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

From: Wei Yang <[email-masked]>
Date: Thu, 6 Feb 2020 06:56:33 +0800

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
Help you, Help me