--- a/src/http/ngx_http_cache.h
+++ b/src/http/ngx_http_cache.h
@@ -18,6 +18,7 @@
 #define NGX_HTTP_CACHE_STALE         3
 #define NGX_HTTP_CACHE_UPDATING      4
 #define NGX_HTTP_CACHE_HIT           5
+#define NGX_HTTP_CACHE_SCARCE        6
 
 #define NGX_HTTP_CACHE_KEY_LEN       16
 
@@ -97,6 +98,7 @@ typedef struct {
     ngx_rbtree_node_t                sentinel;
     ngx_queue_t                      queue;
     ngx_atomic_t                     cold;
+    ngx_atomic_t                     loading;
     off_t                            size;
 } ngx_http_file_cache_sh_t;