[PATCH 3/3] ext3: Explicitly specify fsync dependency on journaling thread

[Vivek Goyal]

Set/reset fsync dependency of fsync on journalling thread. This allows
CFQ to dispatch IO from journalling thread in fsync's time slice.
Otherwise, lots of cfq queue idling takes place if fsync is running
in a separate cgroup and journalling thread is running in root group.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
 fs/ext3/fsync.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index 09b13bb..1e8de9c 100644
--- a/fs/ext3/fsync.c
+++ b/fs/ext3/fsync.c
@@ -82,7 +82,10 @@ int ext3_sync_file(struct file *file, int datasync)
 	    !journal_trans_will_send_data_barrier(journal, commit_tid))
 		needs_barrier = 1;
 	log_start_commit(journal, commit_tid);
+	blk_set_depends_on_task(journal->j_dev->bd_disk->queue,
+				journal->j_task);
 	ret = log_wait_commit(journal, commit_tid);
+	blk_reset_depends_on_task(journal->j_dev->bd_disk->queue);
 
 	/*
 	 * In case we didn't commit a transaction, we have to flush
-- 
1.7.4.4

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