From patchwork Sun Aug 8 07:03:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12424727 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 BC776C4338F for ; Sun, 8 Aug 2021 06:52:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98DFC60FF2 for ; Sun, 8 Aug 2021 06:52:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230262AbhHHGxH (ORCPT ); Sun, 8 Aug 2021 02:53:07 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:16994 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230348AbhHHGxG (ORCPT ); Sun, 8 Aug 2021 02:53:06 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Gj8vT0z80zZydk; Sun, 8 Aug 2021 14:49:09 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Sun, 8 Aug 2021 14:52:45 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Sun, 8 Aug 2021 14:52:45 +0800 From: Yu Kuai To: CC: , , , Subject: [PATCH] block: don't decrement flush request refcount if it's state is idle in flush_end_io() Date: Sun, 8 Aug 2021 15:03:30 +0800 Message-ID: <20210808070330.763177-1-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org flush_end_io() currently decrement request refcount unconditionally. However, it's possible that the request is already idle and it's refcount is zero since that flush_end_io() can be called concurrently. For example, nbd_clear_que() can be called concurrently with normal io completion or io timeout. Thus check idle before decrement to avoid refcount_t underflow warning. Signed-off-by: Yu Kuai --- block/blk-flush.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/blk-flush.c b/block/blk-flush.c index 1002f6c58181..9b65dc43702c 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -222,7 +222,8 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error) /* release the tag's ownership to the req cloned from */ spin_lock_irqsave(&fq->mq_flush_lock, flags); - if (!refcount_dec_and_test(&flush_rq->ref)) { + if (blk_mq_rq_state(flush_rq) == MQ_RQ_IDLE || + !refcount_dec_and_test(&flush_rq->ref)) { fq->rq_status = error; spin_unlock_irqrestore(&fq->mq_flush_lock, flags); return;