Re: [Slub cleanup6 2/5] slub: get_map() function to establish map of free objects in a slab

[David Rientjes <rientjes@google.com>]

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On Fri, 15 Apr 2011, Christoph Lameter wrote:

> The bit map of free objects in a slab page is determined in various functions
> if debugging is enabled.
> 
> Provide a common function for that purpose.
> 

Although it makes writing to /sys/kernel/slab/cache/validate slower 
because of the double iteration in validate_slab().

> Signed-off-by: Christoph Lameter <cl@linux.com>
> 
> ---
>  mm/slub.c |   34 ++++++++++++++++++++++------------
>  1 file changed, 22 insertions(+), 12 deletions(-)
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2011-03-30 14:09:27.000000000 -0500
> +++ linux-2.6/mm/slub.c	2011-03-30 14:30:24.000000000 -0500
> @@ -271,10 +271,6 @@ static inline void set_freepointer(struc
>  	for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
>  			__p += (__s)->size)
>  
> -/* Scan freelist */
> -#define for_each_free_object(__p, __s, __free) \
> -	for (__p = (__free); __p; __p = get_freepointer((__s), __p))
> -
>  /* Determine object index from a given position */
>  static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
>  {
> @@ -330,6 +326,21 @@ static inline int oo_objects(struct kmem
>  	return x.x & OO_MASK;
>  }
>  
> +/*
> + * Determine a map of object in use on a page.
> + *
> + * Slab lock or node listlock must be held to guarantee that the page does
> + * not vanish from under us.
> + */
> +static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
> +{
> +	void *p;
> +	void *addr = page_address(page);
> +
> +	for (p = page->freelist; p; p = get_freepointer(s, p))
> +		set_bit(slab_index(p, s, addr), map);
> +}
> +
>  #ifdef CONFIG_SLUB_DEBUG
>  /*
>   * Debug settings:

This generates a warning without CONFIG_SLUB_DEBUG:

mm/slub.c:335: warning: a??get_mapa?? defined but not used