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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 C7077C433E0 for ; Mon, 8 Jun 2020 23:42:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93A1520659 for ; Mon, 8 Jun 2020 23:42:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591659753; bh=mbz0aRqUQQ5eO9gld4fUJS7d1Lxr2GIYjbbd/6rEfT8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=QXQGiitQYgaYoWICZLdDK7qww7Zf+P2g0BberxMmAO2AMMO9dIP7+5+IfYvr5VjV2 GniZuwLRIqktl/iNjrH2ukLOVNMTTDTuroROjGTO42/flwTU7vEgAs1WdMfQq8fNEN zchU8f23B6R3rZd+5J883yJbOT8tmrfoJ2R1k9LA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732303AbgFHXma (ORCPT ); Mon, 8 Jun 2020 19:42:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:55892 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728111AbgFHX11 (ORCPT ); Mon, 8 Jun 2020 19:27:27 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EE9A22064C; Mon, 8 Jun 2020 23:27:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591658846; bh=mbz0aRqUQQ5eO9gld4fUJS7d1Lxr2GIYjbbd/6rEfT8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RZrdHVrl7pxdsKpzMnH82Fl+YTLKppEvyWzEkKhpudyNtAMlT8GfaoE/SqASv3VI0 veWT6PB+eFFg2WYddjI5+i/ixm2cMsHsJe9CkmS3DGj21MbpkUlADvIjK8Dv7osjlv m0Dsce7Ig9tW4uJQuR9hQdAfrpuW61rbpcv3X4rY= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Guoqing Jiang , Song Liu , Sasha Levin , linux-raid@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 34/50] md: don't flush workqueue unconditionally in md_open Date: Mon, 8 Jun 2020 19:26:24 -0400 Message-Id: <20200608232640.3370262-34-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200608232640.3370262-1-sashal@kernel.org> References: <20200608232640.3370262-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guoqing Jiang [ Upstream commit f6766ff6afff70e2aaf39e1511e16d471de7c3ae ] We need to check mddev->del_work before flush workqueu since the purpose of flush is to ensure the previous md is disappeared. Otherwise the similar deadlock appeared if LOCKDEP is enabled, it is due to md_open holds the bdev->bd_mutex before flush workqueue. kernel: [ 154.522645] ====================================================== kernel: [ 154.522647] WARNING: possible circular locking dependency detected kernel: [ 154.522650] 5.6.0-rc7-lp151.27-default #25 Tainted: G O kernel: [ 154.522651] ------------------------------------------------------ kernel: [ 154.522653] mdadm/2482 is trying to acquire lock: kernel: [ 154.522655] ffff888078529128 ((wq_completion)md_misc){+.+.}, at: flush_workqueue+0x84/0x4b0 kernel: [ 154.522673] kernel: [ 154.522673] but task is already holding lock: kernel: [ 154.522675] ffff88804efa9338 (&bdev->bd_mutex){+.+.}, at: __blkdev_get+0x79/0x590 kernel: [ 154.522691] kernel: [ 154.522691] which lock already depends on the new lock. kernel: [ 154.522691] kernel: [ 154.522694] kernel: [ 154.522694] the existing dependency chain (in reverse order) is: kernel: [ 154.522696] kernel: [ 154.522696] -> #4 (&bdev->bd_mutex){+.+.}: kernel: [ 154.522704] __mutex_lock+0x87/0x950 kernel: [ 154.522706] __blkdev_get+0x79/0x590 kernel: [ 154.522708] blkdev_get+0x65/0x140 kernel: [ 154.522709] blkdev_get_by_dev+0x2f/0x40 kernel: [ 154.522716] lock_rdev+0x3d/0x90 [md_mod] kernel: [ 154.522719] md_import_device+0xd6/0x1b0 [md_mod] kernel: [ 154.522723] new_dev_store+0x15e/0x210 [md_mod] kernel: [ 154.522728] md_attr_store+0x7a/0xc0 [md_mod] kernel: [ 154.522732] kernfs_fop_write+0x117/0x1b0 kernel: [ 154.522735] vfs_write+0xad/0x1a0 kernel: [ 154.522737] ksys_write+0xa4/0xe0 kernel: [ 154.522745] do_syscall_64+0x64/0x2b0 kernel: [ 154.522748] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522749] kernel: [ 154.522749] -> #3 (&mddev->reconfig_mutex){+.+.}: kernel: [ 154.522752] __mutex_lock+0x87/0x950 kernel: [ 154.522756] new_dev_store+0xc9/0x210 [md_mod] kernel: [ 154.522759] md_attr_store+0x7a/0xc0 [md_mod] kernel: [ 154.522761] kernfs_fop_write+0x117/0x1b0 kernel: [ 154.522763] vfs_write+0xad/0x1a0 kernel: [ 154.522765] ksys_write+0xa4/0xe0 kernel: [ 154.522767] do_syscall_64+0x64/0x2b0 kernel: [ 154.522769] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522770] kernel: [ 154.522770] -> #2 (kn->count#253){++++}: kernel: [ 154.522775] __kernfs_remove+0x253/0x2c0 kernel: [ 154.522778] kernfs_remove+0x1f/0x30 kernel: [ 154.522780] kobject_del+0x28/0x60 kernel: [ 154.522783] mddev_delayed_delete+0x24/0x30 [md_mod] kernel: [ 154.522786] process_one_work+0x2a7/0x5f0 kernel: [ 154.522788] worker_thread+0x2d/0x3d0 kernel: [ 154.522793] kthread+0x117/0x130 kernel: [ 154.522795] ret_from_fork+0x3a/0x50 kernel: [ 154.522796] kernel: [ 154.522796] -> #1 ((work_completion)(&mddev->del_work)){+.+.}: kernel: [ 154.522800] process_one_work+0x27e/0x5f0 kernel: [ 154.522802] worker_thread+0x2d/0x3d0 kernel: [ 154.522804] kthread+0x117/0x130 kernel: [ 154.522806] ret_from_fork+0x3a/0x50 kernel: [ 154.522807] kernel: [ 154.522807] -> #0 ((wq_completion)md_misc){+.+.}: kernel: [ 154.522813] __lock_acquire+0x1392/0x1690 kernel: [ 154.522816] lock_acquire+0xb4/0x1a0 kernel: [ 154.522818] flush_workqueue+0xab/0x4b0 kernel: [ 154.522821] md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522823] __blkdev_get+0xea/0x590 kernel: [ 154.522825] blkdev_get+0x65/0x140 kernel: [ 154.522828] do_dentry_open+0x1d1/0x380 kernel: [ 154.522831] path_openat+0x567/0xcc0 kernel: [ 154.522834] do_filp_open+0x9b/0x110 kernel: [ 154.522836] do_sys_openat2+0x201/0x2a0 kernel: [ 154.522838] do_sys_open+0x57/0x80 kernel: [ 154.522840] do_syscall_64+0x64/0x2b0 kernel: [ 154.522842] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522844] kernel: [ 154.522844] other info that might help us debug this: kernel: [ 154.522844] kernel: [ 154.522846] Chain exists of: kernel: [ 154.522846] (wq_completion)md_misc --> &mddev->reconfig_mutex --> &bdev->bd_mutex kernel: [ 154.522846] kernel: [ 154.522850] Possible unsafe locking scenario: kernel: [ 154.522850] kernel: [ 154.522852] CPU0 CPU1 kernel: [ 154.522853] ---- ---- kernel: [ 154.522854] lock(&bdev->bd_mutex); kernel: [ 154.522856] lock(&mddev->reconfig_mutex); kernel: [ 154.522858] lock(&bdev->bd_mutex); kernel: [ 154.522860] lock((wq_completion)md_misc); kernel: [ 154.522861] kernel: [ 154.522861] *** DEADLOCK *** kernel: [ 154.522861] kernel: [ 154.522864] 1 lock held by mdadm/2482: kernel: [ 154.522865] #0: ffff88804efa9338 (&bdev->bd_mutex){+.+.}, at: __blkdev_get+0x79/0x590 kernel: [ 154.522868] kernel: [ 154.522868] stack backtrace: kernel: [ 154.522873] CPU: 1 PID: 2482 Comm: mdadm Tainted: G O 5.6.0-rc7-lp151.27-default #25 kernel: [ 154.522875] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 kernel: [ 154.522878] Call Trace: kernel: [ 154.522881] dump_stack+0x8f/0xcb kernel: [ 154.522884] check_noncircular+0x194/0x1b0 kernel: [ 154.522888] ? __lock_acquire+0x1392/0x1690 kernel: [ 154.522890] __lock_acquire+0x1392/0x1690 kernel: [ 154.522893] lock_acquire+0xb4/0x1a0 kernel: [ 154.522895] ? flush_workqueue+0x84/0x4b0 kernel: [ 154.522898] flush_workqueue+0xab/0x4b0 kernel: [ 154.522900] ? flush_workqueue+0x84/0x4b0 kernel: [ 154.522905] ? md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522908] md_open+0xb6/0xc0 [md_mod] kernel: [ 154.522910] __blkdev_get+0xea/0x590 kernel: [ 154.522912] ? bd_acquire+0xc0/0xc0 kernel: [ 154.522914] blkdev_get+0x65/0x140 kernel: [ 154.522916] ? bd_acquire+0xc0/0xc0 kernel: [ 154.522918] do_dentry_open+0x1d1/0x380 kernel: [ 154.522921] path_openat+0x567/0xcc0 kernel: [ 154.522923] ? __lock_acquire+0x380/0x1690 kernel: [ 154.522926] do_filp_open+0x9b/0x110 kernel: [ 154.522929] ? __alloc_fd+0xe5/0x1f0 kernel: [ 154.522935] ? kmem_cache_alloc+0x28c/0x630 kernel: [ 154.522939] ? do_sys_openat2+0x201/0x2a0 kernel: [ 154.522941] do_sys_openat2+0x201/0x2a0 kernel: [ 154.522944] do_sys_open+0x57/0x80 kernel: [ 154.522946] do_syscall_64+0x64/0x2b0 kernel: [ 154.522948] entry_SYSCALL_64_after_hwframe+0x49/0xbe kernel: [ 154.522951] RIP: 0033:0x7f98d279d9ae And md_alloc also flushed the same workqueue, but the thing is different here. Because all the paths call md_alloc don't hold bdev->bd_mutex, and the flush is necessary to avoid race condition, so leave it as it is. Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu Signed-off-by: Sasha Levin --- drivers/md/md.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index da8708b65356..3485d2a79600 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7101,7 +7101,8 @@ static int md_open(struct block_device *bdev, fmode_t mode) */ mddev_put(mddev); /* Wait until bdev->bd_disk is definitely gone */ - flush_workqueue(md_misc_wq); + if (work_pending(&mddev->del_work)) + flush_workqueue(md_misc_wq); /* Then retry the open from the top */ return -ERESTARTSYS; } -- 2.25.1