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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B6B13C433ED for ; Wed, 12 May 2021 09:24:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74D00611C9 for ; Wed, 12 May 2021 09:24:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230134AbhELJZp (ORCPT ); Wed, 12 May 2021 05:25:45 -0400 Received: from wforward2-smtp.messagingengine.com ([64.147.123.31]:49947 "EHLO wforward2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230118AbhELJZo (ORCPT ); Wed, 12 May 2021 05:25:44 -0400 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailforward.west.internal (Postfix) with ESMTP id 1676513BB; Wed, 12 May 2021 05:24:35 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Wed, 12 May 2021 05:24:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=AlS14c YRLhPU+P4GLvp9xbSWw+jjJh0InCVCD5ZCTZE=; b=hbRelSwbVmADCimMBLnG18 DgGv5ZH683i7jeFcmJEK4T+UIxKc/mnYKqe/F1qYyJHtpyMH+1FV+c7ulh4YAaCi J0UQrjyHVO7bUS3gIY3EhU3Gm3fcRuv1WoKyfa3NNwQ+uIwKpd2EMX5ZY4CM+w/m 2X6Rks5/RuLbfC7LU8FU7rBF3uz1Z65+GxDP/o6KUPVLMyY4cDos5ShC1raIcYUH l4MNOWjhjmI9emOUJcIFXYL42YLzWDjCTmWdOUo1FVCSLQoShVs0cpG7gFKLeJri OeoH39O6FtTX0WS0h62YgrO059ZJlspWo1z1HUIWGax8XE+OFyNOD9UkVYwhFUEw == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledrvdehvddguddvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucenucfjughrpefuvffhfffkgggtgfesthekredttd dtlfenucfhrhhomhepoehgrhgvghhkhheslhhinhhugihfohhunhgurghtihhonhdrohhr gheqnecuggftrfgrthhtvghrnhepieetveehuedvhfdtgfdvieeiheehfeelveevheejud etveeuveeludejjefgteehnecukfhppeekfedrkeeirdejgedrieegnecuvehluhhsthgv rhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepghhrvghgsehkrhhorghhrd gtohhm X-ME-Proxy: Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 12 May 2021 05:24:33 -0400 (EDT) Subject: FAILED: patch "[PATCH] md: split mddev_find" failed to apply to 4.4-stable tree To: hch@lst.de, heming.zhao@suse.com, song@kernel.org Cc: From: Date: Wed, 12 May 2021 11:24:32 +0200 Message-ID: <1620811472201245@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 65aa97c4d2bfd76677c211b9d03ef05a98c6d68e Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sat, 3 Apr 2021 18:15:29 +0200 Subject: [PATCH] md: split mddev_find 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. *** env *** kvm-qemu VM 2C1G with 2 iscsi luns kernel should be non-preempt *** script *** about trigger 1 time with 10 tests `1 node1="15sp3-mdcluster1" 2 node2="15sp3-mdcluster2" 3 4 mdadm -Ss 5 ssh ${node2} "mdadm -Ss" 6 wipefs -a /dev/sda /dev/sdb 7 mdadm -CR /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda \ /dev/sdb --assume-clean 8 9 for i in {1..100}; do 10 echo ==== $i ====; 11 12 echo "test ...." 13 ssh ${node2} "mdadm -A /dev/md0 /dev/sda /dev/sdb" 14 sleep 1 15 16 echo "clean ....." 17 ssh ${node2} "mdadm -Ss" 18 done ` I use mdcluster env to trigger soft lockup, but it isn't mdcluster speical bug. To stop md array in mdcluster env will do more jobs than non-cluster array, which will leave enough time/gap to allow kernel to run md_open. *** stack *** `ID: 2831 TASK: ffff8dd7223b5040 CPU: 0 COMMAND: "mdadm" #0 [ffffa15d00a13b90] __schedule at ffffffffb8f1935f #1 [ffffa15d00a13ba8] exact_lock at ffffffffb8a4a66d #2 [ffffa15d00a13bb0] kobj_lookup at ffffffffb8c62fe3 #3 [ffffa15d00a13c28] __blkdev_get at ffffffffb89273b9 #4 [ffffa15d00a13c98] blkdev_get at ffffffffb8927964 #5 [ffffa15d00a13cb0] do_dentry_open at ffffffffb88dc4b4 #6 [ffffa15d00a13ce0] path_openat at ffffffffb88f0ccc #7 [ffffa15d00a13db8] do_filp_open at ffffffffb88f32bb #8 [ffffa15d00a13ee0] do_sys_open at ffffffffb88ddc7d #9 [ffffa15d00a13f38] do_syscall_64 at ffffffffb86053cb ffffffffb900008c or: [ 884.226509] mddev_put+0x1c/0xe0 [md_mod] [ 884.226515] md_open+0x3c/0xe0 [md_mod] [ 884.226518] __blkdev_get+0x30d/0x710 [ 884.226520] ? bd_acquire+0xd0/0xd0 [ 884.226522] blkdev_get+0x14/0x30 [ 884.226524] do_dentry_open+0x204/0x3a0 [ 884.226531] path_openat+0x2fc/0x1520 [ 884.226534] ? seq_printf+0x4e/0x70 [ 884.226536] do_filp_open+0x9b/0x110 [ 884.226542] ? md_release+0x20/0x20 [md_mod] [ 884.226543] ? seq_read+0x1d8/0x3e0 [ 884.226545] ? kmem_cache_alloc+0x18a/0x270 [ 884.226547] ? do_sys_open+0x1bd/0x260 [ 884.226548] do_sys_open+0x1bd/0x260 [ 884.226551] do_syscall_64+0x5b/0x1e0 [ 884.226554] entry_SYSCALL_64_after_hwframe+0x44/0xa9 ` *** rootcause *** "mdadm -A" (or other array assemble commands) will start a daemon "mdadm --monitor" by default. When "mdadm -Ss" is running, the stop action will wakeup "mdadm --monitor". The "--monitor" daemon will immediately get info from /proc/mdstat. This time mddev in kernel still exist, so /proc/mdstat still show md device, which makes "mdadm --monitor" to open /dev/md0. The previously "mdadm -Ss" is removing action, the "mdadm --monitor" open action will trigger md_open which is creating action. Racing is happening. `: "mdadm -Ss" md_release mddev_put deletes mddev from all_mddevs queue_work for mddev_delayed_delete at this time, "/dev/md0" is still available for opening : "mdadm --monitor ..." md_open + mddev_find can't find mddev of /dev/md0, and create a new mddev and | return. + trigger "if (mddev->gendisk != bdev->bd_disk)" and return -ERESTARTSYS. ` In non-preempt kernel, is occupying on current CPU. and mddev_delayed_delete which was created in also can't be schedule. In preempt kernel, it can also trigger above racing. But kernel doesn't allow one thread running on a CPU all the time. after running some time, the later "mdadm -A" (refer above script line 13) will call md_alloc to alloc a new gendisk for mddev. it will break md_open statement "if (mddev->gendisk != bdev->bd_disk)" and return 0 to caller, the soft lockup is broken. ------------------------------ snip ------------------------------ Cc: stable@vger.kernel.org Fixes: d3374825ce57 ("md: make devices disappear when they are no longer needed.") Reported-by: Heming Zhao Reviewed-by: Heming Zhao Signed-off-by: Christoph Hellwig Signed-off-by: Song Liu diff --git a/drivers/md/md.c b/drivers/md/md.c index e10d91122483..3ce5f4e0f431 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -746,6 +746,22 @@ static struct mddev *mddev_find_locked(dev_t unit) } 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; @@ -5650,7 +5666,7 @@ static int md_alloc(dev_t dev, char *name) * 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; @@ -6530,11 +6546,9 @@ 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