The VM_BUG_ON() check in move_freepages() checks whether the node
id of a page matches the node id of its zone. However, it does this
before having checked whether the struct page pointer refers to a
valid struct page to begin with. This is guaranteed in most cases,
but may not be the case if CONFIG_HOLES_IN_ZONE=y.
So reorder the VM_BUG_ON() with the pfn_valid_within() check.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
mm/page_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f64e7bcb43b7..4e298e31fa86 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1864,14 +1864,14 @@ 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(page_to_nid(page) != zone_to_nid(zone), page);
-
if (!pfn_valid_within(page_to_pfn(page))) {
page++;
continue;
}
+ /* Make sure we are not inadvertently changing nodes */
+ VM_BUG_ON_PAGE(page_to_nid(page) != zone_to_nid(zone), page);
+
if (!PageBuddy(page)) {
page++;
continue;
--
2.7.4
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