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
assertion failed: !cache->nr_nodes :: 0, in fs/btrfs/backref.c:3160
------------[ cut here ]------------
kernel BUG at fs/btrfs/backref.c:3160!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5344 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_backref_release_cache+0x1ef/0x220 fs/btrfs/backref.c:3160
Code: 0f 0b e8 74 3d d7 fd 48 c7 c7 80 0e b0 8b 48 c7 c6 20 17 b0 8b 31 d2 48 c7 c1 20 0f b0 8b 41 b8 58 0c 00 00 e8 c2 bb 3e fd 90 <0f> 0b e8 4a 3d d7 fd 48 c7 c7 80 0e b0 8b 48 c7 c6 60 17 b0 8b 31
RSP: 0018:ffffc9000d3e7830 EFLAGS: 00010246
RAX: 0000000000000043 RBX: ffff888037bdc020 RCX: 0fbf8ed2f72c7700
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffc9000d3e7547 R09: 1ffff92001a7cea8
R10: dffffc0000000000 R11: fffff52001a7cea9 R12: 1ffff11006f7b821
R13: 00000000fffffffe R14: ffff888037bdc0f0 R15: dffffc0000000000
FS:  00007ff40f5f36c0(0000) GS:ffff88808d730000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff40f5f2fc8 CR3: 0000000041317000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 relocate_block_group+0xac6/0xd70 fs/btrfs/relocation.c:3638
 btrfs_relocate_block_group+0x6bc/0xc60 fs/btrfs/relocation.c:3983
 btrfs_relocate_chunk+0x12f/0x5c0 fs/btrfs/volumes.c:3451
 __btrfs_balance+0x1860/0x23f0 fs/btrfs/volumes.c:4227
 btrfs_balance+0xac2/0x11b0 fs/btrfs/volumes.c:4604
 btrfs_ioctl_balance+0x3d3/0x610 fs/btrfs/ioctl.c:3577
 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/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff40e78f6c9
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:00007ff40f5f3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff40e9e6180 RCX: 00007ff40e78f6c9
RDX: 0000200000000180 RSI: 00000000c4009420 RDI: 0000000000000006
RBP: 00007ff40e811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff40e9e6218 R14: 00007ff40e9e6180 R15: 00007ffc706bc608
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:btrfs_backref_release_cache+0x1ef/0x220 fs/btrfs/backref.c:3160
Code: 0f 0b e8 74 3d d7 fd 48 c7 c7 80 0e b0 8b 48 c7 c6 20 17 b0 8b 31 d2 48 c7 c1 20 0f b0 8b 41 b8 58 0c 00 00 e8 c2 bb 3e fd 90 <0f> 0b e8 4a 3d d7 fd 48 c7 c7 80 0e b0 8b 48 c7 c6 60 17 b0 8b 31
RSP: 0018:ffffc9000d3e7830 EFLAGS: 00010246
RAX: 0000000000000043 RBX: ffff888037bdc020 RCX: 0fbf8ed2f72c7700
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffc9000d3e7547 R09: 1ffff92001a7cea8
R10: dffffc0000000000 R11: fffff52001a7cea9 R12: 1ffff11006f7b821
R13: 00000000fffffffe R14: ffff888037bdc0f0 R15: dffffc0000000000
FS:  00007ff40f5f36c0(0000) GS:ffff88808d730000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff40f5f2fc8 CR3: 0000000041317000 CR4: 0000000000352ef0