From patchwork Tue Jun 6 15:22:09 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9769181 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2357960364 for ; Tue, 6 Jun 2017 15:24:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 353B21FFCA for ; Tue, 6 Jun 2017 15:24:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 29F5A20009; Tue, 6 Jun 2017 15:24:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 227B91FFE4 for ; Tue, 6 Jun 2017 15:24:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751422AbdFFPYj (ORCPT ); Tue, 6 Jun 2017 11:24:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51552 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751281AbdFFPYj (ORCPT ); Tue, 6 Jun 2017 11:24:39 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E1AB17F3F5; Tue, 6 Jun 2017 15:24:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E1AB17F3F5 Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx01.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=ming.lei@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com E1AB17F3F5 Received: from localhost (ovpn-12-72.pek2.redhat.com [10.72.12.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id A35445C3FB; Tue, 6 Jun 2017 15:24:29 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig Cc: Bart Van Assche , Ming Lei Subject: [PATCH v5 11/12] blk-mq: clarify dispatch may not be drained/blocked by stopping queue Date: Tue, 6 Jun 2017 23:22:09 +0800 Message-Id: <20170606152210.22806-12-ming.lei@redhat.com> In-Reply-To: <20170606152210.22806-1-ming.lei@redhat.com> References: <20170606152210.22806-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Tue, 06 Jun 2017 15:24:39 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP BLK_MQ_S_STOPPED may not be observed in other concurrent I/O paths, we can't guarantee that dispatching won't happen after returning from the APIs of stopping queue. So clarify the fact and avoid potential misuse. Signed-off-by: Ming Lei Reviewed-by: Bart Van Assche --- block/blk-mq.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index 4eb849bf1d85..7b584bf7d310 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1186,6 +1186,15 @@ static void __blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx, bool sync) set_bit(BLK_MQ_S_STOPPED, &hctx->state); } +/* + * This function is often used for pausing .queue_rq() by driver when + * there isn't enough resource or some conditions aren't satisfied, and + * BLK_MQ_RQ_QUEUE_BUSY is usually returned. + * + * We do not guarantee that dispatch can be drained or blocked + * after blk_mq_stop_hw_queue() returns. Please use + * blk_mq_quiesce_queue() for that requirement. + */ void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx) { __blk_mq_stop_hw_queue(hctx, false); @@ -1201,6 +1210,15 @@ static void __blk_mq_stop_hw_queues(struct request_queue *q, bool sync) __blk_mq_stop_hw_queue(hctx, sync); } +/* + * This function is often used for pausing .queue_rq() by driver when + * there isn't enough resource or some conditions aren't satisfied, and + * BLK_MQ_RQ_QUEUE_BUSY is usually returned. + * + * We do not guarantee that dispatch can be drained or blocked + * after blk_mq_stop_hw_queues() returns. Please use + * blk_mq_quiesce_queue() for that requirement. + */ void blk_mq_stop_hw_queues(struct request_queue *q) { __blk_mq_stop_hw_queues(q, false);