BTRFS error (device loop0): allocation failed flags 10, 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=8257536, used=4096, pinned=0, reserved=0, may_use=98304, readonly=8253440 zone_unusable=0
BTRFS info (device loop0): global_block_rsv: size 1441792 reserved 1441792
BTRFS info (device loop0): trans_block_rsv: size 393216 reserved 389120
BTRFS info (device loop0): chunk_block_rsv: size 98304 reserved 94208
BTRFS info (device loop0): delayed_block_rsv: size 32768 reserved 32768
BTRFS info (device loop0): delayed_refs_rsv: size 131072 reserved 65536
BTRFS info (device loop0): block group 8519680 has 8257536 bytes, 4096 used 0 pinned 0 reserved 0 delalloc 0 super 0 zone_unusable (8253440 bytes available) [readonly]
BTRFS critical (device loop0): entry offset 8519680, bytes 4096, bitmap no
BTRFS critical (device loop0): entry offset 8527872, bytes 8249344, bitmap no
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): 8253440 bytes available across all block groups
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: CPU: 0 PID: 1092 at fs/btrfs/block-group.c:4007 do_chunk_alloc fs/btrfs/block-group.c:4007 [inline]
WARNING: CPU: 0 PID: 1092 at fs/btrfs/block-group.c:4007 btrfs_chunk_alloc+0xe64/0x1430 fs/btrfs/block-group.c:4248
Modules linked in:
CPU: 0 UID: 0 PID: 1092 Comm: kworker/u4:9 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
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
RIP: 0010:do_chunk_alloc fs/btrfs/block-group.c:4007 [inline]
RIP: 0010:btrfs_chunk_alloc+0xe64/0x1430 fs/btrfs/block-group.c:4248
Code: 00 e8 f0 78 b2 fd 84 c0 74 29 e8 07 3d cc fd e9 62 01 00 00 e8 fd 3c cc fd 90 48 c7 c7 80 ce b0 8b 44 89 f6 e8 1d 49 8f fd 90 <0f> 0b 90 90 e9 9a fc ff ff e8 2e a2 54 07 89 c3 31 ff 89 c6 e8 13
RSP: 0018:ffffc900026c7758 EFLAGS: 00010246
RAX: dff132e9d034ba00 RBX: ffff8880510cc001 RCX: ffff888000382480
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bba684 R12: dffffc0000000000
R13: ffff88803f5ed000 R14: ffffffffffffffe4 R15: ffff8880432616f0
FS:  0000000000000000(0000) GS:ffff88808d730000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe1825682b0 CR3: 00000000119d2000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 flush_space+0x30b/0xcd0 fs/btrfs/space-info.c:861
 do_async_reclaim_metadata_space+0x144/0x390 fs/btrfs/space-info.c:1158
 btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1226
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>