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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 780BFC25B08 for ; Sat, 13 Aug 2022 06:00:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238048AbiHMGAn (ORCPT ); Sat, 13 Aug 2022 02:00:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233189AbiHMGAk (ORCPT ); Sat, 13 Aug 2022 02:00:40 -0400 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A107127B2A; Fri, 12 Aug 2022 23:00:39 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4M4VH31lLtzKHCR; Sat, 13 Aug 2022 13:59:11 +0800 (CST) Received: from [10.174.176.73] (unknown [10.174.176.73]) by APP2 (Coremail) with SMTP id Syh0CgC3oLwEPvdiJuUnAQ--.18533S3; Sat, 13 Aug 2022 14:00:36 +0800 (CST) Subject: Re: [PATCH v3] blk-mq: fix io hung due to missing commit_rqs To: Yu Kuai , axboe@kernel.dk Cc: Ming Lei , osandov@fb.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, "yukuai (C)" References: <20220726122224.1790882-1-yukuai1@huaweicloud.com> <1ca6db8a-5780-45c6-064d-dd72c9f274c3@huaweicloud.com> From: Yu Kuai Message-ID: Date: Sat, 13 Aug 2022 14:00:36 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1ca6db8a-5780-45c6-064d-dd72c9f274c3@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: Syh0CgC3oLwEPvdiJuUnAQ--.18533S3 X-Coremail-Antispam: 1UD129KBjvJXoW7ZF18AFWUXr1UAry8uFyUJrb_yoW8KFW5pF s2ka43Jr4Fkr4ktrnFqF1UAFyFgwsrX39rWryxJrWfZrZFkry0gr4xXrnIgFyIkF4kCwnr KF45Xr9xZw1UArJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkG14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jrv_JF1lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvEwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lc7I2V7IY0VAS07AlzVAY IcxG8wCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14 v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkG c2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r4j6FyUMIIF0xvEx4A2jsIE14v26r1j6r4U MIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUp6wZUUU UU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 在 2022/07/29 14:35, Yu Kuai 写道: > Hi, Jens > > Can you please consider this patch for v5.20? > friendly ping ... > Thanks, > Kuai > > 在 2022/07/27 11:08, Ming Lei 写道: >> On Tue, Jul 26, 2022 at 08:22:24PM +0800, Yu Kuai wrote: >>> From: Yu Kuai >>> >>> Currently, in virtio_scsi, if 'bd->last' is not set to true while >>> dispatching request, such io will stay in driver's queue, and driver >>> will wait for block layer to dispatch more rqs. However, if block >>> layer failed to dispatch more rq, it should trigger commit_rqs to >>> inform driver. >>> >>> There is a problem in blk_mq_try_issue_list_directly() that commit_rqs >>> won't be called: >>> >>> // assume that queue_depth is set to 1, list contains two rq >>> blk_mq_try_issue_list_directly >>>   blk_mq_request_issue_directly >>>   // dispatch first rq >>>   // last is false >>>    __blk_mq_try_issue_directly >>>     blk_mq_get_dispatch_budget >>>     // succeed to get first budget >>>     __blk_mq_issue_directly >>>      scsi_queue_rq >>>       cmd->flags |= SCMD_LAST >>>        virtscsi_queuecommand >>>         kick = (sc->flags & SCMD_LAST) != 0 >>>         // kick is false, first rq won't issue to disk >>>   queued++ >>> >>>   blk_mq_request_issue_directly >>>   // dispatch second rq >>>    __blk_mq_try_issue_directly >>>     blk_mq_get_dispatch_budget >>>     // failed to get second budget >>>   ret == BLK_STS_RESOURCE >>>    blk_mq_request_bypass_insert >>>   // errors is still 0 >>> >>>   if (!list_empty(list) || errors && ...) >>>    // won't pass, commit_rqs won't be called >>> >>> In this situation, first rq relied on second rq to dispatch, while >>> second rq relied on first rq to complete, thus they will both hung. >>> >>> Fix the problem by also treat 'BLK_STS_*RESOURCE' as 'errors' since >>> it means that request is not queued successfully. >>> >>> Same problem exists in blk_mq_dispatch_rq_list(), 'BLK_STS_*RESOURCE' >>> can't be treated as 'errors' here, fix the problem by calling >>> commit_rqs if queue_rq return 'BLK_STS_*RESOURCE'. >>> >>> Fixes: d666ba98f849 ("blk-mq: add mq_ops->commit_rqs()") >>> Signed-off-by: Yu Kuai >> >> Reviewed-by: Ming Lei >> >> Thanks, >> Ming >> >> . >> > > . >