2 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 09d381b71fd8..ae19af5ec02c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1137,6 +1137,10 @@ struct mem_section {
         struct page_cgroup *page_cgroup;
         unsigned long pad;
 #endif
+        /*
+         * WARNING: mem_section must be a power-of-2 in size for the
+         * calculation and use of SECTION_ROOT_MASK to make sense.
+         */
 };
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
diff --git a/mm/sparse.c b/mm/sparse.c
index 1c91f0d3f6ab..3194ec414728 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -481,6 +481,9 @@ void __init sparse_init(void)
         struct page **map_map;
 #endif
 
+        /* see include/linux/mmzone.h 'struct mem_section' definition */
+        BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section)));
+
         /* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
         set_pageblock_order();