[DFS] Add dfs_filesystem_get_mounted_path() function.

components/dfs/src/dfs_fs.c

@@ -115,6 +115,37 @@ struct dfs_filesystem *dfs_filesystem_lookup(const char *path)
     return fs;
 }
 
+/**
+ * this function will return the mounted path for specified device. 
+ *
+ * @param device the device object which is mounted.
+ *
+ * @return the mounted path or RT_NULL if none device mounted. 
+ */
+const char* dfs_filesystem_get_mounted_path(struct rt_device* device)
+{
+	const char* path = RT_NULL;
+    struct dfs_filesystem *iter;
+
+    dfs_lock();
+    for (iter = &filesystem_table[0];
+            iter < &filesystem_table[DFS_FILESYSTEMS_MAX]; iter++)
+    {
+		/* fint the mounted device */
+        if (iter->ops == RT_NULL) continue;
+		else if (iter->dev_id == device) 
+		{
+			path = iter->path;
+			break;
+		}
+    }
+
+    /* release filesystem_table lock */
+    dfs_unlock();
+
+	return path;
+}
+
 /**
  * this function will fetch the partition table on specified buffer.
  *