[PATCH v5 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span()

[David Hildenbrand]

If we have holes, the holes will automatically get detected and removed
once we remove the next bigger/smaller section. The extra checks can
go.

Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Oscar Salvador <osalva...@suse.de>
Cc: Michal Hocko <mho...@suse.com>
Cc: David Hildenbrand <da...@redhat.com>
Cc: Pavel Tatashin <pasha.tatas...@soleen.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Wei Yang <richardw.y...@linux.intel.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
 mm/memory_hotplug.c | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 273833612774..22b3623768c8 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;
+               }
        }
-
-       /*
-        * 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