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References: <20180724121139.62570-1-kirill.shutemov@linux.intel.com>
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In-Reply-To: <20180725123924.g2yvgie2iz2txmek@kshutemo-mobl1>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 25 Jul 2018 10:33:41 -0700
Message-ID: <CA+55aFyAo5DK2hLbFF2qg8FY0qFUaYJZNyS2wYhrSm=HfVvsWA@mail.gmail.com>
Subject: Re: [PATCHv3 1/3] mm: Introduce vma_init()
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Sender: owner-linux-mm@kvack.org
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To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andrew Morton <akpm@linux-foundation.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Dmitry Vyukov <dvyukov@google.com>, Oleg Nesterov <oleg@redhat.com>, Andrea Arcangeli <aarcange@redhat.com>, linux-mm <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Wed, Jul 25, 2018 at 5:39 AM Kirill A. Shutemov <kirill@shutemov.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