linux-kernel - Re: [PATCHv3 1/3] mm: Introduce vma

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Date:   Wed, 25 Jul 2018 10:33:41 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 1/3] mm: Introduce vma_init()

On Wed, Jul 25, 2018 at 5:39 AM Kirill A. Shutemov <kirill@...temov.name> wrote:
>
> There are few more:
>
> arch/arm64/include/asm/tlb.h:   struct vm_area_struct vma = { .vm_mm = tlb->mm, };
> arch/arm64/mm/hugetlbpage.c:    struct vm_area_struct vma = { .vm_mm = mm };
> arch/arm64/mm/hugetlbpage.c:    struct vm_area_struct vma = { .vm_mm = mm };

We probably do not care. These are not "real" vma's and are never used
as such. They are literally just fake vmas for the "flush_tlb()"
machinery, which won't ever really cause any VM activity and will just
call back to the architecture TLB flushing routines.

They initialize vm_mm exactly because that's how the mm is passed down
to the tlb flushing (we pass the whole vma because some architectures
than have special flags in vm_flags too that can affect how the TLB
gets flushed - ie "only flush ITLB if it's an execute-only vma" etc).

Using "vma_init()" on them is only confusing, I think.

                 Linus