linux-kernel - Re: [PATCHv5 11/11] x86, mm: enable split page table lock for PMD level

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Date:	Mon, 7 Oct 2013 12:09:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Alex Thorlton <athorlton@....com>, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Eric W . Biederman" <ebiederm@...ssion.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Dave Jones <davej@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Kees Cook <keescook@...omium.org>,
	Mel Gorman <mgorman@...e.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>,
	Robin Holt <robinmholt@...il.com>,
	Sedat Dilek <sedat.dilek@...il.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv5 11/11] x86, mm: enable split page table lock for PMD
 level

On Mon, Oct 07, 2013 at 04:54:13PM +0300, Kirill A. Shutemov wrote:
>  
>  config ARCH_HIBERNATION_HEADER
> diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h
> index b4389a468f..e2fb2b6934 100644
> --- a/arch/x86/include/asm/pgalloc.h
> +++ b/arch/x86/include/asm/pgalloc.h
> @@ -80,12 +80,21 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd,
>  #if PAGETABLE_LEVELS > 2
>  static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
>  {
> -	return (pmd_t *)get_zeroed_page(GFP_KERNEL|__GFP_REPEAT);
> +	struct page *page;
> +	page = alloc_pages(GFP_KERNEL | __GFP_REPEAT| __GFP_ZERO, 0);
> +	if (!page)
> +		return NULL;
> +	if (!pgtable_pmd_page_ctor(page)) {
> +		__free_pages(page, 0);
> +		return NULL;

Thanks for thinking about us -rt folks :-)

Yeah, this is good, as we can't put the lock into the page table.

Consider this and the previous patch:

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> +	}
> +	return (pmd_t *)page_address(page);
>  }
>  
>  static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>  {
>  	BUG_ON((unsigned long)pmd & (PAGE_SIZE-1));
> +	pgtable_pmd_page_dtor(virt_to_page(pmd));
>  	free_page((unsigned long)pmd);
>  }
>  
> -- 
> 1.8.4.rc3
> 
> --
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