BTRFS error (device loop0): allocation failed flags 2, wanted 4096 tree-log 0, relocation: 0
BTRFS info (device loop0): space_info SYSTEM (sub-group id 0) has -98304 free, is not full
BTRFS info (device loop0): space_info total=4194304, used=4096, pinned=0, reserved=0, may_use=98304, readonly=4190208 zone_unusable=0
BTRFS info (device loop0): global_block_rsv: size 983040 reserved 983040
BTRFS info (device loop0): trans_block_rsv: size 0 reserved 0
BTRFS info (device loop0): chunk_block_rsv: size 98304 reserved 94208
BTRFS info (device loop0): remap_block_rsv: size 0 reserved 0
BTRFS info (device loop0): delayed_block_rsv: size 32768 reserved 32768
BTRFS info (device loop0): delayed_refs_rsv: size 131072 reserved 131072
BTRFS info (device loop0): block group 1048576 has 4194304 bytes, 4096 used 0 pinned 0 reserved 0 delalloc 0 super 0 zone_unusable (4190208 bytes available) [readonly]
BTRFS info (device loop0): block group has cluster?: no
BTRFS info (device loop0): 0 free space entries at or bigger than 4096 bytes
BTRFS info (device loop0): 4190208 bytes available across all block groups
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: fs/btrfs/block-group.c:4175 at do_chunk_alloc fs/btrfs/block-group.c:4175 [inline], CPU#0: kworker/u4:3/41
WARNING: fs/btrfs/block-group.c:4175 at btrfs_chunk_alloc+0x101d/0x15e0 fs/btrfs/block-group.c:4416, CPU#0: kworker/u4:3/41
Modules linked in:
CPU: 0 UID: 0 PID: 41 Comm: kworker/u4:3 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
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
RIP: 0010:do_chunk_alloc fs/btrfs/block-group.c:4175 [inline]
RIP: 0010:btrfs_chunk_alloc+0x101f/0x15e0 fs/btrfs/block-group.c:4416
Code: c7 63 ad fd e9 6d 01 00 00 e8 9d 6a 92 fd 84 c0 74 22 e8 b4 63 ad fd e9 5a 01 00 00 e8 aa 63 ad fd 48 8d 3d f3 b5 21 0c 89 de <67> 48 0f b9 3a e9 b3 fc ff ff e8 22 08 91 07 41 89 c6 31 ff 89 c6
RSP: 0018:ffffc900004376d0 EFLAGS: 00010293
RAX: ffffffff84186266 RBX: ffffffffffffffe4 RCX: ffff88801fad8000
RDX: 0000000000000000 RSI: 00000000ffffffe4 RDI: ffffffff903a1860
RBP: 0000000000000000 R08: ffff88801fad8000 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: 1ffff11008494716
R13: ffff88801fc841d8 R14: ffff888042730001 R15: ffff888041c30800
FS:  0000000000000000(0000) GS:ffff88808c891000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f17f8a30120 CR3: 00000000125bf000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 flush_space+0x3fb/0xe20 fs/btrfs/space-info.c:908
 do_async_reclaim_metadata_space+0x3fc/0x960 fs/btrfs/space-info.c:1211
 btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1278
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3397
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3478
 kthread+0x389/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	63 ad fd e9 6d 01    	movsxd 0x16de9fd(%rbp),%ebp
   6:	00 00                	add    %al,(%rax)
   8:	e8 9d 6a 92 fd       	call   0xfd926aaa
   d:	84 c0                	test   %al,%al
   f:	74 22                	je     0x33
  11:	e8 b4 63 ad fd       	call   0xfdad63ca
  16:	e9 5a 01 00 00       	jmp    0x175
  1b:	e8 aa 63 ad fd       	call   0xfdad63ca
  20:	48 8d 3d f3 b5 21 0c 	lea    0xc21b5f3(%rip),%rdi        # 0xc21b61a
  27:	89 de                	mov    %ebx,%esi
* 29:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2e:	e9 b3 fc ff ff       	jmp    0xfffffce6
  33:	e8 22 08 91 07       	call   0x791085a
  38:	41 89 c6             	mov    %eax,%r14d
  3b:	31 ff                	xor    %edi,%edi
  3d:	89 c6                	mov    %eax,%esi