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>

1 files changed, 20 insertions, 19 deletions

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index af36252b5b2d..5f26139a165a 100644
--- 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);