[v6.1] possible deadlock in btrfs_join_transaction (4)
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syzbot
Jun 14, 2026, 2:43:25 PM (7 days ago) Jun 14
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 228da13e907e Linux 6.1.175
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1735c3b6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=29caf4bae4b0566f
dashboard link: https://syzkaller.appspot.com/bug?extid=8d1fbb49d58ce1fcca78
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf27a408696a/disk-228da13e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/264d4943ab43/vmlinux-228da13e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a499b0d2a133/Image-228da13e.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8d1fbb...@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.1037/8437 is trying to acquire lock:
ffff0000eaa48650 (sb_internal#3){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
but task is already holding lock:
ffff0000eaa48558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (sb_pagefaults#4){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_pagefault include/linux/fs.h:1995 [inline]
btrfs_page_mkwrite+0x198/0xb88 fs/btrfs/inode.c:8613
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #6 (&mm->mmap_lock){++++}-{3:3}:
__might_fault+0xc4/0x124 mm/memory.c:5850
filldir64+0x2cc/0x8fc fs/readdir.c:335
dir_emit_dot include/linux/fs.h:3698 [inline]
dir_emit_dots include/linux/fs.h:3709 [inline]
dcache_readdir+0x140/0x62c fs/libfs.c:197
iterate_dir+0x1f0/0x4cc fs/readdir.c:-1
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x11c/0x320 fs/readdir.c:354
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #5 (&type->i_mutex_dir_key#2){++++}-{3:3}:
down_read+0x64/0x300 kernel/locking/rwsem.c:1520
inode_lock_shared include/linux/fs.h:768 [inline]
lookup_slow+0x4c/0x80 fs/namei.c:1714
walk_component+0x270/0x364 fs/namei.c:2006
lookup_last fs/namei.c:2463 [inline]
path_lookupat+0x13c/0x3d0 fs/namei.c:2487
filename_lookup+0x1c4/0x480 fs/namei.c:2516
kern_path+0x48/0x6c fs/namei.c:2614
is_same_device fs/btrfs/volumes.c:695 [inline]
device_list_add+0x129c/0x1c84 fs/btrfs/volumes.c:928
btrfs_scan_one_device+0x368/0x57c fs/btrfs/volumes.c:1461
btrfs_mount_root+0x45c/0x7d0 fs/btrfs/super.c:1796
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #4 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
btrfs_run_dev_stats+0xf8/0xdc8 fs/btrfs/volumes.c:8071
commit_cowonly_roots+0x170/0x71c fs/btrfs/transaction.c:1298
btrfs_commit_transaction+0x10e8/0x2884 fs/btrfs/transaction.c:2444
btrfs_rebuild_free_space_tree+0x2e8/0x6d8 fs/btrfs/free-space-tree.c:1347
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #3 (&fs_info->reloc_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
btrfs_record_root_in_trans fs/btrfs/transaction.c:488 [inline]
start_transaction+0x434/0x1050 fs/btrfs/transaction.c:731
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_create_common+0x148/0x240 fs/btrfs/inode.c:6812
btrfs_create+0x104/0x128 fs/btrfs/inode.c:6858
lookup_open fs/namei.c:3490 [inline]
open_last_lookups fs/namei.c:3558 [inline]
path_openat+0xe18/0x26bc fs/namei.c:3788
do_filp_open+0x194/0x384 fs/namei.c:3818
do_sys_openat2+0x134/0x3f4 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__arm64_sys_openat+0x118/0x14c fs/open.c:1347
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
join_transaction+0x180/0xb68 fs/btrfs/transaction.c:303
start_transaction+0x858/0x1050 fs/btrfs/transaction.c:668
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_rebuild_free_space_tree+0xbc/0x6d8 fs/btrfs/free-space-tree.c:1320
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
join_transaction+0x154/0xb68 fs/btrfs/transaction.c:302
start_transaction+0x858/0x1050 fs/btrfs/transaction.c:668
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_rebuild_free_space_tree+0xbc/0x6d8 fs/btrfs/free-space-tree.c:1320
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #0 (sb_internal#3){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_intwrite include/linux/fs.h:2013 [inline]
start_transaction+0x5c4/0x1050 fs/btrfs/transaction.c:662
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6285
btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6327
inode_update_time fs/inode.c:1958 [inline]
__file_update_time+0xc0/0x21c fs/inode.c:2147
file_update_time+0x270/0x2ec fs/inode.c:2178
btrfs_page_mkwrite+0x39c/0xb88 fs/btrfs/inode.c:8629
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
other info that might help us debug this:
Chain exists of:
sb_internal#3 --> &mm->mmap_lock --> sb_pagefaults#4
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sb_pagefaults#4);
lock(&mm->mmap_lock);
lock(sb_pagefaults#4);
lock(sb_internal#3);
*** DEADLOCK ***
2 locks held by syz.8.1037/8437:
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5320 [inline]
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2e0 mm/memory.c:5382
#1: ffff0000eaa48558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
stack backtrace:
CPU: 0 PID: 8437 Comm: syz.8.1037 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
Call trace:
dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
dump_stack+0x1c/0x5c lib/dump_stack.c:113
print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_intwrite include/linux/fs.h:2013 [inline]
start_transaction+0x5c4/0x1050 fs/btrfs/transaction.c:662
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6285
btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6327
inode_update_time fs/inode.c:1958 [inline]
__file_update_time+0xc0/0x21c fs/inode.c:2147
file_update_time+0x270/0x2ec fs/inode.c:2178
btrfs_page_mkwrite+0x39c/0xb88 fs/btrfs/inode.c:8629
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
---
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syzbot found the following issue on:
HEAD commit: 228da13e907e Linux 6.1.175
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1735c3b6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=29caf4bae4b0566f
dashboard link: https://syzkaller.appspot.com/bug?extid=8d1fbb49d58ce1fcca78
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf27a408696a/disk-228da13e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/264d4943ab43/vmlinux-228da13e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a499b0d2a133/Image-228da13e.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8d1fbb...@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.1037/8437 is trying to acquire lock:
ffff0000eaa48650 (sb_internal#3){.+.+}-{0:0}, at: btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
but task is already holding lock:
ffff0000eaa48558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (sb_pagefaults#4){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_pagefault include/linux/fs.h:1995 [inline]
btrfs_page_mkwrite+0x198/0xb88 fs/btrfs/inode.c:8613
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #6 (&mm->mmap_lock){++++}-{3:3}:
__might_fault+0xc4/0x124 mm/memory.c:5850
filldir64+0x2cc/0x8fc fs/readdir.c:335
dir_emit_dot include/linux/fs.h:3698 [inline]
dir_emit_dots include/linux/fs.h:3709 [inline]
dcache_readdir+0x140/0x62c fs/libfs.c:197
iterate_dir+0x1f0/0x4cc fs/readdir.c:-1
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x11c/0x320 fs/readdir.c:354
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #5 (&type->i_mutex_dir_key#2){++++}-{3:3}:
down_read+0x64/0x300 kernel/locking/rwsem.c:1520
inode_lock_shared include/linux/fs.h:768 [inline]
lookup_slow+0x4c/0x80 fs/namei.c:1714
walk_component+0x270/0x364 fs/namei.c:2006
lookup_last fs/namei.c:2463 [inline]
path_lookupat+0x13c/0x3d0 fs/namei.c:2487
filename_lookup+0x1c4/0x480 fs/namei.c:2516
kern_path+0x48/0x6c fs/namei.c:2614
is_same_device fs/btrfs/volumes.c:695 [inline]
device_list_add+0x129c/0x1c84 fs/btrfs/volumes.c:928
btrfs_scan_one_device+0x368/0x57c fs/btrfs/volumes.c:1461
btrfs_mount_root+0x45c/0x7d0 fs/btrfs/super.c:1796
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #4 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
btrfs_run_dev_stats+0xf8/0xdc8 fs/btrfs/volumes.c:8071
commit_cowonly_roots+0x170/0x71c fs/btrfs/transaction.c:1298
btrfs_commit_transaction+0x10e8/0x2884 fs/btrfs/transaction.c:2444
btrfs_rebuild_free_space_tree+0x2e8/0x6d8 fs/btrfs/free-space-tree.c:1347
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #3 (&fs_info->reloc_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
btrfs_record_root_in_trans fs/btrfs/transaction.c:488 [inline]
start_transaction+0x434/0x1050 fs/btrfs/transaction.c:731
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_create_common+0x148/0x240 fs/btrfs/inode.c:6812
btrfs_create+0x104/0x128 fs/btrfs/inode.c:6858
lookup_open fs/namei.c:3490 [inline]
open_last_lookups fs/namei.c:3558 [inline]
path_openat+0xe18/0x26bc fs/namei.c:3788
do_filp_open+0x194/0x384 fs/namei.c:3818
do_sys_openat2+0x134/0x3f4 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__arm64_sys_openat+0x118/0x14c fs/open.c:1347
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
join_transaction+0x180/0xb68 fs/btrfs/transaction.c:303
start_transaction+0x858/0x1050 fs/btrfs/transaction.c:668
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_rebuild_free_space_tree+0xbc/0x6d8 fs/btrfs/free-space-tree.c:1320
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
join_transaction+0x154/0xb68 fs/btrfs/transaction.c:302
start_transaction+0x858/0x1050 fs/btrfs/transaction.c:668
btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:767
btrfs_rebuild_free_space_tree+0xbc/0x6d8 fs/btrfs/free-space-tree.c:1320
btrfs_start_pre_rw_mount+0x2c8/0x658 fs/btrfs/disk-io.c:3215
open_ctree+0x1e44/0x2604 fs/btrfs/disk-io.c:3812
btrfs_fill_super+0x1b4/0x2d4 fs/btrfs/super.c:1469
btrfs_mount_root+0x780/0x7d0 fs/btrfs/super.c:1834
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
fc_mount fs/namespace.c:1048 [inline]
vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078
btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3078
path_mount+0x5bc/0xe80 fs/namespace.c:3408
do_mount fs/namespace.c:3421 [inline]
__do_sys_mount fs/namespace.c:3629 [inline]
__se_sys_mount fs/namespace.c:3606 [inline]
__arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
-> #0 (sb_internal#3){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_intwrite include/linux/fs.h:2013 [inline]
start_transaction+0x5c4/0x1050 fs/btrfs/transaction.c:662
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6285
btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6327
inode_update_time fs/inode.c:1958 [inline]
__file_update_time+0xc0/0x21c fs/inode.c:2147
file_update_time+0x270/0x2ec fs/inode.c:2178
btrfs_page_mkwrite+0x39c/0xb88 fs/btrfs/inode.c:8629
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
other info that might help us debug this:
Chain exists of:
sb_internal#3 --> &mm->mmap_lock --> sb_pagefaults#4
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sb_pagefaults#4);
lock(&mm->mmap_lock);
lock(sb_pagefaults#4);
lock(sb_internal#3);
*** DEADLOCK ***
2 locks held by syz.8.1037/8437:
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5320 [inline]
#0: ffff0000cd2d3d48 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2e0 mm/memory.c:5382
#1: ffff0000eaa48558 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
stack backtrace:
CPU: 0 PID: 8437 Comm: syz.8.1037 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026
Call trace:
dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
dump_stack+0x1c/0x5c lib/dump_stack.c:113
print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_intwrite include/linux/fs.h:2013 [inline]
start_transaction+0x5c4/0x1050 fs/btrfs/transaction.c:662
btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781
btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6285
btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6327
inode_update_time fs/inode.c:1958 [inline]
__file_update_time+0xc0/0x21c fs/inode.c:2147
file_update_time+0x270/0x2ec fs/inode.c:2178
btrfs_page_mkwrite+0x39c/0xb88 fs/btrfs/inode.c:8629
do_page_mkwrite+0x13c/0x358 mm/memory.c:3009
wp_page_shared+0x148/0x540 mm/memory.c:3358
do_wp_page+0xca0/0xeec mm/memory.c:3508
handle_pte_fault mm/memory.c:5047 [inline]
__handle_mm_fault mm/memory.c:5171 [inline]
handle_mm_fault+0x1514/0x2fb0 mm/memory.c:5292
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x310/0x98c arch/arm64/mm/fault.c:583
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:804
el0_da+0x70/0x144 arch/arm64/kernel/entry-common.c:515
el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
---
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