Commit 7222657e authored by Chengming Zhou's avatar Chengming Zhou Committed by Jens Axboe
Browse files

blk-mq: prealloc tags when increase tagset nr_hw_queues 



Just like blk_mq_alloc_tag_set(), it's better to prepare all tags before
using to map to queue ctxs in blk_mq_map_swqueue(), which now have to
consider empty set->tags[].

The good point is that we can fallback easily if increasing nr_hw_queues
fail, instead of just mapping to hctx[0] when fail in blk_mq_map_swqueue().

And the fallback path already has tags free & clean handling, so all
is good.

Signed-off-by: default avatarChengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230821095602.70742-3-chengming.zhou@linux.dev


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2bc4d7a3

block/blk-mq.c

+10 −0
Original line number Diff line number Diff line
@@ -4397,6 +4397,16 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set, 
		       sizeof(*set->tags));

	kfree(set->tags);

	set->tags = new_tags;



	for (i = set->nr_hw_queues; i < new_nr_hw_queues; i++) {

		if (!__blk_mq_alloc_map_and_rqs(set, i)) {

			while (--i >= set->nr_hw_queues)

				__blk_mq_free_map_and_rqs(set, i);

			return -ENOMEM;

		}

		cond_resched();

	}



done:

	set->nr_hw_queues = new_nr_hw_queues;

	return 0;