linux-kernel - Re: [PATCH] Fix to return wrong pointer in slob

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Date:	Mon, 19 May 2008 12:40:37 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	MinChan Kim <minchan.kim@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Pekka J Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH] Fix to return wrong pointer in slob


On Mon, 2008-05-19 at 22:12 +0900, MinChan Kim wrote:
> Although slob_alloc return NULL, __kmalloc_node returns NULL + align.
> Because align always can be changed, it is very hard for debugging
> problem of no page if it don't return NULL.
> 
> We have to return NULL in case of no page.
> 
> Signed-off-by: MinChan Kim <minchan.kim@...il.com>
> ---
>  mm/slob.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slob.c b/mm/slob.c
> index 6038cba..258d76d 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -469,9 +469,12 @@ void *__kmalloc_node(size_t size, gfp_t gfp, int node)
>  			return ZERO_SIZE_PTR;
>  
>  		m = slob_alloc(size + align, gfp, align, node);
> -		if (m)
> -			*m = size;
> -		return (void *)m + align;
> +		if (!m)
> +			return NULL;
> +		else {
> +			*m = size; 
> +			return (void *)m + align;
> +		}

This looks good, but I would remove the 'else {' and '}' here. It's nice
to have the 'normal path' minimally indented.

Otherwise,

Acked-by: Matt Mackall <mpm@...enic.com>

[cc:ed to Pekka, who manages the allocator tree]

>  	} else {
>  		void *ret;
>  
-- 
Mathematics is the supreme nostalgia of our time.

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