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>

include/linux/page_counter.h

@@ -41,7 +41,8 @@ int page_counter_try_charge(struct page_counter *counter,
 			    struct page_counter **fail);
 void page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages);
 int page_counter_limit(struct page_counter *counter, unsigned long limit);
-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);
 
 static inline void page_counter_reset_watermark(struct page_counter *counter)
 {

mm/hugetlb_cgroup.c

@@ -279,7 +279,7 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
 		return -EINVAL;
 
 	buf = strstrip(buf);
-	ret = page_counter_memparse(buf, &nr_pages);
+	ret = page_counter_memparse(buf, "-1", &nr_pages);
 	if (ret)
 		return ret;
 

mm/memcontrol.c

@@ -3414,7 +3414,7 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
 	int ret;
 
 	buf = strstrip(buf);
-	ret = page_counter_memparse(buf, &nr_pages);
+	ret = page_counter_memparse(buf, "-1", &nr_pages);
 	if (ret)
 		return ret;
 
@@ -3786,7 +3786,7 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
 	unsigned long usage;
 	int i, size, ret;
 
-	ret = page_counter_memparse(args, &threshold);
+	ret = page_counter_memparse(args, "-1", &threshold);
 	if (ret)
 		return ret;
 

mm/page_counter.c

@@ -166,18 +166,19 @@ int page_counter_limit(struct page_counter *counter, unsigned long limit)
 /**
  * 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;
 	}

net/ipv4/tcp_memcontrol.c

@@ -120,7 +120,7 @@ static ssize_t tcp_cgroup_write(struct kernfs_open_file *of,
 	switch (of_cft(of)->private) {
 	case RES_LIMIT:
 		/* see memcontrol.c */
-		ret = page_counter_memparse(buf, &nr_pages);
+		ret = page_counter_memparse(buf, "-1", &nr_pages);
 		if (ret)
 			break;
 		mutex_lock(&tcp_limit_mutex);