linux-kernel - [PATCH v2 2/2] mm,memory_hotplug: Fix shrink_{zone,node}

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Date:   Wed, 17 Jul 2019 11:07:25 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     akpm@...ux-foundation.org
Cc:     dan.j.williams@...el.com, david@...hat.com,
        pasha.tatashin@...een.com, mhocko@...e.com,
        aneesh.kumar@...ux.ibm.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 2/2] mm,memory_hotplug: Fix shrink_{zone,node}_span

Since [1], shrink_{zone,node}_span work on PAGES_PER_SUBSECTION granularity.
We need to adapt the loop that checks whether a zone/node contains only holes,
and skip the whole range to be removed.

Otherwise, since sub-sections belonging to the range to be removed have not yet
been deactivated, pfn_valid() will return true on those and we will be left
with a wrong accounting of spanned_pages, both for the zone and the node.

Fixes: mmotm ("mm/hotplug: prepare shrink_{zone, pgdat}_span for sub-section removal")
Signed-off-by: Oscar Salvador <osalvador@...e.de>
---
 mm/memory_hotplug.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b9ba5b85f9f7..2a9bbddb0e55 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -422,8 +422,8 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
 		if (page_zone(pfn_to_page(pfn)) != zone)
 			continue;
 
-		 /* If the section is current section, it continues the loop */
-		if (start_pfn == pfn)
+		/* Skip range to be removed */
+		if (pfn >= start_pfn && pfn < end_pfn)
 			continue;
 
 		/* If we find valid section, we have nothing to do */
@@ -487,8 +487,8 @@ static void shrink_pgdat_span(struct pglist_data *pgdat,
 		if (pfn_to_nid(pfn) != nid)
 			continue;
 
-		 /* If the section is current section, it continues the loop */
-		if (start_pfn == pfn)
+		/* Skip range to be removed */
+		if (pfn >= start_pfn && pfn < end_pfn)
 			continue;
 
 		/* If we find valid section, we have nothing to do */
-- 
2.12.3