InnoDB: Warning: hash index ref_count (125) is not zero after fil_discard_tablespace() [with link & patch]

Aprox. every 2-3 days, Mysql logs show this "InnoDB: Warning: hash index ref_count (125) is not zero after fil_discard_tablespace()..."

Checking through other reports, on the cause, I ended up on this page [ @ percona-server launchpad ]:

https://code.launchpad.net/~laurynas-biveinis/percona-server/bpage-io-fix

I applied, with some needed MariaDB code merge changes, that 'patch' set, and so far the issue looks to be resolved [with MariaDB].

The notes on the link above, have some good details.