InnoDB: Assertion failure in file buf0buf.cc line 5842 failing assertion ut_a(free_slot != NULL);

Found using:

• innodb_read_io_threads=24
• innodb_write_io_threads=24
• innodb_buffer_pool_instances=32
• innodb_encrypt_tables=1

Problem is that there can be more than pre-allocated number of used slots on encryption/compression because of open I/O requests.