From patchwork Mon Sep 21 16:27:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 309470 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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 68271C43469 for ; Mon, 21 Sep 2020 16:38:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E7F62399C for ; Mon, 21 Sep 2020 16:38:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706306; bh=bW0EaXRL4JdEPEJ5iKs6YM/ztqLoKsKmydV899itcz4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=otSwi2m8+3hgHTlsh/f3nvdQguggPTZlMBD71/kLPDJGGRnjtRaaba5UoysQ2U2TC nVqtEjcIUiC8HrGpw+SW+vl0SgqecUHoyzdCS5HRLBcsLa38nyw/i7ZOla9wwd+kdZ U5eQ1cqpmGzC06XXcKXJPrCODt6LsAbLTJ2KJvm4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729141AbgIUQiK (ORCPT ); Mon, 21 Sep 2020 12:38:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:39048 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729138AbgIUQiK (ORCPT ); Mon, 21 Sep 2020 12:38:10 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AD416238E6; Mon, 21 Sep 2020 16:38:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706289; bh=bW0EaXRL4JdEPEJ5iKs6YM/ztqLoKsKmydV899itcz4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UIYc9sTi6RMy/98sCCEgXj14f7mkqYdI2PYfNL2s4KQRdb1TWcic5plAjam4cIcnk 6sa0HUwY/y5pix3X6wYsASSBX3vzr7Ec6Q5h3tk7wEoeIRzdEwZtEbiF2EK58YNdNS zRcQIk7I000Az8C6esMTRBtjAn0/4YCOyMwaaiiQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nikolay Borisov , Anand Jain , Josef Bacik , David Sterba Subject: [PATCH 4.14 40/94] btrfs: fix lockdep splat in add_missing_dev Date: Mon, 21 Sep 2020 18:27:27 +0200 Message-Id: <20200921162037.384206634@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200921162035.541285330@linuxfoundation.org> References: <20200921162035.541285330@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Josef Bacik commit fccc0007b8dc952c6bc0805cdf842eb8ea06a639 upstream. Nikolay reported a lockdep splat in generic/476 that I could reproduce with btrfs/187. ====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc2+ #1 Tainted: G W ------------------------------------------------------ kswapd0/100 is trying to acquire lock: ffff9e8ef38b6268 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x3f/0x330 but task is already holding lock: ffffffffa9d74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire+0x65/0x80 slab_pre_alloc_hook.constprop.0+0x20/0x200 kmem_cache_alloc_trace+0x3a/0x1a0 btrfs_alloc_device+0x43/0x210 add_missing_dev+0x20/0x90 read_one_chunk+0x301/0x430 btrfs_read_sys_array+0x17b/0x1b0 open_ctree+0xa62/0x1896 btrfs_mount_root.cold+0x12/0xea legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 vfs_kern_mount.part.0+0x71/0xb0 btrfs_mount+0x10d/0x379 legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 path_mount+0x434/0xc00 __x64_sys_mount+0xe3/0x120 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&fs_info->chunk_mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7e0 btrfs_chunk_alloc+0x125/0x3a0 find_free_extent+0xdf6/0x1210 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb0/0x310 alloc_tree_block_no_bg_flush+0x4a/0x60 __btrfs_cow_block+0x11a/0x530 btrfs_cow_block+0x104/0x220 btrfs_search_slot+0x52e/0x9d0 btrfs_lookup_inode+0x2a/0x8f __btrfs_update_delayed_inode+0x80/0x240 btrfs_commit_inode_delayed_inode+0x119/0x120 btrfs_evict_inode+0x357/0x500 evict+0xcf/0x1f0 vfs_rmdir.part.0+0x149/0x160 do_rmdir+0x136/0x1a0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&delayed_node->mutex){+.+.}-{3:3}: __lock_acquire+0x1184/0x1fa0 lock_acquire+0xa4/0x3d0 __mutex_lock+0x7e/0x7e0 __btrfs_release_delayed_node.part.0+0x3f/0x330 btrfs_evict_inode+0x24c/0x500 evict+0xcf/0x1f0 dispose_list+0x48/0x70 prune_icache_sb+0x44/0x50 super_cache_scan+0x161/0x1e0 do_shrink_slab+0x178/0x3c0 shrink_slab+0x17c/0x290 shrink_node+0x2b2/0x6d0 balance_pgdat+0x30a/0x670 kswapd+0x213/0x4c0 kthread+0x138/0x160 ret_from_fork+0x1f/0x30 other info that might help us debug this: Chain exists of: &delayed_node->mutex --> &fs_info->chunk_mutex --> fs_reclaim Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&fs_info->chunk_mutex); lock(fs_reclaim); lock(&delayed_node->mutex); *** DEADLOCK *** 3 locks held by kswapd0/100: #0: ffffffffa9d74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 #1: ffffffffa9d65c50 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x115/0x290 #2: ffff9e8e9da260e0 (&type->s_umount_key#48){++++}-{3:3}, at: super_cache_scan+0x38/0x1e0 stack backtrace: CPU: 1 PID: 100 Comm: kswapd0 Tainted: G W 5.9.0-rc2+ #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x92/0xc8 check_noncircular+0x12d/0x150 __lock_acquire+0x1184/0x1fa0 lock_acquire+0xa4/0x3d0 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 __mutex_lock+0x7e/0x7e0 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 ? __btrfs_release_delayed_node.part.0+0x3f/0x330 ? lock_acquire+0xa4/0x3d0 ? btrfs_evict_inode+0x11e/0x500 ? find_held_lock+0x2b/0x80 __btrfs_release_delayed_node.part.0+0x3f/0x330 btrfs_evict_inode+0x24c/0x500 evict+0xcf/0x1f0 dispose_list+0x48/0x70 prune_icache_sb+0x44/0x50 super_cache_scan+0x161/0x1e0 do_shrink_slab+0x178/0x3c0 shrink_slab+0x17c/0x290 shrink_node+0x2b2/0x6d0 balance_pgdat+0x30a/0x670 kswapd+0x213/0x4c0 ? _raw_spin_unlock_irqrestore+0x46/0x60 ? add_wait_queue_exclusive+0x70/0x70 ? balance_pgdat+0x670/0x670 kthread+0x138/0x160 ? kthread_create_worker_on_cpu+0x40/0x40 ret_from_fork+0x1f/0x30 This is because we are holding the chunk_mutex when we call btrfs_alloc_device, which does a GFP_KERNEL allocation. We don't want to switch that to a GFP_NOFS lock because this is the only place where it matters. So instead use memalloc_nofs_save() around the allocation in order to avoid the lockdep splat. Reported-by: Nikolay Borisov CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Anand Jain Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/volumes.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -16,6 +16,7 @@ * Boston, MA 021110-1307, USA. */ #include +#include #include #include #include @@ -6278,8 +6279,17 @@ static struct btrfs_device *add_missing_ u64 devid, u8 *dev_uuid) { struct btrfs_device *device; + unsigned int nofs_flag; + /* + * We call this under the chunk_mutex, so we want to use NOFS for this + * allocation, however we don't want to change btrfs_alloc_device() to + * always do NOFS because we use it in a lot of other GFP_KERNEL safe + * places. + */ + nofs_flag = memalloc_nofs_save(); device = btrfs_alloc_device(NULL, &devid, dev_uuid); + memalloc_nofs_restore(nofs_flag); if (IS_ERR(device)) return NULL;