aoe: clean device rq_list in aoedev_downdev()

An aoe device's rq_list contains accepted block requests that are
waiting to be transmitted to the aoe target. This queue was added as
part of the conversion to blk_mq. However, the queue was not cleaned out
when an aoe device is downed which caused blk_mq_freeze_queue() to sleep
indefinitely waiting for those requests to complete, causing a hang. This
fix cleans out the queue before calling blk_mq_freeze_queue().

Link: https://bugzilla.kernel.org/show_bug.cgi?id=212665
Fixes: 3582dd291788 ("aoe: convert aoeblk to blk-mq")
Signed-off-by: Justin Sanders <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Tested-By: Valentin Kleibel <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/aoe/aoedev.c

···
 {
 	struct aoetgt *t, **tt, **te;
 	struct list_head *head, *pos, *nx;
+	struct request *rq, *rqnext;
 	int i;
 
 	d->flags &= ~DEVFL_UP;
···
 
 	/* clean out the in-process request (if any) */
 	aoe_failip(d);
+
+	/* clean out any queued block requests */
+	list_for_each_entry_safe(rq, rqnext, &d->rq_list, queuelist) {
+		list_del_init(&rq->queuelist);
+		blk_mq_start_request(rq);
+		blk_mq_end_request(rq, BLK_STS_IOERR);
+	}
 
 	/* fast fail all pending I/O */
 	if (d->blkq) {