[PATCH 05/13] writeback: fix queue_io() ordering

[Wu Fengguang]

This was not a bug, since b_io is empty for kupdate writeback.
The next patch will do requeue_io() for non-kupdate writeback,
so let's fix it.

CC: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Martin Bligh <mbligh@xxxxxxxxxx>
Cc: Michael Rubin <mrubin@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 fs/fs-writeback.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- linux-next.orig/fs/fs-writeback.c	2010-08-05 23:03:37.000000000 +0800
+++ linux-next/fs/fs-writeback.c	2010-08-05 23:21:43.000000000 +0800
@@ -253,10 +253,18 @@ static void move_expired_inodes(struct l
 
 /*
  * Queue all expired dirty inodes for io, eldest first.
+ * Before
+ *         newly dirtied     b_dirty    b_io    b_more_io
+ *         =============>    gf         edc     BA
+ * After
+ *         newly dirtied     b_dirty    b_io    b_more_io
+ *         =============>    g          fBAedc
+ *                                           |
+ *                                           +--> dequeue for IO
  */
 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
 {
-	list_splice_init(&wb->b_more_io, wb->b_io.prev);
+	list_splice_init(&wb->b_more_io, &wb->b_io);
 	move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
 }
 


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