speedup-jbd2_journal_dirty_metadata

   1 jbd2: speedup jbd2_journal_dirty_metadata()
   2
   3 From: Jan Kara <jack@suse.cz>
   4
   5 It is often the case that we mark buffer as having dirty metadata when
   6 the buffer is already in that state (frequent for bitmaps, inode table
   7 blocks, superblock). Thus it is unnecessary to contend on grabbing
   8 journal head reference and bh_state lock. Avoid that by checking whether
   9 any modification to the buffer is needed before grabbing any locks or
  10 references.
  11
  12 Signed-off-by: Jan Kara <jack@suse.cz>
  13 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  14 ---
  15  fs/jbd2/transaction.c | 33 +++++++++++++++++++++++++++------
  16  1 file changed, 27 insertions(+), 6 deletions(-)
  17
  18 diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
  19 index a91f639af6c3..5887c880422b 100644
  20 --- a/fs/jbd2/transaction.c
  21 +++ b/fs/jbd2/transaction.c
  22 @@ -1290,8 +1290,6 @@ void jbd2_buffer_abort_trigger(struct journal_head *jh,
  23         triggers->t_abort(triggers, jh2bh(jh));
  24  }
  25
  26 -
  27 -
  28  /**
  29   * int jbd2_journal_dirty_metadata() -  mark a buffer as containing dirty metadata
  30   * @handle: transaction to add buffer to.
  31 @@ -1325,12 +1323,36 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
  32         WARN_ON(!transaction);
  33         if (is_handle_aborted(handle))
  34                 return -EROFS;
  35 -       journal = transaction->t_journal;
  36 -       jh = jbd2_journal_grab_journal_head(bh);
  37 -       if (!jh) {
  38 +       if (!buffer_jbd(bh)) {
  39                 ret = -EUCLEAN;
  40                 goto out;
  41         }
  42 +       /*
  43 +        * We don't grab jh reference here since the buffer must be part
  44 +        * of the running transaction.
  45 +        */
  46 +       jh = bh2jh(bh);
  47 +       J_ASSERT_JH(jh, jh->b_transaction == transaction ||
  48 +                       jh->b_next_transaction == transaction);
  49 +       if (jh->b_modified == 1) {
  50 +               /*
  51 +                * If it's in our transaction it must be in BJ_Metadata list.
  52 +                * The assertion is unreliable since we may see jh in
  53 +                * inconsistent state unless we grab bh_state lock. But this
  54 +                * is crutial to catch bugs so let's do a reliable check until
  55 +                * the lockless handling is fully proven.
  56 +                */
  57 +               if (jh->b_transaction == transaction &&
  58 +                   jh->b_jlist != BJ_Metadata) {
  59 +                       jbd_lock_bh_state(bh);
  60 +                       J_ASSERT_JH(jh, jh->b_transaction != transaction ||
  61 +                                       jh->b_jlist == BJ_Metadata);
  62 +                       jbd_unlock_bh_state(bh);
  63 +               }
  64 +               goto out;
  65 +       }
  66 +
  67 +       journal = transaction->t_journal;
  68         jbd_debug(5, "journal_head %p\n", jh);
  69         JBUFFER_TRACE(jh, "entry");
  70
  71 @@ -1421,7 +1443,6 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
  72         spin_unlock(&journal->j_list_lock);
  73  out_unlock_bh:
  74         jbd_unlock_bh_state(bh);
  75 -       jbd2_journal_put_journal_head(jh);
  76  out:
  77         JBUFFER_TRACE(jh, "exit");
  78         return ret;
  79 --
  80 2.1.4
  81