blk-mq: fix elevator depth_updated method

Current depth_updated has some problems:

1) depth_updated() will be called for each hctx, while all elevators
will update async_depth for the disk level, this is not related to hctx;
2) In blk_mq_update_nr_requests(), if previous hctx update succeed and
this hctx update failed, q->nr_requests will not be updated, while
async_depth is already updated with new nr_reqeuests in previous
depth_updated();
3) All elevators are using q->nr_requests to calculate async_depth now,
however, q->nr_requests is still the old value when depth_updated() is
called from blk_mq_update_nr_requests();

Those problems are first from error path, then mq-deadline, and recently
for bfq and kyber, fix those problems by:

- pass in request_queue instead of hctx;
- move depth_updated() after q->nr_requests is updated in
  blk_mq_update_nr_requests();
- add depth_updated() call inside init_sched() method to initialize
  async_depth;
- remove init_hctx() method for mq-deadline and bfq that is useless now;

Fixes: 77f1e0a52d ("bfq: update internal depth state when queue depth changes")
Fixes: 39823b47bb ("block/mq-deadline: Fix the tag reservation code")
Fixes: 42e6c6ce03 ("lib/sbitmap: convert shallow_depth from one word to the whole sbitmap")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Li Nan <linan122@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250821060612.1729939-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/kyber-iosched.c

@@ -399,6 +399,14 @@ err:
 	return ERR_PTR(ret);
 }
 
+static void kyber_depth_updated(struct request_queue *q)
+{
+	struct kyber_queue_data *kqd = q->elevator->elevator_data;
+
+	kqd->async_depth = q->nr_requests * KYBER_ASYNC_PERCENT / 100U;
+	blk_mq_set_min_shallow_depth(q, kqd->async_depth);
+}
+
 static int kyber_init_sched(struct request_queue *q, struct elevator_queue *eq)
 {
 	struct kyber_queue_data *kqd;
@@ -413,6 +421,7 @@ static int kyber_init_sched(struct request_queue *q, struct elevator_queue *eq)
 
 	eq->elevator_data = kqd;
 	q->elevator = eq;
+	kyber_depth_updated(q);
 
 	return 0;
 }
@@ -440,15 +449,6 @@ static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
 		INIT_LIST_HEAD(&kcq->rq_list[i]);
 }
 
-static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
-{
-	struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
-	struct blk_mq_tags *tags = hctx->sched_tags;
-
-	kqd->async_depth = hctx->queue->nr_requests * KYBER_ASYNC_PERCENT / 100U;
-	sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);
-}
-
 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 {
 	struct kyber_hctx_data *khd;
@@ -493,7 +493,6 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 	khd->batching = 0;
 
 	hctx->sched_data = khd;
-	kyber_depth_updated(hctx);
 
 	return 0;