[PATCH linux-block-2.6:generic-dispatch] kill max_back_kb handling

[Tejun Heo]

 Hello, Jens.

 This patch kills max_back_kb handling from elv_dispatch_sort() and
kills max_back_kb field from struct request_queue.  The implementation
was broken (subtracted bytes from blocks) and the usefulness of the
feature is doubtful.

Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -136,7 +136,6 @@ static int elevator_attach(request_queue
 	q->elevator = eq;
 	q->end_sector = 0;
 	q->boundary_rq = NULL;
-	q->max_back_kb = 0;
 
 	if (eq->ops->elevator_init_fn)
 		ret = eq->ops->elevator_init_fn(q, eq);
@@ -227,16 +226,13 @@ void elevator_exit(elevator_t *e)
 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 {
 	sector_t boundary;
-	unsigned max_back;
 	struct list_head *entry;
 
 	if (q->last_merge == rq)
 		q->last_merge = NULL;
 
 	boundary = q->end_sector;
-	max_back = q->max_back_kb * 2;
-	boundary = boundary > max_back ? boundary - max_back : 0;
-	
+
 	list_for_each_prev(entry, &q->queue_head) {
 		struct request *pos = list_entry_rq(entry);
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -339,7 +339,6 @@ struct request_queue
 	 */
 	sector_t		end_sector;
 	struct request		*boundary_rq;
-	unsigned int		max_back_kb;
 
 	/*
 	 * Auto-unplugging state
-
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