mod_disk_cache reads and closes hdrs.fd in recall_headers() but clearly closes hdrs.fd in open_entity (the immediately preceding callback).

On unix, the read from the closed file seems to be tolerated because they are open with buffering, but I think this is not intended.

IIUC, hdrs.fd should be left open from branches that return OK, and closed on the others.  Or the relatively short data should be buffered explicitly somewhere in memory / mod_disk_cache.