[RFC][PATCH 2/7] 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: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
 fs/fs-writeback.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- linux.orig/fs/fs-writeback.c	2009-09-09 21:41:14.000000000 +0800
+++ linux/fs/fs-writeback.c	2009-09-09 21:45:15.000000000 +0800
@@ -313,11 +313,14 @@ static void move_expired_inodes(struct l
 }
 
 /*
- * Queue all expired dirty inodes for io, eldest first.
+ * Queue all expired dirty inodes for io, eldest first:
+ * (newly dirtied) => b_dirty inodes
+ *                 => b_more_io inodes
+ *                 => remaining inodes in b_io => (dequeue for sync)
  */
 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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