diff options
| author | Jan Kara <jack@suse.cz> | 2012-12-21 00:15:51 -0500 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-01-16 01:13:11 +0000 |
| commit | 7a55283222cdd70c1cd7a33df0db1e0c96462ac9 (patch) | |
| tree | 2c010b179b3292fc15db671287c11e6b3d729cf6 | |
| parent | f21cf73c565eaff16be12637435dd96b84a8e50f (diff) | |
jbd2: fix assertion failure in jbd2_journal_flush()
commit d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a upstream.
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.
Reported-by: yjwsignal@empal.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | 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 8267de588982..d7dd774f733f 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -179,7 +179,8 @@ 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; } |