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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=unavailable 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 4829EC43381 for ; Mon, 22 Feb 2021 06:55:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A0E864EEC for ; Mon, 22 Feb 2021 06:55:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229949AbhBVGzq (ORCPT ); Mon, 22 Feb 2021 01:55:46 -0500 Received: from out30-43.freemail.mail.aliyun.com ([115.124.30.43]:53291 "EHLO out30-43.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229908AbhBVGzh (ORCPT ); Mon, 22 Feb 2021 01:55:37 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=alimailimapcm10staff010182156082;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UPA9rZC_1613976893; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0UPA9rZC_1613976893) by smtp.aliyun-inc.com(127.0.0.1); Mon, 22 Feb 2021 14:54:53 +0800 From: Jeffle Xu To: axboe@kernel.dk Cc: linux-block@vger.kernel.org, io-uring@vger.kernel.org, joseph.qi@linux.alibaba.com Subject: [PATCH] block: fix potential IO hang when turning off io_poll Date: Mon, 22 Feb 2021 14:54:52 +0800 Message-Id: <20210222065452.21897-1-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org QUEUE_FLAG_POLL flag will be cleared when turning off 'io_poll', while at that moment there may be IOs stuck in hw queue uncompleted. The following polling routine won't help reap these IOs, since blk_poll() will return immediately because of cleared QUEUE_FLAG_POLL flag. Thus these IOs will hang until they finnaly time out. The hang out can be observed by 'fio --engine=io_uring iodepth=1', while turning off 'io_poll' at the same time. To fix this, freeze and flush the request queue first when turning off 'io_poll'. Signed-off-by: Jeffle Xu --- block/blk-sysfs.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index b513f1683af0..10d74741c002 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -430,8 +430,11 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page, if (poll_on) blk_queue_flag_set(QUEUE_FLAG_POLL, q); - else + else { + blk_mq_freeze_queue(q); blk_queue_flag_clear(QUEUE_FLAG_POLL, q); + blk_mq_unfreeze_queue(q); + } return ret; } -- 2.27.0