From patchwork Thu Jan 26 19:48:15 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 9539999 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 D8AB2604A0 for ; Thu, 26 Jan 2017 19:48:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D706A2832B for ; Thu, 26 Jan 2017 19:48:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CBA4E28346; Thu, 26 Jan 2017 19:48:35 +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=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID 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 873222832B for ; Thu, 26 Jan 2017 19:48:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753489AbdAZTse (ORCPT ); Thu, 26 Jan 2017 14:48:34 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:60805 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753437AbdAZTsd (ORCPT ); Thu, 26 Jan 2017 14:48:33 -0500 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.0.20/8.16.0.20) with SMTP id v0QJkgDh011852; Thu, 26 Jan 2017 11:48:23 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=uR2Z6TfuCc0joH+9hXhZ1ACPE1qTOZqYjEZ9w6LOv2I=; b=g/E2QCi/Xo3xN7WYiv6WZxzHZyYZJmPPjBBbQnrJJVQ+T4ZaGhcxIL8TjQQZUCkUpG5c dNsCOEkx6Kcv/inP/xltXOaYkIYlegAJWktI0FZiH9zZZ7S0E8SpRsjW3y82GUfaRcqo VW4nKhZNLVDIbzc4H3AbsoUS7IucEfF9JRg= Received: from mail.thefacebook.com ([199.201.64.23]) by m0001303.ppops.net with ESMTP id 286ht55p87-3 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Thu, 26 Jan 2017 11:48:23 -0800 Received: from localhost.localdomain (192.168.54.13) by mail.thefacebook.com (192.168.16.16) with Microsoft SMTP Server (TLS) id 14.3.294.0; Thu, 26 Jan 2017 11:48:22 -0800 From: Jens Axboe To: CC: , , , , , Jens Axboe Subject: [PATCH 2/5] blk-mq: fix potential race in queue restart and driver tag allocation Date: Thu, 26 Jan 2017 12:48:15 -0700 Message-ID: <1485460098-16608-3-git-send-email-axboe@fb.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1485460098-16608-1-git-send-email-axboe@fb.com> References: <1485460098-16608-1-git-send-email-axboe@fb.com> MIME-Version: 1.0 X-Originating-IP: [192.168.54.13] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-01-26_13:, , signatures=0 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 Once we mark the queue as needing a restart, re-check if we can get a driver tag. This fixes a theoretical issue where the needed IO completes _after_ blk_mq_get_driver_tag() fails, but before we manage to set the restart bit. Signed-off-by: Jens Axboe --- block/blk-mq.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index 223b9b080820..8041ad330289 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -928,7 +928,16 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list) if (!blk_mq_get_driver_tag(rq, &hctx, false)) { if (!queued && reorder_tags_to_front(list)) continue; + + /* + * We failed getting a driver tag. Mark the queue(s) + * as needing a restart. Retry getting a tag again, + * in case the needed IO completed right before we + * marked the queue as needing a restart. + */ blk_mq_sched_mark_restart(hctx); + if (!blk_mq_get_driver_tag(rq, &hctx, false)) + break; break; } list_del_init(&rq->queuelist);