------------[ cut here ]------------
WARNING: CPU: 0 PID: 182 at fs/btrfs/extent-tree.c:3230 __btrfs_free_extent+0x15e4/0x4000 fs/btrfs/extent-tree.c:3230
Modules linked in:
CPU: 0 UID: 0 PID: 182 Comm: kworker/u4:5 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:__btrfs_free_extent+0x15e4/0x4000 fs/btrfs/extent-tree.c:3230
Code: b2 8b f6 fd 85 db 75 0a e8 69 87 f6 fd e9 34 0c 00 00 e8 1f c3 dc fd 84 c0 0f 84 43 02 00 00 e8 52 87 f6 fd e9 1d 0c 00 00 90 <0f> 0b 90 48 8b 44 24 20 42 80 3c 28 00 74 0a 48 8b 7c 24 08 e8 83
RSP: 0018:ffffc90001abf260 EFLAGS: 00010246
RAX: 0000000000000002 RBX: 00000000fffffffe RCX: 0000000000000005
RDX: ffffffff83c97b19 RSI: ffffffff8e4d9800 RDI: 00000000fffffffe
RBP: ffffc90001abf410 R08: ffff888000a5a480 R09: 0000000000000002
R10: 00000000fffffffe R11: 0000000000000000 R12: 00000000fffffffe
R13: dffffc0000000000 R14: 0000000000000005 R15: 0000000000000107
FS:  0000000000000000(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f08ff988000 CR3: 0000000019fbd000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 run_delayed_data_ref fs/btrfs/extent-tree.c:1599 [inline]
 run_one_delayed_ref fs/btrfs/extent-tree.c:1779 [inline]
 btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:1972 [inline]
 __btrfs_run_delayed_refs+0xc39/0x4130 fs/btrfs/extent-tree.c:2047
 btrfs_run_delayed_refs+0xe6/0x3b0 fs/btrfs/extent-tree.c:2159
 flush_space+0x24b/0xcd0 fs/btrfs/space-info.c:-1
 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>