From nobody Thu Dec 18 23:21:38 2025 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5D9D337D533; Tue, 16 Dec 2025 12:40:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.13 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765888824; cv=none; b=Mk7zJxPZlntwwJj+9PQXXyPYwWwE3fmYGUVMbAaCdmQkVwbhiVOrmyebTDdcRz/NE6Znu6BpFFk1byZuULhrEH77L1+T0TULfLIFlxEAIRF0vpwXrmJassMc/Z2tHOqZXInggoowq8+pm8+oB/04bqfHFq1xIOkcotDQ+DvXCOM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765888824; c=relaxed/simple; bh=e8u+Dwo3cMCSsJ6oOZtIucOvQmIiDiyRdf+xGWR/lJw=; h=Message-ID:Subject:From:To:Cc:Date:Content-Type:MIME-Version; b=I2Su80IO3Hn2w6ZqHsFK9lpUJRE99lC4q2lMUSs+GGhMObG8udeB+ihH3BZXQYMPcgYimVTgGBEYWvin8tIK8kPbTjZiCGyQgmYKS9kILlal3XQ04Gahzu58iDIxXxYOKV12gIE4BfbdOnQIRC85kehPEfSVxuzE9+Q8YqIjNZM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=iQ0sxpzN; arc=none smtp.client-ip=192.198.163.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="iQ0sxpzN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1765888822; x=1797424822; h=message-id:subject:from:to:cc:date: content-transfer-encoding:mime-version; bh=e8u+Dwo3cMCSsJ6oOZtIucOvQmIiDiyRdf+xGWR/lJw=; b=iQ0sxpzNKXQwEtBms2C87yMjpnW39Dv+EdYZYCov1YC0JSQbPR9JRcaP ntSg592CUtw0tKDGCVUL9ZiMXCbzbZ3S88lIjNfpi2qOkh0CO/o2b2Sos gi/3PWlw5g2jH3fvRPNgDSThJ+phhv+IAZLjkUYodki2uKs8QIXMt7izI 1mMLXjTUWUeuWWaCsoHGsIi7RpnC4V8uwIBoRyhAsQAXKzA3LxEEBrYq1 BNseG+U704usv5UP0rqxVIwfKOBUxuKfQ9AQPVueywJ4fv2aKB/3hWQuJ ywdNehQIqYi3AE9iOD24o+7bjTAJSewKIOhQ+s0bmHYKa6jhD9tA3g8Vy w==; X-CSE-ConnectionGUID: c8yW/rfCQkGfzUD90n92yg== X-CSE-MsgGUID: FxO18E/3Q0q6wF0hQ7Tn1Q== X-IronPort-AV: E=McAfee;i="6800,10657,11643"; a="70382212" X-IronPort-AV: E=Sophos;i="6.21,153,1763452800"; d="scan'208";a="70382212" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Dec 2025 04:40:21 -0800 X-CSE-ConnectionGUID: F4SvwwxvR5WtsGiBLLN/2w== X-CSE-MsgGUID: rVmYpJX3S1atGBP6Q8uj2g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,153,1763452800"; d="scan'208";a="198065613" Received: from smoticic-mobl1.ger.corp.intel.com (HELO [10.245.244.249]) ([10.245.244.249]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Dec 2025 04:40:20 -0800 Message-ID: <6e55113a22347c3925458a5d840a18401a38b276.camel@linux.intel.com> Subject: btrfs lockdep splat while paging From: Thomas =?ISO-8859-1?Q?Hellstr=F6m?= To: linux-btrfs@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Chris Mason , David Sterba Date: Tue, 16 Dec 2025 13:40:18 +0100 Organization: Intel Sweden AB, Registration Number: 556189-6027 Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-2.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Hi I've been seing the below lockdep splat [1] for quite some time during paging to disc and since it seems persistent I figure it's a bit hard to trigger and nobody's looking at fixing it. May I also suggest to add the following lockdep priming *iff* the delayed_node->mutex is really intended to be taken during reclaim. This will make a similar lockdep splat turn up much earlier without need to wait for paging: diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c index ce6e9f8812e0..4d76d93957f4 100644 --- a/fs/btrfs/delayed-inode.c +++ b/fs/btrfs/delayed-inode.c @@ -61,6 +61,9 @@ static inline void btrfs_init_delayed_node( delayed_node->ins_root =3D RB_ROOT_CACHED; delayed_node->del_root =3D RB_ROOT_CACHED; mutex_init(&delayed_node->mutex); + fs_reclaim_acquire(GFP_KERNEL); + might_lock(&delayed_node->mutex); + fs_reclaim_release(GFP_KERNEL); INIT_LIST_HEAD(&delayed_node->n_list); INIT_LIST_HEAD(&delayed_node->p_list); } Thanks, Thomas [1]: [27386.164433] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D [27386.164574] WARNING: possible circular locking dependency detected [27386.164583] 6.18.0+ #4 Tainted: G U =20 [27386.164591] ------------------------------------------------------ [27386.164599] kswapd0/117 is trying to acquire lock: [27386.164606] ffff8d9b6333c5b8 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.164625]=20 but task is already holding lock: [27386.164633] ffffffffa4ab8ce0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x195/0xc60 [27386.164646]=20 which lock already depends on the new lock. [27386.164657]=20 the existing dependency chain (in reverse order) is: [27386.164667]=20 -> #2 (fs_reclaim){+.+.}-{0:0}: [27386.164677] fs_reclaim_acquire+0x9d/0xd0 [27386.164685] __kmalloc_cache_noprof+0x59/0x750 [27386.164694] btrfs_init_file_extent_tree+0x90/0x100 [27386.164702] btrfs_read_locked_inode+0xc3/0x6b0 [27386.164710] btrfs_iget+0xbb/0xf0 [27386.164716] btrfs_lookup_dentry+0x3c5/0x8e0 [27386.164724] btrfs_lookup+0x12/0x30 [27386.164731] lookup_open.isra.0+0x1aa/0x6a0 [27386.164739] path_openat+0x5f7/0xc60 [27386.164746] do_filp_open+0xd6/0x180 [27386.164753] do_sys_openat2+0x8b/0xe0 [27386.164760] __x64_sys_openat+0x54/0xa0 [27386.164768] do_syscall_64+0x97/0x3e0 [27386.164776] entry_SYSCALL_64_after_hwframe+0x76/0x7e [27386.164784]=20 -> #1 (btrfs-tree-00){++++}-{3:3}: [27386.164794] lock_release+0x127/0x2a0 [27386.164801] up_read+0x1b/0x30 [27386.164808] btrfs_search_slot+0x8e0/0xff0 [27386.164817] btrfs_lookup_inode+0x52/0xd0 [27386.164825] __btrfs_update_delayed_inode+0x73/0x520 [27386.164833] btrfs_commit_inode_delayed_inode+0x11a/0x120 [27386.164842] btrfs_log_inode+0x608/0x1aa0 [27386.164849] btrfs_log_inode_parent+0x249/0xf80 [27386.164857] btrfs_log_dentry_safe+0x3e/0x60 [27386.164865] btrfs_sync_file+0x431/0x690 [27386.164872] do_fsync+0x39/0x80 [27386.164879] __x64_sys_fsync+0x13/0x20 [27386.164887] do_syscall_64+0x97/0x3e0 [27386.164894] entry_SYSCALL_64_after_hwframe+0x76/0x7e [27386.164903]=20 -> #0 (&delayed_node->mutex){+.+.}-{3:3}: [27386.164913] __lock_acquire+0x15e9/0x2820 [27386.164920] lock_acquire+0xc9/0x2d0 [27386.164927] __mutex_lock+0xcc/0x10a0 [27386.164934] __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.164944] btrfs_evict_inode+0x20b/0x4b0 [27386.164952] evict+0x15a/0x2f0 [27386.164958] prune_icache_sb+0x91/0xd0 [27386.164966] super_cache_scan+0x150/0x1d0 [27386.164974] do_shrink_slab+0x155/0x6f0 [27386.164981] shrink_slab+0x48e/0x890 [27386.164988] shrink_one+0x11a/0x1f0 [27386.164995] shrink_node+0xbfd/0x1320 [27386.165002] balance_pgdat+0x67f/0xc60 [27386.165321] kswapd+0x1dc/0x3e0 [27386.165643] kthread+0xff/0x240 [27386.165965] ret_from_fork+0x223/0x280 [27386.166287] ret_from_fork_asm+0x1a/0x30 [27386.166616]=20 other info that might help us debug this: [27386.167561] Chain exists of: &delayed_node->mutex --> btrfs-tree-00 --> fs_reclaim [27386.168503] Possible unsafe locking scenario: [27386.169110] CPU0 CPU1 [27386.169411] ---- ---- [27386.169707] lock(fs_reclaim); [27386.169998] lock(btrfs-tree-00); [27386.170291] lock(fs_reclaim); [27386.170581] lock(&delayed_node->mutex); [27386.170874]=20 *** DEADLOCK *** [27386.171716] 2 locks held by kswapd0/117: [27386.171999] #0: ffffffffa4ab8ce0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x195/0xc60 [27386.172294] #1: ffff8d998344b0e0 (&type->s_umount_key#40){++++}- {3:3}, at: super_cache_scan+0x37/0x1d0 [27386.172596]=20 stack backtrace: [27386.173183] CPU: 11 UID: 0 PID: 117 Comm: kswapd0 Tainted: G U=20 6.18.0+ #4 PREEMPT(lazy)=20 [27386.173185] Tainted: [U]=3DUSER [27386.173186] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 2001 02/01/2023 [27386.173187] Call Trace: [27386.173187] [27386.173189] dump_stack_lvl+0x6e/0xa0 [27386.173192] print_circular_bug.cold+0x17a/0x1c0 [27386.173194] check_noncircular+0x175/0x190 [27386.173197] __lock_acquire+0x15e9/0x2820 [27386.173200] lock_acquire+0xc9/0x2d0 [27386.173201] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.173204] __mutex_lock+0xcc/0x10a0 [27386.173206] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.173208] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.173211] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.173213] __btrfs_release_delayed_node.part.0+0x39/0x2f0 [27386.173215] btrfs_evict_inode+0x20b/0x4b0 [27386.173217] ? lock_acquire+0xc9/0x2d0 [27386.173220] evict+0x15a/0x2f0 [27386.173222] prune_icache_sb+0x91/0xd0 [27386.173224] super_cache_scan+0x150/0x1d0 [27386.173226] do_shrink_slab+0x155/0x6f0 [27386.173228] shrink_slab+0x48e/0x890 [27386.173229] ? shrink_slab+0x2d2/0x890 [27386.173231] shrink_one+0x11a/0x1f0 [27386.173234] shrink_node+0xbfd/0x1320 [27386.173236] ? shrink_node+0xa2d/0x1320 [27386.173236] ? shrink_node+0xbd3/0x1320 [27386.173239] ? balance_pgdat+0x67f/0xc60 [27386.173239] balance_pgdat+0x67f/0xc60 [27386.173241] ? finish_task_switch.isra.0+0xc4/0x2a0 [27386.173246] kswapd+0x1dc/0x3e0 [27386.173247] ? __pfx_autoremove_wake_function+0x10/0x10 [27386.173249] ? __pfx_kswapd+0x10/0x10 [27386.173250] kthread+0xff/0x240 [27386.173251] ? __pfx_kthread+0x10/0x10 [27386.173253] ret_from_fork+0x223/0x280 [27386.173255] ? __pfx_kthread+0x10/0x10 [27386.173257] ret_from_fork_asm+0x1a/0x30 [27386.173260]