jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal_stop

By using an atomic_t for t_updates and t_outstanding credits, this
should allow us to not need to take transaction t_handle_lock in
jbd2_journal_stop().

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

1 files changed, 7 insertions, 6 deletions

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index af056810acb6..fbd2c564e916 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -417,12 +417,12 @@ void jbd2_journal_commit_transaction(journal_t *journal)
                                               stats.run.rs_locked);
 
         spin_lock(&commit_transaction->t_handle_lock);
-        while (commit_transaction->t_updates) {
+        while (atomic_read(&commit_transaction->t_updates)) {
                 DEFINE_WAIT(wait);
 
                 prepare_to_wait(&journal->j_wait_updates, &wait,
                                         TASK_UNINTERRUPTIBLE);
-                if (commit_transaction->t_updates) {
+                if (atomic_read(&commit_transaction->t_updates)) {
                         spin_unlock(&commit_transaction->t_handle_lock);
                         spin_unlock(&journal->j_state_lock);
                         schedule();
@@ -433,7 +433,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
         }
         spin_unlock(&commit_transaction->t_handle_lock);
 
-        J_ASSERT (commit_transaction->t_outstanding_credits <=
+        J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
                         journal->j_max_transaction_buffers);
 
         /*
@@ -527,11 +527,12 @@ void jbd2_journal_commit_transaction(journal_t *journal)
         stats.run.rs_logging = jiffies;
         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
                                                stats.run.rs_logging);
-        stats.run.rs_blocks = commit_transaction->t_outstanding_credits;
+        stats.run.rs_blocks =
+                atomic_read(&commit_transaction->t_outstanding_credits);
         stats.run.rs_blocks_logged = 0;
 
         J_ASSERT(commit_transaction->t_nr_buffers <=
-                 commit_transaction->t_outstanding_credits);
+                 atomic_read(&commit_transaction->t_outstanding_credits));
 
         err = 0;
         descriptor = NULL;
@@ -616,7 +617,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
                  * the free space in the log, but this counter is changed
                  * by jbd2_journal_next_log_block() also.
                  */
-                commit_transaction->t_outstanding_credits--;
+                atomic_dec(&commit_transaction->t_outstanding_credits);
 
                 /* Bump b_count to prevent truncate from stumbling over
                    the shadowed buffer!  @@@ This can go if we ever get