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| author | Ted Ts'o <tytso@mit.edu> | 2011-04-30 13:17:11 -0400 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2011-05-17 13:47:41 +0200 |
| commit | d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36 (patch) | |
| tree | 56a34d3c459bfac781b8f71d866caa7dd092b7c2 | |
| parent | 86c4f6d85595cd7da635dc6985d27bfa43b1ae10 (diff) | |
| download | linux-3.10-d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36.tar.gz linux-3.10-d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36.tar.bz2 linux-3.10-d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36.zip | |
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>
| -rw-r--r-- | fs/jbd/journal.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c index b3713afaaa9..e2d4285fbe9 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_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; } |