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truncate spotted in mem i_size < btree i_size: 192512 < 1048576
WARNING: CPU: 0 PID: 5672 at fs/bcachefs/fs-io.c:457 bchfs_truncate+0xb99/0xc60 fs/bcachefs/fs-io.c:454
Modules linked in:
CPU: 0 UID: 0 PID: 5672 Comm: syz.0.16 Not tainted 6.15.0-rc1-syzkaller-00288-ge618ee89561b #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+0xb99/0xc60 fs/bcachefs/fs-io.c:454
Code: 8b 4c 24 68 80 3c 01 00 74 08 4c 89 e7 e8 2f 46 ba fd 48 8b 94 24 20 01 00 00 48 c7 c7 80 29 94 8c 48 89 de e8 08 40 0f fd 90 <0f> 0b 90 90 49 be 00 00 00 00 00 fc ff df e9 f3 f9 ff ff e8 6f 1e
RSP: 0018:ffffc9000d55f4e0 EFLAGS: 00010246
RAX: 32c37a5cce7f8c00 RBX: 000000000002f000 RCX: ffff888036850000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000d55f758 R08: ffffffff81827952 R09: fffffbfff1d7a970
R10: dffffc0000000000 R11: fffffbfff1d7a970 R12: ffffc9000d55f600
R13: 1ffff11008323188 R14: dffffc0000000000 R15: 0000000000100000
FS:  00007f74b8f606c0(0000) GS:ffff88808c594000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4ddec63f80 CR3: 0000000044618000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 notify_change+0xbca/0xe90 fs/attr.c:552
 do_truncate+0x222/0x310 fs/open.c:65
 handle_truncate fs/namei.c:3466 [inline]
 do_open fs/namei.c:3849 [inline]
 path_openat+0x2e4f/0x35d0 fs/namei.c:4004
 do_filp_open+0x284/0x4e0 fs/namei.c:4031
 do_sys_openat2+0x12b/0x1d0 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_open fs/open.c:1452 [inline]
 __se_sys_open fs/open.c:1448 [inline]
 __x64_sys_open+0x226/0x280 fs/open.c:1448
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f74b818d169
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:00007f74b8f60038 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f74b83a6160 RCX: 00007f74b818d169
RDX: 00000000000001f4 RSI: 000000000014927e RDI: 00002000000000c0
RBP: 00007f74b820e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f74b83a6160 R15: 00007ffee41704a8
 </TASK>