block: fix deadline elevator drain for zoned block devices

damien-lemoal · axboe · commit 854f31ccdd79 · 2018-09-26T19:57:24.000-06:00
When the deadline scheduler is used with a zoned block device, writes to a zone will be dispatched one at a time. This causes the warning message: deadline: forced dispatching is broken (nr_sorted=X), please report this to be displayed when switching to another elevator with the legacy I/O path while write requests to a zone are being retained in the scheduler queue. Prevent this message from being displayed when executing elv_drain_elevator() for a zoned block device. __blk_drain_queue() will loop until all writes are dispatched and completed, resulting in the desired elevator queue drain without extensive modifications to the deadline code itself to handle forced-dispatch calls. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Fixes: 8dc8146 ("deadline-iosched: Introduce zone locking support") Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/elevator.c b/block/elevator.c
@@ -609,7 +609,7 @@ void elv_drain_elevator(struct request_queue *q)
 
 	while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
 		;
-	if (q->nr_sorted && printed++ < 10) {
+	if (q->nr_sorted && !blk_queue_is_zoned(q) && printed++ < 10 ) {
 		printk(KERN_ERR "%s: forced dispatching is broken "
 		       "(nr_sorted=%u), please report this\n",
 		       q->elevator->type->elevator_name, q->nr_sorted);

Original file line number	Diff line number	Diff line change
`@@ -609,7 +609,7 @@ void elv_drain_elevator(struct request_queue *q)`
`609`	`609`
`610`	`610`	`while (e->type->ops.sq.elevator_dispatch_fn(q, 1))`
`611`	`611`	`;`
`612`		`- if (q->nr_sorted && printed++ < 10) {`
	`612`	`+ if (q->nr_sorted && !blk_queue_is_zoned(q) && printed++ < 10 ) {`
`613`	`613`	`printk(KERN_ERR "%s: forced dispatching is broken "`
`614`	`614`	`"(nr_sorted=%u), please report this\n",`
`615`	`615`	`q->elevator->type->elevator_name, q->nr_sorted);`