From: Ming Lei Date: Tue, 27 Aug 2019 11:01:46 +0000 (+0800) Subject: blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue X-Git-Tag: v4.19.176~7 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6ff18507a7c165b90f1fe51822c65d10265f5714;p=thirdparty%2Fkernel%2Fstable.git blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue commit c6ba933358f0d7a6a042b894dba20cc70396a6d3 upstream. blk_mq_map_swqueue() 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, hctx sysfs entries and debugfs are 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_map_swqueue(). Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Greg KH Cc: Mike Snitzer Cc: Bart Van Assche Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Jack Wang Signed-off-by: Greg Kroah-Hartman --- diff --git a/block/blk-mq.c b/block/blk-mq.c index 0df43515ff949..195526b93895e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2324,11 +2324,6 @@ static void blk_mq_map_swqueue(struct request_queue *q) struct blk_mq_ctx *ctx; struct blk_mq_tag_set *set = q->tag_set; - /* - * Avoid others reading imcomplete hctx->cpumask through sysfs - */ - mutex_lock(&q->sysfs_lock); - queue_for_each_hw_ctx(q, hctx, i) { cpumask_clear(hctx->cpumask); hctx->nr_ctx = 0; @@ -2362,8 +2357,6 @@ static void blk_mq_map_swqueue(struct request_queue *q) hctx->ctxs[hctx->nr_ctx++] = ctx; } - mutex_unlock(&q->sysfs_lock); - queue_for_each_hw_ctx(q, hctx, i) { /* * If no software queues are mapped to this hardware queue,