[PATCH 1/2] mm: Export split_page()

[KY Srinivasan]

> -----Original Message-----
> From: Michal Hocko [mailto:mhocko at suse.cz]
> Sent: Monday, March 18, 2013 7:04 AM
> To: KY Srinivasan
> Cc: gregkh at linuxfoundation.org; linux-kernel at vger.kernel.org;
> devel at linuxdriverproject.org; olaf at aepfle.de; apw at canonical.com;
> andi at firstfloor.org; akpm at linux-foundation.org; linux-mm at kvack.org;
> kamezawa.hiroyuki at gmail.com; hannes at cmpxchg.org; yinghan at google.com
> Subject: Re: [PATCH 1/2] mm: Export split_page()
> 
> On Sat 16-03-13 14:42:04, K. Y. Srinivasan wrote:
> > The split_page() function will be very useful for balloon drivers. On Hyper-V,
> > it will be very efficient to use 2M allocations in the guest as this (a) makes
> > the ballooning protocol with the host that much more efficient and (b) moving
> > memory in 2M chunks minimizes fragmentation in the host. Export the
> split_page()
> > function to let the guest allocations be in 2M chunks while the host is free to
> > return this memory at arbitrary granularity.
> >
> > Signed-off-by: K. Y. Srinivasan <kys at microsoft.com>
> 
> I do not have any objections to exporting the symbol (at least we
> prevent drivers code from inventing their own split_page) but the
> Hyper-V specific description should go into Hyper-V patch IMO.
> 
> So for the export with a short note that the symbol will be used by
> Hyper-V

Will do.

K. Y
> Acked-by: Michal Hocko <mhocko at suse.cz>
> 
> > ---
> >  mm/page_alloc.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 6cacfee..7e0ead6 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1404,6 +1404,7 @@ void split_page(struct page *page, unsigned int order)
> >  	for (i = 1; i < (1 << order); i++)
> >  		set_page_refcounted(page + i);
> >  }
> > +EXPORT_SYMBOL_GPL(split_page);
> >
> >  static int __isolate_free_page(struct page *page, unsigned int order)
> >  {
> > --
> > 1.7.4.1
> >
> > --
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> --
> Michal Hocko
> SUSE Labs
>