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| author |   Jan Kara <jack@suse.cz> | 2012-12-21 00:15:51 -0500 |
|---|---|---|
| committer |   Theodore Ts'o <tytso@mit.edu> | 2012-12-21 00:15:51 -0500 |
| commit | d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a (patch) | |
| tree | 3341ce3bdff7f2283e18f0cb02c438f421d746b0 /fs | |
| parent | ext4: check dioread_nolock on remount (diff) | |
| download | linux-dev-d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a.tar.xz linux-dev-d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a.zip | |
jbd2: fix assertion failure in jbd2_journal_flush()
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>
Cc: stable@vger.kernel.org
Diffstat (limited to 'fs')
| -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 deffd945c8e2..cd4485db42b3 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; } |