------------[ cut here ]------------
truncate spotted in mem i_size < btree i_size: 10 < 12288
WARNING: CPU: 0 PID: 5338 at fs/bcachefs/fs-io.c:474 bchfs_truncate+0xa3b/0xc20 fs/bcachefs/fs-io.c:471
Modules linked in:
CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted 6.16.0-rc4-syzkaller-00123-g4c06e63b9203 #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
RIP: 0010:bchfs_truncate+0xa3b/0xc20 fs/bcachefs/fs-io.c:471
Code: 00 74 0a 48 8b 7c 24 20 e8 a2 fe e8 fd 4c 8b 7c 24 20 49 8b 37 48 8b 94 24 00 01 00 00 48 c7 c7 00 b7 d4 8b e8 46 24 49 fd 90 <0f> 0b 90 90 e9 95 fa ff ff e8 a7 7b 85 fd 4c 8b 7c 24 50 4c 89 ff
RSP: 0018:ffffc9000d5cf540 EFLAGS: 00010246
RAX: bc4335e4bfe7ff00 RBX: 1ffff1100a5fd988 RCX: ffff888037230000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc9000d5cf7d0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa9fc R12: ffff888052fecc40
R13: ffff888052fecd00 R14: 000000000000000a R15: ffff888052fec7e8
FS:  00007f80c1f786c0(0000) GS:ffff88808d21c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff53e3fe000 CR3: 0000000044600000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 notify_change+0xb33/0xe40 fs/attr.c:552
 do_truncate+0x1a4/0x220 fs/open.c:68
 handle_truncate fs/namei.c:3517 [inline]
 do_open fs/namei.c:3900 [inline]
 path_openat+0x306c/0x3830 fs/namei.c:4055
 do_filp_open+0x1fa/0x410 fs/namei.c:4082
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f80c118e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f80c1f78038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f80c13b6080 RCX: 00007f80c118e929
RDX: 0000000000020200 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f80c1210b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f80c13b6080 R15: 00007ffdb13a8968
 </TASK>