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Commita63a7a5

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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 parentbb4cfeb commita63a7a5

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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
@@ -1343,8 +1343,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
13431343

13441344
for (fork=0;fork <=MAX_FORKNUM;fork++)
13451345
{
1346-
if (smgrexists(srel,fork))
1347-
smgrdounlink(srel,fork, false);
1346+
smgrdounlink(srel,fork, false);
13481347
}
13491348
smgrclose(srel);
13501349
}

‎src/backend/access/transam/xact.c‎

Lines changed: 4 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -4532,11 +4532,8 @@ xact_redo_commit(xl_xact_commit *xlrec, TransactionId xid, XLogRecPtr lsn)
45324532

45334533
for (fork=0;fork <=MAX_FORKNUM;fork++)
45344534
{
4535-
if (smgrexists(srel,fork))
4536-
{
4537-
XLogDropRelation(xlrec->xnodes[i],fork);
4538-
smgrdounlink(srel,fork, true);
4539-
}
4535+
XLogDropRelation(xlrec->xnodes[i],fork);
4536+
smgrdounlink(srel,fork, true);
45404537
}
45414538
smgrclose(srel);
45424539
}
@@ -4637,11 +4634,8 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
46374634

46384635
for (fork=0;fork <=MAX_FORKNUM;fork++)
46394636
{
4640-
if (smgrexists(srel,fork))
4641-
{
4642-
XLogDropRelation(xlrec->xnodes[i],fork);
4643-
smgrdounlink(srel,fork, true);
4644-
}
4637+
XLogDropRelation(xlrec->xnodes[i],fork);
4638+
smgrdounlink(srel,fork, true);
46454639
}
46464640
smgrclose(srel);
46474641
}

‎src/backend/catalog/storage.c‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -360,8 +360,7 @@ smgrDoPendingDeletes(bool isCommit)
360360
srel=smgropen(pending->relnode,pending->backend);
361361
for (i=0;i <=MAX_FORKNUM;i++)
362362
{
363-
if (smgrexists(srel,i))
364-
smgrdounlink(srel,i, false);
363+
smgrdounlink(srel,i, false);
365364
}
366365
smgrclose(srel);
367366
}

‎src/backend/storage/smgr/md.c‎

Lines changed: 14 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -322,7 +322,13 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
322322
* number until it's safe, because relfilenode assignment skips over any
323323
* existing file.
324324
*
325-
* If isRedo is true, it's okay for the relation to be already gone.
325+
* All the above applies only to the relation's main fork; other forks can
326+
* just be removed immediately, since they are not needed to prevent the
327+
* relfilenode number from being recycled. Also, we do not carefully
328+
* track whether other forks have been created or not, but just attempt to
329+
* unlink them unconditionally; so we should never complain about ENOENT.
330+
*
331+
* If isRedo is true, it's unsurprising for the relation to be already gone.
326332
* Also, we should remove the file immediately instead of queuing a request
327333
* for later, since during redo there's no possibility of creating a
328334
* conflicting relation.
@@ -350,13 +356,10 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
350356
if (isRedo||forkNum!=MAIN_FORKNUM)
351357
{
352358
ret=unlink(path);
353-
if (ret<0)
354-
{
355-
if (!isRedo||errno!=ENOENT)
356-
ereport(WARNING,
357-
(errcode_for_file_access(),
358-
errmsg("could not remove file \"%s\": %m",path)));
359-
}
359+
if (ret<0&&errno!=ENOENT)
360+
ereport(WARNING,
361+
(errcode_for_file_access(),
362+
errmsg("could not remove file \"%s\": %m",path)));
360363
}
361364
else
362365
{
@@ -379,6 +382,9 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
379382
ereport(WARNING,
380383
(errcode_for_file_access(),
381384
errmsg("could not truncate file \"%s\": %m",path)));
385+
386+
/* Register request to unlink first segment later */
387+
register_unlink(rnode);
382388
}
383389

384390
/*
@@ -410,10 +416,6 @@ mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
410416
}
411417

412418
pfree(path);
413-
414-
/* Register request to unlink first segment later */
415-
if (!isRedo&&forkNum==MAIN_FORKNUM)
416-
register_unlink(rnode);
417419
}
418420

419421
/*

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