syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor/4293 is trying to acquire lock:
ffff888148a4b0e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_run_dev_stats+0xdf/0xdf0 fs/btrfs/volumes.c:7991

but task is already holding lock:
ffff88805dd7c720 (&fs_info->tree_log_mutex){+.+.}-{3:3}, at: btrfs_commit_transaction+0x1168/0x3440 fs/btrfs/transaction.c:2369

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       btrfs_commit_transaction+0x1168/0x3440 fs/btrfs/transaction.c:2369
       sync_filesystem+0x1be/0x220 fs/sync.c:66
       generic_shutdown_super+0x6b/0x300 fs/super.c:448
       kill_anon_super+0x36/0x70 fs/super.c:1089
       btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2390
       deactivate_locked_super+0x93/0xf0 fs/super.c:335
       cleanup_mnt+0x418/0x4d0 fs/namespace.c:1148
       task_work_run+0x125/0x1a0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
       do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #3 (&fs_info->reloc_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       btrfs_record_root_in_trans+0x14b/0x180 fs/btrfs/transaction.c:513
       start_transaction+0x3b0/0x1130 fs/btrfs/transaction.c:750
       btrfs_create+0x103/0x5b0 fs/btrfs/inode.c:6915
       lookup_open fs/namei.c:3470 [inline]
       open_last_lookups fs/namei.c:3540 [inline]
       path_openat+0x11e1/0x2f30 fs/namei.c:3747
       do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
       do_sys_openat2+0x142/0x4a0 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_openat fs/open.c:1287 [inline]
       __se_sys_openat fs/open.c:1282 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1282
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (sb_internal#2){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1811 [inline]
       sb_start_intwrite include/linux/fs.h:1928 [inline]
       start_transaction+0x5bc/0x1130 fs/btrfs/transaction.c:680
       btrfs_create+0x103/0x5b0 fs/btrfs/inode.c:6915
       lookup_open fs/namei.c:3470 [inline]
       open_last_lookups fs/namei.c:3540 [inline]
       path_openat+0x11e1/0x2f30 fs/namei.c:3747
       do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
       do_sys_openat2+0x142/0x4a0 fs/open.c:1255
       do_sys_open fs/open.c:1271 [inline]
       __do_sys_openat fs/open.c:1287 [inline]
       __se_sys_openat fs/open.c:1282 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1282
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&type->i_mutex_dir_key#8){++++}-{3:3}:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:797 [inline]
       lookup_slow+0x46/0x70 fs/namei.c:1687
       walk_component+0x319/0x460 fs/namei.c:1984
       lookup_last fs/namei.c:2439 [inline]
       path_lookupat+0x169/0x440 fs/namei.c:2463
       filename_lookup+0x1e2/0x4f0 fs/namei.c:2492
       kern_path+0x37/0x190 fs/namei.c:2590
       lookup_bdev+0xbd/0x270 block/bdev.c:982
       device_matched fs/btrfs/volumes.c:568 [inline]
       btrfs_free_stale_devices+0x6db/0xa60 fs/btrfs/volumes.c:608
       btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1431
       btrfs_control_ioctl+0x104/0x220 fs/btrfs/super.c:2450
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       btrfs_run_dev_stats+0xdf/0xdf0 fs/btrfs/volumes.c:7991
       commit_cowonly_roots+0x17e/0x9c0 fs/btrfs/transaction.c:1292
       btrfs_commit_transaction+0x1229/0x3440 fs/btrfs/transaction.c:2394
       sync_filesystem+0x1be/0x220 fs/sync.c:66
       generic_shutdown_super+0x6b/0x300 fs/super.c:448
       kill_anon_super+0x36/0x70 fs/super.c:1089
       btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2390
       deactivate_locked_super+0x93/0xf0 fs/super.c:335
       cleanup_mnt+0x418/0x4d0 fs/namespace.c:1148
       task_work_run+0x125/0x1a0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
       do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &fs_devs->device_list_mutex --> &fs_info->reloc_mutex --> &fs_info->tree_log_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&fs_info->tree_log_mutex);
                               lock(&fs_info->reloc_mutex);
                               lock(&fs_info->tree_log_mutex);
  lock(&fs_devs->device_list_mutex);

 *** DEADLOCK ***

3 locks held by syz-executor/4293:
 #0: ffff88807c85e0e0 (&type->s_umount_key#54){+.+.}-{3:3}, at: deactivate_super+0xa0/0xd0 fs/super.c:365
 #1: ffff88805dd7cc90 (&fs_info->reloc_mutex){+.+.}-{3:3}, at: btrfs_commit_transaction+0x10b8/0x3440 fs/btrfs/transaction.c:2319
 #2: ffff88805dd7c720 (&fs_info->tree_log_mutex){+.+.}-{3:3}, at: btrfs_commit_transaction+0x1168/0x3440 fs/btrfs/transaction.c:2369

stack backtrace:
CPU: 1 PID: 4293 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 btrfs_run_dev_stats+0xdf/0xdf0 fs/btrfs/volumes.c:7991
 commit_cowonly_roots+0x17e/0x9c0 fs/btrfs/transaction.c:1292
 btrfs_commit_transaction+0x1229/0x3440 fs/btrfs/transaction.c:2394
 sync_filesystem+0x1be/0x220 fs/sync.c:66
 generic_shutdown_super+0x6b/0x300 fs/super.c:448
 kill_anon_super+0x36/0x70 fs/super.c:1089
 btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2390
 deactivate_locked_super+0x93/0xf0 fs/super.c:335
 cleanup_mnt+0x418/0x4d0 fs/namespace.c:1148
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb2f42c0a77
Code: a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fff04b9f438 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fb2f4343d7d RCX: 00007fb2f42c0a77
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff04b9f4f0
RBP: 00007fff04b9f4f0 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007fff04ba0580
R13: 00007fb2f4343d7d R14: 00000000000106a9 R15: 00007fff04ba05c0
 </TASK>