jbd2: add transaction to checkpoint list earlier

We don't otherwise need j_list_lock during the rest of commit phase
#7, so add the transaction to the checkpoint list at the very end of
commit phase #6.  This allows us to drop j_list_lock earlier, which is
a good thing since it is a super hot lock.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index af36252b5b2d5b0133f1148e56c3541ae055c1f9..5f26139a165a7081dd2f835222f26dcbc5d3bf4a 100644 (file)
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -1065,6 +1065,25 @@ restart_loop:
                goto restart_loop;
        }
 
+       /* Add the transaction to the checkpoint list
+        * __journal_remove_checkpoint() can not destroy transaction
+        * under us because it is not marked as T_FINISHED yet */
+       if (journal->j_checkpoint_transactions == NULL) {
+               journal->j_checkpoint_transactions = commit_transaction;
+               commit_transaction->t_cpnext = commit_transaction;
+               commit_transaction->t_cpprev = commit_transaction;
+       } else {
+               commit_transaction->t_cpnext =
+                       journal->j_checkpoint_transactions;
+               commit_transaction->t_cpprev =
+                       commit_transaction->t_cpnext->t_cpprev;
+               commit_transaction->t_cpnext->t_cpprev =
+                       commit_transaction;
+               commit_transaction->t_cpprev->t_cpnext =
+                               commit_transaction;
+       }
+       spin_unlock(&journal->j_list_lock);
+
        /* Done with this transaction! */
 
        jbd_debug(3, "JBD2: commit phase 7\n");
@@ -1103,24 +1122,6 @@ restart_loop:
 
        write_unlock(&journal->j_state_lock);
 
-       if (journal->j_checkpoint_transactions == NULL) {
-               journal->j_checkpoint_transactions = commit_transaction;
-               commit_transaction->t_cpnext = commit_transaction;
-               commit_transaction->t_cpprev = commit_transaction;
-       } else {
-               commit_transaction->t_cpnext =
-                       journal->j_checkpoint_transactions;
-               commit_transaction->t_cpprev =
-                       commit_transaction->t_cpnext->t_cpprev;
-               commit_transaction->t_cpnext->t_cpprev =
-                       commit_transaction;
-               commit_transaction->t_cpprev->t_cpnext =
-                               commit_transaction;
-       }
-       spin_unlock(&journal->j_list_lock);
-       /* Drop all spin_locks because commit_callback may be block.
-        * __journal_remove_checkpoint() can not destroy transaction
-        * under us because it is not marked as T_FINISHED yet */
        if (journal->j_commit_callback)
                journal->j_commit_callback(journal, commit_transaction);
 
@@ -1131,7 +1132,7 @@ restart_loop:
        write_lock(&journal->j_state_lock);
        spin_lock(&journal->j_list_lock);
        commit_transaction->t_state = T_FINISHED;
-       /* Recheck checkpoint lists after j_list_lock was dropped */
+       /* Check if the transaction can be dropped now that we are finished */
        if (commit_transaction->t_checkpoint_list == NULL &&
            commit_transaction->t_checkpoint_io_list == NULL) {
                __jbd2_journal_drop_transaction(journal, commit_transaction);