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authorRusty Russell <rusty@rustcorp.com.au>2009-07-30 11:52:08 +0930
committerStefan Metzmacher <metze@samba.org>2009-07-31 14:40:28 +0200
commit3b2f074bda8734a0b30a3e31117c0217d890809c (patch)
treed31c49e0b44eacdeeca18eb9a18e26e05e2f7b60
parentfa91bc67199f0d45a0e570b43aeafd816a5491bf (diff)
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tdb: Reimplementation of Metze's "lib/tdb: if we know pwrite and pread are thread/fork safe tdb_reopen_all() should be a noop".
This version just wraps the reopen code, so we still re-grab the lock and do the normal sanity checks. The reason we do this at all is to avoid global fd limits, see: http://forums.fedoraforum.org/showthread.php?t=210393 Note also that this whole reopen concept is fundamentally racy: if the parent goes away before the child calls tdb_reopen_all, the database can be left without an active lock and another TDB_CLEAR_IF_FIRST opener will clear it. A fork_with_tdbs() wrapper could use a pipe to solve this, but it's hardly elegant (what if there are other independent things which have similar needs?). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Stefan Metzmacher <metze@samba.org>
-rw-r--r--lib/tdb/common/open.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/lib/tdb/common/open.c b/lib/tdb/common/open.c
index b19e4cea29..49b8e85f12 100644
--- a/lib/tdb/common/open.c
+++ b/lib/tdb/common/open.c
@@ -425,6 +425,9 @@ int tdb_reopen(struct tdb_context *tdb)
goto fail;
}
+/* If we have real pread & pwrite, we can skip reopen. */
+#if !defined(LIBREPLACE_PREAD_NOT_REPLACED) || \
+ !defined(LIBREPLACE_PWRITE_NOT_REPLACED)
if (tdb_munmap(tdb) != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: munmap failed (%s)\n", strerror(errno)));
goto fail;
@@ -436,11 +439,6 @@ int tdb_reopen(struct tdb_context *tdb)
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: open failed (%s)\n", strerror(errno)));
goto fail;
}
- if ((tdb->flags & TDB_CLEAR_IF_FIRST) &&
- (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0, 1) == -1)) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: failed to obtain active lock\n"));
- goto fail;
- }
if (fstat(tdb->fd, &st) != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: fstat failed (%s)\n", strerror(errno)));
goto fail;
@@ -450,6 +448,13 @@ int tdb_reopen(struct tdb_context *tdb)
goto fail;
}
tdb_mmap(tdb);
+#endif /* fake pread or pwrite */
+
+ if ((tdb->flags & TDB_CLEAR_IF_FIRST) &&
+ (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0, 1) == -1)) {
+ TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_reopen: failed to obtain active lock\n"));
+ goto fail;
+ }
return 0;