mm: use existing helper to convert "on"/"off" to boolean

It's more convenient to use existing function helper to convert string
"on/off" to boolean.

Link: http://lkml.kernel.org/r/1461908824-16129-1-git-send-email-mnghuan@gmail.com
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -613,14 +613,7 @@ static int __init early_debug_pagealloc(char *buf)
 {
 	if (!buf)
 		return -EINVAL;
-
-	if (strcmp(buf, "on") == 0)
-		_debug_pagealloc_enabled = true;
-
-	if (strcmp(buf, "off") == 0)
-		_debug_pagealloc_enabled = false;
-
-	return 0;
+	return kstrtobool(buf, &_debug_pagealloc_enabled);
 }
 early_param("debug_pagealloc", early_debug_pagealloc);
 

mm/page_poison.c

@@ -13,13 +13,7 @@ static int early_page_poison_param(char *buf)
 {
 	if (!buf)
 		return -EINVAL;
-
-	if (strcmp(buf, "on") == 0)
-		want_page_poisoning = true;
-	else if (strcmp(buf, "off") == 0)
-		want_page_poisoning = false;
-
-	return 0;
+	return strtobool(buf, &want_page_poisoning);
 }
 early_param("page_poison", early_page_poison_param);