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ext4: disable synchronous transaction batching if max_batch_time==0

PATCH Applied Eric Sandeen 2 participants 2 messages Jun 10, 2014 – Jul 5, 2014

Subsystems (2)
ext4 file system Journalling layer for block devices (JBD2)
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Eric Sandeen

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#0 lore raw

PATCH 1/1 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. ;)

fs/ext4/super.c +0 -2
index 6f9e6fa..ab5a791 100644
@@ -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;
fs/jbd2/transaction.c +4 -1
index 38cfcf5..6f0f590 100644
@@ -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;
maintainer Applied
#1 lore raw
Quoted 9 lines · Eric Sandeen

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