From patchwork Tue Jul 26 11:01:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yufen Yu X-Patchwork-Id: 12929152 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA320C433EF for ; Tue, 26 Jul 2022 10:49:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232355AbiGZKtO (ORCPT ); Tue, 26 Jul 2022 06:49:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238790AbiGZKtM (ORCPT ); Tue, 26 Jul 2022 06:49:12 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66B7A2409B for ; Tue, 26 Jul 2022 03:49:10 -0700 (PDT) Received: from dggpeml500020.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4LsYVc2FtszjX5b; Tue, 26 Jul 2022 18:46:16 +0800 (CST) Received: from dggpeml500009.china.huawei.com (7.185.36.209) by dggpeml500020.china.huawei.com (7.185.36.88) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 26 Jul 2022 18:49:08 +0800 Received: from huawei.com (10.175.127.227) by dggpeml500009.china.huawei.com (7.185.36.209) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 26 Jul 2022 18:49:08 +0800 From: Yufen Yu To: CC: , , , Yufen Yu Subject: [PATCH v2] blk-mq: run queue no matter whether the request is the last request Date: Tue, 26 Jul 2022 19:01:11 +0800 Message-ID: <20220726110111.1557859-1-yuyufen@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500009.china.huawei.com (7.185.36.209) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org We do test on a virtio scsi device (/dev/sda) and the default mq scheduler is 'none'. We found a IO hung as following: blk_finish_plug blk_mq_plug_issue_direct scsi_mq_get_budget //get budget_token fail and sdev->restarts=1 scsi_end_request scsi_run_queue_async //sdev->restart=0 and run queue blk_mq_request_bypass_insert //add request to hctx->dispatch list //continue to dispath plug list blk_mq_dispatch_plug_list blk_mq_try_issue_list_directly //success issue all requests from plug list After .get_budget fail, scsi_mq_get_budget will increase 'restarts'. Normally, it will run hw queue when io complete and set 'restarts' as 0. But if we run queue before adding request to the dispatch list and blk_mq_dispatch_plug_list also success issue all requests, then on one will run queue, and the request will be stall in the dispatch list and cannot complete forever. It is wrong to use last request of plug list to decide if run queue is needed since all the remained requests in plug list may be from other hctxs. To fix the bug, pass run_queue as true always to blk_mq_request_bypass_insert(). Fix-suggested-by: Ming Lei Signed-off-by: Yufen Yu Reviewed-by: Ming Lei --- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 93d9d60980fb..1eb13d57a946 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2568,7 +2568,7 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule) break; case BLK_STS_RESOURCE: case BLK_STS_DEV_RESOURCE: - blk_mq_request_bypass_insert(rq, false, last); + blk_mq_request_bypass_insert(rq, false, true); blk_mq_commit_rqs(hctx, &queued, from_schedule); return; default: