linux-kernel - Re: [PATCH v3 1/4] mm: hugetlb: disable freeing vmemmap pages when struct page crosses page boundaries

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Message-ID: <YiY0QkE+efo1hyda@bombadil.infradead.org>
Date:   Mon, 7 Mar 2022 08:35:14 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, akpm@...ux-foundation.org,
        keescook@...omium.org, yzaikin@...gle.com, osalvador@...e.de,
        david@...hat.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com, smuchun@...il.com
Subject: Re: [PATCH v3 1/4] mm: hugetlb: disable freeing vmemmap pages when
 struct page crosses page boundaries

On Mon, Mar 07, 2022 at 09:07:05PM +0800, Muchun Song wrote:
> If the size of "struct page" is not the power of two and this
> feature is enabled, then the vmemmap pages of HugeTLB will be
> corrupted after remapping (panic is about to happen in theory).

Huh what? If a panic is possible best we prevent this in kconfig
all together. I'd instead just put some work into this instead of
adding all this run time hacks.

Can you try to add kconfig magic to detect if a PAGE_SIZE is PO2?

  Luis