Re: [PATCH] nommu: Push kobjsize() slab-specific logic down to ksize().

[Christoph Lameter <clameter@sgi.com>]

On Wed, 21 May 2008, Pekka J Enberg wrote:

> So I suggest we fix up kobjsize() instead. Paul, does the following 
> untested patch work for you?

Regardless of the test : Pekka's patch is a bugfix and should go via 
stable. kobjsize seems to assume that page->index contains the order
of a page. For a pagecache page it contains the page number in the 
mapping. So this should bug frequently if used on arbitrary objects.

> diff --git a/mm/nommu.c b/mm/nommu.c
> index ef8c62c..a573aeb 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -115,10 +115,7 @@ unsigned int kobjsize(const void *objp)
>  	if (PageSlab(page))
>  		return ksize(objp);
>  
> -	BUG_ON(page->index < 0);
> -	BUG_ON(page->index >= MAX_ORDER);
> -
> -	return (PAGE_SIZE << page->index);
> +	return PAGE_SIZE << compound_order(page);
>  }
>  
>  /*
> diff --git a/mm/slab.c b/mm/slab.c
> 

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