As explained in Manual:File cache#Limitations:

The file names of the cache files are determined by the according page titles. Depending on the language, which is used in the page titles, some characters in the file names will have to be encoded in order to make up a valid file name for the according file system. For languages like Arabic, Chinese and so on this may result in the follwing PHP warning:

PHP Warning: file_put_contents(cache/......html.gz): failed to open stream: File name too long in includes/cache/FileCacheBase.php on line 171

This is a known limitation.

But I haven't found a bug filed to say it's a *known* limitation. So let's use this to track that limitation.