[syzbot] [btrfs?] possible deadlock in btrfs_finish_one_ordered (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c1f49dea2b8f Merge tag 'mm-hotfixes-stable-2026-04-19-00-1..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12a7d4ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2b4ac2aaea441e9b
dashboard link: https://syzkaller.appspot.com/bug?extid=639b46ea64e2a7c2b93d
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/305242213735/disk-c1f49dea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1da8423852f9/vmlinux-c1f49dea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d8bb8e7b4ae2/bzImage-c1f49dea.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+639b46...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
kworker/u8:12/27491 is trying to acquire lock:
ffff888077978600 (sb_internal#2){.+.+}-{0:0}, at: btrfs_finish_one_ordered+0x88e/0x2680 fs/btrfs/inode.c:3254

but task is already holding lock:
ffff88803966a758 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x39c/0x2680 fs/btrfs/inode.c:3216

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (btrfs_ordered_extent){++++}-{0:0}:
btrfs_start_ordered_extent_nowriteback+0x390/0x700 fs/btrfs/ordered-data.c:890
btrfs_start_ordered_extent fs/btrfs/ordered-data.h:203 [inline]
btrfs_wait_ordered_range+0x154/0x260 fs/btrfs/ordered-data.c:942
btrfs_sync_file+0x78a/0x1200 fs/btrfs/file.c:1662
generic_write_sync include/linux/fs.h:2654 [inline]
btrfs_do_write_iter+0x6a3/0x840 fs/btrfs/file.c:1468
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:688
ksys_write+0x150/0x270 fs/read_write.c:740
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (&ei->i_mmap_lock){++++}-{4:4}:
down_read+0x47/0x2e0 kernel/locking/rwsem.c:1568
btrfs_page_mkwrite+0x636/0x1a60 fs/btrfs/file.c:1918
do_page_mkwrite+0x14d/0x310 mm/memory.c:3668
wp_page_shared mm/memory.c:4069 [inline]
do_wp_page+0x19ba/0x4cc0 mm/memory.c:4288
handle_pte_fault mm/memory.c:6427 [inline]
__handle_mm_fault mm/memory.c:6549 [inline]
handle_mm_fault+0x151d/0x3170 mm/memory.c:6718
do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

-> #6 (sb_pagefaults#3){.+.+}-{0:0}:
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs/super.h:19 [inline]
sb_start_pagefault include/linux/fs/super.h:159 [inline]
btrfs_page_mkwrite+0x351/0x1a60 fs/btrfs/file.c:1873
do_page_mkwrite+0x14d/0x310 mm/memory.c:3668
wp_page_shared mm/memory.c:4069 [inline]
do_wp_page+0x19ba/0x4cc0 mm/memory.c:4288
handle_pte_fault mm/memory.c:6427 [inline]
__handle_mm_fault mm/memory.c:6549 [inline]
handle_mm_fault+0x151d/0x3170 mm/memory.c:6718
do_user_addr_fault+0x75b/0x1340 arch/x86/mm/fault.c:1385
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
_inline_copy_to_user include/linux/uaccess.h:206 [inline]
_copy_to_user+0x85/0xb0 lib/usercopy.c:26
copy_to_user include/linux/uaccess.h:236 [inline]
do_pipe2+0xd4/0x190 fs/pipe.c:1040
__do_sys_pipe fs/pipe.c:1061 [inline]
__se_sys_pipe fs/pipe.c:1059 [inline]
__x64_sys_pipe+0x3a/0x50 fs/pipe.c:1059
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&mm->mmap_lock){++++}-{4:4}:
down_write_killable+0xa6/0x240 kernel/locking/rwsem.c:1637
mmap_write_lock_killable include/linux/mmap_lock.h:554 [inline]
upgrade_mmap_lock_carefully+0xba/0x1b0 mm/mmap_lock.c:474
lock_mm_and_find_vma+0x12b/0x340 mm/mmap_lock.c:527
do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
filldir64+0x2b2/0x640 fs/readdir.c:368
dir_emit include/linux/fs.h:3578 [inline]
offset_dir_emit fs/libfs.c:499 [inline]
offset_iterate_dir fs/libfs.c:515 [inline]
offset_readdir+0x3fc/0x530 fs/libfs.c:564
iterate_dir+0x399/0x570 fs/readdir.c:110
__do_sys_getdents64 fs/readdir.c:399 [inline]
__se_sys_getdents64+0xf1/0x280 fs/readdir.c:384
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&type->i_mutex_dir_key#5){++++}-{4:4}:
down_read+0x47/0x2e0 kernel/locking/rwsem.c:1568
inode_lock_shared include/linux/fs.h:1044 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1931
walk_component fs/namei.c:2278 [inline]
lookup_last fs/namei.c:2785 [inline]
path_lookupat+0x3f5/0x8c0 fs/namei.c:2809
filename_lookup+0x256/0x5d0 fs/namei.c:2838
kern_path+0x3d/0x150 fs/namei.c:3044
is_same_device fs/btrfs/volumes.c:764 [inline]
device_list_add+0xfd1/0x2280 fs/btrfs/volumes.c:898
btrfs_scan_one_device+0x3ef/0x680 fs/btrfs/volumes.c:1499
btrfs_get_tree_super fs/btrfs/super.c:1858 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2087 [inline]
btrfs_get_tree+0x4ab/0x1910 fs/btrfs/super.c:2121
vfs_get_tree+0x92/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3758 [inline]
do_new_mount+0x341/0xd30 fs/namespace.c:3834
do_mount fs/namespace.c:4167 [inline]
__do_sys_mount fs/namespace.c:4383 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4360
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:632 [inline]
__mutex_lock+0x1a3/0x1550 kernel/locking/mutex.c:806
insert_dev_extents fs/btrfs/block-group.c:2876 [inline]
btrfs_create_pending_block_groups+0x77b/0x1b40 fs/btrfs/block-group.c:2927
__btrfs_end_transaction+0x140/0x650 fs/btrfs/transaction.c:1091
flush_space+0x406/0xe20 fs/btrfs/space-info.c:912
do_async_reclaim_data_space+0x145/0x520 fs/btrfs/space-info.c:1448
btrfs_async_reclaim_data_space+0x41/0x90 fs/btrfs/space-info.c:1512
process_one_work kernel/workqueue.c:3302 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
join_transaction+0x192/0xe40 fs/btrfs/transaction.c:324
start_transaction+0xbef/0x1820 fs/btrfs/transaction.c:719
btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6441
touch_atime+0x2f8/0x6b0 fs/inode.c:2265
file_accessed include/linux/fs.h:2264 [inline]
filemap_read+0x1053/0x1230 mm/filemap.c:2878
__kernel_read+0x504/0x9b0 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
ima_calc_file_hash+0x446/0x860 security/integrity/ima/ima_crypto.c:280
ima_collect_measurement+0x51d/0x9c0 security/integrity/ima/ima_api.c:300
process_measurement+0x12cd/0x1c80 security/integrity/ima/ima_main.c:425
ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
security_file_post_open+0xb3/0x260 security/security.c:2755
do_open fs/namei.c:4701 [inline]
path_openat+0x2e4d/0x3860 fs/namei.c:4858
do_file_open+0x23e/0x4a0 fs/namei.c:4887
do_sys_openat2+0x113/0x200 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1381
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
join_transaction+0x171/0xe40 fs/btrfs/transaction.c:323
start_transaction+0xbef/0x1820 fs/btrfs/transaction.c:719
btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6441
touch_atime+0x2f8/0x6b0 fs/inode.c:2265
file_accessed include/linux/fs.h:2264 [inline]
filemap_read+0x1053/0x1230 mm/filemap.c:2878
__kernel_read+0x504/0x9b0 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
ima_calc_file_hash+0x446/0x860 security/integrity/ima/ima_crypto.c:280
ima_collect_measurement+0x51d/0x9c0 security/integrity/ima/ima_api.c:300
process_measurement+0x12cd/0x1c80 security/integrity/ima/ima_main.c:425
ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
security_file_post_open+0xb3/0x260 security/security.c:2755
do_open fs/namei.c:4701 [inline]
path_openat+0x2e4d/0x3860 fs/namei.c:4858
do_file_open+0x23e/0x4a0 fs/namei.c:4887
do_sys_openat2+0x113/0x200 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1381
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal#2){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs/super.h:19 [inline]
sb_start_intwrite include/linux/fs/super.h:177 [inline]
start_transaction+0xaa9/0x1820 fs/btrfs/transaction.c:713
btrfs_finish_one_ordered+0x88e/0x2680 fs/btrfs/inode.c:3254
btrfs_work_helper+0x37b/0xc20 fs/btrfs/async-thread.c:312
process_one_work kernel/workqueue.c:3302 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
sb_internal#2 --> &ei->i_mmap_lock --> btrfs_ordered_extent

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(btrfs_ordered_extent);
lock(&ei->i_mmap_lock);
lock(btrfs_ordered_extent);
rlock(sb_internal#2);

*** DEADLOCK ***

3 locks held by kworker/u8:12/27491:
#0: ffff88807c47f940 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3277 [inline]
#0: ffff88807c47f940 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3385
#1: ffffc90006627c40 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3278 [inline]
#1: ffffc90006627c40 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3385
#2: ffff88803966a758 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x39c/0x2680 fs/btrfs/inode.c:3216

stack backtrace:
CPU: 1 UID: 0 PID: 27491 Comm: kworker/u8:12 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: btrfs-endio-write btrfs_work_helper
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 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 kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs/super.h:19 [inline]
sb_start_intwrite include/linux/fs/super.h:177 [inline]
start_transaction+0xaa9/0x1820 fs/btrfs/transaction.c:713
btrfs_finish_one_ordered+0x88e/0x2680 fs/btrfs/inode.c:3254
btrfs_work_helper+0x37b/0xc20 fs/btrfs/async-thread.c:312
process_one_work kernel/workqueue.c:3302 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


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