With dynamic numa, pages are going to be gradully moved from one node to
another, causing the page ranges that move_freepages() examines to
contain pages that actually belong to another node.

When dynamic numa is enabled, we skip these pages instead of VM_BUGing
out on them.

This additionally moves the VM_BUG_ON() (which detects a change in node)
so that it follows the pfn_valid_within() check.

Signed-off-by: Cody P Schafer <c...@linux.vnet.ibm.com>
---
 mm/page_alloc.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1fbf5f2..75192eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -957,6 +957,7 @@ int move_freepages(struct zone *zone,
        struct page *page;
        unsigned long order;
        int pages_moved = 0;
+       int zone_nid = zone_to_nid(zone);
 
 #ifndef CONFIG_HOLES_IN_ZONE
        /*
@@ -970,14 +971,24 @@ int move_freepages(struct zone *zone,
 #endif
 
        for (page = start_page; page <= end_page;) {
-               /* Make sure we are not inadvertently changing nodes */
-               VM_BUG_ON(page_to_nid(page) != zone_to_nid(zone));
-
                if (!pfn_valid_within(page_to_pfn(page))) {
                        page++;
                        continue;
                }
 
+               if (page_to_nid(page) != zone_nid) {
+#ifndef CONFIG_DYNAMIC_NUMA
+                       /*
+                        * In the normal case (without Dynamic NUMA), all pages
+                        * in a pageblock should belong to the same zone (and
+                        * as a result all have the same nid).
+                        */
+                       VM_BUG_ON(page_to_nid(page) != zone_nid);
+#endif
+                       page++;
+                       continue;
+               }
+
                if (!PageBuddy(page)) {
                        page++;
                        continue;
-- 
1.8.2.1

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