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

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Date:   Fri, 11 Dec 2020 22:08:43 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        David Hildenbrand <david@...hat.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v8 07/12] mm/hugetlb: Set the PageHWPoison
 to the raw error page

On Fri, Dec 11, 2020 at 9:36 PM Oscar Salvador <osalvador@...e.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