On Tue, Apr 26, 2011 at 07:45:33AM -0500, Martin_Zielinski@xxxxxxxxxx wrote:
> I will port the jbd2 debugging code to jbd an will try to get the
> new kernel into production. After a reboot we will have to wait
> several weeks. (Strange: all machines failed within 72 hours).
Great, thanks.
> With sqlite I can currently produce ~10.000.000 commits in one hour
> with a program that does nothing else. I doubt that it is possible
> to have an overflow in such a short time that we are observing.
> Maybe the __log_start_commit commit call comes with a corrupt target
> id from elsewhere. But your patch will catch that, too.
Agreed; that's why I don't really believe the wraparound theory. For
your convenience, this is the revised (cleaned up) patch for the
ext3/jbd (it just cleans up how we print the warning).
- Ted
commit 4ea00445c7f5d3dfa6219262598a2a8319df07c7
Author: Theodore Ts'o <tytso@xxxxxxx>
Date: Tue Apr 26 13:14:55 2011 -0400
jbd: fix fsync() tid wraparound bug
If an application program does not make any changes to the indirect
blocks or extent tree, i_datasync_tid will not get updated. If there
are enough commits (i.e., 2**31) such that tid_geq()'s calculations
wrap, and there isn't a currently active transaction at the time of
the fdatasync() call, this can end up triggering a BUG_ON in
fs/jbd/commit.c:
J_ASSERT(journal->j_running_transaction != NULL);
It's pretty rare that this can happen, since it requires the use of
fdatasync() plus *very* frequent and excessive use of fsync(). But
with the right workload, it can.
We fix this by replacing the use of tid_geq() with an equality test,
since there's only one valid transaction id that we is valid for us to
wait until it is commited: namely, the currently running transaction
(if it exists).
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index b3713af..1b71ce6 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -437,9 +437,12 @@ int __log_space_left(journal_t *journal)
int __log_start_commit(journal_t *journal, tid_t target)
{
/*
- * Are we already doing a recent enough commit?
+ * The only transaction we can possibly wait upon is the
+ * currently running transaction (if it exists). Otherwise,
+ * the target tid must be an old one.
*/
- if (!tid_geq(journal->j_commit_request, target)) {
+ if (journal->j_running_transaction &&
+ journal->j_running_transaction->t_tid == target) {
/*
* We want a new commit: OK, mark the request and wakeup the
* commit thread. We do _not_ do the commit ourselves.
@@ -451,7 +454,14 @@ int __log_start_commit(journal_t *journal, tid_t target)
journal->j_commit_sequence);
wake_up(&journal->j_wait_commit);
return 1;
- }
+ } else if (!tid_geq(journal->j_commit_request, target))
+ /* This should never happen, but if it does, preserve
+ the evidence before kjournald goes into a loop and
+ increments j_commit_sequence beyond all recognition. */
+ WARN(1, "jbd: bad log_start_commit: %u %u %u %u\n",
+ journal->j_commit_request, journal->j_commit_sequence,
+ target, journal->j_running_transaction ?
+ journal->j_running_transaction->t_tid : 0);
return 0;
}
--
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