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Commitf8a0516

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Bgwriter should PANIC if it runs out of memory for pending-fsyncs
hash table. This is a pretty unlikely scenario, since the tableshould be tiny, but we can't guarantee continued correct operationif it does occur. Spotted by Qingqing Zhou.
1 parent6d9ee03 commitf8a0516

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‎src/backend/postmaster/bgwriter.c

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.15 2005/03/04 20:21:06 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/postmaster/bgwriter.c,v 1.16 2005/05/28 17:21:32 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -616,7 +616,7 @@ ForwardFsyncRequest(RelFileNode rnode, BlockNumber segno)
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*
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* This is exported because it must be called during CreateCheckPoint;
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* we have to be sure we have accepted all pending requests *after* we
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* establish the checkpointredo pointer. Since CreateCheckPoint
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* establish the checkpointREDO pointer. Since CreateCheckPoint
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* sometimes runs in non-bgwriter processes, do nothing if not bgwriter.
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*/
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void
@@ -629,6 +629,15 @@ AbsorbFsyncRequests(void)
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if (!am_bg_writer)
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return;
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/*
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* We have to PANIC if we fail to absorb all the pending requests
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* (eg, because our hashtable runs out of memory). This is because
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* the system cannot run safely if we are unable to fsync what we
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* have been told to fsync. Fortunately, the hashtable is so small
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* that the problem is quite unlikely to arise in practice.
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*/
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START_CRIT_SECTION();
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/*
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* We try to avoid holding the lock for a long time by copying the
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* request array.
@@ -647,6 +656,9 @@ AbsorbFsyncRequests(void)
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for (request=requests;n>0;request++,n--)
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RememberFsyncRequest(request->rnode,request->segno);
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if (requests)
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pfree(requests);
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END_CRIT_SECTION();
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}

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