[syzbot] [btrfs?] WARNING in btrfs_add_to_free_space_tree

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 44fc84337b6e Merge tag 'arm64-upstream' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ca94c2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e613d5a6bd72b912
dashboard link: https://syzkaller.appspot.com/bug?extid=fa6623c288cdedf3f41c
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 (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-44fc8433.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/62d35c4f6e28/vmlinux-44fc8433.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b8d61aa183d4/bzImage-44fc8433.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fa6623...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
BTRFS: device fsid c9fe44da-de57-406a-8241-57ec7d4412cf devid 1 transid 8 /dev/loop0 (7:0) scanned by syz.0.0 (5338)
BTRFS info (device loop0): first mount of filesystem c9fe44da-de57-406a-8241-57ec7d4412cf
BTRFS info (device loop0): using crc32c (crc32c-lib) checksum algorithm
BTRFS info (device loop0): setting nodatasum
BTRFS info (device loop0): allowing degraded mounts
BTRFS info (device loop0): disabling tree log
BTRFS info (device loop0): turning on async discard
BTRFS info (device loop0): enabling free space tree
BTRFS info (device loop0): balance: start -d -m
BTRFS info (device loop0): relocating block group 6881280 flags data|metadata
BTRFS info (device loop0): relocating block group 5242880 flags data|metadata
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: fs/btrfs/free-space-tree.c:1051 at 0x0, CPU#0: syz.0.0/5338
Modules linked in:
CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:btrfs_add_to_free_space_tree+0x4ad/0x580 fs/btrfs/free-space-tree.c:1051
Code: f7 cf fd e9 bd 00 00 00 e8 40 e7 b5 fd 84 c0 74 23 e8 17 f7 cf fd e9 aa 00 00 00 e8 0d f7 cf fd 48 8d 3d a6 5d 98 0b 44 89 e6 <67> 48 0f b9 3a e9 27 fd ff ff e8 c4 50 57 07 41 89 c6 31 ff 89 c6
RSP: 0018:ffffc9000d4deed0 EFLAGS: 00010287
RAX: ffffffff83f11723 RBX: ffff888000b5c800 RCX: 0000000000100000
RDX: ffffc90020001000 RSI: 00000000ffffffe4 RDI: ffffffff8f8974d0
RBP: ffff888019e099a0 R08: ffff888033ad0000 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000002 R12: 00000000ffffffe4
R13: 0000000000000000 R14: ffff888051710001 R15: 1ffff110033c1334
FS: 00007f3ba2c276c0(0000) GS:ffff88808d6b7000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555574ecd7c8 CR3: 00000000123e7000 CR4: 0000000000352ef0
Call Trace:
<TASK>
do_free_extent_accounting fs/btrfs/extent-tree.c:3003 [inline]
__btrfs_free_extent+0x12f8/0x3f80 fs/btrfs/extent-tree.c:3372
run_delayed_tree_ref fs/btrfs/extent-tree.c:1749 [inline]
run_one_delayed_ref fs/btrfs/extent-tree.c:1775 [inline]
btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:1972 [inline]
__btrfs_run_delayed_refs+0xe38/0x40c0 fs/btrfs/extent-tree.c:2047
btrfs_run_delayed_refs+0xe6/0x3a0 fs/btrfs/extent-tree.c:2159
btrfs_commit_transaction+0x269/0x3950 fs/btrfs/transaction.c:2211
prepare_to_relocate+0x39f/0x490 fs/btrfs/relocation.c:3489
relocate_block_group+0x132/0xd70 fs/btrfs/relocation.c:3514
btrfs_relocate_block_group+0x6bc/0xc60 fs/btrfs/relocation.c:3983
btrfs_relocate_chunk+0x12f/0x5c0 fs/btrfs/volumes.c:3448
__btrfs_balance+0x1860/0x23f0 fs/btrfs/volumes.c:4224
btrfs_balance+0xac2/0x11b0 fs/btrfs/volumes.c:4601
btrfs_ioctl_balance+0x3d3/0x610 fs/btrfs/ioctl.c:3560
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3ba1d8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3ba2c27038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f3ba1fe5fa0 RCX: 00007f3ba1d8f7c9
RDX: 0000200000000180 RSI: 00000000c4009420 RDI: 0000000000000006
RBP: 00007f3ba1e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3ba1fe6038 R14: 00007f3ba1fe5fa0 R15: 00007ffd7cf29928
</TASK>
----------------
Code disassembly (best guess):
0: f7 cf fd e9 bd 00 test $0xbde9fd,%edi
6: 00 00 add %al,(%rax)
8: e8 40 e7 b5 fd call 0xfdb5e74d
d: 84 c0 test %al,%al
f: 74 23 je 0x34
11: e8 17 f7 cf fd call 0xfdcff72d
16: e9 aa 00 00 00 jmp 0xc5
1b: e8 0d f7 cf fd call 0xfdcff72d
20: 48 8d 3d a6 5d 98 0b lea 0xb985da6(%rip),%rdi # 0xb985dcd
27: 44 89 e6 mov %r12d,%esi
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: e9 27 fd ff ff jmp 0xfffffd5b
34: e8 c4 50 57 07 call 0x75750fd
39: 41 89 c6 mov %eax,%r14d
3c: 31 ff xor %edi,%edi
3e: 89 c6 mov %eax,%esi


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