mm: page_counter: pull "-1" handling out of page_counter_memparse()

The unified hierarchy interface for memory cgroups will no longer use "-1"
to mean maximum possible resource value.  In preparation for this, make
the string an argument and let the caller supply it.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_counter.c b/mm/page_counter.c
index a009574..11b4bed 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -166,18 +166,19 @@
 /**
  * page_counter_memparse - memparse() for page counter limits
  * @buf: string to parse
+ * @max: string meaning maximum possible value
  * @nr_pages: returns the result in number of pages
  *
  * Returns -EINVAL, or 0 and @nr_pages on success.  @nr_pages will be
  * limited to %PAGE_COUNTER_MAX.
  */
-int page_counter_memparse(const char *buf, unsigned long *nr_pages)
+int page_counter_memparse(const char *buf, const char *max,
+			  unsigned long *nr_pages)
 {
-	char unlimited[] = "-1";
 	char *end;
 	u64 bytes;
 
-	if (!strncmp(buf, unlimited, sizeof(unlimited))) {
+	if (!strcmp(buf, max)) {
 		*nr_pages = PAGE_COUNTER_MAX;
 		return 0;
 	}