linux-kernel - Re: Linux 2.6.26-rc7

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Date:	Mon, 23 Jun 2008 23:21:09 +0800
From:	"Jeff Chua" <jeff.chua.linux@...il.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>
Cc:	ecollins@...are.com,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	support@...are.com
Subject: Re: Linux 2.6.26-rc7

On Mon, Jun 23, 2008 at 1:26 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> So assuming it's not the XIP fix, you could try this patch instead. It
> replaces the (insane) use of VM_LOCKED with VM_SHARED (which is a lot more
> meaningful for the case of ZERO_PAGE, but strictly speaking probably
> doesn't matter either), and it teaches it about the fact that
> non-anonymous pages can be populated not just with the "->fault" handler,
> but with "->nopfn" too.
>
> I really don't think it's due to this (nobody sane really uses '->nopfn'),
> but if the XIP disabling patch doesn't make a difference, give it a try.

Linus,

This one fixes the problem! So, it's something strange that VMware is
doing, but anyway, glad you fix it!!!

Thanks for the patch.

Jeff.



> (Most of the patch is obviously the fact that I moved the conditionals
> into a helper inline function to make the dang thing more readable). The
> actual change is trivial.
>
>                Linus
>
> ---
>  mm/memory.c |   12 ++++++++++--
>  1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 9aefaae..8c5675f 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1045,6 +1045,15 @@ no_page_table:
>        return page;
>  }
>
> +/* Can we do the FOLL_ANON optimization? */
> +static inline int use_zero_page(struct vm_area_struct *vma)
> +{
> +       if (vma->vm_flags & VM_SHARED)
> +               return 0;
> +       return !vma->vm_ops ||
> +               (!vma->vm_ops->fault && !vma->vm_ops->nopfn);
> +}
> +
>  int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
>                unsigned long start, int len, int write, int force,
>                struct page **pages, struct vm_area_struct **vmas)
> @@ -1119,8 +1128,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
>                foll_flags = FOLL_TOUCH;
>                if (pages)
>                        foll_flags |= FOLL_GET;
> -               if (!write && !(vma->vm_flags & VM_LOCKED) &&
> -                   (!vma->vm_ops || !vma->vm_ops->fault))
> +               if (!write && use_zero_page(vma))
>                        foll_flags |= FOLL_ANON;
>
>                do {
>
--
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