------------[ cut here ]------------
truncate spotted in mem i_size < btree i_size: 65007 < 1048576
WARNING: fs/bcachefs/fs-io.c:472 at bchfs_truncate+0xa4a/0xc50 fs/bcachefs/fs-io.c:469, CPU#1: syz.7.3563/20861
Modules linked in:
CPU: 1 UID: 0 PID: 20861 Comm: syz.7.3563 Not tainted 6.16.0-rc6-next-20250718-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:bchfs_truncate+0xa4a/0xc50 fs/bcachefs/fs-io.c:469
Code: 00 74 0a 48 8b 7c 24 18 e8 e3 27 e4 fd 4c 8b 7c 24 18 49 8b 37 48 8b 94 24 50 01 00 00 48 c7 c7 40 09 d5 8b e8 47 5f 44 fd 90 <0f> 0b 90 90 4c 89 f3 e9 a0 fa ff ff e8 a5 d7 80 fd 4c 8b 7c 24 58
RSP: 0018:ffffc900048a74a0 EFLAGS: 00010246
RAX: b7df87713f40f500 RBX: dffffc0000000000 RCX: 0000000000080000
RDX: ffffc9000d9a2000 RSI: 00000000000049b4 RDI: 00000000000049b5
RBP: ffffc900048a7790 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa7f0 R12: ffff8880579caaa0
R13: 1ffff92000914ea8 R14: dffffc0000000000 R15: ffff8880579ca648
FS:  00007f6db1e7e6c0(0000) GS:ffff888125ce3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6614ade000 CR3: 000000004a39a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 bch2_setattr+0x195/0x230 fs/bcachefs/fs.c:1215
 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: 0033:0x7f6db0f8e9a9
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:00007f6db1e7e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f6db11b6160 RCX: 00007f6db0f8e9a9
RDX: 0000000000123380 RSI: 00002000000001c0 RDI: ffffffffffffff9c
RBP: 00007f6db1010d69 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000000d4 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f6db11b6160 R15: 00007ffe63cf4ca8
 </TASK>