mm/vmalloc.c: fix "unused function" warning

compute_subtree_max_size() is unused, when building with
DEBUG_AUGMENT_PROPAGATE_CHECK=y.

  mm/vmalloc.c:785:1: warning: unused function 'compute_subtree_max_size' [-Wunused-function].

Link: https://lkml.kernel.org/r/20220129034652.75359-1-jiapeng.chong@linux.alibaba.com
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmalloc.c

@@ -775,17 +775,6 @@ get_subtree_max_size(struct rb_node *node)
 	return va ? va->subtree_max_size : 0;
 }
 
-/*
- * Gets called when remove the node and rotate.
- */
-static __always_inline unsigned long
-compute_subtree_max_size(struct vmap_area *va)
-{
-	return max3(va_size(va),
-		get_subtree_max_size(va->rb_node.rb_left),
-		get_subtree_max_size(va->rb_node.rb_right));
-}
-
 RB_DECLARE_CALLBACKS_MAX(static, free_vmap_area_rb_augment_cb,
 	struct vmap_area, rb_node, unsigned long, subtree_max_size, va_size)
 
@@ -973,6 +962,17 @@ unlink_va(struct vmap_area *va, struct rb_root *root)
 }
 
 #if DEBUG_AUGMENT_PROPAGATE_CHECK
+/*
+ * Gets called when remove the node and rotate.
+ */
+static __always_inline unsigned long
+compute_subtree_max_size(struct vmap_area *va)
+{
+	return max3(va_size(va),
+		get_subtree_max_size(va->rb_node.rb_left),
+		get_subtree_max_size(va->rb_node.rb_right));
+}
+
 static void
 augment_tree_propagate_check(void)
 {