[PATCH 3.12 159/170] ext4: disable synchronous transaction batching if max_batch_time==0

From: Jiri Slaby
Date: Fri Jul 18 2014 - 09:41:42 EST


From: Eric Sandeen <sandeen@xxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

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@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
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 a8b886851ff6..9afc4ba21611 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1500,8 +1500,6 @@ 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;
--
2.0.0

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