[syzbot] [bcachefs?] WARNING in bchfs_truncate

[syzbot <syzbot+247ac87eabcb1f8fa990@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    3d25a941ea50 Merge tag 'block-6.9-20240503' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e71b9b180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3310e643b6ef5d69
dashboard link: https://syzkaller.appspot.com/bug?extid=247ac87eabcb1f8fa990
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a743748c2da4/disk-3d25a941.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9a51bb4cf9ba/vmlinux-3d25a941.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f4a1ba4b268a/bzImage-3d25a941.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+247ac87eabcb1f8fa990@syzkaller.appspotmail.com

------------[ cut here ]------------
truncate spotted in mem i_size < btree i_size: 4 < 65536
WARNING: CPU: 0 PID: 29645 at fs/bcachefs/fs-io.c:434 bchfs_truncate+0x7ad/0xd70 fs/bcachefs/fs-io.c:434
Modules linked in:
CPU: 0 PID: 29645 Comm: syz-executor.3 Not tainted 6.9.0-rc6-syzkaller-00227-g3d25a941ea50 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:bchfs_truncate+0x7ad/0xd70 fs/bcachefs/fs-io.c:434
Code: 24 38 84 c0 0f 85 d3 fc ff ff e8 7e 4b 8e fd c6 05 91 7f 89 0b 01 90 48 c7 c7 80 52 5f 8b 4c 89 ea 4c 89 fe e8 14 b6 50 fd 90 <0f> 0b 90 90 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 48 48 c1 ea
RSP: 0018:ffffc900032d7758 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff888064756cf8 RCX: ffffc9000c7d0000
RDX: 0000000000040000 RSI: ffffffff81503286 RDI: 0000000000000001
RBP: ffffc900032d7920 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000008d6b8 R12: ffff8880647567b0
R13: 0000000000010000 R14: ffffc900032d7a18 R15: 0000000000000004
FS:  00007fb75c3de6c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020ee5000 CR3: 000000002ac62000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bch2_setattr+0x1ab/0x250 fs/bcachefs/fs.c:882
 notify_change+0x742/0x11c0 fs/attr.c:497
 do_truncate+0x15c/0x220 fs/open.c:65
 handle_truncate fs/namei.c:3300 [inline]
 do_open fs/namei.c:3646 [inline]
 path_openat+0x24b9/0x2990 fs/namei.c:3799
 do_filp_open+0x1dc/0x430 fs/namei.c:3826
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
 do_sys_open fs/open.c:1421 [inline]
 __do_sys_open fs/open.c:1429 [inline]
 __se_sys_open fs/open.c:1425 [inline]
 __x64_sys_open+0x154/0x1e0 fs/open.c:1425
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb75c87dca9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb75c3de0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fb75c9ac050 RCX: 00007fb75c87dca9
RDX: 0000000000000000 RSI: 000000000014927e RDI: 0000000020000180
RBP: 00007fb75c8c947e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007fb75c9ac050 R15: 00007ffdfe29fbb8
 </TASK>


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