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Commitbd1cfde

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Fix RBM_ZERO_AND_LOCK mode to not acquire lock on local buffers.
Commit81c4508 introduced a new RBM_ZERO_AND_LOCK mode to ReadBuffer, whichtakes a lock on the buffer before zeroing it. However, you cannot take alock on a local buffer, and you got a segfault instead. The version of thatpatch committed to master included a check for !isLocalBuf, and thereforedidn't crash, but oddly I missed that in the back-patched versions. Thispatch adds that check to the back-branches too.RBM_ZERO_AND_LOCK mode is only used during WAL replay, and in hash indexes.WAL replay only deals with shared buffers, so the only way to trigger thebug is with a temporary hash index.Reported by Artem Ignatyev, analysis by Tom Lane.
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‎src/backend/storage/buffer/bufmgr.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -483,7 +483,8 @@ ReadBuffer_common(SMgrRelation smgr, bool isLocalBuf, ForkNumber forkNum,
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* (Note that we cannot use LockBuffer() of LockBufferForCleanup() here,
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* because they assert that the buffer is already valid.)
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*/
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if (mode==RBM_ZERO_AND_LOCK||mode==RBM_ZERO_AND_CLEANUP_LOCK)
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if ((mode==RBM_ZERO_AND_LOCK||mode==RBM_ZERO_AND_CLEANUP_LOCK)&&
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!isLocalBuf)
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LWLockAcquire(bufHdr->content_lock,LW_EXCLUSIVE);
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if (isLocalBuf)

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