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

Baoquan He
2020-02-05T14:48:36Z

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?

> }
>
>

Like this, I believe both David and I will be satisfactory. Even though
I still think his 2nd resetting is not needed :-)

> /* The zone has no valid section */
> if (!pfn) {
> zone->zone_start_pfn = 0;
> zone->spanned_pages = 0;
> }
>
> out:
> zone_span_writeunlock(zone);
>
> Well, this is just my personal taste :-)
>
> >-
> >- /*
> >- * The section is not biggest or smallest mem_section in the zone, it
> >- * only creates a hole in the zone. So in this case, we need not
> >- * change the zone. But perhaps, the zone has only hole data. Thus
> >- * it check the zone has only hole or not.
> >- */
> >- pfn = zone_start_pfn;
> >- for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUBSECTION) {
> >- if (unlikely(!pfn_to_online_page(pfn)))
> >- continue;
> >-
> >- if (page_zone(pfn_to_page(pfn)) != zone)
> >- continue;
> >-
> >- /* Skip range to be removed */
> >- if (pfn >= start_pfn && pfn < end_pfn)
> >- continue;
> >-
> >- /* If we find valid section, we have nothing to do */
> >- zone_span_writeunlock(zone);
> >- return;
> >- }
> >-
> >- /* The zone has no valid section */
> >- zone->zone_start_pfn = 0;
> >- zone->spanned_pages = 0;
> > zone_span_writeunlock(zone);
> > }
> >
> >--
> >2.21.0
>
> --
> Wei Yang
> Help you, Help me
>