------------[ cut here ]------------
truncate spotted in mem i_size < btree i_size: 65249 < 1048576
WARNING: CPU: 0 PID: 10511 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: 10511 Comm: syz.5.389 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:bchfs_truncate+0xa3b/0xc20 fs/bcachefs/fs-io.c:471
Code: 00 74 0a 48 8b 7c 24 20 e8 52 f6 e7 fd 4c 8b 7c 24 20 49 8b 37 48 8b 94 24 00 01 00 00 48 c7 c7 80 bd 54 8b e8 76 80 4d fd 90 <0f> 0b 90 90 e9 95 fa ff ff e8 97 af 88 fd 4c 8b 7c 24 50 4c 89 ff
RSP: 0000:ffffc90005f8f4e0 EFLAGS: 00010246
RAX: 00048b5ce75d5d00 RBX: 1ffff1100bae2bfe RCX: 0000000000080000
RDX: ffffc90016d0b000 RSI: 0000000000001646 RDI: 0000000000001647
RBP: ffffc90005f8f770 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1017104863 R12: ffff88805d715ff0
R13: ffff88805d7160a0 R14: 000000000000fee1 R15: ffff88805d715b10
FS:  00007f2e754316c0(0000) GS:ffff8881268bc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f943d104000 CR3: 000000005ce7e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 notify_change+0xb34/0xe60 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+0x3078/0x3840 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_open fs/open.c:1458 [inline]
 __se_sys_open fs/open.c:1454 [inline]
 __x64_sys_open+0x11e/0x150 fs/open.c:1454
 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: 0033:0x7f2e7762eec9
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:00007f2e75431038 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f2e77886270 RCX: 00007f2e7762eec9
RDX: 0000000000000002 RSI: 000000000014927e RDI: 00002000000001c0
RBP: 00007f2e776b1f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2e77886308 R14: 00007f2e77886270 R15: 00007ffd038afeb8
 </TASK>