mm, hugetlb: generalize writes to nr_hugepages

Three different interfaces alter the maximum number of hugepages for an
hstate:

 - /proc/sys/vm/nr_hugepages for global number of hugepages of the default
   hstate,

 - /sys/kernel/mm/hugepages/hugepages-X/nr_hugepages for global number of
   hugepages for a specific hstate, and

 - /sys/kernel/mm/hugepages/hugepages-X/nr_hugepages/mempolicy for number of
   hugepages for a specific hstate over the set of allowed nodes.

Generalize the code so that a single function handles all of these
writes instead of duplicating the code in two different functions.

This decreases the number of lines of code, but also reduces the size of
.text by about half a percent since set_max_huge_pages() can be inlined.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -1734,21 +1734,13 @@ static ssize_t nr_hugepages_show_common(struct kobject *kobj,
 	return sprintf(buf, "%lu\n", nr_huge_pages);
 }
 
-static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
-			struct kobject *kobj, struct kobj_attribute *attr,
-			const char *buf, size_t len)
+static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
+					   struct hstate *h, int nid,
+					   unsigned long count, size_t len)
 {
 	int err;
-	int nid;
-	unsigned long count;
-	struct hstate *h;
 	NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
 
-	err = kstrtoul(buf, 10, &count);
-	if (err)
-		goto out;
-
-	h = kobj_to_hstate(kobj, &nid);
 	if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
 		err = -EINVAL;
 		goto out;
@@ -1784,6 +1776,23 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
 	return err;
 }
 
+static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
+					 struct kobject *kobj, const char *buf,
+					 size_t len)
+{
+	struct hstate *h;
+	unsigned long count;
+	int nid;
+	int err;
+
+	err = kstrtoul(buf, 10, &count);
+	if (err)
+		return err;
+
+	h = kobj_to_hstate(kobj, &nid);
+	return __nr_hugepages_store_common(obey_mempolicy, h, nid, count, len);
+}
+
 static ssize_t nr_hugepages_show(struct kobject *kobj,
 				       struct kobj_attribute *attr, char *buf)
 {
@@ -1793,7 +1802,7 @@ static ssize_t nr_hugepages_show(struct kobject *kobj,
 static ssize_t nr_hugepages_store(struct kobject *kobj,
 	       struct kobj_attribute *attr, const char *buf, size_t len)
 {
-	return nr_hugepages_store_common(false, kobj, attr, buf, len);
+	return nr_hugepages_store_common(false, kobj, buf, len);
 }
 HSTATE_ATTR(nr_hugepages);
 
@@ -1812,7 +1821,7 @@ static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
 static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
 	       struct kobj_attribute *attr, const char *buf, size_t len)
 {
-	return nr_hugepages_store_common(true, kobj, attr, buf, len);
+	return nr_hugepages_store_common(true, kobj, buf, len);
 }
 HSTATE_ATTR(nr_hugepages_mempolicy);
 #endif
@@ -2248,36 +2257,21 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
 			 void __user *buffer, size_t *length, loff_t *ppos)
 {
 	struct hstate *h = &default_hstate;
-	unsigned long tmp;
+	unsigned long tmp = h->max_huge_pages;
 	int ret;
 
 	if (!hugepages_supported())
 		return -ENOTSUPP;
 
-	tmp = h->max_huge_pages;
-
-	if (write && hstate_is_gigantic(h) && !gigantic_page_supported())
-		return -EINVAL;
-
 	table->data = &tmp;
 	table->maxlen = sizeof(unsigned long);
 	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
 	if (ret)
 		goto out;
 
-	if (write) {
-		NODEMASK_ALLOC(nodemask_t, nodes_allowed,
-						GFP_KERNEL | __GFP_NORETRY);
-		if (!(obey_mempolicy &&
-			       init_nodemask_of_mempolicy(nodes_allowed))) {
-			NODEMASK_FREE(nodes_allowed);
-			nodes_allowed = &node_states[N_MEMORY];
-		}
-		h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);
-
-		if (nodes_allowed != &node_states[N_MEMORY])
-			NODEMASK_FREE(nodes_allowed);
-	}
+	if (write)
+		ret = __nr_hugepages_store_common(obey_mempolicy, h,
+						  NUMA_NO_NODE, tmp, *length);
 out:
 	return ret;
 }