diff options
| author | Tom Lane | 2006-01-21 04:38:54 +0000 |
|---|---|---|
| committer | Tom Lane | 2006-01-21 04:38:54 +0000 |
| commit | 3cbc8b6fb483ae4bf3011abe49030cb057a2722b (patch) | |
| tree | b41630ece8bea8f65a3e2990fcf0e28bf5c8430f | |
| parent | a6cc7db9a67663d59ceb6328d2b0ccea7b384ef6 (diff) | |
Repair longstanding bug in slru/clog logic: it is possible for two backends
to try to create a log segment file concurrently, but the code erroneously
specified O_EXCL to open(), resulting in a needless failure. Before 7.4,
it was even a PANIC condition :-(. Correct code is actually simpler than
what we had, because we can just say O_CREAT to start with and not need a
second open() call. I believe this accounts for several recent reports of
hard-to-reproduce "could not create file ...: File exists" errors in both
pg_clog and pg_subtrans.
| -rw-r--r-- | src/backend/access/transam/clog.c | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index 3f50c79331b..dca6b70dacc 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -13,7 +13,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.11.2.1 2005/11/03 00:23:57 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.11.2.2 2006/01/21 04:38:54 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -598,17 +598,15 @@ CLOGPhysicalWritePage(int pageno, int slotno) * that have already been truncated from the commit log. Easiest way * to deal with that is to accept references to nonexistent files here * and in CLOGPhysicalReadPage.) + * + * Note: it is possible for more than one backend to be executing + * this code simultaneously for different pages of the same file. + * Hence, don't use O_EXCL or O_TRUNC or anything like that. */ - fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR); + fd = BasicOpenFile(path, O_RDWR | O_CREAT | PG_BINARY, + S_IRUSR | S_IWUSR); if (fd < 0) - { - if (errno != ENOENT) - elog(PANIC, "open of %s failed: %m", path); - fd = BasicOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY, - S_IRUSR | S_IWUSR); - if (fd < 0) - elog(PANIC, "creation of file %s failed: %m", path); - } + elog(PANIC, "open of %s failed: %m", path); if (lseek(fd, (off_t) offset, SEEK_SET) < 0) elog(PANIC, "lseek of clog file %u, offset %u failed: %m", |