hugetlb: add an inline helper for finding hstate index

Add an inline helper and use it in the code.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/hugetlb.h

@@ -302,6 +302,11 @@ static inline unsigned hstate_index_to_shift(unsigned index)
 	return hstates[index].order + PAGE_SHIFT;
 }
 
+static inline int hstate_index(struct hstate *h)
+{
+	return h - hstates;
+}
+
 #else
 struct hstate {};
 #define alloc_huge_page_node(h, nid) NULL
@@ -320,6 +325,7 @@ static inline unsigned int pages_per_huge_page(struct hstate *h)
 	return 1;
 }
 #define hstate_index_to_shift(index) 0
+#define hstate_index(h) 0
 #endif
 
 #endif /* _LINUX_HUGETLB_H */

mm/hugetlb.c

@@ -1646,7 +1646,7 @@ static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
 				    struct attribute_group *hstate_attr_group)
 {
 	int retval;
-	int hi = h - hstates;
+	int hi = hstate_index(h);
 
 	hstate_kobjs[hi] = kobject_create_and_add(h->name, parent);
 	if (!hstate_kobjs[hi])
@@ -1741,11 +1741,13 @@ void hugetlb_unregister_node(struct node *node)
 	if (!nhs->hugepages_kobj)
 		return;		/* no hstate attributes */
 
-	for_each_hstate(h)
-		if (nhs->hstate_kobjs[h - hstates]) {
-			kobject_put(nhs->hstate_kobjs[h - hstates]);
-			nhs->hstate_kobjs[h - hstates] = NULL;
+	for_each_hstate(h) {
+		int idx = hstate_index(h);
+		if (nhs->hstate_kobjs[idx]) {
+			kobject_put(nhs->hstate_kobjs[idx]);
+			nhs->hstate_kobjs[idx] = NULL;
 		}
+	}
 
 	kobject_put(nhs->hugepages_kobj);
 	nhs->hugepages_kobj = NULL;
@@ -1848,7 +1850,7 @@ static void __exit hugetlb_exit(void)
 	hugetlb_unregister_all_nodes();
 
 	for_each_hstate(h) {
-		kobject_put(hstate_kobjs[h - hstates]);
+		kobject_put(hstate_kobjs[hstate_index(h)]);
 	}
 
 	kobject_put(hugepages_kobj);
@@ -1869,7 +1871,7 @@ static int __init hugetlb_init(void)
 		if (!size_to_hstate(default_hstate_size))
 			hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
 	}
-	default_hstate_idx = size_to_hstate(default_hstate_size) - hstates;
+	default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size));
 	if (default_hstate_max_huge_pages)
 		default_hstate.max_huge_pages = default_hstate_max_huge_pages;
 
@@ -2687,7 +2689,7 @@ retry:
 		 */
 		if (unlikely(PageHWPoison(page))) {
 			ret = VM_FAULT_HWPOISON |
-			      VM_FAULT_SET_HINDEX(h - hstates);
+				VM_FAULT_SET_HINDEX(hstate_index(h));
 			goto backout_unlocked;
 		}
 	}
@@ -2760,7 +2762,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			return 0;
 		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
 			return VM_FAULT_HWPOISON_LARGE |
-			       VM_FAULT_SET_HINDEX(h - hstates);
+				VM_FAULT_SET_HINDEX(hstate_index(h));
 	}
 
 	ptep = huge_pte_alloc(mm, address, huge_page_size(h));