Re: [syzbot] WARNING in follow_hugetlb_page

Mike Kravetz
2022-05-13T18:10:36Z

On 5/13/22 10:26, Andrew Morton wrote:
> On Fri, 13 May 2022 09:43:24 -0700 syzbot <syzbot+acf65ca584991f3cc447@syzkaller.appspotmail.com> wrote:
>
>> syzbot has found a reproducer for the following issue on:
>
> Thanks.
>
>> HEAD commit: 1e1b28b936ae Add linux-next specific files for 20220513
>> git tree: linux-next
>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=174ae715f00000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=e4eb3c0c4b289571
>> dashboard link: https://syzkaller.appspot.com/bug?extid=acf65ca584991f3cc447
>> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11531766f00000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ce5a9ef00000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+acf65ca584991f3cc447@syzkaller.appspotmail.com
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 3611 at mm/hugetlb.c:6250 follow_hugetlb_page+0x1326/0x1c80 mm/hugetlb.c:6250
>
> The try_grab_folio() added by 822951d84684d ("mm/hugetlb: Use
> try_grab_folio() instead of try_grab_compound_head()"). That commit
> has been there over a month so I guess it's something else. Does
> someone have the time to bisect?

I can recreate in my 'easy to debug' environment, so I can bisect in
parallel with other things I need to do today.

If someone else has dedicated time and resources, feel free. You may
beat me to the answer.
--
Mike Kravetz