From: Ming Lei Date: Mon, 5 May 2025 14:18:00 +0000 (+0800) Subject: block: move hctx debugfs/sysfs registering out of freezing queue X-Git-Tag: for-6.16/block-20250523~73 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=9dc7a882ce96;p=linux-block.git block: move hctx debugfs/sysfs registering out of freezing queue Move hctx debugfs/sysfs register out of freezing queue in __blk_mq_update_nr_hw_queues(), so that the following lockdep dependency can be killed: #2 (&q->q_usage_counter(io)#16){++++}-{0:0}: #1 (fs_reclaim){+.+.}-{0:0}: #0 (&sb->s_type->i_mutex_key#3){+.+.}-{4:4}: //debugfs And registering/un-registering hctx debugfs/sysfs does not require queue to be frozen: - hctx sysfs attributes show() are drained when removing kobject, and there isn't store() implementation for hctx sysfs attributes - debugfs entry read() is drained too when removing debugfs directory, and there isn't write() implementation for hctx debugfs too - so it is safe to register/unregister hctx sysfs/debugfs without freezing queue because the cod paths changes nothing, and we just need to keep hctx live Reviewed-by: Hannes Reinecke Reviewed-by: Nilay Shroff Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20250505141805.2751237-23-ming.lei@redhat.com Signed-off-by: Jens Axboe --- diff --git a/block/blk-mq.c b/block/blk-mq.c index 263bbe34d3f0..a4ab7779e020 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -5005,14 +5005,14 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, return; memflags = memalloc_noio_save(); - list_for_each_entry(q, &set->tag_list, tag_set_list) - blk_mq_freeze_queue_nomemsave(q); - list_for_each_entry(q, &set->tag_list, tag_set_list) { blk_mq_debugfs_unregister_hctxs(q); blk_mq_sysfs_unregister_hctxs(q); } + list_for_each_entry(q, &set->tag_list, tag_set_list) + blk_mq_freeze_queue_nomemsave(q); + if (blk_mq_realloc_tag_set_tags(set, nr_hw_queues) < 0) goto reregister; @@ -5035,16 +5035,15 @@ fallback: blk_mq_map_swqueue(q); } + /* elv_update_nr_hw_queues() unfreeze queue for us */ + list_for_each_entry(q, &set->tag_list, tag_set_list) + elv_update_nr_hw_queues(q); + reregister: list_for_each_entry(q, &set->tag_list, tag_set_list) { blk_mq_sysfs_register_hctxs(q); blk_mq_debugfs_register_hctxs(q); } - - /* elv_update_nr_hw_queues() unfreeze queue for us */ - list_for_each_entry(q, &set->tag_list, tag_set_list) - elv_update_nr_hw_queues(q); - memalloc_noio_restore(memflags); /* Free the excess tags when nr_hw_queues shrink. */