[PATCH] jbd: journal_dirty_metadata locking speedup

Reduce the locking coverage of the oft-used j_list_lock: the per-bh
jbd_lock_bh_state() gives us sufficient locking of buffer_head and
journal_head internals.

diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 67a793a5dcf93d154b70b1e3150ed7ad82465b4d..14d40be76d4dffd4e54ceefa2ff764808be02e9a 100644 (file)
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -1111,26 +1111,21 @@ int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
         * I _think_ we're OK here with SMP barriers - a mistaken decision will
         * result in this test being false, so we go in and take the locks.
         */
-       if (jh->b_transaction == handle->h_transaction &&
-                                       jh->b_jlist == BJ_Metadata) {
+       if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) {
                JBUFFER_TRACE(jh, "fastpath");
                J_ASSERT_JH(jh, jh->b_transaction ==
                                        journal->j_running_transaction);
                goto out_unlock_bh;
        }
 
-       spin_lock(&journal->j_list_lock);
        set_buffer_jbddirty(bh);
 
-       J_ASSERT_JH(jh, jh->b_transaction != NULL);
-
        /* 
         * Metadata already on the current transaction list doesn't
         * need to be filed.  Metadata on another transaction's list must
         * be committing, and will be refiled once the commit completes:
         * leave it alone for now. 
         */
-
        if (jh->b_transaction != transaction) {
                JBUFFER_TRACE(jh, "already on other transaction");
                J_ASSERT_JH(jh, jh->b_transaction ==
@@ -1138,17 +1133,15 @@ int journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
                J_ASSERT_JH(jh, jh->b_next_transaction == transaction);
                /* And this case is illegal: we can't reuse another
                 * transaction's data buffer, ever. */
-               /* FIXME: writepage() should be journalled */
-               goto out_unlock_list;
+               goto out_unlock_bh;
        }
 
        /* That test should have eliminated the following case: */
        J_ASSERT_JH(jh, jh->b_frozen_data == 0);
 
        JBUFFER_TRACE(jh, "file as BJ_Metadata");
+       spin_lock(&journal->j_list_lock);
        __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
-
-out_unlock_list:
        spin_unlock(&journal->j_list_lock);
 out_unlock_bh:
        jbd_unlock_bh_state(bh);