Attachment on-disk file cache leaks open file descriptor

Monitoring the opened file descriptors related to the attachement-cache, with the following command

while :; do F=`lsof | grep attachment-cache | wc -l`; if [[ "$F" != "$OF" ]]; then echo `date` $F; OF=$F; fi; sleep 1; done

the number of opened attachement keep slowly growing while our production wiki farm is in use. I currently got an increase of about 70 FD on the first hour.

Most of the leaked FD are read-write or write-only descriptors. These does not seems to be duplicates, names and sizes varies.