auto create non-existing cache directory

fix https://github.com/chrislusf/seaweedfs/issues/1350

weed/filesys/wfs.go

@@ -89,6 +89,7 @@ func NewSeaweedFileSystem(option *Option) *WFS {
 		},
 	}
 	if option.CacheSizeMB > 0 {
+		os.MkdirAll(option.CacheDir, 0755)
 		wfs.chunkCache = chunk_cache.NewChunkCache(256, option.CacheDir, option.CacheSizeMB)
 		grace.OnInterrupt(func() {
 			wfs.chunkCache.Shutdown()

weed/util/file_util.go

@@ -49,6 +49,10 @@ func CheckFile(filename string) (exists, canRead, canWrite bool, modTime time.Ti
 		exists = false
 		return
 	}
+	if err != nil {
+		glog.Errorf("check %s: %v", filename, err)
+		return
+	}
 	if fi.Mode()&0400 != 0 {
 		canRead = true
 	}