[v6.6] WARNING in btrfs_remove_chunk

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 60a9e718726f Linux 6.6.106
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13596362580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=d81c84c17a84aee2cdcd
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: https://storage.googleapis.com/syzbot-assets/eca27e056a5a/disk-60a9e718.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc64d4eeb7f6/vmlinux-60a9e718.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a345041561ac/bzImage-60a9e718.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d81c84...@syzkaller.appspotmail.com

BTRFS info (device loop6): block group has cluster?: no
BTRFS info (device loop6): 0 free space entries at or bigger than 4096 bytes
BTRFS info (device loop6): 4194304 bytes available across all block groups
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: CPU: 1 PID: 11781 at fs/btrfs/volumes.c:3236 btrfs_remove_chunk+0x1601/0x1920 fs/btrfs/volumes.c:3236
Modules linked in:
CPU: 1 PID: 11781 Comm: syz.6.1284 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:btrfs_remove_chunk+0x1601/0x1920 fs/btrfs/volumes.c:3236
Code: e8 44 69 cf fd 0f 0b 49 be 00 00 00 00 00 fc ff df e9 8e fd ff ff e8 5e ed 04 fe 48 c7 c7 00 94 ed 8a 44 89 e6 e8 1f 69 cf fd <0f> 0b 49 be 00 00 00 00 00 fc ff df e9 d5 fd ff ff e8 39 ed 04 fe
RSP: 0000:ffffc9000508f8e0 EFLAGS: 00010246
RAX: a732a2f571803900 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000d8da000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffc9000508fad0 R08: ffffc9000508f4e7 R09: 1ffff92000a11e9c
R10: dffffc0000000000 R11: fffff52000a11e9d R12: ffffffffffffffe4
R13: 0000000000000001 R14: ffff88807b2ec001 R15: 1ffff11004b5f2c0
FS: 00007f13bf6dc6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8883006000 CR3: 0000000024fea000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
btrfs_relocate_chunk+0x292/0x3b0 fs/btrfs/volumes.c:3366
__btrfs_balance+0x187b/0x21c0 fs/btrfs/volumes.c:4067
btrfs_balance+0xcb1/0x11c0 fs/btrfs/volumes.c:4444
btrfs_ioctl_balance+0x4a2/0x730 fs/btrfs/ioctl.c:3647
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f13be78eba9
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:00007f13bf6dc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f13be9d5fa0 RCX: 00007f13be78eba9
RDX: 0000200000000200 RSI: 00000000c4009420 RDI: 0000000000000005
RBP: 00007f13be811e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f13be9d6038 R14: 00007f13be9d5fa0 R15: 00007ffc5df6cc88
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 60a9e718726f Linux 6.6.106
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=17a85642580000

kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=d81c84c17a84aee2cdcd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11c1eb12580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11a7bd62580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/eca27e056a5a/disk-60a9e718.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc64d4eeb7f6/vmlinux-60a9e718.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a345041561ac/bzImage-60a9e718.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/7cdbb9fad6e5/mount_2.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=117f6362580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d81c84...@syzkaller.appspotmail.com

BTRFS info (device loop0): block group has cluster?: no
BTRFS info (device loop0): 1 free space entries at or bigger than 4096 bytes
BTRFS info (device loop0): 12447744 bytes available across all block groups

------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)

WARNING: CPU: 0 PID: 6301 at fs/btrfs/volumes.c:3236 btrfs_remove_chunk+0x1601/0x1920 fs/btrfs/volumes.c:3236
Modules linked in:
CPU: 0 PID: 6301 Comm: syz.0.36 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:btrfs_remove_chunk+0x1601/0x1920 fs/btrfs/volumes.c:3236
Code: e8 44 69 cf fd 0f 0b 49 be 00 00 00 00 00 fc ff df e9 8e fd ff ff e8 5e ed 04 fe 48 c7 c7 00 94 ed 8a 44 89 e6 e8 1f 69 cf fd <0f> 0b 49 be 00 00 00 00 00 fc ff df e9 d5 fd ff ff e8 39 ed 04 fe

RSP: 0018:ffffc90004e1f8e0 EFLAGS: 00010246
RAX: 8928c91fe3188900 RBX: 0000000000000000 RCX: ffff888030d40000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffffc90004e1fad0 R08: ffffc90004e1f5e7 R09: 1ffff920009c3ebc
R10: dffffc0000000000 R11: fffff520009c3ebd R12: ffffffffffffffe4
R13: 0000000000000001 R14: ffff88802673c001 R15: 1ffff11005f86170
FS: 00007ff97fded6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007ff97ef71fe0 CR3: 00000000608a9000 CR4: 00000000003506f0

Call Trace:
<TASK>
btrfs_relocate_chunk+0x292/0x3b0 fs/btrfs/volumes.c:3366
__btrfs_balance+0x187b/0x21c0 fs/btrfs/volumes.c:4067
btrfs_balance+0xcb1/0x11c0 fs/btrfs/volumes.c:4444
btrfs_ioctl_balance+0x4a2/0x730 fs/btrfs/ioctl.c:3647
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7ff97ef8eba9

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:00007ff97fded038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff97f1d5fa0 RCX: 00007ff97ef8eba9
RDX: 0000200000000200 RSI: 00000000c4009420 RDI: 0000000000000004
RBP: 00007ff97f011e19 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ff97f1d6038 R14: 00007ff97f1d5fa0 R15: 00007ffc1a4fa6e8
</TASK>


---
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