------------[ cut here ]------------
truncate spotted in mem i_size < btree i_size: 10 < 12288
WARNING: CPU: 0 PID: 5358 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: 5358 Comm: syz.0.0 Not tainted 6.16.0-syzkaller-11852-g479058002c32 #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 82 40 e4 fd 4c 8b 7c 24 20 49 8b 37 48 8b 94 24 00 01 00 00 48 c7 c7 80 15 d5 8b e8 06 e6 42 fd 90 <0f> 0b 90 90 e9 95 fa ff ff e8 27 57 7f fd 4c 8b 7c 24 50 4c 89 ff
RSP: 0018:ffffc9000d37f540 EFLAGS: 00010246
RAX: 77f639ef43b36700 RBX: 1ffff110024ef988 RCX: ffff888000654880
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc9000d37f7d0 R08: ffff88801fc24253 R09: 1ffff11003f8484a
R10: dffffc0000000000 R11: ffffed1003f8484b R12: ffff88801277cc40
R13: ffff88801277cd00 R14: 000000000000000a R15: ffff88801277c7e8
FS:  00007f2b9f7f56c0(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000439a8000 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:3508 [inline]
 do_open fs/namei.c:3891 [inline]
 path_openat+0x306c/0x3830 fs/namei.c:4046
 do_filp_open+0x1fa/0x410 fs/namei.c:4073
 do_sys_openat2+0x121/0x1c0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1461
 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: 0033:0x7f2ba338ebe9
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:00007f2b9f7f5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2ba35b6090 RCX: 00007f2ba338ebe9
RDX: 0000000000020200 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007f2ba3411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2ba35b6128 R14: 00007f2ba35b6090 R15: 00007fff71a690c8
 </TASK>