jbd: need to hold j_state_lock to updates to transaction t_state to T_COMMIT

Updating the current transaction's t_state is protected by j_state_lock.  We
need to do the same when updating the t_state to T_COMMIT.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Acked-by: Jan Kara <jack@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/jbd/commit.c

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index cd931ef..5a8ca61 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -470,7 +470,9 @@
 	 * transaction!  Now comes the tricky part: we need to write out
 	 * metadata.  Loop over the transaction's entire buffer list:
 	 */
+	spin_lock(&journal->j_state_lock);
 	commit_transaction->t_state = T_COMMIT;
+	spin_unlock(&journal->j_state_lock);
 
 	J_ASSERT(commit_transaction->t_nr_buffers <=
 		 commit_transaction->t_outstanding_credits);