Re: [PATCH v8 16/19] fsnotify: generate pre-content permission event on page fault

Klara Modin
2024-12-09T12:56:52Z

Hi,

On 2024-12-09 13:31, Jan Kara wrote:
> Hello!
>
> On Sun 08-12-24 17:58:42, Klara Modin wrote:
>> On 2024-11-15 16:30, Josef Bacik wrote:
>>> FS_PRE_ACCESS or FS_PRE_MODIFY will be generated on page fault depending
>>> on the faulting method.
>>>
>>> This pre-content event is meant to be used by hierarchical storage
>>> managers that want to fill in the file content on first read access.
>>>
>>> Export a simple helper that file systems that have their own ->fault()
>>> will use, and have a more complicated helper to be do fancy things with
>>> in filemap_fault.
>>>
>>
>> This patch (0790303ec869d0fd658a548551972b51ced7390c in next-20241206)
>> interacts poorly with some programs which hang and are stuck at 100 % sys
>> cpu usage (examples of programs are logrotate and atop with root
>> privileges).
>>
>> I also retested the new version on Jan Kara's for_next branch and it behaves
>> the same way.
>
> Thanks for report! What is your kernel config please? I've just fixed a
> bug reported by [1] which manifested in the same way with
> CONFIG_FANOTIFY_ACCESS_PERMISSIONS=n.
>
> Can you perhaps test with my for_next branch I've just pushed out? Thanks!
>
> Honza

My config was attached, but yes, I have
CONFIG_FANOTIFY_ACCESS_PERMISSIONS=n. I tried the tip by Srikanth Aithal
to enable it and that resolved the issue.

Your new for_next branch resolved the
CONFIG_FANOTIFY_ACCESS_PERMISSIONS=n case for me.

Thanks,
Klara Modin