* [PATCH] jbd2: Fix assertion failure in jbd2_journal_flush()
@ 2012-12-12 15:17 Jan Kara
2012-12-21 5:16 ` Theodore Ts'o
0 siblings, 1 reply; 2+ messages in thread
From: Jan Kara @ 2012-12-12 15:17 UTC (permalink / raw)
To: Ted Tso; +Cc: linux-ext4, Jan Kara, stable
The following race is possible between start_this_handle() and someone
calling jbd2_journal_flush().
Process A Process B
start_this_handle().
if (journal->j_barrier_count) # false
if (!journal->j_running_transaction) { #true
read_unlock(&journal->j_state_lock);
jbd2_journal_lock_updates()
jbd2_journal_flush()
write_lock(&journal->j_state_lock);
if (journal->j_running_transaction) {
# false
... wait for committing trans ...
write_unlock(&journal->j_state_lock);
...
write_lock(&journal->j_state_lock);
if (!journal->j_running_transaction) { # true
jbd2_get_transaction(journal, new_transaction);
write_unlock(&journal->j_state_lock);
goto repeat; # eventually blocks on j_barrier_count > 0
...
J_ASSERT(!journal->j_running_transaction);
# fails
We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
in exclusive mode.
CC: stable@vger.kernel.org
Reported-by:yjwsignal@empal.com
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/jbd2/transaction.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a74ba46..6873d24 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -209,7 +209,8 @@ repeat:
if (!new_transaction)
goto alloc_transaction;
write_lock(&journal->j_state_lock);
- if (!journal->j_running_transaction) {
+ if (!journal->j_running_transaction &&
+ !journal->j_barrier_count) {
jbd2_get_transaction(journal, new_transaction);
new_transaction = NULL;
}
--
1.7.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] jbd2: Fix assertion failure in jbd2_journal_flush()
2012-12-12 15:17 [PATCH] jbd2: Fix assertion failure in jbd2_journal_flush() Jan Kara
@ 2012-12-21 5:16 ` Theodore Ts'o
0 siblings, 0 replies; 2+ messages in thread
From: Theodore Ts'o @ 2012-12-21 5:16 UTC (permalink / raw)
To: Jan Kara; +Cc: linux-ext4, stable
On Wed, Dec 12, 2012 at 04:17:42PM +0100, Jan Kara wrote:
> The following race is possible between start_this_handle() and someone
> calling jbd2_journal_flush().
>
> Process A Process B
> start_this_handle().
> if (journal->j_barrier_count) # false
> if (!journal->j_running_transaction) { #true
> read_unlock(&journal->j_state_lock);
> jbd2_journal_lock_updates()
> jbd2_journal_flush()
> write_lock(&journal->j_state_lock);
> if (journal->j_running_transaction) {
> # false
> ... wait for committing trans ...
> write_unlock(&journal->j_state_lock);
> ...
> write_lock(&journal->j_state_lock);
> if (!journal->j_running_transaction) { # true
> jbd2_get_transaction(journal, new_transaction);
> write_unlock(&journal->j_state_lock);
> goto repeat; # eventually blocks on j_barrier_count > 0
> ...
> J_ASSERT(!journal->j_running_transaction);
> # fails
>
> We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
> in exclusive mode.
>
> CC: stable@vger.kernel.org
> Reported-by:yjwsignal@empal.com
> Signed-off-by: Jan Kara <jack@suse.cz>
Thanks, applied.
- Ted
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