[10/67] mm/memory_hotplug: don't check for "all holes" in shrink_zone_span()

Commit Message

Andrew Morton Feb. 4, 2020, 1:34 a.m. UTC

From: David Hildenbrand <[e-mail]>
Subject: mm/memory_hotplug: don't check for "all holes" in shrink_zone_span()

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.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: "Matthew Wilcox (Oracle)" <[e-mail]>
Cc: "Aneesh Kumar K.V" <[e-mail]>
Cc: Pavel Tatashin <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Logan Gunthorpe <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Pankaj Gupta <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memory_hotplug.c |   34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

Patch

--- a/mm/memory_hotplug.c~mm-memory_hotplug-dont-check-for-all-holes-in-shrink_zone_span
+++ a/mm/memory_hotplug.c
@@ -411,6 +411,9 @@  static void shrink_zone_span(struct zone
 		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) {
 		/*
@@ -423,34 +426,11 @@  static void shrink_zone_span(struct zone
 					       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);
 }