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Wed, 2 Apr 2025 04:39:49 +0000 (UTC) Received: from localhost (unknown [10.72.120.17]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7E56C1800BE2; Wed, 2 Apr 2025 04:39:47 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org Cc: =?utf-8?q?Valdis_Kl=C4=93tnieks?= , Nilay Shroff , Christoph Hellwig , Ming Lei , syzbot+4c7e0f9b94ad65811efb@syzkaller.appspotmail.com Subject: [PATCH 3/3] block: use blk_mq_no_io() for avoiding lock dependency Date: Wed, 2 Apr 2025 12:38:49 +0800 Message-ID: <20250402043851.946498-4-ming.lei@redhat.com> In-Reply-To: <20250402043851.946498-1-ming.lei@redhat.com> References: <20250402043851.946498-1-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Use blk_mq_no_io() to prevent IO from entering queue for avoiding lock dependency between freeze lock and elevator lock, and we have got many such reports: Reported-by: syzbot+4c7e0f9b94ad65811efb@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-block/67e6b425.050a0220.2f068f.007b.GAE@google.com/ Reported-by: Valdis Klētnieks Closes: https://lore.kernel.org/linux-block/7755.1743228130@turing-police/#t Signed-off-by: Ming Lei Reviewed-by: Nilay Shroff --- block/blk-mq.c | 7 ++----- block/blk-sysfs.c | 8 ++++---- block/elevator.c | 4 ++-- 3 files changed, 8 insertions(+), 11 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 075ee51066b3..022d8139910d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4882,9 +4882,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) int ret; unsigned long i; - if (WARN_ON_ONCE(!q->mq_freeze_depth)) - return -EINVAL; - if (!set) return -EINVAL; @@ -5025,7 +5022,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, memflags = memalloc_noio_save(); list_for_each_entry(q, &set->tag_list, tag_set_list) - blk_mq_freeze_queue_nomemsave(q); + blk_mq_enter_no_io(q); /* * Switch IO scheduler to 'none', cleaning up the data associated @@ -5074,7 +5071,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, blk_mq_elv_switch_back(&head, q); list_for_each_entry(q, &set->tag_list, tag_set_list) - blk_mq_unfreeze_queue_nomemrestore(q); + blk_mq_exit_no_io(q); memalloc_noio_restore(memflags); /* Free the excess tags when nr_hw_queues shrink. */ diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index a2882751f0d2..e866875c17be 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -76,7 +76,7 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count) if (ret < 0) return ret; - memflags = blk_mq_freeze_queue(q); + memflags = blk_mq_enter_no_io_memsave(q); mutex_lock(&q->elevator_lock); if (nr < BLKDEV_MIN_RQ) nr = BLKDEV_MIN_RQ; @@ -85,7 +85,7 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count) if (err) ret = err; mutex_unlock(&q->elevator_lock); - blk_mq_unfreeze_queue(q, memflags); + blk_mq_exit_no_io_memrestore(q, memflags); return ret; } @@ -592,7 +592,7 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page, if (val < -1) return -EINVAL; - memflags = blk_mq_freeze_queue(q); + memflags = blk_mq_enter_no_io_memsave(q); mutex_lock(&q->elevator_lock); rqos = wbt_rq_qos(q); @@ -623,7 +623,7 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page, blk_mq_unquiesce_queue(q); out: mutex_unlock(&q->elevator_lock); - blk_mq_unfreeze_queue(q, memflags); + blk_mq_exit_no_io_memrestore(q, memflags); return ret; } diff --git a/block/elevator.c b/block/elevator.c index 4d3a8f996c91..c9cb8386bf5e 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -724,13 +724,13 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, elv_iosched_load_module(name); - memflags = blk_mq_freeze_queue(q); + memflags = blk_mq_enter_no_io_memsave(q); mutex_lock(&q->elevator_lock); ret = elevator_change(q, name); if (!ret) ret = count; mutex_unlock(&q->elevator_lock); - blk_mq_unfreeze_queue(q, memflags); + blk_mq_exit_no_io_memrestore(q, memflags); return ret; }