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Commite848be6

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author
Amit Kapila
committed
Fix cleanup lock acquisition in SPLIT_ALLOCATE_PAGE replay.
During XLOG_HASH_SPLIT_ALLOCATE_PAGE replay, we were checking for acleanup lock on the new bucket page after acquiring an exclusive lock onit and raising a PANIC error on failure. However, it is quite possiblethat checkpointer can acquire the pin on the same page before acquiring alock on it, and then the replay will lead to an error. So instead, directlyacquire the cleanup lock on the new bucket page duringXLOG_HASH_SPLIT_ALLOCATE_PAGE replay operation.Reported-by: Andres FreundAuthor: Robert HaasReviewed-By: Amit Kapila, Andres Freund, Vignesh CBackpatch-through: 11Discussion:https://postgr.es/m/20220810022617.fvjkjiauaykwrbse@awork3.anarazel.de
1 parentad6c528 commite848be6

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2 files changed

+9
-6
lines changed

2 files changed

+9
-6
lines changed

‎src/backend/access/hash/hash_xlog.c

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -351,11 +351,10 @@ hash_xlog_split_allocate_page(XLogReaderState *record)
351351
}
352352

353353
/* replay the record for new bucket */
354-
newbuf=XLogInitBufferForRedo(record,1);
354+
XLogReadBufferForRedoExtended(record,1,RBM_ZERO_AND_CLEANUP_LOCK, true,
355+
&newbuf);
355356
_hash_initbuf(newbuf,xlrec->new_bucket,xlrec->new_bucket,
356357
xlrec->new_bucket_flag, true);
357-
if (!IsBufferCleanupOK(newbuf))
358-
elog(PANIC,"hash_xlog_split_allocate_page: failed to acquire cleanup lock");
359358
MarkBufferDirty(newbuf);
360359
PageSetLSN(BufferGetPage(newbuf),lsn);
361360

‎src/backend/access/hash/hashpage.c

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -805,9 +805,13 @@ _hash_expandtable(Relation rel, Buffer metabuf)
805805
/*
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* Physically allocate the new bucket's primary page. We want to do this
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* before changing the metapage's mapping info, in case we can't get the
808-
* disk space. Ideally, we don't need to check for cleanup lock on new
809-
* bucket as no other backend could find this bucket unless meta page is
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* updated. However, it is good to be consistent with old bucket locking.
808+
* disk space.
809+
*
810+
* XXX It doesn't make sense to call _hash_getnewbuf first, zeroing the
811+
* buffer, and then only afterwards check whether we have a cleanup lock.
812+
* However, since no scan can be accessing the buffer yet, any concurrent
813+
* accesses will just be from processes like the bgwriter or checkpointer
814+
* which don't care about its contents, so it doesn't really matter.
811815
*/
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buf_nblkno=_hash_getnewbuf(rel,start_nblkno,MAIN_FORKNUM);
813817
if (!IsBufferCleanupOK(buf_nblkno))

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