mm/page_owner: set correct gfp_mask on page_owner

Currently, we set wrong gfp_mask to page_owner info in case of isolated
freepage by compaction and split page. It causes incorrect mixed
pageblock report that we can get from '/proc/pagetypeinfo'. This metric
is really useful to measure fragmentation effect so should be accurate.
This patch fixes it by setting correct information.

Without this patch, after kernel build workload is finished, number of
mixed pageblock is 112 among roughly 210 movable pageblocks.

But, with this fix, output shows that mixed pageblock is just 57.

Signed-off-by: Joonsoo Kim <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/page_owner.h

···
 extern void __reset_page_owner(struct page *page, unsigned int order);
 extern void __set_page_owner(struct page *page,
 			unsigned int order, gfp_t gfp_mask);
+extern gfp_t __get_page_owner_gfp(struct page *page);
 
 static inline void reset_page_owner(struct page *page, unsigned int order)
 {
···
 
 	__set_page_owner(page, order, gfp_mask);
 }
+
+static inline gfp_t get_page_owner_gfp(struct page *page)
+{
+	if (likely(!page_owner_inited))
+		return 0;
+
+	return __get_page_owner_gfp(page);
+}
 #else
 static inline void reset_page_owner(struct page *page, unsigned int order)
 {
···
 static inline void set_page_owner(struct page *page,
 			unsigned int order, gfp_t gfp_mask)
 {
+}
+static inline gfp_t get_page_owner_gfp(struct page *page)
+{
+	return 0;
 }
 
 #endif /* CONFIG_PAGE_OWNER */

mm/page_alloc.c

···
 void split_page(struct page *page, unsigned int order)
 {
 	int i;
+	gfp_t gfp_mask;
 
 	VM_BUG_ON_PAGE(PageCompound(page), page);
 	VM_BUG_ON_PAGE(!page_count(page), page);
···
 		split_page(virt_to_page(page[0].shadow), order);
 #endif
 
-	set_page_owner(page, 0, 0);
+	gfp_mask = get_page_owner_gfp(page);
+	set_page_owner(page, 0, gfp_mask);
 	for (i = 1; i < (1 << order); i++) {
 		set_page_refcounted(page + i);
-		set_page_owner(page + i, 0, 0);
+		set_page_owner(page + i, 0, gfp_mask);
 	}
 }
 EXPORT_SYMBOL_GPL(split_page);
···
 	zone->free_area[order].nr_free--;
 	rmv_page_order(page);
 
-	set_page_owner(page, order, 0);
+	set_page_owner(page, order, __GFP_MOVABLE);
 
 	/* Set the pageblock if the isolated page is at least a pageblock */
 	if (order >= pageblock_order - 1) {

mm/page_owner.c

···
 	__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
 }
 
+gfp_t __get_page_owner_gfp(struct page *page)
+{
+	struct page_ext *page_ext = lookup_page_ext(page);
+
+	return page_ext->gfp_mask;
+}
+
 static ssize_t
 print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 		struct page *page, struct page_ext *page_ext)