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 0 reserved 0
BTRFS info (device loop0): delayed_refs_rsv: size 458752 reserved 458752
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_abort_should_print_stack(__error)
WARNING: fs/btrfs/block-group.c:4203 at do_chunk_alloc fs/btrfs/block-group.c:4203 [inline], CPU#0: kworker/u4:1/13
WARNING: fs/btrfs/block-group.c:4203 at btrfs_chunk_alloc+0x10cc/0x1330 fs/btrfs/block-group.c:4444, CPU#0: kworker/u4:1/13
Modules linked in:
CPU: 0 UID: 0 PID: 13 Comm: kworker/u4:1 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_data_space
RIP: 0010:do_chunk_alloc fs/btrfs/block-group.c:4203 [inline]
RIP: 0010:btrfs_chunk_alloc+0x10cc/0x1330 fs/btrfs/block-group.c:4444
Code: 07 38 c1 0f 8c e9 ef ff ff 48 89 df e8 4d a4 16 fe e9 dc ef ff ff e8 53 7f a7 fd eb 10 e8 4c 7f a7 fd eb 09 e8 45 7f a7 fd 90 <0f> 0b 90 44 89 f1 f7 d9 e9 38 fd ff ff 48 8b 4c 24 08 48 83 c1 5b
RSP: 0018:ffffc9000026f7d8 EFLAGS: 00010293
RAX: ffffffff841ec1ab RBX: 1ffff1100a060a16 RCX: ffff88801b3c0000
RDX: 0000000000000000 RSI: ffffffff8efbd080 RDI: 00000000ffffffe4
RBP: ffff888052650001 R08: ffff88801b3c0000 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: 1ffff1100a060a16
R13: 00000000ffffffe4 R14: ffffffffffffffe4 R15: ffff88801322e180
FS:  0000000000000000(0000) GS:ffff88808c81f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000005c0000 CR3: 00000000126cf000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 flush_space+0x3df/0xde0 fs/btrfs/space-info.c:908
 do_async_reclaim_data_space+0x137/0x550 fs/btrfs/space-info.c:1455
 btrfs_async_reclaim_data_space+0x41/0x90 fs/btrfs/space-info.c:1519
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 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>