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=-14.4 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=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 87B7EC43460 for ; Wed, 12 May 2021 16:53:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 544CF6112D for ; Wed, 12 May 2021 16:53:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245232AbhELQwQ (ORCPT ); Wed, 12 May 2021 12:52:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:51338 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234312AbhELPv0 (ORCPT ); Wed, 12 May 2021 11:51:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1FEAE60FE9; Wed, 12 May 2021 15:26:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620833181; bh=7WL8eamTbY8OeH4qiYW4xUGzjX1FxHghoA8QBUgtahk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Pkyzoznnd+3LWHZqKWe+ISrsuUTmVNhMiIuWjtCACfXKFpKA0sOdyiScxQCXSZL6h 07POiMPKYqtYRzCFpZoq35zGnp4mmuhnHl+8CKwHIcUuAIYhzBwSxtVNL4si0u5Pk0 4yQOSX+sRjPpWIqVEmx8t/lXuFsg0R3IU/S2qQQ0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org Subject: [PATCH 5.11 050/601] md: split mddev_find Date: Wed, 12 May 2021 16:42:07 +0200 Message-Id: <20210512144829.466434623@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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -754,6 +754,22 @@ 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) @@ -5657,7 +5673,7 @@ 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); 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