2014-06-10 00:10:46

by Eric Sandeen

Subject: [PATCH] ext4: disable synchronous transaction batching if max_batch_time==0

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 <[email protected]>
---

Lightly tested: it mounts, accepts the mount option == 0,
shows "0" in /proc/mounts, and does basic IO & unmounts
without crashing. ;)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6f9e6fa..ab5a791 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1524,8 +1524,6 @@ 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 38cfcf5..6f0f590 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1588,9 +1588,12 @@ 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;

2014-07-05 22:39:31

by Theodore Ts'o

Subject: Re: [PATCH] ext4: disable synchronous transaction batching if max_batch_time==0

On Mon, Jun 09, 2014 at 07:10:45PM -0500, Eric Sandeen wrote:
> 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 <[email protected]>

Thanks, applied.

- Ted