mmzone: introduce folio_migratetype()

Introduce folio_migratetype() as a folio equivalent for
get_pageblock_migratetype().  This function intends to return the
migratetype the folio is located in, hence the name choice.

Link: https://lkml.kernel.org/r/20230614021312.34085-3-vishal.moola@gmail.comSigned-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mmzone.h

@@ -105,6 +105,9 @@ extern int page_group_by_mobility_disabled;
 #define get_pageblock_migratetype(page)					\
 	get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK)
 
+#define folio_migratetype(folio)				\
+	get_pfnblock_flags_mask(&folio->page, folio_pfn(folio),		\
+			MIGRATETYPE_MASK)
 struct free_area {
 	struct list_head	free_list[MIGRATE_TYPES];
 	unsigned long		nr_free;