From nobody Tue Dec 16 11:49:25 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 912D52F6583 for ; Tue, 14 Oct 2025 11:47:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760442462; cv=none; b=je70gRnceSEHABO5T6Mis7EI9nKoEi+iI8hLdrUtIXh8DmHk9N/USlWS+WhzYlZ7MrbZl3Ex67Zlslqz5ZnKWJolxi2UH8VdFoQBoNF6KWlGgcUIe9mfCwUGjWaI5N8iKl6Lj2gnCEbXsNYVgkXo9NwwgwP6FEOkqShRYLjLuPo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760442462; c=relaxed/simple; bh=j+g5Eqjx0MTwUbgaKhhj1vRq4cBecflGOLWMsOYorwQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=loUW6jQDp6RDdCNjG3NeXgixwO/A6JrD8hBmRuRdX9f0xUkg0Iu/VXtw+oB4r4sAwgvEFsP98yOQm6g3vrwDndKa7MTXUvzXkUZp/Bvz1vlxVIt+4BpzhnfYgHmDy2zAbiH/CO7lhqb8iEs1ARbgV+Sdewvh6CXg3lNy45m4Y5Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pfQRHsVl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pfQRHsVl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 974A5C4CEE7; Tue, 14 Oct 2025 11:47:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760442462; bh=j+g5Eqjx0MTwUbgaKhhj1vRq4cBecflGOLWMsOYorwQ=; h=From:To:Cc:Subject:Date:From; b=pfQRHsVlEdAfotQL8PbTVDwkCzk5lXak3c4QP7+q1t1M+sP0RX3jm/Vr7Nfz2Jeff czAjLAL4cqo4+RFkjZuxRFzZx16wxrPd8WcBTvO53wDdSw+UmpNN2D01s9l2tF8AwS V3g15OWr3APajnKEimIBWLQ1WoV8oLcQrWWDgPzzDjA7+sBdggQcGwNI6q63/X3NKc 9tGO3AC5NpBSk2PtOOGA8lDfzXROqsBUxPxfb/LAj/drqmA3y7IoiHZ2FCKDktrEd1 g4XdCPjdrrMg+pLY1IAn4P4DYMEJjuiNOcmk6lA54VsIZbSGFV4dnjPS1Fro6jjqPF peFjqwedbnwdw== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , stable@kernel.org, syzbot+14b90e1156b9f6fc1266@syzkaller.appspotmail.com, Jiaming Zhang Subject: [PATCH] f2fs: fix to avoid potential deadlock Date: Tue, 14 Oct 2025 19:47:35 +0800 Message-ID: <20251014114735.1840965-1-chao@kernel.org> X-Mailer: git-send-email 2.51.0.760.g7b8bcc2412-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As Jiaming Zhang and syzbot reported, there is potential deadlock in f2fs as below: Chain exists of: &sbi->cp_rwsem --> fs_reclaim --> sb_internal#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(sb_internal#2); lock(fs_reclaim); lock(sb_internal#2); rlock(&sbi->cp_rwsem); *** DEADLOCK *** 3 locks held by kswapd0/73: #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan= .c:7015 [inline] #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/= vmscan.c:7389 #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_trylo= ck_shared fs/super.c:562 [inline] #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_cache= _scan+0x91/0x4b0 fs/super.c:197 #2: ffff888011840610 (sb_internal#2){.+.+}-{0:0}, at: f2fs_evict_inode+0x8= d9/0x1b60 fs/f2fs/inode.c:890 stack backtrace: CPU: 0 UID: 0 PID: 73 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16= .3-2~bpo12+1 04/01/2014 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1537 f2fs_down_read fs/f2fs/f2fs.h:2278 [inline] f2fs_lock_op fs/f2fs/f2fs.h:2357 [inline] f2fs_do_truncate_blocks+0x21c/0x10c0 fs/f2fs/file.c:791 f2fs_truncate_blocks+0x10a/0x300 fs/f2fs/file.c:867 f2fs_truncate+0x489/0x7c0 fs/f2fs/file.c:925 f2fs_evict_inode+0x9f2/0x1b60 fs/f2fs/inode.c:897 evict+0x504/0x9c0 fs/inode.c:810 f2fs_evict_inode+0x1dc/0x1b60 fs/f2fs/inode.c:853 evict+0x504/0x9c0 fs/inode.c:810 dispose_list fs/inode.c:852 [inline] prune_icache_sb+0x21b/0x2c0 fs/inode.c:1000 super_cache_scan+0x39b/0x4b0 fs/super.c:224 do_shrink_slab+0x6ef/0x1110 mm/shrinker.c:437 shrink_slab_memcg mm/shrinker.c:550 [inline] shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628 shrink_one+0x28a/0x7c0 mm/vmscan.c:4955 shrink_many mm/vmscan.c:5016 [inline] lru_gen_shrink_node mm/vmscan.c:5094 [inline] shrink_node+0x315d/0x3780 mm/vmscan.c:6081 kswapd_shrink_node mm/vmscan.c:6941 [inline] balance_pgdat mm/vmscan.c:7124 [inline] kswapd+0x147c/0x2800 mm/vmscan.c:7389 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 The root cause is deadlock among four locks as below: kswapd - fs_reclaim --- Lock A - shrink_one - evict - f2fs_evict_inode - sb_start_intwrite --- Lock B - iput - evict - f2fs_evict_inode - sb_start_intwrite --- Lock B - f2fs_truncate - f2fs_truncate_blocks - f2fs_do_truncate_blocks - f2fs_lock_op --- Lock C ioctl - f2fs_ioc_commit_atomic_write - f2fs_lock_op --- Lock C - __f2fs_commit_atomic_write - __replace_atomic_write_block - f2fs_get_dnode_of_data - __get_node_folio - f2fs_check_nid_range - f2fs_handle_error - f2fs_record_errors - f2fs_down_write --- Lock D open - do_open - do_truncate - security_inode_need_killpriv - f2fs_getxattr - lookup_all_xattrs - f2fs_handle_error - f2fs_record_errors - f2fs_down_write --- Lock D - f2fs_commit_super - read_mapping_folio - filemap_alloc_folio_noprof - prepare_alloc_pages - fs_reclaim_acquire --- Lock A In order to avoid such deadlock, we need to avoid grabbing sb_lock in f2fs_handle_error(), so, let's use asynchronous method instead: - remove f2fs_handle_error() implementation - rename f2fs_handle_error_async() to f2fs_handle_error() - spread f2fs_handle_error() Fixes: 95fa90c9e5a7 ("f2fs: support recording errors into superblock") Cc: stable@kernel.org Reported-by: syzbot+14b90e1156b9f6fc1266@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-f2fs-devel/68eae49b.050a0220.ac43.000= 1.GAE@google.com Reported-by: Jiaming Zhang Closes: https://lore.kernel.org/lkml/CANypQFa-Gy9sD-N35o3PC+FystOWkNuN8pv6S= 75HLT0ga-Tzgw@mail.gmail.com Signed-off-by: Chao Yu --- Please notice that this patch is base on below patch: f2fs: fix to do sanity check on node footer in {read,write}_end_io fs/f2fs/compress.c | 5 +---- fs/f2fs/f2fs.h | 1 - fs/f2fs/node.c | 6 ++---- fs/f2fs/super.c | 41 ----------------------------------------- 4 files changed, 3 insertions(+), 50 deletions(-) diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c index 6ad8d3bc6df7..811bfe38e5c0 100644 --- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -759,10 +759,7 @@ void f2fs_decompress_cluster(struct decompress_io_ctx = *dic, bool in_task) ret =3D -EFSCORRUPTED; =20 /* Avoid f2fs_commit_super in irq context */ - if (!in_task) - f2fs_handle_error_async(sbi, ERROR_FAIL_DECOMPRESSION); - else - f2fs_handle_error(sbi, ERROR_FAIL_DECOMPRESSION); + f2fs_handle_error(sbi, ERROR_FAIL_DECOMPRESSION); goto out_release; } =20 diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index c589aed069d9..c3e968787d7e 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -3815,7 +3815,6 @@ void f2fs_quota_off_umount(struct super_block *sb); void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag); void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char re= ason); void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error); -void f2fs_handle_error_async(struct f2fs_sb_info *sbi, unsigned char error= ); int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover); int f2fs_sync_fs(struct super_block *sb, int sync); int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi); diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index e70c970a3047..ce471e033774 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -1550,10 +1550,8 @@ int f2fs_sanity_check_node_footer(struct f2fs_sb_inf= o *sbi, ntype, nid, nid_of_node(folio), ino_of_node(folio), ofs_of_node(folio), cpver_of_node(folio), next_blkaddr_of_node(folio)); - if (in_irq) - f2fs_handle_error_async(sbi, ERROR_INCONSISTENT_FOOTER); - else - f2fs_handle_error(sbi, ERROR_INCONSISTENT_FOOTER); + + f2fs_handle_error(sbi, ERROR_INCONSISTENT_FOOTER); return -EFSCORRUPTED; } =20 diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 2ae341768a39..1dd4a93ba4bb 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -4544,48 +4544,7 @@ void f2fs_save_errors(struct f2fs_sb_info *sbi, unsi= gned char flag) spin_unlock_irqrestore(&sbi->error_lock, flags); } =20 -static bool f2fs_update_errors(struct f2fs_sb_info *sbi) -{ - unsigned long flags; - bool need_update =3D false; - - spin_lock_irqsave(&sbi->error_lock, flags); - if (sbi->error_dirty) { - memcpy(F2FS_RAW_SUPER(sbi)->s_errors, sbi->errors, - MAX_F2FS_ERRORS); - sbi->error_dirty =3D false; - need_update =3D true; - } - spin_unlock_irqrestore(&sbi->error_lock, flags); - - return need_update; -} - -static void f2fs_record_errors(struct f2fs_sb_info *sbi, unsigned char err= or) -{ - int err; - - f2fs_down_write(&sbi->sb_lock); - - if (!f2fs_update_errors(sbi)) - goto out_unlock; - - err =3D f2fs_commit_super(sbi, false); - if (err) - f2fs_err_ratelimited(sbi, - "f2fs_commit_super fails to record errors:%u, err:%d", - error, err); -out_unlock: - f2fs_up_write(&sbi->sb_lock); -} - void f2fs_handle_error(struct f2fs_sb_info *sbi, unsigned char error) -{ - f2fs_save_errors(sbi, error); - f2fs_record_errors(sbi, error); -} - -void f2fs_handle_error_async(struct f2fs_sb_info *sbi, unsigned char error) { f2fs_save_errors(sbi, error); =20 --=20 2.49.0