From nobody Fri Oct 3 03:16:50 2025 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 1B721239E7F; Mon, 8 Sep 2025 06:24:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757312701; cv=none; b=aeUlhBtNtmRGUNkGZEAlYp8pXtrLZ6LnK75f9FcF3SC0nZUOu64oswnag6PUgSLZ5Kb2zJMjmnrdqUoOabxzZPtzvBt1hF2S/t/MEKBXR4ErnwUePETt55Tx2bmCtEM8KgEwQQu1qXrRZKSsh29Y4INQlMb5qdrb4C+VjDMJr10= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757312701; c=relaxed/simple; bh=sVkzsW6DvvNj+oP0kCEtKRPpDU5Cl0/OUmbzikDQKR4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=FkXB29mmUKzPdhPLwwvTtjN88gFqDFfnk2QTCVdjRbumHgfRnobYBFayo9Ah80A7k0h19ITq2DmU5mF5NiJkmuaUKT/Nmlz78gSjRINouSUaaDlWqEG3snDNPaHfXSFUydOURt3jMLQzXvBytpVJGKfKFbI4/HWp4I8jeopcTGU= 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=45.249.212.51 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 [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4cKxky67F3zYQvMn; Mon, 8 Sep 2025 14:24:58 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 595511A1C46; Mon, 8 Sep 2025 14:24:57 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgD3QY6xdr5oCGEjBw--.62066S12; Mon, 08 Sep 2025 14:24:55 +0800 (CST) From: Yu Kuai To: nilay@linux.ibm.com, ming.lei@redhat.com, axboe@kernel.dk 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 for-6.18/block 08/10] blk-mq: fix potential deadlock while nr_requests grown Date: Mon, 8 Sep 2025 14:15:31 +0800 Message-Id: <20250908061533.3062917-9-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20250908061533.3062917-1-yukuai1@huaweicloud.com> References: <20250908061533.3062917-1-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: gCh0CgD3QY6xdr5oCGEjBw--.62066S12 X-Coremail-Antispam: 1UD129KBjvJXoWxAF13uFWkZrW7JFykCw1Utrb_yoWrAFW3pF W5Ja12k3ySqr18XrW8Aw47XwnxKws2gr1xGrWSy34S9rnrKrs7Z3W8GFy8XrW0yrWkCFsr Ar4DJrZ8uF97W37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUma14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCw CI42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4UJVWxJrUvcSsG vfC2KfnxnUUI43ZEXa7VUbPC7UUUUUU== X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Content-Type: text/plain; charset="utf-8" From: Yu Kuai Allocate and free sched_tags while queue is freezed can deadlock[1], this is a long term problem, hence allocate memory before freezing queue and free memory after queue is unfreezed. [1] https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@linux.= ibm.com/ Fixes: e3a2b3f931f5 ("blk-mq: allow changing of queue depth through sysfs") Signed-off-by: Yu Kuai Reviewed-by: Nilay Shroff --- block/blk-mq.c | 22 ++++++++++------------ block/blk-mq.h | 5 ++++- block/blk-sysfs.c | 25 +++++++++++++++++-------- 3 files changed, 31 insertions(+), 21 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 82fa81036115..d85afbb9f031 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4917,11 +4917,13 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set) } EXPORT_SYMBOL(blk_mq_free_tag_set); =20 -int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) +struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q, + struct elevator_tags *et, + unsigned int nr) { struct blk_mq_tag_set *set =3D q->tag_set; + struct elevator_tags *old_et =3D NULL; struct blk_mq_hw_ctx *hctx; - int ret =3D 0; unsigned long i; =20 blk_mq_quiesce_queue(q); @@ -4946,23 +4948,19 @@ int blk_mq_update_nr_requests(struct request_queue = *q, unsigned int nr) nr - hctx->sched_tags->nr_reserved_tags); } } else { - queue_for_each_hw_ctx(q, hctx, i) { - if (!hctx->sched_tags) - continue; - blk_mq_tag_update_depth(hctx, &hctx->sched_tags, nr); - if (ret) - goto out; - } + queue_for_each_hw_ctx(q, hctx, i) + hctx->sched_tags =3D et->tags[i]; + + old_et =3D q->elevator->et; + q->elevator->et =3D et; } =20 q->nr_requests =3D nr; if (q->elevator && q->elevator->type->ops.depth_updated) q->elevator->type->ops.depth_updated(q); =20 -out: blk_mq_unquiesce_queue(q); - - return ret; + return old_et; } =20 /* diff --git a/block/blk-mq.h b/block/blk-mq.h index 731f4578d9a8..6c9d03625ba1 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -6,6 +6,7 @@ #include "blk-stat.h" =20 struct blk_mq_tag_set; +struct elevator_tags; =20 struct blk_mq_ctxs { struct kobject kobj; @@ -45,7 +46,9 @@ void blk_mq_submit_bio(struct bio *bio); int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, struct io_comp_b= atch *iob, unsigned int flags); void blk_mq_exit_queue(struct request_queue *q); -int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr); +struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q, + struct elevator_tags *tags, + unsigned int nr); void blk_mq_wake_waiters(struct request_queue *q); bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head = *, bool); diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 7ea15bf68b4b..a0a7ebad378f 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -64,11 +64,12 @@ static ssize_t queue_requests_show(struct gendisk *disk= , char *page) static ssize_t queue_requests_store(struct gendisk *disk, const char *page, size_t count) { - unsigned long nr; - int ret, err; - unsigned int memflags; struct request_queue *q =3D disk->queue; struct blk_mq_tag_set *set =3D q->tag_set; + struct elevator_tags *et =3D NULL; + unsigned int memflags; + unsigned long nr; + int ret; =20 ret =3D queue_var_store(&nr, page, count); if (ret < 0) @@ -90,16 +91,24 @@ queue_requests_store(struct gendisk *disk, const char *= page, size_t count) goto unlock; } =20 + if (q->elevator && nr > q->elevator->et->nr_requests) { + /* allocate memory before freezing queue to prevent deadlock */ + et =3D blk_mq_alloc_sched_tags(set, q->nr_hw_queues, nr); + if (!et) { + ret =3D -ENOMEM; + goto unlock; + } + } + 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; - + et =3D blk_mq_update_nr_requests(q, et, nr); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); =20 + if (et) + blk_mq_free_sched_tags(et, set); + unlock: up_write(&set->update_nr_hwq_lock); return ret; --=20 2.39.2