resource: add __adjust_resource() for internal use

Add __adjust_resource(), which is called by adjust_resource() internally
after the resource_lock is held.  There is no interface change to
adjust_resource().  This change allows other functions to call
__adjust_resource() internally while the resource_lock is held.
Signed-off-by: NToshi Kani <toshi.kani@hp.com>
Reviewed-by: NYasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: T Makphaibulchoke <tmac@hp.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/resource.c

@@ -706,24 +706,13 @@ void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
 	write_unlock(&resource_lock);
 }
 
-/**
- * adjust_resource - modify a resource's start and size
- * @res: resource to modify
- * @start: new start value
- * @size: new size
- *
- * Given an existing resource, change its start and size to match the
- * arguments.  Returns 0 on success, -EBUSY if it can't fit.
- * Existing children of the resource are assumed to be immutable.
- */
-int adjust_resource(struct resource *res, resource_size_t start, resource_size_t size)
+static int __adjust_resource(struct resource *res, resource_size_t start,
+				resource_size_t size)
 {
 	struct resource *tmp, *parent = res->parent;
 	resource_size_t end = start + size - 1;
 	int result = -EBUSY;
 
-	write_lock(&resource_lock);
-
 	if (!parent)
 		goto skip;
 
@@ -751,6 +740,26 @@ int adjust_resource(struct resource *res, resource_size_t start, resource_size_t
 	result = 0;
 
  out:
+	return result;
+}
+
+/**
+ * adjust_resource - modify a resource's start and size
+ * @res: resource to modify
+ * @start: new start value
+ * @size: new size
+ *
+ * Given an existing resource, change its start and size to match the
+ * arguments.  Returns 0 on success, -EBUSY if it can't fit.
+ * Existing children of the resource are assumed to be immutable.
+ */
+int adjust_resource(struct resource *res, resource_size_t start,
+			resource_size_t size)
+{
+	int result;
+
+	write_lock(&resource_lock);
+	result = __adjust_resource(res, start, size);
 	write_unlock(&resource_lock);
 	return result;
 }