From patchwork Wed May 12 14:42:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 438401 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=-14.4 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=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 561C8C4646E for ; Wed, 12 May 2021 15:57:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3AE3261E15 for ; Wed, 12 May 2021 15:57:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233595AbhELP57 (ORCPT ); Wed, 12 May 2021 11:57:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:51532 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230479AbhELPvl (ORCPT ); Wed, 12 May 2021 11:51:41 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F0147613EE; Wed, 12 May 2021 15:26:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620833186; bh=dOMc6MlAF4/7etUqhWyYxIma7cT6ESQt1Vv6lu2N11M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MM96m/AUNDLlw5ysoX85Un8ZyLmUakpR7R0HPAkiSpfk8P5n+1fFD45XS/AttRErP uZhO1uI4qZ19kh1UcrMHm9a1A53YHmXw8TEZr/Hu6ar+UGqKsckL91l6QNr83PsJSk dWZApWLBsluGW6ihYQ18BPB4E5rBooSJRD3UDa74= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org Subject: [PATCH 5.11 052/601] md: md_open returns -EBUSY when entering racing area Date: Wed, 12 May 2021 16:42:09 +0200 Message-Id: <20210512144829.528915169@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144827.811958675@linuxfoundation.org> References: <20210512144827.811958675@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -7856,8 +7856,7 @@ 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);