blk-mq: fix stale tag depth for shared sched tags in blk_mq_update_nr_requests()

Commit 7f2799c ("blk-mq: cleanup shared tags case in
blk_mq_update_nr_requests()") moves blk_mq_tag_update_sched_shared_tags()
before q->nr_requests is updated, however, it's still using the old
q->nr_requests to resize tag depth.

Fix this problem by passing in expected new tag depth.

Fixes: 7f2799c ("blk-mq: cleanup shared tags case in blk_mq_update_nr_requests()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reported-by: Chris Mason <clm@meta.com>
Link: https://lore.kernel.org/linux-block/20251014130507.4187235-2-clm@meta.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: YuKuai-huawei

block/blk-mq-sched.c

@@ -557,7 +557,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e,
 	if (blk_mq_is_shared_tags(flags)) {
 		/* Shared tags are stored at index 0 in @et->tags. */
 		q->sched_shared_tags = et->tags[0];
-		blk_mq_tag_update_sched_shared_tags(q);
+		blk_mq_tag_update_sched_shared_tags(q, et->nr_requests);
 	}
 
 	queue_for_each_hw_ctx(q, hctx, i) {

block/blk-mq-tag.c

@@ -622,10 +622,11 @@ void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set, unsigned int size
 	sbitmap_queue_resize(&tags->bitmap_tags, size - set->reserved_tags);
 }
 
-void blk_mq_tag_update_sched_shared_tags(struct request_queue *q)
+void blk_mq_tag_update_sched_shared_tags(struct request_queue *q,
+					 unsigned int nr)
 {
 	sbitmap_queue_resize(&q->sched_shared_tags->bitmap_tags,
-			     q->nr_requests - q->tag_set->reserved_tags);
+			     nr - q->tag_set->reserved_tags);
 }
 
 /**

block/blk-mq.c

@@ -4941,7 +4941,7 @@ struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q,
 		 * tags can't grow, see blk_mq_alloc_sched_tags().
 		 */
 		if (q->elevator)
-			blk_mq_tag_update_sched_shared_tags(q);
+			blk_mq_tag_update_sched_shared_tags(q, nr);
 		else
 			blk_mq_tag_resize_shared_tags(set, nr);
 	} else if (!q->elevator) {

block/blk-mq.h

@@ -186,7 +186,8 @@ void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
 void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags);
 void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set,
 		unsigned int size);
-void blk_mq_tag_update_sched_shared_tags(struct request_queue *q);
+void blk_mq_tag_update_sched_shared_tags(struct request_queue *q,
+					 unsigned int nr);
 
 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_tag_iter_fn *fn,