Re: reply: [RFC] pin_user_pages_fast failure count increased

[John Hubbard <jhubbard@nvidia.com>]

On 5/22/25 7:37 PM, 김재원 wrote:
...
> I think this is what you meant, please let me know if you have an idea to make this nicer.
> We may be to able to prepare the patch next week.
> 
>  static long
>  check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs)
>  {
> +       bool any_unpinnable;
>         LIST_HEAD(movable_folio_list);
>  
> -       collect_longterm_unpinnable_folios(&movable_folio_list, pofs);
> -       if (list_empty(&movable_folio_list))
> -               return 0;
> +       any_unpinnable = collect_longterm_unpinnable_folios(&movable_folio_list, pofs);
> +       if (list_empty(&movable_folio_list)) {
> +               if (any_unpinnable)
> +                       pofs_unpin(pofs);

I think this is correct, although as I mentioned in the other thread,
that implies that commit 1aaf8c122918 (which didn't add nor remove 
any pof unpinning) is probably not the true or only culprit, right?

> +               return any_unpinnable ? -EAGAIN : 0;

Ha, the "?" operator almost always does more harm than good.

Here, for example, it has obscured from you the fact that any_unpinnable
is being checked twice, when you could have merged those into a single "if".

> +       }
>  
>         return migrate_longterm_unpinnable_folios(&movable_folio_list, pofs);
>  }
thanks,
-- 
John Hubbard