blk_mq_realloc_hw_ctxs() is called from blk_mq_init_allocated_queue() and blk_mq_update_nr_hw_queues(). For the former caller, the kobject isn't exposed to userspace yet. For the latter caller, sysfs/debugfs is un-registered before updating nr_hw_queues.
On the other hand, commit 2f8f1336a48b ("blk-mq: always free hctx after request queue is freed") moves freeing hctx into queue's release handler, so there won't be race with queue release path too. So don't hold q->sysfs_lock in blk_mq_realloc_hw_ctxs(). Cc: Christoph Hellwig <h...@infradead.org> Cc: Hannes Reinecke <h...@suse.com> Cc: Greg KH <gre...@linuxfoundation.org> Cc: Mike Snitzer <snit...@redhat.com> Cc: Bart Van Assche <bvanass...@acm.org> Signed-off-by: Ming Lei <ming....@redhat.com> --- block/blk-mq.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index b0ee0cac737f..d4c8692aca1f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2768,8 +2768,6 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, int i, j, end; struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx; - /* protect against switching io scheduler */ - mutex_lock(&q->sysfs_lock); for (i = 0; i < set->nr_hw_queues; i++) { int node; struct blk_mq_hw_ctx *hctx; @@ -2820,7 +2818,6 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, hctxs[j] = NULL; } } - mutex_unlock(&q->sysfs_lock); } /* -- 2.20.1