linux-kernel - Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in hugetlb_mcopy_atomic

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Date:   Fri, 15 Jul 2022 10:50:32 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Peter Xu <peterx@...hat.com>
CC:     Axel Rasmussen <axelrasmussen@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Muchun Song <songmuchun@...edance.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in
 hugetlb_mcopy_atomic_pte

On 2022/7/14 23:45, Peter Xu wrote:
> On Thu, Jul 14, 2022 at 06:09:49PM +0800, Miaohe Lin wrote:
>> As discussed in another thread, we might call page_dup_file_rmap for newly
>> allocated page (regardless of this patch). So should we come up a seperate
>> patch to call page_add_file_rmap here instead?
> 
> Hmm, why we need page_add_file_rmap() even if a new page allocated?  Say,
> we're at least also using page_dup_file_rmap() in hugetlb_no_page().
> 
> I see majorly two things extra there: memcg accounts on NR_FILE_MAPPED, and
> mlock.  But I assume both of them will not apply to hugetlb pages?

I think you are right. PageDoubleMap is also irrelevant for hugetlb.
page_add_file_rmap shouldn't be called for hugetlb page. It seems
page_dup_file_rmap can be regarded as hugetlb variant of page_add_file_rmap.
Sorry for making noise.

> 

Thanks.