From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3077C433F5 for ; Wed, 29 Sep 2021 04:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B89CF613D3 for ; Wed, 29 Sep 2021 04:17:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233040AbhI2ETG (ORCPT ); Wed, 29 Sep 2021 00:19:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24410 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232353AbhI2ETF (ORCPT ); Wed, 29 Sep 2021 00:19:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632889044; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KrY+IS0jZG6xj97OVcmzVVUHAeJrr7PBDGZWgu5Io0k=; b=iJZx3SrcFEa9DI9Syv/L7hKZa+oXFe6dbBdCQexkBKanuTLq6VFuFmyYc8IsxQHoDnhuOt U6DBESRxJVzcknWu9AlihyBvXN8mlKGnsLbkX84GPynF9dretkvsuOcHvX/CFSMhxwUmDD 5PlIt0eEYbH9Tc7miu8D9CDh/la6+5o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-220-TXdVKvJuNLu7Y0fl6E3Atw-1; Wed, 29 Sep 2021 00:17:20 -0400 X-MC-Unique: TXdVKvJuNLu7Y0fl6E3Atw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DDB9C801B3D; Wed, 29 Sep 2021 04:17:18 +0000 (UTC) Received: from localhost (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id D8D2519C79; Wed, 29 Sep 2021 04:17:07 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org Cc: Sagi Grimberg , linux-nvme@lists.infradead.org, Keith Busch , Ming Lei Subject: [PATCH 5/5] blk-mq: support nested blk_mq_quiesce_queue() Date: Wed, 29 Sep 2021 12:15:59 +0800 Message-Id: <20210929041559.701102-6-ming.lei@redhat.com> In-Reply-To: <20210929041559.701102-1-ming.lei@redhat.com> References: <20210929041559.701102-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Turns out that blk_mq_freeze_queue() isn't stronger[1] than blk_mq_quiesce_queue() because dispatch may still be in-progress after queue is frozen, and in several cases, such as switching io scheduler, updating nr_requests & wbt latency, we still need to quiesce queue as a supplement of freezing queue. As we need to extend uses of blk_mq_quiesce_queue(), it is inevitable for us to need support nested quiesce, especailly we can't let unquiesce happen when there is quiesce originated from other contexts. This patch introduces q->mq_quiesce_depth to deal concurrent quiesce, and we only unquiesce queue when it is the last one from all contexts. One kernel panic issue has been reported[2] when running stress test on dm-mpath's updating nr_requests and suspending queue, and the similar issue should exist on almost all drivers which use quiesce/unquiesce. [1] https://marc.info/?l=linux-block&m=150993988115872&w=2 [2] https://listman.redhat.com/archives/dm-devel/2021-September/msg00189.html Signed-off-by: Ming Lei --- block/blk-mq.c | 20 +++++++++++++++++--- include/linux/blkdev.h | 2 ++ 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 21bf4c3f0825..10f8a3d4e3a1 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -209,7 +209,12 @@ EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue); */ void blk_mq_quiesce_queue_nowait(struct request_queue *q) { - blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q); + unsigned long flags; + + spin_lock_irqsave(&q->queue_lock, flags); + if (!q->quiesce_depth++) + blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q); + spin_unlock_irqrestore(&q->queue_lock, flags); } EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait); @@ -250,10 +255,19 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue); */ void blk_mq_unquiesce_queue(struct request_queue *q) { - blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q); + unsigned long flags; + bool run_queue = false; + + spin_lock_irqsave(&q->queue_lock, flags); + if (q->quiesce_depth > 0 && !--q->quiesce_depth) { + blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q); + run_queue = true; + } + spin_unlock_irqrestore(&q->queue_lock, flags); /* dispatch requests which are inserted during quiescing */ - blk_mq_run_hw_queues(q, true); + if (run_queue) + blk_mq_run_hw_queues(q, true); } EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 0e960d74615e..74c60e2d61f9 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -315,6 +315,8 @@ struct request_queue { */ struct mutex mq_freeze_lock; + int quiesce_depth; + struct blk_mq_tag_set *tag_set; struct list_head tag_set_list; struct bio_set bio_split; -- 2.31.1