From nobody Sat Oct 4 16:09:10 2025 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BECC4245031; Fri, 15 Aug 2025 08:10:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755245413; cv=none; b=QmmcNX0nM/G5hQL8ivxCpoXh+MQS9BovvfkIydpe4f+Nu0CJ7i9O9M/nqm+zmXVAFS9P8emk1o82syjseC5QoYKszcxrUN+id2QN9dNaf0H5eJ2aEsK+uZ5lfsAGxwTGWJXB+JakfzGE/SFjLfVDusgNlQ+vxn3JhJvIzp4vuuU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755245413; c=relaxed/simple; bh=uwS4uv6TNa9vAE2OG+ULMVRqXVzT2KChvnTDwkVYLe4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Xf08ZpBOzZdIAILIGiXkFkbG2kfuYxL+tG0Jvah8+ymr46zjCAamnXjekp1nWyUtRM1ReSZT/2gcqlxYOhscDA7BUog/l0OeE1JOD4nN+Hk0j0rTHaNm83S4yQgsX7kMak2o/bcZsFjIzxD0WA4rQLb3Jg4nJAfQclBhQHbL14o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4c3FCP0BsbzKHMl9; Fri, 15 Aug 2025 16:10:09 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 539A91A018D; Fri, 15 Aug 2025 16:10:08 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgDHjxBc655o+xX_Dg--.53834S8; Fri, 15 Aug 2025 16:10:08 +0800 (CST) From: Yu Kuai To: axboe@kernel.dk, hare@suse.de, nilay@linux.ibm.com, ming.lei@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com Subject: [PATCH 04/10] blk-mq: serialize updating nr_requests with update_nr_hwq_lock Date: Fri, 15 Aug 2025 16:02:10 +0800 Message-Id: <20250815080216.410665-5-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20250815080216.410665-1-yukuai1@huaweicloud.com> References: <20250815080216.410665-1-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: gCh0CgDHjxBc655o+xX_Dg--.53834S8 X-Coremail-Antispam: 1UD129KBjvJXoW7WFWxZF17AF47tw1fAr1UKFg_yoW8ZF4rpF Z8C39Fkw1vq3W8X34UA3W7Ww17J3y0gr13GrWxtF13uFnrta97Zr18KFy7Wr48CrZ3ArsF vw4kJFZ5AFyDZF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUma14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCw CI42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4UJVWxJrUvcSsG vfC2KfnxnUUI43ZEXa7VUbPC7UUUUUU== X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Content-Type: text/plain; charset="utf-8" From: Yu Kuai request_queue->nr_requests can be changed by: a) switching elevator by update nr_hw_queues b) switching elevator by elevator sysfs attribute c) configue queue sysfs attribute nr_requests Current lock order is: 1) update_nr_hwq_lock, case a,b - allocate elevator tags 2) freeze_queue 3) elevator_lock, cas a,b,c - update nr_requests The update_nr_hwq_lock is not held by case c for now, and we need to check nr_requests while elevator_lock is held, however, we can't allocate elevator_tags whih queue freezed. Hence also require update_nr_hwq_lock and check nr_requests, make it possible to allocate new elevator_tags without queue freezed, also prevent nr_requests to be changed concurrently by other contexts. Signed-off-by: Yu Kuai --- block/blk-sysfs.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index f3d08edcc34f..37eae7927b45 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -68,13 +68,14 @@ queue_requests_store(struct gendisk *disk, const char *= page, size_t count) int ret, err; unsigned int memflags; struct request_queue *q =3D disk->queue; + struct blk_mq_tag_set *set =3D q->tag_set; =20 ret =3D queue_var_store(&nr, page, count); if (ret < 0) return ret; =20 - memflags =3D blk_mq_freeze_queue(q); - mutex_lock(&q->elevator_lock); + /* serialize with switching elevator */ + down_write(&set->update_nr_hwq_lock); =20 if (q->nr_requests =3D=3D nr) goto unlock; @@ -89,13 +90,17 @@ queue_requests_store(struct gendisk *disk, const char *= page, size_t count) goto unlock; } =20 + memflags =3D blk_mq_freeze_queue(q); + mutex_lock(&q->elevator_lock); err =3D blk_mq_update_nr_requests(disk->queue, nr); if (err) ret =3D err; =20 -unlock: mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); + +unlock: + up_write(&set->update_nr_hwq_lock); return ret; } =20 --=20 2.39.2