From d76a3a77113db020d9bb1e894822869410450bd9 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Wed, 3 Apr 2013 22:02:52 -0400 Subject: ext4/jbd2: don't wait (forever) for stale tid caused by wraparound In the case where an inode has a very stale transaction id (tid) in i_datasync_tid or i_sync_tid, it's possible that after a very large (2**31) number of transactions, that the tid number space might wrap, causing tid_geq()'s calculations to fail. Commit deeeaf13 "jbd2: fix fsync() tid wraparound bug", later modified by commit e7b04ac0 "jbd2: don't wake kjournald unnecessarily", attempted to fix this problem, but it only avoided kjournald spinning forever by fixing the logic in jbd2_log_start_commit(). Unfortunately, in the codepaths in fs/ext4/fsync.c and fs/ext4/inode.c that might call jbd2_log_start_commit() with a stale tid, those functions will subsequently call jbd2_log_wait_commit() with the same stale tid, and then wait for a very long time. To fix this, we replace the calls to jbd2_log_start_commit() and jbd2_log_wait_commit() with a call to a new function, jbd2_complete_transaction(), which will correctly handle stale tid's. As a bonus, jbd2_complete_transaction() will avoid locking j_state_lock for writing unless a commit needs to be started. This should have a small (but probably not measurable) improvement for ext4's scalability. Signed-off-by: "Theodore Ts'o" Reported-by: Ben Hutchings Reported-by: George Barnett Cc: stable@vger.kernel.org --- include/linux/jbd2.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index 50e5a5e6a712..f0289754b464 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -1200,6 +1200,7 @@ int __jbd2_log_start_commit(journal_t *journal, tid_t tid); int jbd2_journal_start_commit(journal_t *journal, tid_t *tid); int jbd2_journal_force_commit_nested(journal_t *journal); int jbd2_log_wait_commit(journal_t *journal, tid_t tid); +int jbd2_complete_transaction(journal_t *journal, tid_t tid); int jbd2_log_do_checkpoint(journal_t *journal); int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid); -- cgit v1.2.3-70-g09d2