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Date: Thu, 17 Oct 2013 18:17:02 -0700
Message-ID: <CA+55aFxjBoLYbRM5hsASsLWxXkmizVY6Th2niOz2x3GQQgU+ig@mail.gmail.com>
Subject: Re: [PATCH 3/3] vdso: preallocate new vmas
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Davidlohr Bueso <davidlohr@hp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@kernel.org>,
        Michel Lespinasse <walken@google.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Rik van Riel <riel@redhat.com>, Tim Chen <tim.c.chen@linux.intel.com>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        linux-mm <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Russell King <linux@arm.linux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>, Richard Kuo <rkuo@codeaurora.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Paul Mundt <lethal@linux-sh.org>, Chris Metcalf <cmetcalf@tilera.com>,
        Jeff Dike <jdike@addtoit.com>, Richard Weinberger <richard@nod.at>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>
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This seems somewhat insane:

   int install_special_mapping(struct mm_struct *mm,
                              unsigned long addr, unsigned long len,
  +                           unsigned long vm_flags, struct page **pages,
  +                           struct vm_area_struct **vma_prealloc)
   {
  +       int ret = 0;
  +       struct vm_area_struct *vma = *vma_prealloc;

(removed the "old" lines to make it more readable).

Why pass in "struct vm_area_struct **vma_prealloc" when you could just
pass in a plain and more readable "struct vm_area_struct *vma"?

My *guess* is that you originally cleared the vma_prealloc thing if
you used it, but in the patch you sent out you definitely don't (the
_only_ use of that "vma_prealloc" is the line that loads the content
into "vma", so this interface looks like it is some remnant of an
earlier and more complicated patch?

            Linus
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