Re: [External] Re: [PATCH v8 07/12] mm/hugetlb: Set the PageHWPoison to the raw error page

[Muchun Song <songmuchun@bytedance.com>]

On Fri, Dec 11, 2020 at 9:36 PM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Thu, Dec 10, 2020 at 11:55:21AM +0800, Muchun Song wrote:
> > +static inline void subpage_hwpoison_deliver(struct hstate *h, struct page *head)
> > +{
> > +     struct page *page = head;
> > +
> > +     if (!free_vmemmap_pages_per_hpage(h))
> > +             return;
> > +
> > +     if (PageHWPoison(head))
> > +             page = head + page_private(head + 4);
> > +
> > +     /*
> > +      * Move PageHWPoison flag from head page to the raw error page,
> > +      * which makes any subpages rather than the error page reusable.
> > +      */
> > +     if (page != head) {
> > +             SetPageHWPoison(page);
> > +             ClearPageHWPoison(head);
> > +     }
> > +}
>
> I would make the names coherent.
> I am not definitely goot at names, but something like:
> hwpoison_subpage_{foo,bar} looks better.

It's better than mine. Thank you.

>
> Also, could not subpage_hwpoison_deliver be rewritten like:
>
>   static inline void subpage_hwpoison_deliver(struct hstate *h, struct page *head)
>   {
>        struct page *page;
>
>        if (!PageHWPoison(head) || !free_vmemmap_pages_per_hpage(h))
>                return;
>
>        page = head + page_private(head + 4);
>        /*
>         * Move PageHWPoison flag from head page to the raw error page,
>         * which makes any subpages rather than the error page reusable.
>         */
>        if (page != head) {
>                SetPageHWPoison(page);
>                ClearPageHWPoison(head);
>        }
>   }
>
> I think it is better code-wise.

Will do. Thank you.

>
> > +      * Move PageHWPoison flag from head page to the raw error page,
> > +      * which makes any subpages rather than the error page reusable.
> > +      */
> > +     if (page != head) {
> > +             SetPageHWPoison(page);
> > +             ClearPageHWPoison(head);
> > +     }
>
> I would put this in an else-if above:
>
>         if (free_vmemmap_pages_per_hpage(h)) {
>                 set_page_private(head + 4, page - head);
>                 return;
>         } else if (page != head) {
>                 SetPageHWPoison(page);
>                 ClearPageHWPoison(head);
>         }
>
> or will we lose the optimization in case free_vmemmap_pages_per_hpage gets compiled out?
>

Either is OK. The compiler will help us optimize the code when
free_vmemmap_pages_per_hpage always returns false.

Thanks for your suggestions. :-)

>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun