linux-kernel - Re: [PATCH] mm/memory_hotplug: use helper function zone_end_pfn() to get end

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Date:   Thu, 28 Jan 2021 09:58:57 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     David Hildenbrand <david@...hat.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/memory_hotplug: use helper function zone_end_pfn() to
 get end_pfn

Hi:
On 2021/1/27 17:40, David Hildenbrand wrote:
> On 27.01.21 10:32, Miaohe Lin wrote:
>> Commit 108bcc96ef70 ("mm: add & use zone_end_pfn() and zone_spans_pfn()")
>> introduced the helper zone_end_pfn() to calculate the zone end pfn.  But
>> update_pgdat_span() forgot to use it. Use this helper and re-name local
>> variable zone_end_pfn to end_pfn to fix below compilation error:
>>
>> mm/memory_hotplug.c: In function ‘update_pgdat_span’:
>> mm/memory_hotplug.c:448:32: error: called object ‘zone_end_pfn’ is not a
>> function or function pointer
>>     unsigned long zone_end_pfn = zone_end_pfn(zone);
>>                                  ^~~~~~~~~~~~
>> mm/memory_hotplug.c:448:17: note: declared here
>>     unsigned long zone_end_pfn = zone_end_pfn(zone);
>>                   ^~~~~~~~~~~~
>>
> 
> Please don't talk about compilation issues your changes introduce in that detail, that's just confusing and looks like something would already be broken. Please simplify to something like

I will keep this in mind. Thanks.

> 
> "Let's use zone_end_pfn(zone). We have to rename the local variable to avoid an identifier clash (variable vs. function)."
> 
> With that
> 
> Reviewed-by: David Hildenbrand <david@...hat.com>
> 

Many thanks for review and reply.

>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>   mm/memory_hotplug.c | 9 ++++-----
>>   1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 710e469fb3a1..0483db52b85f 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -493,20 +493,19 @@ static void update_pgdat_span(struct pglist_data *pgdat)
>>         for (zone = pgdat->node_zones;
>>            zone < pgdat->node_zones + MAX_NR_ZONES; zone++) {
>> -        unsigned long zone_end_pfn = zone->zone_start_pfn +
>> -                         zone->spanned_pages;
>> +        unsigned long end_pfn = zone_end_pfn(zone);
>>             /* No need to lock the zones, they can't change. */
>>           if (!zone->spanned_pages)
>>               continue;
>>           if (!node_end_pfn) {
>>               node_start_pfn = zone->zone_start_pfn;
>> -            node_end_pfn = zone_end_pfn;
>> +            node_end_pfn = end_pfn;
>>               continue;
>>           }
>>   -        if (zone_end_pfn > node_end_pfn)
>> -            node_end_pfn = zone_end_pfn;
>> +        if (end_pfn > node_end_pfn)
>> +            node_end_pfn = end_pfn;
>>           if (zone->zone_start_pfn < node_start_pfn)
>>               node_start_pfn = zone->zone_start_pfn;
>>       }
>>
> 
>