path: root/fs/jbd
diff options
authorTed Ts'o <tytso@mit.edu>2011-04-30 13:17:11 -0400
committerJan Kara <jack@suse.cz>2011-05-17 13:47:41 +0200
commitd9b01934d56a96d9f4ae2d6204d4ea78a36f5f36 (patch)
tree56a34d3c459bfac781b8f71d866caa7dd092b7c2 /fs/jbd
parentext3: Fix fs corruption when make_indexed_dir() fails (diff)
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 is valid for us to start: namely, the currently running transaction (if it exists). CC: stable@kernel.org Reported-by: Martin_Zielinski@McAfee.com Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/jbd')
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index b3713afaaa9e..e2d4285fbe90 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)
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_ONCE(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;