mm: allow pgtable_page_ctor() to fail

Change pgtable_page_ctor() return type from void to bool. Returns true,
if initialization is successful and false otherwise.

Current implementation never fails, but it will change later.

Signed-off-by: Kirill A. Shutemov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/mm.h

···
 #define pte_lockptr(mm, pmd)	({(void)(pmd); &(mm)->page_table_lock;})
 #endif /* USE_SPLIT_PTE_PTLOCKS */
 
-static inline void pgtable_page_ctor(struct page *page)
+static inline bool pgtable_page_ctor(struct page *page)
 {
 	pte_lock_init(page);
 	inc_zone_page_state(page, NR_PAGETABLE);
+	return true;
 }
 
 static inline void pgtable_page_dtor(struct page *page)