Commit f83e8261 authored Apr 04, 2011 by Konstantin Khlebnikov Committed by Jens Axboe Apr 05, 2011

block: fix request sorting at unplug



Comparison function for list_sort() must be anticommutative,
otherwise it is not sorting in ordinary meaning.

But fortunately list_sort() always check ((*cmp)(priv, a, b) <= 0)
it not distinguish negative and zero, so comparison function can
implement only less-or-equal instead of full three-way comparison.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent a63a5cf8

block/blk-core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2665,7 +2665,7 @@ static int plug_rq_cmp(void priv, struct list_head a, struct list_head *b)
		struct request *rqa = container_of(a, struct request, queuelist);
		struct request *rqb = container_of(b, struct request, queuelist);

		return !(rqa->q == rqb->q);
		return !(rqa->q <= rqb->q);
		}

		static void flush_plug_list(struct blk_plug *plug)