linux-kernel - Re: [External] Re: [PATCH v2] mm/page_isolation: do not isolate the max order page

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Message-ID: <CAMZfGtVdFtLB8f2uDfJ1H-YG4CsJ+RxxFbAWzePDnqBB1MU0ig@mail.gmail.com>
Date:   Sat, 5 Dec 2020 00:12:06 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [External] Re: [PATCH v2] mm/page_isolation: do not isolate the
 max order page

On Fri, Dec 4, 2020 at 12:28 AM David Hildenbrand <david@...hat.com> wrote:
>
> On 03.12.20 17:22, Muchun Song wrote:
> > The max order page has no buddy page and never merge to other order.
> > So isolating and then freeing it is pointless. And if order == MAX_ORDER
> > - 1, then the buddy can actually be a !pfn_valid() in some corner case?
> > pfn_valid_within(buddy_pfn) that follows would only catch it on archs
> > with holes in zone. Then is_migrate_isolate_page(buddy) might access an
> > invalid buddy. So this is also a bug fix.
> >
> > Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
>
> As just replied to v1, I don't think this is required and the patch

You mean we should remove the Fixes tag? Thanks.

> description can be simplified - e.g., stating that we have/had not such
> users.
>
>
> --
> Thanks,
>
> David / dhildenb
>


-- 
Yours,
Muchun