linux-kernel - Re: [PATCH v2] mm: incorporate zero pages into transparent huge pages

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Message-ID: <20150211221600.GN11755@redhat.com>
Date:	Wed, 11 Feb 2015 23:16:00 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Ebru Akagunduz <ebru.akagunduz@...il.com>
Cc:	linux-mm@...ck.org, akpm@...ux-foundation.org,
	kirill@...temov.name, mhocko@...e.cz, mgorman@...e.de,
	rientjes@...gle.com, sasha.levin@...cle.com, hughd@...gle.com,
	hannes@...xchg.org, vbabka@...e.cz, linux-kernel@...r.kernel.org,
	riel@...hat.com
Subject: Re: [PATCH v2] mm: incorporate zero pages into transparent huge pages

On Wed, Feb 11, 2015 at 11:03:55PM +0200, Ebru Akagunduz wrote:
> Changes in v2:
>  - Check zero pfn in release_pte_pages() (Andrea Arcangeli)

.. and in:

> @@ -2237,7 +2237,7 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
>  		pte_t pteval = *_pte;
>  		struct page *src_page;
>  
> -		if (pte_none(pteval)) {
> +		if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
>  			clear_user_highpage(page, address);
>  			add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
>  		} else {

__collapse_huge_page_copy, both were needed as far as I can tell.

I haven't tested it but it's looking good.

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>
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