!178 当从hashtable中获取Vnode缓存时，需要刷新Vnode的parent指针

Merge pull request !178 from Far/fatfs

fs/fat/os_adapt/fatfs.c

@@ -313,6 +313,7 @@ int fatfs_lookup(struct Vnode *parent, const char *path, int len, struct Vnode *
             goto ERROR_UNLOCK;
         }
     } else {
+        vp->parent = parent;
         free(dfp); /* hash hit dfp is no needed */
     }