jbd2-minimize-j_list_lock-in-journal_get_create_access

   1 jbd2: minimize region locked by j_list_lock in journal_get_create_access()
   2
   3 It's not needed until we start trying to modifying fields in the
   4 journal_head which are protected by j_list_lock.
   5
   6 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
   7 ---
   8  fs/jbd2/transaction.c | 3 ++-
   9  1 file changed, 2 insertions(+), 1 deletion(-)
  10
  11 diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
  12 index 78900a1..357f3dc 100644
  13 --- a/fs/jbd2/transaction.c
  14 +++ b/fs/jbd2/transaction.c
  15 @@ -1073,7 +1073,6 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
  16          * reused here.
  17          */
  18         jbd_lock_bh_state(bh);
  19 -       spin_lock(&journal->j_list_lock);
  20         J_ASSERT_JH(jh, (jh->b_transaction == transaction ||
  21                 jh->b_transaction == NULL ||
  22                 (jh->b_transaction == journal->j_committing_transaction &&
  23 @@ -1096,12 +1095,14 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
  24                 jh->b_modified = 0;
  25
  26                 JBUFFER_TRACE(jh, "file as BJ_Reserved");
  27 +               spin_lock(&journal->j_list_lock);
  28                 __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
  29         } else if (jh->b_transaction == journal->j_committing_transaction) {
  30                 /* first access by this transaction */
  31                 jh->b_modified = 0;
  32
  33                 JBUFFER_TRACE(jh, "set next transaction");
  34 +               spin_lock(&journal->j_list_lock);
  35                 jh->b_next_transaction = transaction;
  36         }
  37         spin_unlock(&journal->j_list_lock);