perform standard buffered reads, and don't try+ * to bypass or discard the operating system cache. If you want to check the+ * actual storage, you have to discard the operating system cache before+ * running those functions.+ *+ * To avoid torn page and possible false positive when reading data, and+ * keeping overhead as low as possible, the following heuristics are used:+ *+ * - a shared LWLock is taken on the target buffer pool partition mapping, and+ * we detect if a block is in shared_buffers or not. See check_get_buffer()+ * comments for more details about the locking strategy.+ *+ * - if a block is dirty in shared_buffers, it's ignored as it'll be flushed to+ * disk either before the end of the next checkpoint or during recovery in+ * case of unsafe shutdown+ *+ * - if a block is otherwise found in shared_buffers, an IO lock is taken on+ * the block and the block is then read from storage, ignoring the block in+ * shared_buffers+ *+ * - if a block is not found in shared_buffers, the LWLock is released and the+ * block is read from disk without taking any lock. If an error is detected,+ * the read block will be discarded and retrieved again while holding the+ * LWLock. This is because an error due to concurrent write is possible but+ * very unlikely, so it's better to have an optimistic approach to limit+ * locking overhead+ *+ * The check can be performed using an SQL function, returning the list of+ * problematic blocks.+ * ----------------+ */++static bool check_buffer(char *buffer, uint32 blkno, uint16 *chk_expected,+ uint16 *chk_found);+static void check_relation_fork(TupleDesc tupdesc, Tuplestorestate *tupstore,+ Relation relation, ForkNumber forknum);+static void check_delay_point(void);+static void check_get_buffer(Relation relation, ForkNumber forknum,+ BlockNumber blkno, char *buffer, bool needlock,+ bool *checkit, bool *found_in_sb);++/*+ * Perform a checksum check on the passed page. Returns whether the page is+ * valid or not, and assign the expected and found checksum in chk_expected and+ * chk_found, respectively. Note that a page can look like new but could be+ * the result of a corruption. We still check for this case, but we can't+ * compute its checksum as pg_checksum_page() is explicitly checking for non-new+ * pages, so NoComputedChecksum will be set in chk_found.+ */+static bool+check_buffer(char *buffer, uint32 blkno, uint16 *chk_expected,+ uint16 *chk_found)+{+ PageHeader hdr = (PageHeader) buffer;++ Assert(chk_expected && chk_found);++ if (PageIsNew(hdr))+ {+ if (PageIsVerified(buffer, blkno))+ {+ /*+ * If the page is really new, there won't by any checksum to be+ * computed or expected.+ */+ *chk_expected = *chk_found = NoComputedChecksum;+ return true;+ }+ else+ {+ /*+ * There's a corruption, but since this affect PageIsNew, we+ * can't compute a checksum, so set NoComputedChecksum for the+ * expected checksum.+ */+ *chk_expected = NoComputedChecksum;+ *chk_found = hdr->pd_checksum;+ }+ return false;+ }++ *chk_expected = pg_checksum_page(buffer, blkno);+ *chk_found = hdr->pd_checksum;++ return (*chk_expected == *chk_found);+}++/*+ * Perform the check on a single relation, possibly filtered with a single+ * fork. This function will check if the given relation exists or not, as+ * a relation could be dropped after checking for the list of relations and+ * before getting here, and we don't want to error out in this case.+ */+void+check_one_relation(TupleDesc tupdesc, Tuplestorestate *tupstore,+ Oid relid, ForkNumber single_forknum)+{+ Relation relation = NULL;+ ForkNumber forknum;++ /* Check if the relation (still) exists */+ if (SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relid)))+ {+ /*+ * We use a standard relation_open() to acquire the initial lock. It+ * means that this will block until the lock is acquired, or will+ * raise an ERROR if lock_timeout has been set. If caller wants to+ * check multiple tables while relying on a maximum wait time, it+ * should process tables one by one instead of relying on a global+ * processing with the main SRF.+ */+ relation = relation_open(relid, AccessShareLock);+ }++ if (!RelationIsValid(relation))+ ereport(ERROR,+ (errcode(ERRCODE_UNDEFINED_TABLE),+ errmsg("relation with OID %u does not exist", relid)));++ if (!RELKIND_HAS_STORAGE(relation->rd_rel->relkind))+ ereport(ERROR,+ (errcode(ERRCODE_WRONG_OBJECT_TYPE),+ errmsg("Relation \"%s\" does not have storage to be checked.",+ quote_qualified_identifier(+ get_namespace_name(get_rel_namespace(relid)),+ get_rel_name(relid)))));++ RelationOpenSmgr(relation);++ for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)+ {+ if (single_forknum != InvalidForkNumber && single_forknum != forknum)+ continue;++ if (smgrexists(relation->rd_smgr, forknum))+ check_relation_fork(tupdesc, tupstore, relation, forknum);+ }++ relation_close(relation, AccessShareLock); /* release the lock */+}++/*+ * For a given relation and fork, Do the real work of iterating over all pages+ * and doing the check. Caller must hold an AccessShareLock lock on the given+ * relation.+ */+static void+check_relation_fork(TupleDesc tupdesc, Tuplestorestate *tupstore,+ Relation relation, ForkNumber forknum)+{+ BlockNumber blkno,+ nblocks;+ char buffer[BLCKSZ];+ bool checkit,+ found_in_sb;++ /*+ * We remember the number of blocks here. Since caller must hold a lock on+ * the relation, we know that it won't be truncated while we're iterating+ * over the blocks. Any block added after this function started won't be+ * checked, but this is out of scope as such pages will be flushed before+ * the next checkpoint's completion.+ */+ nblocks = RelationGetNumberOfBlocksInFork(relation, forknum);++#define SRF_COLS 5 /* Number of output arguments in the SRF */+ for (blkno = 0; blkno < nblocks; blkno++)+ {+ bool force_lock = false;+ uint16 chk_expected,+ chk_found;+ Datum values[SRF_COLS];+ bool nulls[SRF_COLS];+ int i = 0;++ memset(values, 0, sizeof(values));+ memset(nulls, 0, sizeof(nulls));++ /*+ * To avoid too much overhead, the buffer will be first read without+ * the locks that would guarantee the lack of false positive, as such+ * events should be quite rare.+ */+Retry:+ check_get_buffer(relation, forknum, blkno, buffer, force_lock,+ &checkit, &found_in_sb);++ if (!checkit)+ continue;++ if (check_buffer(buffer, blkno, &chk_expected, &chk_found))+ continue;++ /*+ * If we get a failure and the buffer wasn't found in shared buffers,+ * reread the buffer with suitable lock to avoid false positive. See+ * check_get_buffer for more details.+ */+ if (!found_in_sb && !force_lock)+ {+ force_lock = true;+ goto Retry;+ }++ values[i++] = ObjectIdGetDatum(relation->rd_id);+ values[i++] = Int32GetDatum(forknum);+ values[i++] = UInt32GetDatum(blkno);+ /*+ * This can happen if a corruption makes the block appears as+ * PageIsNew() but isn't a new page.+ */+ if (chk_expected == NoComputedChecksum)+ nulls[i++] = true;+ else+ values[i++] = UInt16GetDatum(chk_expected);+ values[i++] = UInt16GetDatum(chk_found);++ Assert(i == SRF_COLS);++ /* Report the failure to the stat collector and the logs. */+ pgstat_report_checksum_failure();+ ereport(WARNING,+ (errcode(ERRCODE_DATA_CORRUPTED),+ errmsg("invalid page in block %u of relation %s",+ blkno,+ relpath(relation->rd_smgr->smgr_rnode, forknum))));++ /* Save the corrupted blocks in the tuplestore. */+ tuplestore_putvalues(tupstore, tupdesc, values, nulls);+ }+}++/*+ * Check for interrupts and cost-based delay.+ */+static void+check_delay_point(void)+{+ /* Always check for interrupts */+ CHECK_FOR_INTERRUPTS();++ if (!ChecksumCostActive || InterruptPending)+ return;++ /* Nap if appropriate */+ if (ChecksumCostBalance >= ChecksumCostLimit)+ {+ int msec;++ msec = ChecksumCostDelay * ChecksumCostBalance / ChecksumCostLimit;+ if (msec > ChecksumCostDelay * 4)+ msec = ChecksumCostDelay * 4;++ pg_usleep(msec * 1000L);++ ChecksumCostBalance = 0;++ /* Might have gotten an interrupt while sleeping */+ CHECK_FOR_INTERRUPTS();+ }+}++/*+ * Safely read the wanted buffer from disk, dealing with possible concurrency+ * issue. Note that if a buffer is found dirty in shared_buffers, no read will+ * be performed and the caller will be informed that no check should be done.+ * We can safely ignore such buffers as they'll be written before next+ * checkpoint's completion..+ *+ * The following locks can be used in this function:+ *+ * - shared LWLock on the target buffer pool partition mapping.+ * - IOLock on the buffer+ *+ * The IOLock is taken when reading the buffer from disk if it exists in+ * shared_buffers, to avoid torn pages.+ *+ * If the buffer isn't in shared_buffers, it'll be read from disk without any+ * lock unless caller asked otherwise, setting needlock. In this case, the+ * read will be done while the buffer mapping partition LWLock is still being+ * held. Reading with this lock is to avoid the unlikely but possible case+ * that a buffer wasn't present in shared buffers when we checked but it then+ * alloc'ed in shared_buffers, modified and flushed concurrently when we+ * later try to read it, leading to false positive due to torn page. Caller+ * can read first the buffer without holding the target buffer mapping+ * partition LWLock to have an optimistic approach, and reread the buffer+ * from disk in case of error.+ *+ * Caller should hold an AccessShareLock on the Relation+ */+static void+check_get_buffer(Relation relation, ForkNumber forknum,+ BlockNumber blkno, char *buffer, bool needlock, bool *checkit,+ bool *found_in_sb)+{+ BufferTag buf_tag; /* identity of requested block */+ uint32 buf_hash; /* hash value for buf_tag */+ LWLock *partLock; /* buffer partition lock for the buffer */+ BufferDesc *bufdesc;+ int buf_id;++ *checkit = true;+ *found_in_sb = false;++ /* Check for interrupts and take throttling into account. */+ check_delay_point();++ /* create a tag so we can lookup the buffer */+ INIT_BUFFERTAG(buf_tag, relation->rd_smgr->smgr_rnode.node, forknum, blkno);++ /* determine its hash code and partition lock ID */+ buf_hash = BufTableHashCode(&buf_tag);+ partLock = BufMappingPartitionLock(buf_hash);++ /* see if the block is in the buffer pool already */+ LWLockAcquire(partLock, LW_SHARED);+ buf_id = BufTableLookup(&buf_tag, buf_hash);+ if (buf_id >= 0)+ {+ uint32 buf_state;++ *found_in_sb = true;++ /*+ * Found it. Now, retrieve its state to know what to do with it, and+ * release the pin immediately. We do so to limit overhead as much+ * as possible. We'll keep the shared lightweight lock on the target+ * buffer mapping partition, so this buffer can't be evicted, and+ * we'll acquire an IOLock on the buffer if we need to read the+ * content on disk.+ */+ bufdesc = GetBufferDescriptor(buf_id);++ buf_state = LockBufHdr(bufdesc);+ UnlockBufHdr(bufdesc, buf_state);++ /* Dirty pages are ignored as they'll be flushed soon. */+ if (buf_state & BM_DIRTY)+ *checkit = false;++ /*+ * Read the buffer from disk, taking on IO lock to prevent torn-page+ * reads, in the unlikely event that it was concurrently dirtied and+ * flushed.+ */+ if (*checkit)+ {+ LWLockAcquire(BufferDescriptorGetIOLock(bufdesc), LW_SHARED);+ smgrread(relation->rd_smgr, forknum, blkno, buffer);+ LWLockRelease(BufferDescriptorGetIOLock(bufdesc));++ /*+ * Add a page miss cost, as we're always reading outside the+ * shared buffers.+ */+ ChecksumCostBalance += ChecksumCostPageMiss;+ }+ }+ else if (needlock)+ {+ /*+ * Caller asked to read the buffer while we have a lock on the target+ * partition.+ */+ smgrread(relation->rd_smgr, forknum, blkno, buffer);++ /*+ * Add a page miss cost, as we're always reading outside the shared+ * buffers.+ */+ ChecksumCostBalance += ChecksumCostPageMiss;+ }++ LWLockRelease(partLock);++ if (*found_in_sb || needlock)+ return;++ /*+ * Didn't find it in the buffer pool and didn't read it while holding the+ * buffer mapping partition lock. We'll have to try to read it from+ * disk, after releasing the target partition lock to avoid too much+ * overhead. It means that it's possible to get a torn page later, so+ * we'll have to retry with a suitable lock in case of error to avoid+ * false positive.+ */+ smgrread(relation->rd_smgr, forknum, blkno, buffer);++ /*+ * Add a page miss cost, as we're always reading outside the shared+ * buffers.+ */+ ChecksumCostBalance += ChecksumCostPageMiss;+}diff --git a/src/backend/utils/adt/Makefile b/src/backend/utils/adt/Makefileindex 13efa9338c..27dc524e00 100644--- a/src/backend/utils/adt/Makefile+++ b/src/backend/utils/adt/Makefile@@ -22,6 +22,7 @@ OBJS = \
bool.o \
cash.o \
char.o \
+ checksumfuncs.o \
cryptohashes.o \
date.o \
datetime.o \
diff --git a/src/backend/utils/adt/checksumfuncs.c b/src/backend/utils/adt/checksumfuncs.cnew file mode 100644index 0000000000..b53b4c0bbf--- /dev/null+++ b/src/backend/utils/adt/checksumfuncs.c@@ -0,0 +1,96 @@+/*-------------------------------------------------------------------------+ *+ * checksumfuncs.c+ * Functions for checksums related feature such as online verification+ *+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ *+ * IDENTIFICATION+ * src/backend/utils/adt/checksumfuncs.c+ *+ *-------------------------------------------------------------------------+ */+#include "postgres.h"++#include "access/xlog.h"+#include "catalog/pg_authid_d.h"+#include "funcapi.h"+#include "miscadmin.h"+#include "storage/checksum.h"+#include "utils/acl.h"+#include "utils/builtins.h"++Datum+pg_check_relation(PG_FUNCTION_ARGS)+{+ ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;+ TupleDesc tupdesc;+ Tuplestorestate *tupstore;+ MemoryContext per_query_ctx;+ MemoryContext oldcontext;+ ForkNumber forknum = InvalidForkNumber;+ Oid relid = InvalidOid;+ const char *forkname;++ if (!DataChecksumsEnabled())+ ereport(ERROR,+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),+ errmsg("data checksums are not enabled in cluster")));++ if (!is_member_of_role(GetUserId(), DEFAULT_ROLE_READ_SERVER_FILES))+ ereport(ERROR,+ (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),+ errmsg("only superuser or a member of the pg_read_server_files role may use this function")));++ if (PG_ARGISNULL(0))+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),+ errmsg("relation cannot be null")));++ /* check to see if caller supports us returning a tuplestore */+ if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))+ ereport(ERROR,+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),+ errmsg("set-valued function called in context that cannot accept a set")));+ if (!(rsinfo->allowedModes & SFRM_Materialize))+ ereport(ERROR,+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),+ errmsg("materialize mode required, but it is not " \+ "allowed in this context")));++ /* Switch into long-lived context to construct returned data structures */+ per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;+ oldcontext = MemoryContextSwitchTo(per_query_ctx);++ /* Build a tuple descriptor for our result type */+ if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)+ elog(ERROR, "return type must be a row type");++ tupstore = tuplestore_begin_heap(true, false, work_mem);+ rsinfo->returnMode = SFRM_Materialize;+ rsinfo->setResult = tupstore;+ rsinfo->setDesc = tupdesc;++ MemoryContextSwitchTo(oldcontext);++ relid = PG_GETARG_OID(0);++ if (PG_NARGS() == 2 && !PG_ARGISNULL(1))+ {+ forkname = TextDatumGetCString(PG_GETARG_TEXT_PP(1));+ forknum = forkname_to_number(forkname);+ }++ /* Set cost-based vacuum delay */+ ChecksumCostActive = (ChecksumCostDelay > 0);+ ChecksumCostBalance = 0;++ check_one_relation(tupdesc, tupstore, relid, forknum);++ tuplestore_donestoring(tupstore);++ return (Datum) 0;+}+diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.cindex eb19644419..37f63e747c 100644--- a/src/backend/utils/init/globals.c+++ b/src/backend/utils/init/globals.c@@ -134,6 +134,14 @@ int max_worker_processes = 8;
int max_parallel_workers = 8;
int MaxBackends = 0;
+int ChecksumCostPageHit = 1; /* GUC parameters for checksum check */+int ChecksumCostPageMiss = 10;+int ChecksumCostLimit = 200;+double ChecksumCostDelay = 0;++int ChecksumCostBalance = 0; /* working state for checksums check */+bool ChecksumCostActive = false;+
int VacuumCostPageHit = 1; /* GUC parameters for vacuum */
int VacuumCostPageMiss = 10;
int VacuumCostPageDirty = 20;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.cindex 68082315ac..9749e3048b 100644--- a/src/backend/utils/misc/guc.c+++ b/src/backend/utils/misc/guc.c@@ -693,6 +693,8 @@ const char *const config_group_names[] =
gettext_noop("Resource Usage / Disk"),
/* RESOURCES_KERNEL */
gettext_noop("Resource Usage / Kernel Resources"),
+ /* RESOURCES_CHECKSUM_DELAY */+ gettext_noop("Resource Usage / Cost-Based Checksum Verification Delay"),
/* RESOURCES_VACUUM_DELAY */
gettext_noop("Resource Usage / Cost-Based Vacuum Delay"),
/* RESOURCES_BGWRITER */
@@ -2376,6 +2378,36 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {+ {"checksum_cost_page_hit", PGC_USERSET, RESOURCES_CHECKSUM_DELAY,+ gettext_noop("Checksum cost for a page found in the buffer cache."),+ NULL+ },+ &ChecksumCostPageHit,+ 1, 0, 10000,+ NULL, NULL, NULL+ },++ {+ {"checksum_cost_page_miss", PGC_USERSET, RESOURCES_CHECKSUM_DELAY,+ gettext_noop("Checksum cost for a page not found in the buffer cache."),+ NULL+ },+ &ChecksumCostPageMiss,+ 10, 0, 10000,+ NULL, NULL, NULL+ },++ {+ {"checksum_cost_limit", PGC_USERSET, RESOURCES_CHECKSUM_DELAY,+ gettext_noop("Checksum cost amount available before napping."),+ NULL+ },+ &ChecksumCostLimit,+ 200, 1, 10000,+ NULL, NULL, NULL+ },+
{
{"vacuum_cost_page_hit", PGC_USERSET, RESOURCES_VACUUM_DELAY,
gettext_noop("Vacuum cost for a page found in the buffer cache."),
@@ -3498,6 +3530,17 @@ static struct config_real ConfigureNamesReal[] =
check_random_seed, assign_random_seed, show_random_seed
},
+ {+ {"checksum_cost_delay", PGC_USERSET, RESOURCES_CHECKSUM_DELAY,+ gettext_noop("Checksum cost delay in milliseconds."),+ NULL,+ GUC_UNIT_MS+ },+ &ChecksumCostDelay,+ 0, 0, 100,+ NULL, NULL, NULL+ },+
{
{"vacuum_cost_delay", PGC_USERSET, RESOURCES_VACUUM_DELAY,
gettext_noop("Vacuum cost delay in milliseconds."),
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.datindex 7fb574f9dc..73fa7cdf51 100644--- a/src/include/catalog/pg_proc.dat+++ b/src/include/catalog/pg_proc.dat@@ -10741,6 +10741,14 @@
proallargtypes => '{oid,text,int8,timestamptz}', proargmodes => '{i,o,o,o}',
proargnames => '{tablespace,name,size,modification}',
prosrc => 'pg_ls_tmpdir_1arg' },
+{ oid => '9147', descr => 'check data integrity for one or all relations',+ proname => 'pg_check_relation', proisstrict => 'f', procost => '10000',+ prorows => '20', proretset => 't', proparallel => 'r',+ provolatile => 'v', prorettype => 'record', proargtypes => 'regclass text',+ proallargtypes => '{regclass,text,oid,int4,int8,int4,int4}',+ proargmodes => '{i,i,o,o,o,o,o}',+ proargnames => '{relation,fork,relid,forknum,failed_blocknum,expected_checksum,found_checksum}',+ prosrc => 'pg_check_relation' },
# hash partitioning constraint function
{ oid => '5028', descr => 'hash partition CHECK constraint',
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.hindex 14fa127ab1..f2fc143872 100644--- a/src/include/miscadmin.h+++ b/src/include/miscadmin.h@@ -246,6 +246,14 @@ extern PGDLLIMPORT int work_mem;
extern PGDLLIMPORT int maintenance_work_mem;
extern PGDLLIMPORT int max_parallel_maintenance_workers;
+extern int ChecksumCostPageHit;+extern int ChecksumCostPageMiss;+extern int ChecksumCostLimit;+extern double ChecksumCostDelay;++extern int ChecksumCostBalance;+extern bool ChecksumCostActive;+
extern int VacuumCostPageHit;
extern int VacuumCostPageMiss;
extern int VacuumCostPageDirty;
diff --git a/src/include/storage/checksum.h b/src/include/storage/checksum.hindex 6e77744cbc..29ca52d8c9 100644--- a/src/include/storage/checksum.h+++ b/src/include/storage/checksum.h@@ -13,8 +13,15 @@
#ifndef CHECKSUM_H
#define CHECKSUM_H
+#include "postgres.h"++#include "access/tupdesc.h"+#include "common/relpath.h"
#include "storage/block.h"
+#include "utils/tuplestore.h"+extern void check_one_relation(TupleDesc tupdesc, Tuplestorestate *tupstore,+ Oid relid, ForkNumber single_forknum);
/*
* Compute the checksum for a Postgres page. The page must be aligned on a
* 4-byte boundary.
diff --git a/src/include/utils/guc_tables.h b/src/include/utils/guc_tables.hindex 454c2df487..84965d3f09 100644--- a/src/include/utils/guc_tables.h+++ b/src/include/utils/guc_tables.h@@ -62,6 +62,7 @@ enum config_group
RESOURCES_MEM,
RESOURCES_DISK,
RESOURCES_KERNEL,
+ RESOURCES_CHECKSUM_DELAY,
RESOURCES_VACUUM_DELAY,
RESOURCES_BGWRITER,
RESOURCES_ASYNCHRONOUS,
diff --git a/src/test/Makefile b/src/test/Makefileindex efb206aa75..832868099f 100644--- a/src/test/Makefile+++ b/src/test/Makefile@@ -12,7 +12,8 @@ subdir = src/test
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
-SUBDIRS = perl regress isolation modules authentication recovery subscription+SUBDIRS = perl regress isolation modules authentication check_relation \+ recovery subscription
# Test suites that are not safe by default but can be run if selected
# by the user via the whitespace-separated list in variable
diff --git a/src/test/check_relation/.gitignore b/src/test/check_relation/.gitignorenew file mode 100644index 0000000000..871e943d50--- /dev/null+++ b/src/test/check_relation/.gitignore@@ -0,0 +1,2 @@+# Generated by test suite+/tmp_check/diff --git a/src/test/check_relation/Makefile b/src/test/check_relation/Makefilenew file mode 100644index 0000000000..792098fa65--- /dev/null+++ b/src/test/check_relation/Makefile@@ -0,0 +1,23 @@+#-------------------------------------------------------------------------+#+# Makefile for src/test/check_relation+#+# Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group+# Portions Copyright (c) 1994, Regents of the University of California+#+# src/test/check_relation/Makefile+#+#-------------------------------------------------------------------------++subdir = src/test/check_relation+top_builddir = ../../..+include $(top_builddir)/src/Makefile.global++check:+ $(prove_check)++installcheck:+ $(prove_installcheck)++clean distclean maintainer-clean:+ rm -rf tmp_checkdiff --git a/src/test/check_relation/README b/src/test/check_relation/READMEnew file mode 100644index 0000000000..415c4b21ad--- /dev/null+++ b/src/test/check_relation/README@@ -0,0 +1,23 @@+src/test/check_relation/README++Regression tests for online checksums verification+==================================================++This directory contains a test suite for online checksums verification.++Running the tests+=================++NOTE: You must have given the --enable-tap-tests argument to configure.++Run+ make check+or+ make installcheck+You can use "make installcheck" if you previously did "make install".+In that case, the code in the installation tree is tested. With+"make check", a temporary installation tree is built from the current+sources and then tested.++Either way, this test initializes, starts, and stops a test Postgres+cluster.diff --git a/src/test/check_relation/t/01_checksums_check.pl b/src/test/check_relation/t/01_checksums_check.plnew file mode 100644index 0000000000..af67252ea1--- /dev/null+++ b/src/test/check_relation/t/01_checksums_check.pl@@ -0,0 +1,276 @@+use strict;+use warnings;++use PostgresNode;+use TestLib;+use Test::More tests => 59;++our $CHECKSUM_UINT16_OFFSET = 4;+our $PD_UPPER_UINT16_OFFSET = 7;+our $BLOCKSIZE;+our $TOTAL_NB_ERR = 0;++sub get_block+{+ my ($filename, $blkno) = @_;+ my $block;++ open(my $infile, '<', $filename) or die;+ binmode($infile);++ my $success = read($infile, $block, $BLOCKSIZE, ($blkno * $BLOCKSIZE));+ die($!) if not defined $success;++ close($infile);++ return($block);+}++sub overwrite_block+{+ my ($filename, $block, $blkno) = @_;++ open(my $outfile, '>', $filename) or die;+ binmode ($outfile);++ my $nb = syswrite($outfile, $block, $BLOCKSIZE, ($blkno * $BLOCKSIZE));++ die($!) if not defined $nb;+ die("Write error") if ($nb != $BLOCKSIZE);++ $outfile->flush();++ close($outfile);+}++sub get_uint16_from_page+{+ my ($block, $offset) = @_;++ return (unpack("S*", $block))[$offset];+}++sub set_uint16_to_page+{+ my ($block, $data, $offset) = @_;++ my $pack = pack("S", $data);++ # vec with 16B or more won't preserve endianness+ vec($block, 2*$offset, 8) = (unpack('C*', $pack))[0];+ vec($block, (2*$offset) + 1, 8) = (unpack('C*', $pack))[1];++ return $block;+}++sub check_checksums_call+{+ my ($node, $relname) = @_;++ my ($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT COUNT(*)"+ . " FROM pg_catalog.pg_check_relation('$relname')"+ );++ return ($stderr eq '');+}++sub check_checksums_nb_error+{+ my ($node, $nb, $pattern) = @_;++ my ($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT COUNT(*)"+ . " FROM (SELECT pg_catalog.pg_check_relation(oid)"+ . " FROM pg_class WHERE relkind in ('r', 'i', 'm')) AS s"+ );++ is($cmdret, 0, 'Function should run successfully');+ like($stderr, $pattern, 'Error output should match expectations');+ is($stdout, $nb, "Should have $nb error");++ $TOTAL_NB_ERR += $nb;+}++sub check_pg_stat_database_nb_error+{+ my ($node) = @_;++ my ($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT "+ . " sum(checksum_failures)"+ . " FROM pg_catalog.pg_stat_database"+ );++ is($cmdret, 0, 'Function should run successfully');+ is($stderr, '', 'Function should run successfully');+ is($stdout, $TOTAL_NB_ERR, "Should have $TOTAL_NB_ERR error");+}++sub get_checksums_errors+{+ my ($node, $nb, $pattern) = @_;++ my ($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT"+ . " relid::regclass::text, forknum, failed_blocknum,"+ . " expected_checksum, found_checksum"+ . " FROM (SELECT (pg_catalog.pg_check_relation(oid)).*"+ . " FROM pg_class WHERE relkind in ('r','i', 'm')) AS s"+ );++ is($cmdret, '0', 'Function should run successfully');+ like($stderr, $pattern, 'Error output should match expectations');++ $TOTAL_NB_ERR += $nb;++ return $stdout;+}++# This function will perform various test by modifying the specified block at+# the specified uint16 offset, checking that the corruption is correctly+# detected, and finally restore the specified block to its original content.+sub corrupt_and_test_block+{+ my ($node, $filename, $blkno, $offset, $fake_data) = @_;++ check_checksums_nb_error($node, 0, qr/^$/);++check_pg_stat_database_nb_error($node);++ $node->stop();++ my $original_block = get_block($filename, 0);+ my $original_data = get_uint16_from_page($original_block, $offset);++ isnt($original_data, $fake_data,+ "The fake data at offset $offset should be different"+ . " from the existing one");++ my $new_block = set_uint16_to_page($original_block, $fake_data, $offset);+ isnt($original_data, get_uint16_from_page($new_block, $offset),+ "The fake data at offset $offset should have been changed in memory");++ overwrite_block($filename, $new_block, 0);++ my $written_data = get_uint16_from_page(get_block($filename, 0), $offset);+ isnt($original_data, $written_data,+ "The data written at offset $offset should be different"+ . " from the original one");+ is(get_uint16_from_page($new_block, $offset), $written_data,+ "The data written at offset $offset should be the same"+ . " as the one in memory");+ is($written_data, $fake_data,+ "The data written at offset $offset should be the one"+ . " we wanted to write");++ $node->start();++ check_checksums_nb_error($node, 1, qr/invalid page in block $blkno/);++ my $expected_checksum;+ my $found_checksum = get_uint16_from_page($new_block,+ $CHECKSUM_UINT16_OFFSET);+ if ($offset == $PD_UPPER_UINT16_OFFSET)+ {+ # A checksum can't be computed if it's detected as PageIsNew(), so the+ # function returns NULL for the computed checksum+ $expected_checksum = '';+ }+ else+ {+ $expected_checksum = get_uint16_from_page($original_block,+ $CHECKSUM_UINT16_OFFSET);+ }++ my $det = get_checksums_errors($node, 1, qr/invalid page in block $blkno/);+ is($det, "t1|0|0|$expected_checksum|$found_checksum",+ "The checksums error for modification at offset $offset"+ . " should be detected");++ $node->stop();++ $new_block = set_uint16_to_page($original_block, $original_data, $offset);+ is($original_data, get_uint16_from_page($new_block, $offset),+ "The data at offset $offset should have been restored in memory");++ overwrite_block($filename, $new_block, 0);+ is($original_data, get_uint16_from_page(get_block($filename, $blkno),+ $offset),+ "The data at offset $offset should have been restored on disk");++ $node->start();++ check_checksums_nb_error($node, 0, qr/^$/);+}++if (exists $ENV{MY_PG_REGRESS})+{+ $ENV{PG_REGRESS} = $ENV{MY_PG_REGRESS};+}++my $node = get_new_node('main');++my %params;+$params{'extra'} = ['--data-checksums'];+$node->init(%params);++$node->start();++$ENV{PGOPTIONS} = '--client-min-messages=WARNING';++my ($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT"+ . " current_setting('data_checksums')");++is($stdout, 'on', 'Data checksums shoud be enabled');++($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT"+ . " current_setting('block_size')");++$BLOCKSIZE = $stdout;++$node->safe_psql(+ 'postgres', q|+ CREATE TABLE public.t1(id integer);+ CREATE INDEX t1_id_idx ON public.t1 (id);+ INSERT INTO public.t1 SELECT generate_series(1, 100);+ CREATE VIEW public.v1 AS SELECT * FROM t1;+ CREATE MATERIALIZED VIEW public.mv1 AS SELECT * FROM t1;+ CREATE SEQUENCE public.s1;+ CREATE UNLOGGED TABLE public.u_t1(id integer);+ CREATE INDEX u_t1_id_idx ON public.u_t1 (id);+ INSERT INTO public.u_t1 SELECT generate_series(1, 100);+ CHECKPOINT;+|);++# Check sane behavior on various objects type, including those that don't have+# a storage.+is(check_checksums_call($node, 't1'), '1', 'Can check a table');+is(check_checksums_call($node, 't1_id_idx'), '1', 'Can check an index');+is(check_checksums_call($node, 'v1'), '', 'Cannot check a view');+is(check_checksums_call($node, 'mv1'), '1', 'Can check a materialized view');+is(check_checksums_call($node, 's1'), '1', 'Can check a sequence');+is(check_checksums_call($node, 'u_t1'), '1', 'Can check an unlogged table');+is(check_checksums_call($node, 'u_t1_id_idx'), '1', 'Can check an unlogged index');++# get the underlying heap absolute path+($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT"+ . " current_setting('data_directory') || '/' || pg_relation_filepath('t1')"+);++isnt($stdout, '', 'A relfinode should be returned');++my $filename = $stdout;++check_checksums_nb_error($node, 0, qr/^$/);++check_pg_stat_database_nb_error($node);++my $fake_uint16 = hex '0x0000';++# Test with a modified checksum. We use a zero checksum here as it's the only+# one that cannot exist on a checksummed page. We also don't have an easy way+# to compute what the checksum would be after a modification in a random place+# in the block.+corrupt_and_test_block($node, $filename, 0, $CHECKSUM_UINT16_OFFSET,+ $fake_uint16);++# Test corruption making the block looks like it's PageIsNew().+corrupt_and_test_block($node, $filename, 0, $PD_UPPER_UINT16_OFFSET,+ $fake_uint16);--
2.20.1
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To: pgsql-hackers@postgresql.org
Cc: rjuju123@gmail.com, michael@paquier.xyz, robertmhaas@gmail.com, pgsql-hackers@lists.postgresql.org, sawada.mshk@gmail.com
Subject: Re: Online checksums verification in the backend
In-Reply-To: <20200318101055.GA36918@nol>
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