[PATCH] sync_dirty_buffer: Use WRITE_SYNC instead of WRITE

[Theodore Ts'o]

The sync_dirty_buffer() function submits a buffer for write, and then
synchronously waits for it.  It clearly should use WRITE_SYNC instead
of WRITE.  This significantly reduces ext3's fsync() latency when
there is a huge background task writing data asyncronously in the
background, since ext3 uses sync_dirty_buffer() to write the commit
block.

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
 fs/buffer.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 2ed4b68..78ed086 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3038,7 +3038,7 @@ int sync_dirty_buffer(struct buffer_head *bh)
 	if (test_clear_buffer_dirty(bh)) {
 		get_bh(bh);
 		bh->b_end_io = end_buffer_write_sync;
-		ret = submit_bh(WRITE, bh);
+		ret = submit_bh(WRITE_SYNC, bh);
 		wait_on_buffer(bh);
 		if (buffer_eopnotsupp(bh)) {
 			clear_buffer_eopnotsupp(bh);
-- 
1.5.6.3

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