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=-13.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 30A75C433E7 for ; Tue, 1 Sep 2020 21:40:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05A05207EA for ; Tue, 1 Sep 2020 21:40:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=toxicpanda-com.20150623.gappssmtp.com header.i=@toxicpanda-com.20150623.gappssmtp.com header.b="xLsOUcXh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729656AbgIAVkv (ORCPT ); Tue, 1 Sep 2020 17:40:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729624AbgIAVko (ORCPT ); Tue, 1 Sep 2020 17:40:44 -0400 Received: from mail-qk1-x744.google.com (mail-qk1-x744.google.com [IPv6:2607:f8b0:4864:20::744]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85389C061245 for ; Tue, 1 Sep 2020 14:40:44 -0700 (PDT) Received: by mail-qk1-x744.google.com with SMTP id o64so2468917qkb.10 for ; Tue, 01 Sep 2020 14:40:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=X3icFpv4MZ7BFuk/N7WqVemM3OsYZe1RmrGTB7OHI0k=; b=xLsOUcXhAXuM/ON3H1eaj5+zYdD9dEhpNU9iTmGGKCJ6vjICbzvKGQ0Pbyy0WJhVvN PiIMTC/rfolNmnDN+HcSTmFil34f+wuDpbpLWHROs5yljjtg3UoRquD2MgdehNC3gmqv VcyB9/PEstLskwJRJcEr/miT+qymiWjorFJ5WEVPhfVxm4I1ElcIaQgLOcDeHD8wg4N3 JK8cqDQZ4wl1u/X7ety+SiP+0Aeb8/Jk06Dpo/cc9wI72umogKatKN/fgE/sIrO9GS2c S9Bug1UmAVKhrsp8kymHPVbFkP8y/xlAzcVS6sblJ5O2i+x4U7sfUgJpCubvmmAsoJro GtMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=X3icFpv4MZ7BFuk/N7WqVemM3OsYZe1RmrGTB7OHI0k=; b=rqS48YuRJI8Xc168Gt1X6ctpquP9boAHH3SgAlmODA0tQqB9/hk5R8Mzej8xnBB+Q9 JHJ3WtfH42wKbnn91EshSMMGiABslyxxVr26cFcJPNzI51U48jfT0NaTWAvuw4/9Rnit /dOAMUWe6jX2cLUuAqPj/L2MyUZkvj7jCELej2m4Pf4iJQrgWFmOLRvIta6LvicToBlK QTeZQCMww8PoJIJe52EHbWZ9etXVMgThuNXMgP6e8BdqEXwuZLbSIkamwe9d4nIL3Y/s KPHE1LiyEwuByCHmM13XoJVslgAeUuI86F/crVN39pxvOG/w8cVEYTeDnWa9NweoQ/n/ +x3g== X-Gm-Message-State: AOAM531/JrQeHEpgctU/ejXxWnm/J4d2s9cynXyNu3zzBx9Ap+Dq02Va yncowP7XY5hOkdEh1b4663yQvysr+YVdvG88 X-Google-Smtp-Source: ABdhPJyjBRRFoCH/5f8qH63VFs20xGHtkDB1pu6CLiMBbcdA1H04mETw5bB/vnr3+a1dHDpbwNnIEg== X-Received: by 2002:a37:e508:: with SMTP id e8mr3843765qkg.380.1598996443198; Tue, 01 Sep 2020 14:40:43 -0700 (PDT) Received: from localhost (cpe-174-109-172-136.nc.res.rr.com. [174.109.172.136]) by smtp.gmail.com with ESMTPSA id y18sm3025699qkf.93.2020.09.01.14.40.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2020 14:40:42 -0700 (PDT) From: Josef Bacik To: linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: [PATCH 2/4] btrfs: init sysfs for devices outside of the chunk_mutex Date: Tue, 1 Sep 2020 17:40:36 -0400 Message-Id: <5dccee8f9d7fe7b5072090327854fcbfdbd45b28.1598996236.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org While running btrfs/187 I hit the following lockdep splat ====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc3+ #4 Not tainted ------------------------------------------------------ kswapd0/100 is trying to acquire lock: ffff96ecc22ef4a0 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x3f/0x330 but task is already holding lock: ffffffff8dd74700 (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: -> #3 (fs_reclaim){+.+.}-{0:0}: fs_reclaim_acquire+0x65/0x80 slab_pre_alloc_hook.constprop.0+0x20/0x200 kmem_cache_alloc+0x37/0x270 alloc_inode+0x82/0xb0 iget_locked+0x10d/0x2c0 kernfs_get_inode+0x1b/0x130 kernfs_get_tree+0x136/0x240 sysfs_get_tree+0x16/0x40 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 -> #2 (kernfs_mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7e0 kernfs_add_one+0x23/0x150 kernfs_create_link+0x63/0xa0 sysfs_do_create_link_sd+0x5e/0xd0 btrfs_sysfs_add_devices_dir+0x81/0x130 btrfs_init_new_device+0x67f/0x1250 btrfs_ioctl+0x1ef/0x2e20 __x64_sys_ioctl+0x83/0xb0 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_insert_empty_items+0x64/0xb0 btrfs_insert_delayed_items+0x90/0x4f0 btrfs_commit_inode_delayed_items+0x93/0x140 btrfs_log_inode+0x5de/0x2020 btrfs_log_inode_parent+0x429/0xc90 btrfs_log_new_name+0x95/0x9b btrfs_rename2+0xbb9/0x1800 vfs_rename+0x64f/0x9f0 do_renameat2+0x320/0x4e0 __x64_sys_rename+0x1f/0x30 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&delayed_node->mutex){+.+.}-{3:3}: __lock_acquire+0x119c/0x1fc0 lock_acquire+0xa7/0x3d0 __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 --> kernfs_mutex --> fs_reclaim Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(kernfs_mutex); lock(fs_reclaim); lock(&delayed_node->mutex); *** DEADLOCK *** 3 locks held by kswapd0/100: #0: ffffffff8dd74700 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 #1: ffffffff8dd65c50 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x115/0x290 #2: ffff96ed2ade30e0 (&type->s_umount_key#36){++++}-{3:3}, at: super_cache_scan+0x38/0x1e0 stack backtrace: CPU: 0 PID: 100 Comm: kswapd0 Not tainted 5.9.0-rc3+ #4 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x8b/0xb8 check_noncircular+0x12d/0x150 __lock_acquire+0x119c/0x1fc0 lock_acquire+0xa7/0x3d0 ? __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+0xa7/0x3d0 ? 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+0x41/0x50 ? 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 happens because we are holding the chunk_mutex at the time of adding in a new device. However we only need to hold the device_list_mutex, as we're going to iterate over the fs_devices devices. Move the sysfs init stuff outside of the chunk_mutex to get rid of this lockdep splat. Signed-off-by: Josef Bacik --- fs/btrfs/volumes.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index d6bbbe1986bb..77b7da42c651 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2599,9 +2599,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path btrfs_set_super_num_devices(fs_info->super_copy, orig_super_num_devices + 1); - /* add sysfs device entry */ - btrfs_sysfs_add_devices_dir(fs_devices, device); - /* * we've got more storage, clear any full flags on the space * infos @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path btrfs_clear_space_info_full(fs_info); mutex_unlock(&fs_info->chunk_mutex); + + /* add sysfs device entry */ + btrfs_sysfs_add_devices_dir(fs_devices, device); + mutex_unlock(&fs_devices->device_list_mutex); if (seeding_dev) { -- 2.26.2