From patchwork Wed May 12 14:42:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 437102 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 4B9B0C46461 for ; Wed, 12 May 2021 15:16:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1075661979 for ; Wed, 12 May 2021 15:16:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231987AbhELPRF (ORCPT ); Wed, 12 May 2021 11:17:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:50766 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232929AbhELPOD (ORCPT ); Wed, 12 May 2021 11:14:03 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 81EDA61459; Wed, 12 May 2021 15:04:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620831868; bh=kBVCEtgUNjlcNC94Z58lqLy3lJ4j1EuTCiR7O3K1TP4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IXs4sc8Pp2YOqnQ0zyhxYOOftCTD6P7PPk54tRzKGSgPsCkCsIPRE7sjzEEuqAp/7 ExOgeqUOhoxLs4j135U6gCR/t+f72duobEEklg1C4LMkEbw5Kha3VSK0K6s3VPJ1T/ ETwWQoJkK7ni9yjvFpuMX5cGF5hrdNcvV2em654k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org Subject: [PATCH 5.10 048/530] md: split mddev_find Date: Wed, 12 May 2021 16:42:38 +0200 Message-Id: <20210512144821.324676488@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144819.664462530@linuxfoundation.org> References: <20210512144819.664462530@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Christoph Hellwig commit 65aa97c4d2bfd76677c211b9d03ef05a98c6d68e upstream. Split mddev_find into a simple mddev_find that just finds an existing mddev by the unit number, and a more complicated mddev_find that deals with find or allocating a mddev. This turns out to fix this bug reported by Zhao Heming. ----------------------------- snip ------------------------------ 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. --- drivers/md/md.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -750,6 +750,22 @@ EXPORT_SYMBOL_GPL(mddev_init); static struct mddev *mddev_find(dev_t unit) { + struct mddev *mddev; + + if (MAJOR(unit) != MD_MAJOR) + unit &= ~((1 << MdpMinorShift) - 1); + + spin_lock(&all_mddevs_lock); + mddev = mddev_find_locked(unit); + if (mddev) + mddev_get(mddev); + spin_unlock(&all_mddevs_lock); + + return mddev; +} + +static struct mddev *mddev_find_or_alloc(dev_t unit) +{ struct mddev *mddev, *new = NULL; if (unit && MAJOR(unit) != MD_MAJOR) @@ -5656,7 +5672,7 @@ static int md_alloc(dev_t dev, char *nam * writing to /sys/module/md_mod/parameters/new_array. */ static DEFINE_MUTEX(disks_mutex); - struct mddev *mddev = mddev_find(dev); + struct mddev *mddev = mddev_find_or_alloc(dev); struct gendisk *disk; int partitioned; int shift; @@ -6539,11 +6555,9 @@ static void autorun_devices(int part) md_probe(dev, NULL, NULL); mddev = mddev_find(dev); - if (!mddev || !mddev->gendisk) { - if (mddev) - mddev_put(mddev); + if (!mddev) break; - } + if (mddev_lock(mddev)) pr_warn("md: %s locked, cannot run\n", mdname(mddev)); else if (mddev->raid_disks || mddev->major_version