jbd2-minimize-j_state_lock-in-jbd2_journal_forget

   1 jbd2: minimize region locked by j_list_lock in jbd2_journal_forget()
   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 ---
   9  fs/jbd2/transaction.c | 6 ++++--
  10  1 file changed, 4 insertions(+), 2 deletions(-)
  11
  12 diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
  13 index 357f3dc..d999b1f 100644
  14 --- a/fs/jbd2/transaction.c
  15 +++ b/fs/jbd2/transaction.c
  16 @@ -1416,7 +1416,6 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
  17         BUFFER_TRACE(bh, "entry");
  18
  19         jbd_lock_bh_state(bh);
  20 -       spin_lock(&journal->j_list_lock);
  21
  22         if (!buffer_jbd(bh))
  23                 goto not_jbd;
  24 @@ -1469,6 +1468,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
  25                  * we know to remove the checkpoint after we commit.
  26                  */
  27
  28 +               spin_lock(&journal->j_list_lock);
  29                 if (jh->b_cp_transaction) {
  30                         __jbd2_journal_temp_unlink_buffer(jh);
  31                         __jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
  32 @@ -1481,6 +1481,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
  33                                 goto drop;
  34                         }
  35                 }
  36 +               spin_unlock(&journal->j_list_lock);
  37         } else if (jh->b_transaction) {
  38                 J_ASSERT_JH(jh, (jh->b_transaction ==
  39                                  journal->j_committing_transaction));
  40 @@ -1492,7 +1493,9 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
  41
  42                 if (jh->b_next_transaction) {
  43                         J_ASSERT(jh->b_next_transaction == transaction);
  44 +                       spin_lock(&journal->j_list_lock);
  45                         jh->b_next_transaction = NULL;
  46 +                       spin_unlock(&journal->j_list_lock);
  47
  48                         /*
  49                          * only drop a reference if this transaction modified
  50 @@ -1504,7 +1507,6 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
  51         }
  52
  53  not_jbd:
  54 -       spin_unlock(&journal->j_list_lock);
  55         jbd_unlock_bh_state(bh);
  56         __brelse(bh);
  57  drop: