thp: don't allow transparent hugepage support without PSE

Archs implementing Transparent Hugepage Support must implement a function
called has_transparent_hugepage to be sure the virtual or physical CPU
supports Transparent Hugepages.

Signed-off-by: Andrea Arcangeli <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86/include/asm/pgtable.h

···
 {
 	return pmd_val(pmd) & _PAGE_PSE;
 }
+
+static inline int has_transparent_hugepage(void)
+{
+	return cpu_has_pse;
+}
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline pte_t pte_set_flags(pte_t pte, pteval_t set)

mm/huge_memory.c

···
 	int err;
 #ifdef CONFIG_SYSFS
 	static struct kobject *hugepage_kobj;
+#endif
 
+	err = -EINVAL;
+	if (!has_transparent_hugepage()) {
+		transparent_hugepage_flags = 0;
+		goto out;
+	}
+
+#ifdef CONFIG_SYSFS
 	err = -ENOMEM;
 	hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 	if (unlikely(!hugepage_kobj)) {