linux-kernel - Re: [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables

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Message-ID: <20190220210315.GM12668@bombadil.infradead.org>
Date:   Wed, 20 Feb 2019 13:03:15 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Jun Yao <yaojun8558363@...il.com>,
        Laura Abbott <labbott@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables

On Mon, Feb 18, 2019 at 10:32:05PM -0700, Yu Zhao wrote:
> pgtable_pmd_page_ctor() must be used on user pmd. For kernel pmd,
> it's okay to use pgtable_page_ctor() instead only because kernel
> doesn't have thp.

I'm not sure that's true.  I think you can create THPs in vmalloc
these days.  See HAVE_ARCH_HUGE_VMAP which is supported by arm64.