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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04166C10F03 for ; Tue, 26 Mar 2019 01:18:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C757E206DF for ; Tue, 26 Mar 2019 01:18:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="A2+sc/nz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730180AbfCZBSG (ORCPT ); Mon, 25 Mar 2019 21:18:06 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:50632 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726553AbfCZBSF (ORCPT ); Mon, 25 Mar 2019 21:18:05 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2Q1FvgT022959; Tue, 26 Mar 2019 01:17:31 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=/Kl0K4H2oLqA9ZCxH7NCR8HsssQuahLQEpvi0trC9h8=; b=A2+sc/nzx/vW4i55Lyyr6ggK/XnrmAe+8sjda7zqYwQ5sr5MXYdqLX0EN1bPoacnn/mq f7+0mE9BTh3TdW5TOdXBYTalXlRapkUm9roIf/LGkI/TKLkQb79ySlwmDrKJ4tO2IT1K Hqd1cPk3mHkqYmp9jJ5MxJct8RmMDEwjo6esTLMJsS6d+2WxuqpoGEROqrwuBDVE3bSb roQLVlvgdSJu+iHF16m6xhOD5YGxpgFtL8P9r7ThYneZRzzhk20/KGTxiW0q/KMUdNFS SspYMvT1hfXeaxAcJ9alFCNeaKO/W4sRKwD/S5sp7P3eJZleiT/WwJCVG6mphhyMydN7 ag== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2130.oracle.com with ESMTP id 2re6g0qeas-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Mar 2019 01:17:31 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2Q1HTh8000458 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Mar 2019 01:17:30 GMT Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x2Q1HOFl021687; Tue, 26 Mar 2019 01:17:25 GMT Received: from [10.182.69.118] (/10.182.69.118) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 25 Mar 2019 18:17:24 -0700 Subject: Re: [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter To: Keith Busch Cc: axboe@kernel.dk, linux-block@vger.kernel.org, jsmart2021@gmail.com, bvanassche@acm.org, josef@toxicpanda.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, keith.busch@intel.com, hare@suse.de, jthumshirn@suse.de, hch@lst.de, sagi@grimberg.me References: <1553492318-1810-1-git-send-email-jianchao.w.wang@oracle.com> <1553492318-1810-8-git-send-email-jianchao.w.wang@oracle.com> <20190325134917.GA4328@localhost.localdomain> From: "jianchao.wang" Message-ID: <70e14e12-2ffc-37db-dd8f-229bc580546e@oracle.com> Date: Tue, 26 Mar 2019 09:17:24 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190325134917.GA4328@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9206 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903260007 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Keith On 3/25/19 9:49 PM, Keith Busch wrote: > On Mon, Mar 25, 2019 at 01:38:37PM +0800, Jianchao Wang wrote: >> blk_mq_tagset_inflight_iter is not safe that it could get stale request >> in tags->rqs[]. Use blk_mq_queue_tag_inflight_iter here. A new helper >> interface nvme_iterate_inflight_rqs is introduced to iterate >> all of the ns under a ctrl. > > Nak, NVMe only iterates tags when new requests can't enter, allocated > requests can't dispatch, and dispatched commands can't complete. So > it is perfectly safe to iterate if the driver takes reasonable steps > beforehand. nvme_dev_disable just quiesce and freeze the request_queue, but not drain the enters. So there still could be someone escapes the queue freeze checking and tries to allocate request. > Further, for M tags and N namespaces, we complete teardown > in O(M) time, but this makes in O(M*N) without gaining anything. > Yes, it is indeed inefficient. Thanks Jianchao