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Message-ID: <685d1b6d.a00a0220.34b642.00fd.GAE@google.com>
Date: Thu, 26 Jun 2025 03:05:33 -0700
From: syzbot <syzbot+872fc61967352fcc3535@...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_join_transaction (2)
Hello,
syzbot found the following issue on:
HEAD commit: 9aa9b43d689e Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1796cdd4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=27f179c74d5c35cd
dashboard link: https://syzkaller.appspot.com/bug?extid=872fc61967352fcc3535
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
userspace arch: arm64
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/974f3ac1c6a5/disk-9aa9b43d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a5b5075d317f/vmlinux-9aa9b43d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f0ba7fec19b/Image-9aa9b43d.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+872fc61967352fcc3535@...kaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc2-syzkaller-g9aa9b43d689e #0 Not tainted
------------------------------------------------------
syz.2.224/7634 is trying to acquire lock:
ffff0000c6b20618 (sb_internal#3){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
but task is already holding lock:
ffff0000d0c2b7d0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:374 [inline]
ffff0000d0c2b7d0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x180/0x43c mm/util.c:577
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (&mm->mmap_lock){++++}-{4:4}:
down_read_killable+0x60/0x32c kernel/locking/rwsem.c:1547
mmap_read_lock_killable+0x28/0x8c include/linux/mmap_lock.h:421
get_mmap_lock_carefully mm/mmap_lock.c:197 [inline]
lock_mm_and_find_vma+0x2a4/0x2d8 mm/mmap_lock.c:248
do_page_fault+0x51c/0x1554 arch/arm64/mm/fault.c:668
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:783
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:919
el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:455
el1h_64_sync_handler+0x50/0xcc arch/arm64/kernel/entry-common.c:533
el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:595
__uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:169 [inline]
filldir64+0x2ec/0x6bc fs/readdir.c:379
dir_emit include/linux/fs.h:3917 [inline]
kernfs_fop_readdir+0x498/0x79c fs/kernfs/dir.c:1910
iterate_dir+0x458/0x5e0 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:410 [inline]
__se_sys_getdents64 fs/readdir.c:396 [inline]
__arm64_sys_getdents64+0x110/0x2fc fs/readdir.c:396
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
down_write+0x50/0xc0 kernel/locking/rwsem.c:1577
kernfs_add_one+0x48/0x60c fs/kernfs/dir.c:791
kernfs_create_dir_ns+0xd4/0x12c fs/kernfs/dir.c:1093
sysfs_create_dir_ns+0x114/0x24c fs/sysfs/dir.c:59
create_dir lib/kobject.c:73 [inline]
kobject_add_internal+0x5a8/0xb20 lib/kobject.c:240
kobject_add_varg lib/kobject.c:374 [inline]
kobject_init_and_add+0x118/0x17c lib/kobject.c:457
btrfs_sysfs_add_qgroups+0x110/0x268 fs/btrfs/sysfs.c:2635
btrfs_quota_enable+0x224/0x1c70 fs/btrfs/qgroup.c:1030
btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3673
btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5323
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
-> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
__mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799
btrfs_quota_enable+0x270/0x1c70 fs/btrfs/qgroup.c:1059
btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3673
btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5323
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
join_transaction+0x190/0xb5c fs/btrfs/transaction.c:321
start_transaction+0x778/0x155c fs/btrfs/transaction.c:705
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
__cow_file_range_inline+0x140/0xf14 fs/btrfs/inode.c:618
cow_file_range_inline+0x27c/0x338 fs/btrfs/inode.c:690
cow_file_range+0x324/0xc70 fs/btrfs/inode.c:1293
btrfs_run_delalloc_range+0x33c/0xd7c fs/btrfs/inode.c:2348
writepage_delalloc+0x8f0/0x103c fs/btrfs/extent_io.c:1386
extent_writepage fs/btrfs/extent_io.c:1717 [inline]
extent_write_cache_pages fs/btrfs/extent_io.c:2403 [inline]
btrfs_writepages+0x115c/0x20dc fs/btrfs/extent_io.c:2536
do_writepages+0x270/0x468 mm/page-writeback.c:2636
__writeback_single_inode+0x15c/0x13e8 fs/fs-writeback.c:1680
writeback_sb_inodes+0x558/0xe38 fs/fs-writeback.c:1976
wb_writeback+0x3cc/0xd70 fs/fs-writeback.c:2156
wb_do_writeback fs/fs-writeback.c:2303 [inline]
wb_workfn+0x338/0xdc0 fs/fs-writeback.c:2343
process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
process_scheduled_works kernel/workqueue.c:3321 [inline]
worker_thread+0x958/0xed8 kernel/workqueue.c:3402
kthread+0x5fc/0x75c kernel/kthread.c:464
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847
-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
join_transaction+0x164/0xb5c fs/btrfs/transaction.c:320
start_transaction+0x778/0x155c fs/btrfs/transaction.c:705
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
__cow_file_range_inline+0x140/0xf14 fs/btrfs/inode.c:618
cow_file_range_inline+0x27c/0x338 fs/btrfs/inode.c:690
cow_file_range+0x324/0xc70 fs/btrfs/inode.c:1293
btrfs_run_delalloc_range+0x33c/0xd7c fs/btrfs/inode.c:2348
writepage_delalloc+0x8f0/0x103c fs/btrfs/extent_io.c:1386
extent_writepage fs/btrfs/extent_io.c:1717 [inline]
extent_write_cache_pages fs/btrfs/extent_io.c:2403 [inline]
btrfs_writepages+0x115c/0x20dc fs/btrfs/extent_io.c:2536
do_writepages+0x270/0x468 mm/page-writeback.c:2636
__writeback_single_inode+0x15c/0x13e8 fs/fs-writeback.c:1680
writeback_sb_inodes+0x558/0xe38 fs/fs-writeback.c:1976
wb_writeback+0x3cc/0xd70 fs/fs-writeback.c:2156
wb_do_writeback fs/fs-writeback.c:2303 [inline]
wb_workfn+0x338/0xdc0 fs/fs-writeback.c:2343
process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
process_scheduled_works kernel/workqueue.c:3321 [inline]
worker_thread+0x958/0xed8 kernel/workqueue.c:3402
kthread+0x5fc/0x75c kernel/kthread.c:464
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847
-> #0 (sb_internal#3){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5240
lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871
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:1793 [inline]
sb_start_intwrite include/linux/fs.h:1976 [inline]
start_transaction+0x5bc/0x155c fs/btrfs/transaction.c:699
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
btrfs_dirty_inode+0x90/0x190 fs/btrfs/inode.c:6225
btrfs_update_time+0xa0/0xd0 fs/btrfs/inode.c:6259
inode_update_time fs/inode.c:2076 [inline]
touch_atime+0x2e4/0x818 fs/inode.c:2149
file_accessed include/linux/fs.h:2650 [inline]
btrfs_file_mmap+0xac/0x118 fs/btrfs/file.c:1988
call_mmap include/linux/fs.h:2284 [inline]
mmap_file mm/internal.h:167 [inline]
__mmap_new_file_vma mm/vma.c:2405 [inline]
__mmap_new_vma mm/vma.c:2467 [inline]
__mmap_region mm/vma.c:2622 [inline]
mmap_region+0xe9c/0x1c0c mm/vma.c:2692
do_mmap+0x968/0xfac mm/mmap.c:561
vm_mmap_pgoff+0x2b8/0x43c mm/util.c:579
ksys_mmap_pgoff+0x394/0x5b8 mm/mmap.c:607
__do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
__se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
__arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
other info that might help us debug this:
Chain exists of:
sb_internal#3 --> &root->kernfs_rwsem --> &mm->mmap_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_lock);
lock(&root->kernfs_rwsem);
lock(&mm->mmap_lock);
rlock(sb_internal#3);
*** DEADLOCK ***
2 locks held by syz.2.224/7634:
#0: ffff0000d0c2b7d0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:374 [inline]
#0: ffff0000d0c2b7d0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x180/0x43c mm/util.c:577
#1: ffff0000c6b20428 (sb_writers#23){.+.+}-{0:0}, at: file_accessed include/linux/fs.h:2650 [inline]
#1: ffff0000c6b20428 (sb_writers#23){.+.+}-{0:0}, at: btrfs_file_mmap+0xac/0x118 fs/btrfs/file.c:1988
stack backtrace:
CPU: 1 UID: 0 PID: 7634 Comm: syz.2.224 Not tainted 6.16.0-rc2-syzkaller-g9aa9b43d689e #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:501 (C)
__dump_stack+0x30/0x40 lib/dump_stack.c:94
dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
dump_stack+0x1c/0x28 lib/dump_stack.c:129
print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2046
check_noncircular+0x154/0x174 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5240
lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871
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:1793 [inline]
sb_start_intwrite include/linux/fs.h:1976 [inline]
start_transaction+0x5bc/0x155c fs/btrfs/transaction.c:699
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:830
btrfs_dirty_inode+0x90/0x190 fs/btrfs/inode.c:6225
btrfs_update_time+0xa0/0xd0 fs/btrfs/inode.c:6259
inode_update_time fs/inode.c:2076 [inline]
touch_atime+0x2e4/0x818 fs/inode.c:2149
file_accessed include/linux/fs.h:2650 [inline]
btrfs_file_mmap+0xac/0x118 fs/btrfs/file.c:1988
call_mmap include/linux/fs.h:2284 [inline]
mmap_file mm/internal.h:167 [inline]
__mmap_new_file_vma mm/vma.c:2405 [inline]
__mmap_new_vma mm/vma.c:2467 [inline]
__mmap_region mm/vma.c:2622 [inline]
mmap_region+0xe9c/0x1c0c mm/vma.c:2692
do_mmap+0x968/0xfac mm/mmap.c:561
vm_mmap_pgoff+0x2b8/0x43c mm/util.c:579
ksys_mmap_pgoff+0x394/0x5b8 mm/mmap.c:607
__do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
__se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
__arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
---
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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