Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span()

Wei Yang
2020-02-05T22:56:22Z

On Wed, Feb 05, 2020 at 10:48:11PM +0800, Baoquan He wrote:
>Hi Wei Yang,
>
>On 02/05/20 at 05:59pm, Wei Yang wrote:
>> >diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> >index f294918f7211..8dafa1ba8d9f 100644
>> >--- a/mm/memory_hotplug.c
>> >+++ b/mm/memory_hotplug.c
>> >@@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>> > if (pfn) {
>> > zone->zone_start_pfn = pfn;
>> > zone->spanned_pages = zone_end_pfn - pfn;
>> >+ } else {
>> >+ zone->zone_start_pfn = 0;
>> >+ zone->spanned_pages = 0;
>> > }
>> > } else if (zone_end_pfn == end_pfn) {
>> > /*
>> >@@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>> > start_pfn);
>> > if (pfn)
>> > zone->spanned_pages = pfn - zone_start_pfn + 1;
>> >+ else {
>> >+ zone->zone_start_pfn = 0;
>> >+ zone->spanned_pages = 0;
>> >+ }
>> > }
>>
>> If it is me, I would like to take out these two similar logic out.
>
>I also like this style.
>>
>> For example:
>>
>> if () {
>> } else if () {
>> } else {
>> goto out;
>Here the last else is unnecessary, right?
>

I am afraid not.

If the range is not the first or last, we would leave pfn not initialized.

--
Wei Yang
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