------------[ cut here ]------------
WARNING: CPU: 0 PID: 4704 at fs/bcachefs/fs-io-buffered.c:456 bch2_writepage_io_done+0x765/0x800 fs/bcachefs/fs-io-buffered.c:456
Modules linked in:
CPU: 0 UID: 0 PID: 4704 Comm: kworker/u5:1 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: bcachefs bch2_write_point_do_index_updates
RIP: 0010:bch2_writepage_io_done+0x765/0x800 fs/bcachefs/fs-io-buffered.c:456
Code: 0e 48 3b 84 24 80 00 00 00 75 72 4c 89 f7 48 81 c4 88 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d e9 51 24 64 00 e8 8c 73 7d fd 90 <0f> 0b 90 42 80 3c 3b 00 74 08 4c 89 ef e8 29 60 e2 fd 4d 8b 65 00
RSP: 0018:ffffc9000d517930 EFLAGS: 00010293
RAX: ffffffff844247b4 RBX: 1ffff1100a59ee1c RCX: ffff88801c6aa440
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000000
RBP: 0000000000000800 R08: ffffc9000d5179af R09: 0000000000000000
R10: ffffc9000d517980 R11: fffff52001aa2f36 R12: 0000000000000008
R13: ffff888052cf70e0 R14: ffff888052cf72e8 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88808d210000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f44401d3fc8 CR3: 0000000043846000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bch2_write_point_do_index_updates+0x9e/0x570 fs/bcachefs/io_write.c:723
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>