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Date: Tue, 10 Feb 2009 23:13:12 +0900
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Subject: Re: [PATCH] introduce for_each_populated_zone() macro
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       Andrew Morton <akpm@linux-foundation.org>
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Hi

>> +#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
>> +
>> +
>> +
>> +
>
> There is tabs vs whitespace damage in there.

??
I'm look at it again. but I don't found whitespace damage.

> Multiple empty lines are introduced for no apparent reason.

Will fix. thanks.

> It's not clear why you did not use if (populated_zone(zone))
> instead of an if/else.

Good question.
if we make following macro,

#define for_each_populated_zone(zone)                        \
     for (zone = (first_online_pgdat())->node_zones; \
          zone;                                      \
          zone = next_zone(zone))                    \
             if (populated_zone(zone))

and, writing following caller code.

if (always_true_assumption)
  for_each_populated_zone(){
     /* some code */
  }
else
  panic();

expand to

if (always_true_assumption)
  for()
     if (populated_zone() {
     /* some code */
  }
else
  panic();

then, memoryless node cause panic().


>
> Otherwise, I did not spot anything out of the ordinary. Nice cleanup.