ext4 uses rb_node = NULL; to zero rb_root at few places.  Using
RB_ROOT as the initializer is more portable in case the underlying
implementation of rbtrees changes in the future.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Eric Paris <eparis@redhat.com>
                entry = rb_entry(n, struct ext4_system_zone, node);
                kmem_cache_free(ext4_system_zone_cachep, entry);
                if (!parent)
-                       EXT4_SB(sb)->system_blks.rb_node = NULL;
+                       EXT4_SB(sb)->system_blks = RB_ROOT;
                else if (parent->rb_left == n)
                        parent->rb_left = NULL;
                else if (parent->rb_right == n)
                        parent->rb_right = NULL;
                n = parent;
        }
-       EXT4_SB(sb)->system_blks.rb_node = NULL;
+       EXT4_SB(sb)->system_blks = RB_ROOT;
 }
 
 /*
 
                        kfree(old);
                }
                if (!parent)
-                       root->rb_node = NULL;
+                       *root = RB_ROOT;
                else if (parent->rb_left == n)
                        parent->rb_left = NULL;
                else if (parent->rb_right == n)
 
 
        INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
        init_rwsem(&meta_group_info[i]->alloc_sem);
-       meta_group_info[i]->bb_free_root.rb_node = NULL;
+       meta_group_info[i]->bb_free_root = RB_ROOT;
 
 #ifdef DOUBLE_CHECK
        {