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>
diff --git a/block/blk-core.c b/block/blk-core.c
index 4fdf895..725091d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2665,7 +2665,7 @@
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)