linux-kernel - Re: [PATCH v1] hugetlb: pass head page to remove_hugetlb

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Date:   Thu, 27 May 2021 01:31:47 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>
Cc:     linux-mm@...ck.org, Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] hugetlb: pass head page to remove_hugetlb_page()

On Thu, May 27, 2021 at 08:52:57AM +0900, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> When memory_failure() or soft_offline_page() is called on a tail page of
> some hugetlb page, "BUG: unable to handle page fault" error can be
> triggered.
> 
> remove_hugetlb_page() dereferences page->lru, so it's assumed that the
> page points to a head page, but one of the caller,
> dissolve_free_huge_page(), provides remove_hugetlb_page() with 'page'
> which could be a tail page.  So pass 'head' to it, instead.

I'd like to point out that with folios, this is a compile-time error,
not a run-time error.