Re: [PATCH v2] fs/proc/page: Skip uninitialized page when iterating page structures

[Waiman Long]

On 8/28/19 10:09 AM, Michal Hocko wrote:
> On Wed 28-08-19 09:46:21, Waiman Long wrote:
>> On 8/28/19 4:00 AM, Michal Hocko wrote:
>>> On Tue 27-08-19 16:22:38, Michal Hocko wrote:
>>>> Dan, isn't this something we have discussed recently?
>>> This was http://lkml.kernel.org/r/20190725023100.31141-3-t-fukasawa@xxxxxxxxxxxxx
>>> and talked about /proc/kpageflags but this is essentially the same thing
>>> AFAIU. I hope we get a consistent solution for both issues.
>>>
>> Yes, it is the same problem. The uninitialized page structure problem
>> affects all the 3 /proc/kpage{cgroup,count,flags) files.
>>
>> Toshiki's patch seems to fix it just for /proc/kpageflags, though.
> Yup. I was arguing that whacking a mole kinda fix is far from good. Dan
> had some arguments on why initializing those struct pages is a problem.
> The discussion had a half open end though. I hoped that Dan would try
> out the initialization side but I migh have misunderstood.

If the page structures of the reserved PFNs are always initialized, that
will fix the problem too. I am not familiar with the zone device code.
So I didn't attempt to do that.

Cheers,
Longman