diff options
| author | Jan Kara <jack@suse.cz> | 2013-06-04 12:22:15 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-06-04 12:22:15 -0400 |
| commit | fe1e8db598b259eafdffbe3dd5fe849cd2ad97d5 (patch) | |
| tree | a5f7f35d95ab0737457f3ab6ea3a0234c3009df8 /fs/jbd2 | |
| parent | 76c39904561004ac8675f858a290129e439d5168 (diff) | |
| download | lwn-fe1e8db598b259eafdffbe3dd5fe849cd2ad97d5.tar.gz lwn-fe1e8db598b259eafdffbe3dd5fe849cd2ad97d5.zip | |
jbd2: fix race in t_outstanding_credits update in jbd2_journal_extend()
jbd2_journal_extend() first checked whether transaction can accept
extending handle with more credits and then added credits to
t_outstanding_credits. This can race with start_this_handle() adding
another handle to a transaction and thus overbooking a transaction.
Make jbd2_journal_extend() use atomic_add_return() to close the race.
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2')
| -rw-r--r-- | fs/jbd2/transaction.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index f9cd43190b43..f14288b04042 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -433,11 +433,13 @@ int jbd2_journal_extend(handle_t *handle, int nblocks) } spin_lock(&transaction->t_handle_lock); - wanted = atomic_read(&transaction->t_outstanding_credits) + nblocks; + wanted = atomic_add_return(nblocks, + &transaction->t_outstanding_credits); if (wanted > journal->j_max_transaction_buffers) { jbd_debug(3, "denied handle %p %d blocks: " "transaction too large\n", handle, nblocks); + atomic_sub(nblocks, &transaction->t_outstanding_credits); goto unlock; } @@ -445,6 +447,7 @@ int jbd2_journal_extend(handle_t *handle, int nblocks) jbd2_log_space_left(journal)) { jbd_debug(3, "denied handle %p %d blocks: " "insufficient log space\n", handle, nblocks); + atomic_sub(nblocks, &transaction->t_outstanding_credits); goto unlock; } @@ -456,7 +459,6 @@ int jbd2_journal_extend(handle_t *handle, int nblocks) handle->h_buffer_credits += nblocks; handle->h_requested_credits += nblocks; - atomic_add(nblocks, &transaction->t_outstanding_credits); result = 0; jbd_debug(3, "extended handle %p by %d\n", handle, nblocks); |