linux-kernel - Re: [PATCH 1/2] mm: Export split

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Message-ID: <20130318110334.GI10192@dhcp22.suse.cz>
Date:	Mon, 18 Mar 2013 12:03:34 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
	andi@...stfloor.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
	kamezawa.hiroyuki@...il.com, hannes@...xchg.org, yinghan@...gle.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@...rosoft.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
Acked-by: Michal Hocko <mhocko@...e.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
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