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authorTheodore Ts'o <tytso@mit.edu>2011-05-01 18:16:26 -0400
committerTheodore Ts'o <tytso@mit.edu>2011-05-01 18:16:26 -0400
commitdeeeaf13b291420fe4a4a52606b9fc9128387340 (patch)
tree2e7cbab5f598839771022453e8ed4ea18fb1e0af /fs/jbd2
parent59802db0745ddfe5cfd0d965e9d489f1b4713868 (diff)
downloadlinux-deeeaf13b291420fe4a4a52606b9fc9128387340.tar.bz2
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.c16
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;
}