From patchwork Tue Jun 6 15:22:07 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9769173 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 B60D960364 for ; Tue, 6 Jun 2017 15:24:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C7019283FD for ; Tue, 6 Jun 2017 15:24:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BA83C2847E; Tue, 6 Jun 2017 15:24:18 +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 75317283FD for ; Tue, 6 Jun 2017 15:24:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751431AbdFFPYS (ORCPT ); Tue, 6 Jun 2017 11:24:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49644 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751422AbdFFPYR (ORCPT ); Tue, 6 Jun 2017 11:24:17 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 41F1880C1C; Tue, 6 Jun 2017 15:24:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 41F1880C1C Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=ming.lei@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 41F1880C1C Received: from localhost (ovpn-12-72.pek2.redhat.com [10.72.12.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4A9F46031D; Tue, 6 Jun 2017 15:24:08 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig Cc: Bart Van Assche , Ming Lei Subject: [PATCH v5 09/12] blk-mq: update comments on blk_mq_quiesce_queue() Date: Tue, 6 Jun 2017 23:22:07 +0800 Message-Id: <20170606152210.22806-10-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 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 06 Jun 2017 15:24:17 +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 Actually what we want to get from blk_mq_quiesce_queue() isn't only to wait for completion of all ongoing .queue_rq(). In the typical context of canceling requests, we need to make sure that the following is done in the dispatch path before starting to cancel requests: - failed dispatched request is finished - busy dispatched request is requeued, and the STARTED flag is cleared So update comment to keep code, doc and our expection consistent. Signed-off-by: Ming Lei --- block/blk-mq.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 7369810d3dc0..abfa2b3bff74 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -155,12 +155,13 @@ void blk_mq_unfreeze_queue(struct request_queue *q) EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue); /** - * blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished + * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished * @q: request queue. * * Note: this function does not prevent that the struct request end_io() - * callback function is invoked. Additionally, it is not prevented that - * new queue_rq() calls occur unless the queue has been stopped first. + * callback function is invoked. Once this function is returned, we make + * sure no dispatch can happen until the queue is unquiesced via + * blk_mq_unquiesce_queue(). */ void blk_mq_quiesce_queue(struct request_queue *q) {