ext4: add fsync batch tuning knobs

Add new mount options, min_batch_time and max_batch_time, which
controls how long the jbd2 layer should wait for additional filesystem
operations to get batched with a synchronous write transaction.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 74d87290381c..fd1d7557a098 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -964,6 +964,8 @@ static journal_t * journal_init_common (void)
         spin_lock_init(&journal->j_state_lock);
 
         journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);
+        journal->j_min_batch_time = 0;
+        journal->j_max_batch_time = 15000; /* 15ms */
 
         /* The journal is marked for error until we succeed with recovery! */
         journal->j_flags = JBD2_ABORT;