jbd2-add-transaction-to-checkpoint-list-earlier

   1 jbd2: add transaction to checkpoint list earlier
   2
   3 We don't otherwise need j_list_lock during the rest of commit phase
   4 #7, so add the transaction to the checkpoint list at the very end of
   5 commit phase #6.  This allows us to drop j_list_lock earlier, which is
   6 a good thing since it is a super hot lock.
   7
   8 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
   9 ---
  10  fs/jbd2/commit.c | 39 ++++++++++++++++++++-------------------
  11  1 file changed, 20 insertions(+), 19 deletions(-)
  12
  13 diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
  14 index af36252..5f26139 100644
  15 --- a/fs/jbd2/commit.c
  16 +++ b/fs/jbd2/commit.c
  17 @@ -1065,6 +1065,25 @@ restart_loop:
  18                 goto restart_loop;
  19         }
  20
  21 +       /* Add the transaction to the checkpoint list
  22 +        * __journal_remove_checkpoint() can not destroy transaction
  23 +        * under us because it is not marked as T_FINISHED yet */
  24 +       if (journal->j_checkpoint_transactions == NULL) {
  25 +               journal->j_checkpoint_transactions = commit_transaction;
  26 +               commit_transaction->t_cpnext = commit_transaction;
  27 +               commit_transaction->t_cpprev = commit_transaction;
  28 +       } else {
  29 +               commit_transaction->t_cpnext =
  30 +                       journal->j_checkpoint_transactions;
  31 +               commit_transaction->t_cpprev =
  32 +                       commit_transaction->t_cpnext->t_cpprev;
  33 +               commit_transaction->t_cpnext->t_cpprev =
  34 +                       commit_transaction;
  35 +               commit_transaction->t_cpprev->t_cpnext =
  36 +                               commit_transaction;
  37 +       }
  38 +       spin_unlock(&journal->j_list_lock);
  39 +
  40         /* Done with this transaction! */
  41
  42         jbd_debug(3, "JBD2: commit phase 7\n");
  43 @@ -1103,24 +1122,6 @@ restart_loop:
  44
  45         write_unlock(&journal->j_state_lock);
  46
  47 -       if (journal->j_checkpoint_transactions == NULL) {
  48 -               journal->j_checkpoint_transactions = commit_transaction;
  49 -               commit_transaction->t_cpnext = commit_transaction;
  50 -               commit_transaction->t_cpprev = commit_transaction;
  51 -       } else {
  52 -               commit_transaction->t_cpnext =
  53 -                       journal->j_checkpoint_transactions;
  54 -               commit_transaction->t_cpprev =
  55 -                       commit_transaction->t_cpnext->t_cpprev;
  56 -               commit_transaction->t_cpnext->t_cpprev =
  57 -                       commit_transaction;
  58 -               commit_transaction->t_cpprev->t_cpnext =
  59 -                               commit_transaction;
  60 -       }
  61 -       spin_unlock(&journal->j_list_lock);
  62 -       /* Drop all spin_locks because commit_callback may be block.
  63 -        * __journal_remove_checkpoint() can not destroy transaction
  64 -        * under us because it is not marked as T_FINISHED yet */
  65         if (journal->j_commit_callback)
  66                 journal->j_commit_callback(journal, commit_transaction);
  67
  68 @@ -1131,7 +1132,7 @@ restart_loop:
  69         write_lock(&journal->j_state_lock);
  70         spin_lock(&journal->j_list_lock);
  71         commit_transaction->t_state = T_FINISHED;
  72 -       /* Recheck checkpoint lists after j_list_lock was dropped */
  73 +       /* Check if the transaction can be dropped now that we are finished */
  74         if (commit_transaction->t_checkpoint_list == NULL &&
  75             commit_transaction->t_checkpoint_io_list == NULL) {
  76                 __jbd2_journal_drop_transaction(journal, commit_transaction);