[PATCH] memcg: fix typo in kmemcg cache walk macro

[PATCH] memcg: fix typo in kmemcg cache walk macro

[Lord Glauber Costa of Sealand]

From: Glauber Costa <glommer@parallels.com>

The macro for_each_memcg_cache_index contains a silly yet potentially
deadly mistake. Although the macro parameter is _idx, the loop tests are
done over i, not _idx.

This hasn't generated any problems so far, because all users use i as a
loop index. However, while playing with an extension of the code I
ended using another loop index and the compiler was quick to complain.

Unfortunately, this is not the kind of thing that testing reveals =(

Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/memcontrol.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 904084f..2a876a3 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -424,7 +424,7 @@ extern int memcg_limited_groups_array_size;
  * the slab_mutex must be held when looping through those caches
  */
 #define for_each_memcg_cache_index(_idx)	\
-	for ((_idx) = 0; i < memcg_limited_groups_array_size; (_idx)++)
+	for ((_idx) = 0; (_idx) < memcg_limited_groups_array_size; (_idx)++)
 
 static inline bool memcg_kmem_enabled(void)
 {
-- 
1.8.1

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Re: [PATCH] memcg: fix typo in kmemcg cache walk macro

[Michal Hocko]

On Fri 25-01-13 16:17:55, Glauber Costa wrote:
> From: Glauber Costa <glommer@parallels.com>
> 
> The macro for_each_memcg_cache_index contains a silly yet potentially
> deadly mistake. Although the macro parameter is _idx, the loop tests are
> done over i, not _idx.
> 
> This hasn't generated any problems so far, because all users use i as a
> loop index. However, while playing with an extension of the code I
> ended using another loop index and the compiler was quick to complain.
> 
> Unfortunately, this is not the kind of thing that testing reveals =(
> 
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.cz>
> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>

Ouch.
Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
>  include/linux/memcontrol.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 904084f..2a876a3 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -424,7 +424,7 @@ extern int memcg_limited_groups_array_size;
>   * the slab_mutex must be held when looping through those caches
>   */
>  #define for_each_memcg_cache_index(_idx)	\
> -	for ((_idx) = 0; i < memcg_limited_groups_array_size; (_idx)++)
> +	for ((_idx) = 0; (_idx) < memcg_limited_groups_array_size; (_idx)++)
>  
>  static inline bool memcg_kmem_enabled(void)
>  {
> -- 
> 1.8.1
> 

-- 
Michal Hocko
SUSE Labs

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