From: Ming Lei Date: Wed, 15 Oct 2025 10:30:39 +0000 (+0800) Subject: block: Remove elevator_lock usage from blkg_conf frozen operations X-Git-Tag: v6.18-rc2~19^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=08823e89e3e269bf4c4a20b4c24a8119920cc7a4;p=thirdparty%2Fkernel%2Fstable.git block: Remove elevator_lock usage from blkg_conf frozen operations Remove the acquisition and release of q->elevator_lock in the blkg_conf_open_bdev_frozen() and blkg_conf_exit_frozen() functions. The elevator lock is no longer needed in these code paths since commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()") which introduces `disk->rqos_state_mutex` for protecting wbt state change, and not necessary to abuse elevator_lock for this purpose. This change helps to solve the lockdep warning reported from Yu Kuai[1]. Pass blktests/throtl with lockdep enabled. Links: https://lore.kernel.org/linux-block/e5e7ac3f-2063-473a-aafb-4d8d43e5576e@yukuai.org.cn/ [1] Fixes: commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()") Signed-off-by: Ming Lei Reviewed-by: Nilay Shroff Signed-off-by: Jens Axboe --- diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index f93de34fe87d..3cffb68ba5d8 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -812,8 +812,7 @@ int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx) } /* * Similar to blkg_conf_open_bdev, but additionally freezes the queue, - * acquires q->elevator_lock, and ensures the correct locking order - * between q->elevator_lock and q->rq_qos_mutex. + * ensures the correct locking order between freeze queue and q->rq_qos_mutex. * * This function returns negative error on failure. On success it returns * memflags which must be saved and later passed to blkg_conf_exit_frozen @@ -834,13 +833,11 @@ unsigned long __must_check blkg_conf_open_bdev_frozen(struct blkg_conf_ctx *ctx) * At this point, we haven’t started protecting anything related to QoS, * so we release q->rq_qos_mutex here, which was first acquired in blkg_ * conf_open_bdev. Later, we re-acquire q->rq_qos_mutex after freezing - * the queue and acquiring q->elevator_lock to maintain the correct - * locking order. + * the queue to maintain the correct locking order. */ mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex); memflags = blk_mq_freeze_queue(ctx->bdev->bd_queue); - mutex_lock(&ctx->bdev->bd_queue->elevator_lock); mutex_lock(&ctx->bdev->bd_queue->rq_qos_mutex); return memflags; @@ -995,9 +992,8 @@ void blkg_conf_exit(struct blkg_conf_ctx *ctx) EXPORT_SYMBOL_GPL(blkg_conf_exit); /* - * Similar to blkg_conf_exit, but also unfreezes the queue and releases - * q->elevator_lock. Should be used when blkg_conf_open_bdev_frozen - * is used to open the bdev. + * Similar to blkg_conf_exit, but also unfreezes the queue. Should be used + * when blkg_conf_open_bdev_frozen is used to open the bdev. */ void blkg_conf_exit_frozen(struct blkg_conf_ctx *ctx, unsigned long memflags) { @@ -1005,7 +1001,6 @@ void blkg_conf_exit_frozen(struct blkg_conf_ctx *ctx, unsigned long memflags) struct request_queue *q = ctx->bdev->bd_queue; blkg_conf_exit(ctx); - mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); } }