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Message-ID: <68a79a4e.050a0220.13802c.0002.GAE@google.com>
Date: Thu, 21 Aug 2025 15:14:38 -0700
From: syzbot <syzbot+7c044bb36ac38f98889f@...kaller.appspotmail.com>
To: kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [bcachefs?] possible deadlock in trans_set_locked (2)
Hello,
syzbot found the following issue on:
HEAD commit: 8f5ae30d69d7 Linux 6.17-rc1
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=160daba2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
dashboard link: https://syzkaller.appspot.com/bug?extid=7c044bb36ac38f98889f
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7c044bb36ac38f98889f@...kaller.appspotmail.com
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
======================================================
WARNING: possible circular locking dependency detected
6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 Not tainted
------------------------------------------------------
syz.2.330/8664 is trying to acquire lock:
ffff000102c481b0 (bcachefs_btree){+.+.}-{0:0}, at: trans_set_locked+0x68/0x200 fs/bcachefs/btree_locking.h:205
but task is already holding lock:
ffff0000f6b182e8 (mapping.invalidate_lock#7){.+.+}-{4:4}, at: filemap_invalidate_lock_shared include/linux/fs.h:934 [inline]
ffff0000f6b182e8 (mapping.invalidate_lock#7){.+.+}-{4:4}, at: filemap_fault+0x3fc/0x1280 mm/filemap.c:3433
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (mapping.invalidate_lock#7){.+.+}-{4:4}:
down_read+0x58/0x2f8 kernel/locking/rwsem.c:1537
filemap_invalidate_lock_shared include/linux/fs.h:934 [inline]
filemap_fault+0x3fc/0x1280 mm/filemap.c:3433
bch2_page_fault+0x2cc/0x700 fs/bcachefs/fs-io-pagecache.c:594
__do_fault+0x1fc/0x4cc mm/memory.c:5152
do_read_fault mm/memory.c:5573 [inline]
do_fault mm/memory.c:5707 [inline]
do_pte_missing mm/memory.c:4234 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0x2c90/0x4d34 mm/memory.c:6364
do_page_fault+0x57c/0x13cc arch/arm64/mm/fault.c:696
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:789
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
el0_da+0x64/0x164 arch/arm64/kernel/entry-common.c:697
el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:901
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
-> #2 (&mm->mmap_lock){++++}-{4:4}:
__might_fault+0xc4/0x124 mm/memory.c:6958
_inline_copy_to_user include/linux/uaccess.h:192 [inline]
copy_to_user include/linux/uaccess.h:223 [inline]
copy_to_user_errcode fs/bcachefs/util.h:701 [inline]
bch2_ioctl_read_super fs/bcachefs/chardev.c:611 [inline]
bch2_fs_ioctl+0xb3c/0x13e0 fs/bcachefs/chardev.c:718
bch2_fs_file_ioctl+0x4dc/0x1964 fs/bcachefs/fs-ioctl.c:411
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584
__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+0x58/0x180 arch/arm64/kernel/entry-common.c:879
el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
-> #1 (&c->sb_lock){+.+.}-{4:4}:
__mutex_lock_common+0x1d0/0x24ac kernel/locking/mutex.c:598
__mutex_lock kernel/locking/mutex.c:760 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812
__bch2_trans_mark_dev_sb fs/bcachefs/buckets.c:1129 [inline]
bch2_trans_mark_dev_sb+0xd8/0x67c fs/bcachefs/buckets.c:1176
bch2_trans_mark_dev_sbs_flags+0x414/0x47c fs/bcachefs/buckets.c:1186
bch2_mark_superblocks fs/bcachefs/btree_gc.c:805 [inline]
bch2_check_allocations+0x52c/0x3c34 fs/bcachefs/btree_gc.c:1089
bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
__bch2_run_recovery_passes+0x2b8/0xd54 fs/bcachefs/recovery_passes.c:539
bch2_run_recovery_passes+0x174/0x1f4 fs/bcachefs/recovery_passes.c:610
bch2_fs_recovery+0x1c34/0x2fb4 fs/bcachefs/recovery.c:1016
bch2_fs_start+0x940/0xbec fs/bcachefs/super.c:1213
bch2_fs_get_tree+0x880/0x107c fs/bcachefs/fs.c:2488
vfs_get_tree+0x90/0x28c fs/super.c:1815
do_new_mount+0x278/0x7f4 fs/namespace.c:3805
path_mount+0x5b4/0xde0 fs/namespace.c:4120
do_mount fs/namespace.c:4133 [inline]
__do_sys_mount fs/namespace.c:4344 [inline]
__se_sys_mount fs/namespace.c:4321 [inline]
__arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4321
__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+0x58/0x180 arch/arm64/kernel/entry-common.c:879
el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
-> #0 (bcachefs_btree){+.+.}-{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+0x1774/0x30a4 kernel/locking/lockdep.c:5237
lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868
trans_set_locked+0x94/0x200 fs/bcachefs/btree_locking.h:206
bch2_trans_begin+0x800/0xd30 fs/bcachefs/btree_iter.c:3403
bch2_read_err_msg_trans+0x64/0x298 fs/bcachefs/io_read.c:374
__bch2_read_extent+0x25f0/0x3638 fs/bcachefs/io_read.c:1070
bch2_read_extent fs/bcachefs/io_read.h:147 [inline]
bchfs_read+0x107c/0x17e8 fs/bcachefs/fs-io-buffered.c:226
bch2_read_single_folio+0x498/0x6e4 fs/bcachefs/fs-io-buffered.c:360
bch2_read_folio+0x40/0x84 fs/bcachefs/fs-io-buffered.c:378
filemap_read_folio+0xec/0x2f8 mm/filemap.c:2413
filemap_fault+0xd48/0x1280 mm/filemap.c:3537
bch2_page_fault+0x2cc/0x700 fs/bcachefs/fs-io-pagecache.c:594
__do_fault+0x1fc/0x4cc mm/memory.c:5152
do_read_fault mm/memory.c:5573 [inline]
do_fault mm/memory.c:5707 [inline]
do_pte_missing mm/memory.c:4234 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0x2c90/0x4d34 mm/memory.c:6364
do_page_fault+0x8a0/0x13cc arch/arm64/mm/fault.c:696
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:789
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
el0_da+0x64/0x164 arch/arm64/kernel/entry-common.c:697
el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:901
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
other info that might help us debug this:
Chain exists of:
bcachefs_btree --> &mm->mmap_lock --> mapping.invalidate_lock#7
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(mapping.invalidate_lock#7);
lock(&mm->mmap_lock);
lock(mapping.invalidate_lock#7);
lock(bcachefs_btree);
*** DEADLOCK ***
2 locks held by syz.2.330/8664:
#0: ffff0000c2c65e50 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:472 [inline]
#0: ffff0000c2c65e50 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:277 [inline]
#0: ffff0000c2c65e50 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x38/0x2d8 mm/mmap_lock.c:337
#1: ffff0000f6b182e8 (mapping.invalidate_lock#7){.+.+}-{4:4}, at: filemap_invalidate_lock_shared include/linux/fs.h:934 [inline]
#1: ffff0000f6b182e8 (mapping.invalidate_lock#7){.+.+}-{4:4}, at: filemap_fault+0x3fc/0x1280 mm/filemap.c:3433
stack backtrace:
CPU: 0 UID: 0 PID: 8664 Comm: syz.2.330 Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (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:2043
check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5237
lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868
trans_set_locked+0x94/0x200 fs/bcachefs/btree_locking.h:206
bch2_trans_begin+0x800/0xd30 fs/bcachefs/btree_iter.c:3403
bch2_read_err_msg_trans+0x64/0x298 fs/bcachefs/io_read.c:374
__bch2_read_extent+0x25f0/0x3638 fs/bcachefs/io_read.c:1070
bch2_read_extent fs/bcachefs/io_read.h:147 [inline]
bchfs_read+0x107c/0x17e8 fs/bcachefs/fs-io-buffered.c:226
bch2_read_single_folio+0x498/0x6e4 fs/bcachefs/fs-io-buffered.c:360
bch2_read_folio+0x40/0x84 fs/bcachefs/fs-io-buffered.c:378
filemap_read_folio+0xec/0x2f8 mm/filemap.c:2413
filemap_fault+0xd48/0x1280 mm/filemap.c:3537
bch2_page_fault+0x2cc/0x700 fs/bcachefs/fs-io-pagecache.c:594
__do_fault+0x1fc/0x4cc mm/memory.c:5152
do_read_fault mm/memory.c:5573 [inline]
do_fault mm/memory.c:5707 [inline]
do_pte_missing mm/memory.c:4234 [inline]
handle_pte_fault mm/memory.c:6052 [inline]
__handle_mm_fault mm/memory.c:6195 [inline]
handle_mm_fault+0x2c90/0x4d34 mm/memory.c:6364
do_page_fault+0x8a0/0x13cc arch/arm64/mm/fault.c:696
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:789
do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929
el0_da+0x64/0x164 arch/arm64/kernel/entry-common.c:697
el0t_64_sync_handler+0x90/0x12c arch/arm64/kernel/entry-common.c:901
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
bcachefs (loop2): /file3 offset 0: no_devices_valid
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
bcachefs (loop2): /file3 offset 0: no_devices_valid
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
bcachefs (loop2): /file3 offset 0: no_devices_valid
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
bcachefs (loop2): /file3 offset 0: no_devices_valid
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
bcachefs (loop2): /file3 offset 0: no_devices_valid
u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 0 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0 compress lz4 ptr: 237:893353206280 gen 0
---
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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