Re: [PATCH] mm: Simplify for_each_populated_zone()

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Oct 19, 2012 at 04:25:47PM +0530, Srivatsa S. Bhat wrote:
> Move the check for populated_zone() to the control statement of the
> 'for' loop and get rid of the odd looking if/else block.
> 
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
> 
>  include/linux/mmzone.h |    7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 50aaca8..5bdf02e 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -913,11 +913,8 @@ extern struct zone *next_zone(struct zone *zone);
>  
>  #define for_each_populated_zone(zone)		        \
>  	for (zone = (first_online_pgdat())->node_zones; \
> -	     zone;					\
> -	     zone = next_zone(zone))			\
> -		if (!populated_zone(zone))		\
> -			; /* do nothing */		\
> -		else
> +	     zone && populated_zone(zone);		\
> +	     zone = next_zone(zone))

I don't think we want to /abort/ the loop when encountering an
unpopulated zone.