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Message-ID: <68fb03b4.050a0220.346f24.0091.GAE@google.com>
Date: Thu, 23 Oct 2025 21:42:28 -0700
From: syzbot <syzbot+473ef2d15099286c23bb@...kaller.appspotmail.com>
To: clm@...com, dsterba@...e.com, josef@...icpanda.com,
linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: [syzbot] [btrfs?] possible deadlock in btrfs_finish_one_ordered (2)
Hello,
syzbot found the following issue on:
HEAD commit: d9043c79ba68 Merge tag 'sched_urgent_for_v6.18_rc2' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c36b04580000
kernel config: https://syzkaller.appspot.com/x/.config?x=af9170887d81dea1
dashboard link: https://syzkaller.appspot.com/bug?extid=473ef2d15099286c23bb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4cfd59a0fd17/disk-d9043c79.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6a2cad21d523/vmlinux-d9043c79.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a466aca5efb9/bzImage-d9043c79.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+473ef2d15099286c23bb@...kaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u8:0/12 is trying to acquire lock:
ffff88803cfb8770 (sb_internal#3){.+.+}-{0:0}, at: btrfs_finish_one_ordered+0x7b0/0x21a0 fs/btrfs/inode.c:3143
but task is already holding lock:
ffff88805da8afc0 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x30b/0x21a0 fs/btrfs/inode.c:3105
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (btrfs_ordered_extent){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
btrfs_start_ordered_extent_nowriteback+0x39c/0x6e0 fs/btrfs/ordered-data.c:896
btrfs_start_ordered_extent fs/btrfs/ordered-data.h:199 [inline]
btrfs_page_mkwrite+0x84d/0x1a80 fs/btrfs/file.c:1946
do_page_mkwrite+0x150/0x310 mm/memory.c:3488
wp_page_shared mm/memory.c:3889 [inline]
do_wp_page+0x25c8/0x4930 mm/memory.c:4108
handle_pte_fault mm/memory.c:6193 [inline]
__handle_mm_fault mm/memory.c:6318 [inline]
handle_mm_fault+0x97c/0x3400 mm/memory.c:6487
do_user_addr_fault+0xa7c/0x1380 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
-> #6 (sb_pagefaults#2){.+.+}-{0:0}:
lock_acquire+0x120/0x360 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.h:1916 [inline]
sb_start_pagefault include/linux/fs.h:2081 [inline]
btrfs_page_mkwrite+0x32c/0x1a80 fs/btrfs/file.c:1874
do_page_mkwrite+0x150/0x310 mm/memory.c:3488
do_shared_fault mm/memory.c:5774 [inline]
do_fault mm/memory.c:5836 [inline]
do_pte_missing mm/memory.c:4361 [inline]
handle_pte_fault mm/memory.c:6177 [inline]
__handle_mm_fault mm/memory.c:6318 [inline]
handle_mm_fault+0x124b/0x3400 mm/memory.c:6487
do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
-> #5 (&mm->mmap_lock){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377
get_mmap_lock_carefully mm/mmap_lock.c:377 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:428
do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
user_access_begin arch/x86/include/asm/uaccess.h:-1 [inline]
filldir+0x29c/0x6c0 fs/readdir.c:290
dir_emit include/linux/fs.h:3986 [inline]
kernfs_fop_readdir+0x53a/0x870 fs/kernfs/dir.c:1910
iterate_dir+0x3a5/0x580 fs/readdir.c:108
__do_sys_getdents fs/readdir.c:326 [inline]
__se_sys_getdents+0xe4/0x250 fs/readdir.c:312
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x3a/0x50 kernel/locking/rwsem.c:1590
kernfs_add_one+0x41/0x520 fs/kernfs/dir.c:791
kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1093
sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59
create_dir lib/kobject.c:73 [inline]
kobject_add_internal+0x5a5/0xb50 lib/kobject.c:240
kobject_add_varg lib/kobject.c:374 [inline]
kobject_init_and_add+0x125/0x190 lib/kobject.c:457
btrfs_sysfs_add_qgroups+0x111/0x2b0 fs/btrfs/sysfs.c:2645
btrfs_quota_enable+0x25d/0x2920 fs/btrfs/qgroup.c:1022
btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
__mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline]
mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:547
btrfs_quota_enable+0x29c/0x2920 fs/btrfs/qgroup.c:1051
btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
join_transaction+0x1a4/0xca0 fs/btrfs/transaction.c:321
start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705
btrfs_quota_enable+0x28f/0x2920 fs/btrfs/qgroup.c:1049
btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
join_transaction+0x182/0xca0 fs/btrfs/transaction.c:320
start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705
btrfs_quota_enable+0x28f/0x2920 fs/btrfs/qgroup.c:1049
btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3667
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (sb_internal#3){.+.+}-{0:0}:
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
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.h:1916 [inline]
sb_start_intwrite include/linux/fs.h:2099 [inline]
start_transaction+0x56e/0x1620 fs/btrfs/transaction.c:699
btrfs_finish_one_ordered+0x7b0/0x21a0 fs/btrfs/inode.c:3143
btrfs_work_helper+0x39b/0xc00 fs/btrfs/async-thread.c:312
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
kthread+0x711/0x8a0 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
other info that might help us debug this:
Chain exists of:
sb_internal#3 --> sb_pagefaults#2 --> btrfs_ordered_extent
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(btrfs_ordered_extent);
lock(sb_pagefaults#2);
lock(btrfs_ordered_extent);
rlock(sb_internal#3);
*** DEADLOCK ***
3 locks held by kworker/u8:0/12:
#0: ffff88803dc68138 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
#0: ffff88803dc68138 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
#1: ffffc90000117ba0 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
#1: ffffc90000117ba0 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
#2: ffff88805da8afc0 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x30b/0x21a0 fs/btrfs/inode.c:3105
stack backtrace:
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: btrfs-endio-write btrfs_work_helper
Call Trace:
<TASK>
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
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.h:1916 [inline]
sb_start_intwrite include/linux/fs.h:2099 [inline]
start_transaction+0x56e/0x1620 fs/btrfs/transaction.c:699
btrfs_finish_one_ordered+0x7b0/0x21a0 fs/btrfs/inode.c:3143
btrfs_work_helper+0x39b/0xc00 fs/btrfs/async-thread.c:312
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
kthread+0x711/0x8a0 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
</TASK>
bridge0: port 2(bridge_slave_1) entered blocking state
bridge0: port 2(bridge_slave_1) entered forwarding state
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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