linux-kernel - Re: [PATCH] x86/mm: stop allocating pmd page if failed

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Message-ID: <5010D82C.4050802@goop.org>
Date:	Wed, 25 Jul 2012 22:39:56 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Yuanhan Liu <yliu.null@...il.com>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/mm: stop allocating pmd page if failed

On 07/24/2012 06:15 AM, Yuanhan Liu wrote:
> The old code would call __get_free_page() even though previous
> allocation fail met. This is not needed.

Yeah, I guess, but its hardly worth changing.

    J


>
> Signed-off-by: Yuanhan Liu <yliu.null@...il.com>
> Cc: Jeremy Fitzhardinge <jeremy@...p.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> ---
>  arch/x86/mm/pgtable.c |   18 +++++++++---------
>  1 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index 8573b83..6760348 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -181,24 +181,24 @@ static void free_pmds(pmd_t *pmds[])
>  {
>  	int i;
>  
> -	for(i = 0; i < PREALLOCATED_PMDS; i++)
> -		if (pmds[i])
> -			free_page((unsigned long)pmds[i]);
> +	for(i = 0; i < PREALLOCATED_PMDS; i++) {
> +		if (pmds[i] == NULL)
> +			break;
> +		free_page((unsigned long)pmds[i]);
> +	}
>  }
>  
>  static int preallocate_pmds(pmd_t *pmds[])
>  {
>  	int i;
> -	bool failed = false;
>  
>  	for(i = 0; i < PREALLOCATED_PMDS; i++) {
> -		pmd_t *pmd = (pmd_t *)__get_free_page(PGALLOC_GFP);
> -		if (pmd == NULL)
> -			failed = true;
> -		pmds[i] = pmd;
> +		pmds[i] = (pmd_t *)__get_free_page(PGALLOC_GFP);
> +		if (pmds[i] == NULL)
> +			break;
>  	}
>  
> -	if (failed) {
> +	if (i < PREALLOCATED_PMDS) {
>  		free_pmds(pmds);
>  		return -ENOMEM;
>  	}

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