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    SubjectRe: [PATCH 4/8] asm-generic: pgalloc: provide generic pmd_alloc_one() and pmd_free_one()
    On Sat, Jun 27, 2020 at 08:03:04PM +0100, Matthew Wilcox wrote:
    > On Sat, Jun 27, 2020 at 05:34:49PM +0300, Mike Rapoport wrote:
    > > More elaborate versions on arm64 and x86 account memory for the user page
    > > tables and call to pgtable_pmd_page_ctor() as the part of PMD page
    > > initialization.
    > >
    > > Move the arm64 version to include/asm-generic/pgalloc.h and use the generic
    > > version on several architectures.
    > >
    > > The pgtable_pmd_page_ctor() is a NOP when ARCH_ENABLE_SPLIT_PMD_PTLOCK is
    > > not enabled, so there is no functional change for most architectures except
    > > of the addition of __GFP_ACCOUNT for allocation of user page tables.
    >
    > Thanks for including this line; it reminded me that we're not setting
    > the PageTable flag on the page, nor accounting it to the zone page stats.
    > Hope you don't mind me tagging a patch to do that on as 9/8.

    We also never set PageTable flag for early page tables and for the page
    tables allocated directly with get_free_page(), e.g PTI, KASAN.

    > We could also do with a pud_page_[cd]tor and maybe even p4d/pgd versions.
    > But that brings me to the next question -- could/should some of this
    > be moved over to asm-generic/pgalloc.h? The ctor/dtor aren't called
    > from anywhere else, and there's value to reducing the total amount of
    > code in mm.h, but then there's also value to keeping all the ifdef
    > ARCH_ENABLE_SPLIT_PMD_PTLOCK code together too. So I'm a bit torn.
    > What do you think?

    --
    Sincerely yours,
    Mike.

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