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| author | Theodore Ts'o <tytso@mit.edu> | 2011-05-02 00:16:26 +0200 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2011-05-02 00:16:26 +0200 |
| commit | deeeaf13b291420fe4a4a52606b9fc9128387340 (patch) | |
| tree | 2e7cbab5f598839771022453e8ed4ea18fb1e0af /fs/jbd2 | |
| parent | ext4: remove obsolete mount options from ext4's documentation (diff) | |
| download | linux-deeeaf13b291420fe4a4a52606b9fc9128387340.tar.xz linux-deeeaf13b291420fe4a4a52606b9fc9128387340.zip | |
jbd2: 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/jbd2/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@mit.edu>
Diffstat (limited to 'fs/jbd2')
| -rw-r--r-- | fs/jbd2/journal.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index e0ec3db1c395..8c10004f7876 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -479,9 +479,12 @@ int __jbd2_log_space_left(journal_t *journal) int __jbd2_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. @@ -493,7 +496,14 @@ int __jbd2_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; } |