diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 0b0ae5084e60..59314d228ec3 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -631,6 +631,12 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
  * Please note that, confusingly, "page_mapping" refers to the inode
  * address_space which maps the page from disk; whereas "page_mapped"
  * refers to user virtual address space into which the page is mapped.
+ *
+ * For slab pages, since slab reuses the bits in struct page to store its
+ * internal states, the page->mapping does not exist as such, nor do these
+ * flags below.  So in order to avoid testing non-existent bits, please
+ * make sure that PageSlab(page) actually evaluates to false before calling
+ * the following functions (e.g., PageAnon).  See mm/slab.h.
  */
 #define PAGE_MAPPING_ANON	0x1
 #define PAGE_MAPPING_MOVABLE	0x2
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 433dbce13fe1..4d0506537621 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -69,6 +69,8 @@ static void page_table_check_clear(struct mm_struct *mm, unsigned long addr,
 
 	page = pfn_to_page(pfn);
 	page_ext = page_ext_get(page);
+
+	BUG_ON(PageSlab(page));
 	anon = PageAnon(page);
 
 	for (i = 0; i < pgcnt; i++) {
@@ -105,6 +107,8 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
 
 	page = pfn_to_page(pfn);
 	page_ext = page_ext_get(page);
+
+	BUG_ON(PageSlab(page));
 	anon = PageAnon(page);
 
 	for (i = 0; i < pgcnt; i++) {
@@ -131,6 +135,8 @@ void __page_table_check_zero(struct page *page, unsigned int order)
 	struct page_ext *page_ext;
 	unsigned long i;
 
+	BUG_ON(PageSlab(page));
+
 	page_ext = page_ext_get(page);
 	BUG_ON(!page_ext);
 	for (i = 0; i < (1ul << order); i++) {