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

[Pekka Enberg <penberg@cs.helsinki.fi>]

Pekka J Enberg wrote:
> As pointed out by Christoph, it. ksize() works with SLUB and SLOB 
> accidentally because they do page allocator pass-through and thus need to 
> deal with non-PageSlab pages. SLAB, however, does not do that which is why 
> all pages passed to it must have PageSlab set (we ought to add a WARN_ON() 
> there btw).
> 
> So I suggest we fix up kobjsize() instead. Paul, does the following 
> untested patch work for you?
> 
> 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);

Hmm, actually this needs more fixing with SLOB as it never sets PageSlab.

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