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Commitd0024cd

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committed
Avoid crashing when we have problems unlinking files post-commit.
smgrdounlink takes care to not throw an ERROR if it fails to unlinksomething, but that caution was rendered useless by commit3396000, which put an smgrexists call infront of it; smgrexists *does* throw error if anything looks funny, suchas getting a permissions error from trying to open the file. If thathappens post-commit, you get a PANIC, and what's worse the same logicappears in the WAL replay code, so the database even fails to restart.Restore the intended behavior by removing the smgrexists call --- it isn'taccomplishing anything that we can't do better by adjusting mdunlink'sideas of whether it ought to warn about ENOENT or not.Per report from Joseph Shraibman of unrecoverable crash after trying todrop a table whose FSM fork had somehow gotten chmod'd to 000 permissions.Backpatch to 8.4, where the bogus coding was introduced.
1 parent7292055 commitd0024cd

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4 files changed

+20
-26
lines changed

4 files changed

+20
-26
lines changed

‎src/backend/access/transam/twophase.c‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1366,8 +1366,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
13661366

13671367
for (fork=0;fork <=MAX_FORKNUM;fork++)
13681368
{
1369-
if (smgrexists(srel,fork))
1370-
smgrdounlink(srel,fork, false);
1369+
smgrdounlink(srel,fork, false);
13711370
}
13721371
smgrclose(srel);
13731372
}

‎src/backend/access/transam/xact.c‎

Lines changed: 4 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -4595,11 +4595,8 @@ xact_redo_commit_internal(TransactionId xid, XLogRecPtr lsn,
45954595

45964596
for (fork=0;fork <=MAX_FORKNUM;fork++)
45974597
{
4598-
if (smgrexists(srel,fork))
4599-
{
4600-
XLogDropRelation(xnodes[i],fork);
4601-
smgrdounlink(srel,fork, true);
4602-
}
4598+
XLogDropRelation(xnodes[i],fork);
4599+
smgrdounlink(srel,fork, true);
46034600
}
46044601
smgrclose(srel);
46054602
}
@@ -4738,11 +4735,8 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
47384735

47394736
for (fork=0;fork <=MAX_FORKNUM;fork++)
47404737
{
4741-
if (smgrexists(srel,fork))
4742-
{
4743-
XLogDropRelation(xlrec->xnodes[i],fork);
4744-
smgrdounlink(srel,fork, true);
4745-
}
4738+
XLogDropRelation(xlrec->xnodes[i],fork);
4739+
smgrdounlink(srel,fork, true);
47464740
}
47474741
smgrclose(srel);
47484742
}

‎src/backend/catalog/storage.c‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -361,8 +361,7 @@ smgrDoPendingDeletes(bool isCommit)
361361
srel=smgropen(pending->relnode,pending->backend);
362362
for (i=0;i <=MAX_FORKNUM;i++)
363363
{
364-
if (smgrexists(srel,i))
365-
smgrdounlink(srel,i, false);
364+
smgrdounlink(srel,i, false);
366365
}
367366
smgrclose(srel);
368367
}

‎src/backend/storage/smgr/md.c‎

Lines changed: 14 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -323,7 +323,13 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
323323
* number until it's safe, because relfilenode assignment skips over any
324324
* existing file.
325325
*
326-
* If isRedo is true, it's okay for the relation to be already gone.
326+
* All the above applies only to the relation's main fork; other forks can
327+
* just be removed immediately, since they are not needed to prevent the
328+
* relfilenode number from being recycled. Also, we do not carefully
329+
* track whether other forks have been created or not, but just attempt to
330+
* unlink them unconditionally; so we should never complain about ENOENT.
331+
*
332+
* If isRedo is true, it's unsurprising for the relation to be already gone.
327333
* Also, we should remove the file immediately instead of queuing a request
328334
* for later, since during redo there's no possibility of creating a
329335
* conflicting relation.
@@ -351,13 +357,10 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
351357
if (isRedo||forkNum!=MAIN_FORKNUM)
352358
{
353359
ret=unlink(path);
354-
if (ret<0)
355-
{
356-
if (!isRedo||errno!=ENOENT)
357-
ereport(WARNING,
358-
(errcode_for_file_access(),
359-
errmsg("could not remove file \"%s\": %m",path)));
360-
}
360+
if (ret<0&&errno!=ENOENT)
361+
ereport(WARNING,
362+
(errcode_for_file_access(),
363+
errmsg("could not remove file \"%s\": %m",path)));
361364
}
362365
else
363366
{
@@ -380,6 +383,9 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
380383
ereport(WARNING,
381384
(errcode_for_file_access(),
382385
errmsg("could not truncate file \"%s\": %m",path)));
386+
387+
/* Register request to unlink first segment later */
388+
register_unlink(rnode);
383389
}
384390

385391
/*
@@ -411,10 +417,6 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
411417
}
412418

413419
pfree(path);
414-
415-
/* Register request to unlink first segment later */
416-
if (!isRedo&&forkNum==MAIN_FORKNUM)
417-
register_unlink(rnode);
418420
}
419421

420422
/*

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