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=-14.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 6FC8DC43461 for ; Thu, 20 May 2021 09:49:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56AD161468 for ; Thu, 20 May 2021 09:49:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234035AbhETJvE (ORCPT ); Thu, 20 May 2021 05:51:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:47674 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234004AbhETJsS (ORCPT ); Thu, 20 May 2021 05:48:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CFDA961460; Thu, 20 May 2021 09:34:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621503281; bh=qP4NFxlmQnQxwdA++yLYy8b2CS2DrgjVBNwh0wCd1qc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xtMFkVkdciqGcmyPxHchdUsytdocXuZcuoiQnxPKEMCIaEs236TOEfqBE4ao9Xl6z Oop7+EZmV/SBMPF4T2DPw0Ts8zhCsODskeCoJyUmPJecbCLI5ttq4U4LQwfzZWXxf3 S3jFbUrv/BaZs7l3CdayoUNt/lyIfcv1El2PVttM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org Subject: [PATCH 4.19 143/425] md: md_open returns -EBUSY when entering racing area Date: Thu, 20 May 2021 11:18:32 +0200 Message-Id: <20210520092136.129209099@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092131.308959589@linuxfoundation.org> References: <20210520092131.308959589@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhao Heming commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream. commit d3374825ce57 ("md: make devices disappear when they are no longer needed.") introduced protection between mddev creating & removing. The md_open shouldn't create mddev when all_mddevs list doesn't contain mddev. With currently code logic, there will be very easy to trigger soft lockup in non-preempt env. This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which will break the infinitely retry when md_open enter racing area. This patch is partly fix soft lockup issue, full fix needs mddev_find is split into two functions: mddev_find & mddev_find_or_alloc. And md_open should call new mddev_find (it only does searching job). For more detail, please refer with Christoph's "split mddev_find" patch in later commits. --- drivers/md/md.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7481,8 +7481,7 @@ static int md_open(struct block_device * /* Wait until bdev->bd_disk is definitely gone */ if (work_pending(&mddev->del_work)) flush_workqueue(md_misc_wq); - /* Then retry the open from the top */ - return -ERESTARTSYS; + return -EBUSY; } BUG_ON(mddev != bdev->bd_disk->private_data);