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Add test to WAL replay to verify that xl_prev points back to the previous

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WAL record; this is necessary to be sure we recognize stale WAL records
when a WAL page was only partially written during a system crash.
This commit is contained in:
Tom Lane 2005-05-31 19:11:14 +00:00
parent 4f142baf37
commit 2e1229671a
1 changed files with 34 additions and 3 deletions
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37
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.109.2.4 2004/08/11 04:08:39 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.109.2.5 2005/05/31 19:11:14 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -431,8 +431,8 @@ static uint32 readOff = 0;
static char *readBuf = NULL; static char *readBuf = NULL;
/* State information for XLOG reading */ /* State information for XLOG reading */
static XLogRecPtr ReadRecPtr; static XLogRecPtr ReadRecPtr; /* start of last record read */
static XLogRecPtr EndRecPtr; static XLogRecPtr EndRecPtr; /* end+1 of last record read */
static XLogRecord *nextRecord = NULL; static XLogRecord *nextRecord = NULL;
static StartUpID lastReadSUI; static StartUpID lastReadSUI;
@ -1866,6 +1866,37 @@ got_record:;
RecPtr->xlogid, RecPtr->xrecoff); RecPtr->xlogid, RecPtr->xrecoff);
goto next_record_is_invalid; goto next_record_is_invalid;
} }
if (!nextmode)
{
/*
* We can't exactly verify the prev-link, but surely it should be
* less than the record's own address.
*/
if (!XLByteLT(record->xl_prev, *RecPtr))
{
elog(emode,
"ReadRecord: record with incorrect prev-link %X/%X at %X/%X",
record->xl_prev.xlogid, record->xl_prev.xrecoff,
RecPtr->xlogid, RecPtr->xrecoff);
goto next_record_is_invalid;
}
}
else
{
/*
* Record's prev-link should exactly match our previous location.
* This check guards against torn WAL pages where a stale but
* valid-looking WAL record starts on a sector boundary.
*/
if (!XLByteEQ(record->xl_prev, ReadRecPtr))
{
elog(emode,
"record with incorrect prev-link %X/%X at %X/%X",
record->xl_prev.xlogid, record->xl_prev.xrecoff,
RecPtr->xlogid, RecPtr->xrecoff);
goto next_record_is_invalid;
}
}
/* /*
* Compute total length of record including any appended backup * Compute total length of record including any appended backup