[3.11.y.z extended stable] Patch "ext4: disable synchronous transaction batching if max_batch_time==0" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4: disable synchronous transaction batching if max_batch_time==0

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From caed8433140795657b9ef44f0796103917d0268c Mon Sep 17 00:00:00 2001
From: Eric Sandeen <sandeen at redhat.com>
Date: Sat, 5 Jul 2014 19:18:22 -0400
Subject: [PATCH 14/41] ext4: disable synchronous transaction batching if
 max_batch_time==0

commit 5dd214248f94d430d70e9230bda72f2654ac88a8 upstream.

The mount manpage says of the max_batch_time option,

	This optimization can be turned off entirely
	by setting max_batch_time to 0.

But the code doesn't do that.  So fix the code to do
that.

Signed-off-by: Eric Sandeen <sandeen at redhat.com>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/super.c       | 2 --
 fs/jbd2/transaction.c | 5 ++++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f9659f067147..e38c344a521e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1501,8 +1501,6 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 			arg = JBD2_DEFAULT_MAX_COMMIT_AGE;
 		sbi->s_commit_interval = HZ * arg;
 	} else if (token == Opt_max_batch_time) {
-		if (arg == 0)
-			arg = EXT4_DEF_MAX_BATCH_TIME;
 		sbi->s_max_batch_time = arg;
 	} else if (token == Opt_min_batch_time) {
 		sbi->s_min_batch_time = arg;
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 7272cc6977ec..ab3815c856dc 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1590,9 +1590,12 @@ int jbd2_journal_stop(handle_t *handle)
 	 * to perform a synchronous write.  We do this to detect the
 	 * case where a single process is doing a stream of sync
 	 * writes.  No point in waiting for joiners in that case.
+	 *
+	 * Setting max_batch_time to 0 disables this completely.
 	 */
 	pid = current->pid;
-	if (handle->h_sync && journal->j_last_sync_writer != pid) {
+	if (handle->h_sync && journal->j_last_sync_writer != pid &&
+	    journal->j_max_batch_time) {
 		u64 commit_time, trans_time;

 		journal->j_last_sync_writer = pid;
--
1.9.1