mm: convert page_to_section() to memdesc_section()

Pass in the memdesc_flags_t instead of a pointer to the page. This will
allow us to remove a few conversions to struct page in upcoming patches.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: Zi Yan <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/asm-generic/memory_model.h

···
  */
 #define __page_to_pfn(pg)					\
 ({	const struct page *__pg = (pg);				\
-	int __sec = page_to_section(__pg);			\
+	int __sec = memdesc_section(__pg->flags);		\
 	(unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec)));	\
 })
 

include/linux/mm.h

···
 	page->flags.f |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT;
 }
 
-static inline unsigned long page_to_section(const struct page *page)
+static inline unsigned long memdesc_section(memdesc_flags_t mdf)
 {
-	return (page->flags.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
+	return (mdf.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
 }
 #endif
 

mm/sparse.c

···
 
 int page_to_nid(const struct page *page)
 {
-	return section_to_node_table[page_to_section(page)];
+	return section_to_node_table[memdesc_section(page->flags)];
 }
 EXPORT_SYMBOL(page_to_nid);