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Date:   Wed, 2 Mar 2022 13:21:49 -0800
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     corbet@lwn.net, mike.kravetz@oracle.com, akpm@linux-foundation.org,
        keescook@chromium.org, yzaikin@google.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com,
        Adam Manzanares <a.manzanares@samsung.com>,
        Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v2 1/3] mm: hugetlb: disable freeing vmemmap pages when
 struct page crosses page boundaries
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On Wed, Mar 02, 2022 at 04:37:56PM +0800, Muchun Song wrote:
> If CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON is enabled and the size
> of "struct page" is not power of two, we cannot optimize vmemmap pages
> of HugeTLB pages. We should disable this feature in this case.

The commit log does not descrie what happens if this is left enabled in
that case? Is this a fix? Why would it be a fix? Was something failing?
How did you spot this issue? What are the consequences of not applying
this patch?

  Luis