path: root/fs
diff options
authorTheodore Ts'o <>2013-07-01 08:12:40 -0400
committerGreg Kroah-Hartman <>2013-07-21 18:21:22 -0700
commit15f26a4c4820d1fb5f1ba979b4fe4d00a2d38b7d (patch)
tree64b275628cb168feb2e2e1a457658827a5b7e0b7 /fs
parent5f81e313889bcaf53faec9c05a4c92e0b43823f4 (diff)
jbd2: fix theoretical race in jbd2__journal_restart
commit 39c04153fda8c32e85b51c96eb5511a326ad7609 upstream. Once we decrement transaction->t_updates, if this is the last handle holding the transaction from closing, and once we release the t_handle_lock spinlock, it's possible for the transaction to commit and be released. In practice with normal kernels, this probably won't happen, since the commit happens in a separate kernel thread and it's unlikely this could all happen within the space of a few CPU cycles. On the other hand, with a real-time kernel, this could potentially happen, so save the tid found in transaction->t_tid before we release t_handle_lock. It would require an insane configuration, such as one where the jbd2 thread was set to a very high real-time priority, perhaps because a high priority real-time thread is trying to read or write to a file system. But some people who use real-time kernels have been known to do insane things, including controlling laser-wielding industrial robots. :-) Signed-off-by: "Theodore Ts'o" <> Signed-off-by: Greg Kroah-Hartman <>
Diffstat (limited to 'fs')
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 10f524c59ea8..e0c0bc275924 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -517,10 +517,10 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
if (atomic_dec_and_test(&transaction->t_updates))
+ tid = transaction->t_tid;
jbd_debug(2, "restarting handle %p\n", handle);
- tid = transaction->t_tid;
need_to_start = !tid_geq(journal->j_commit_request, tid);
if (need_to_start)