[syzbot] [btrfs?] WARNING in do_nonremap_reloc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0f23d56f17fd Merge tag 'linux_kselftest-next-7.3-rc1' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=163fb679580000
kernel config: https://syzkaller.appspot.com/x/.config?x=71fc77aa899cc4af
dashboard link: https://syzkaller.appspot.com/bug?extid=ee138e182230b96006c6
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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-0f23d56f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f14e4b85231d/vmlinux-0f23d56f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/824989a16f1e/bzImage-0f23d56f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ee138e...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
btrfs: Deprecated parameter 'usebackuproot'
BTRFS warning: 'usebackuproot' is deprecated, use 'rescue=usebackuproot' instead
BTRFS: device fsid c9fe44da-de57-406a-8241-57ec7d4412cf devid 1 transid 8 /dev/loop0 (7:0) scanned by syz.0.0 (5310)
BTRFS info (device loop0): first mount of filesystem c9fe44da-de57-406a-8241-57ec7d4412cf
BTRFS info (device loop0): using crc32c checksum algorithm
BTRFS error (device loop0): failed to load root extent
BTRFS warning (device loop0): try to load backup roots slot 1
BTRFS warning (device loop0): couldn't read tree root
BTRFS warning (device loop0): try to load backup roots slot 2
BTRFS warning (device loop0): couldn't read tree root
BTRFS warning (device loop0): try to load backup roots slot 3
BTRFS info (device loop0): rebuilding free space tree
BTRFS info (device loop0): checking UUID tree
BTRFS info (device loop0): enabling ssd optimizations
BTRFS info (device loop0): turning off barriers
BTRFS info (device loop0): turning on sync discard
BTRFS info (device loop0): enabling free space tree
BTRFS info (device loop0): force clearing of disk cache
BTRFS info (device loop0): enabling auto defrag
BTRFS info (device loop0): trying to use backup root at mount time
BTRFS info (device loop0): use zlib compression, level 3
BTRFS info (device loop0): max_inline set to 0
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
BTRFS info (device loop0): found 7 extents, stage: move data extents
------------[ cut here ]------------
rc->block_group->reserved > 0
WARNING: fs/btrfs/relocation.c:5389 at do_nonremap_reloc+0x53b/0x560 fs/btrfs/relocation.c:5389, CPU#0: syz.0.0/5310
Modules linked in:
CPU: 0 UID: 0 PID: 5310 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 04/01/2014
RIP: 0010:do_nonremap_reloc+0x53b/0x560 fs/btrfs/relocation.c:5389
Code: 5d 41 5e 41 5f 5d e9 04 1f b0 07 cc e8 8e e8 9d fd 90 0f 0b 90 80 3c 2b 00 0f 85 57 ff ff ff e9 5a ff ff ff e8 76 e8 9d fd 90 <0f> 0b 90 80 3c 2b 00 75 84 eb 8a e8 65 e8 9d fd 90 0f 0b 90 eb b5
RSP: 0018:ffffc9000f5b79c8 EFLAGS: 00010283
RAX: ffffffff84292aba RBX: 1ffff11002447400 RCX: 0000000000100000
RDX: ffffc9000ec59000 RSI: 00000000000507c1 RDI: 00000000000507c2
RBP: dffffc0000000000 R08: ffffc9000f5b7947 R09: 1ffff92001eb6f28
R10: dffffc0000000000 R11: fffff52001eb6f29 R12: 0000000000000000
R13: ffff88801223a628 R14: 0000000000006000 R15: ffff88801223a000
FS: 00007f7d4eb846c0(0000) GS:ffff88808c534000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7d4a1d3fe8 CR3: 000000004508e000 CR4: 0000000000352ef0
Call Trace:
<TASK>
btrfs_relocate_block_group+0x6e2/0xaf0 fs/btrfs/relocation.c:5520
btrfs_relocate_chunk+0x114/0x810 fs/btrfs/volumes.c:3729
__btrfs_balance+0x1b5f/0x29d0 fs/btrfs/volumes.c:4668
btrfs_balance+0xaa6/0x1180 fs/btrfs/volumes.c:5055
btrfs_ioctl_balance+0x3da/0x640 fs/btrfs/ioctl.c:3481
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+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7d4dd9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7d4eb83fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7d4e025fa0 RCX: 00007f7d4dd9e0d9
RDX: 0000200000000180 RSI: 00000000c4009420 RDI: 0000000000000007
RBP: 00007f7d4de35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7d4e026038 R14: 00007f7d4e025fa0 R15: 00007fffd2839a78
</TASK>


---
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 syzk...@googlegroups.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