jbd2-check-b_transaction-wo-taking-j_list_lock

   1 jbd2: check jh->b_transaction without taking j_list_lock
   2
   3 jh->b_transaction is adequately protected for reading by the
   4 jbd_lock_bh_state(bh), so we don't need to take j_list_lock in
   5 __journal_try_to_free_buffer().
   6
   7 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
   8 ---
   9  fs/jbd2/transaction.c | 4 ++--
  10  1 file changed, 2 insertions(+), 2 deletions(-)
  11
  12 diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
  13 index 60bb365..78900a1 100644
  14 --- a/fs/jbd2/transaction.c
  15 +++ b/fs/jbd2/transaction.c
  16 @@ -1821,11 +1821,11 @@ __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
  17         if (buffer_locked(bh) || buffer_dirty(bh))
  18                 goto out;
  19
  20 -       if (jh->b_next_transaction != NULL)
  21 +       if (jh->b_next_transaction != NULL || jh->b_transaction != NULL)
  22                 goto out;
  23
  24         spin_lock(&journal->j_list_lock);
  25 -       if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) {
  26 +       if (jh->b_cp_transaction != NULL) {
  27                 /* written-back checkpointed metadata buffer */
  28                 JBUFFER_TRACE(jh, "remove from checkpoint list");
  29                 __jbd2_journal_remove_checkpoint(jh);