Re: [Xen-devel] [PATCH 02/12] mm: add 'foreign' alias for the 'pinned' page flag

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Jan 06, 2015 at 06:57:27PM +0000, David Vrabel wrote:
> From: Jenny Herbert <jennifer.herbert@xxxxxxxxxx>
> 
> The foreign page flag will be used by Xen guests to mark pages that
> have grant mappings of frames from other (foreign) guests.
> 
> The foreign flag is an aliases the existing (Xen-specific) pinned

is an alias for the ..
> flag.  This is safe because pinned is only used on pages used for page
> tables and these cannot also be foreign.
> 
> Signed-off-by: Jenny Herbert <jennifer.herbert@xxxxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  include/linux/page-flags.h |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index e1f5fcd..7734cc8 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -123,6 +123,7 @@ enum pageflags {
>       /* XEN */
>       PG_pinned = PG_owner_priv_1,
>       PG_savepinned = PG_dirty,
> +     PG_foreign = PG_owner_priv_1,
>  
>       /* SLOB */
>       PG_slob_free = PG_private,
> @@ -215,6 +216,7 @@ __PAGEFLAG(Slab, slab)
>  PAGEFLAG(Checked, checked)           /* Used by some filesystems */
>  PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)  /* Xen */
>  PAGEFLAG(SavePinned, savepinned);                    /* Xen */
> +PAGEFLAG(Foreign, foreign);                          /* Xen */
>  PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
>  PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
>       __SETPAGEFLAG(SwapBacked, swapbacked)
> -- 
> 1.7.10.4
> 

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