This is a bogus debug assertion failure that should be possible
starting with MariaDB 10.2.2 (which merged WL#7142 via MySQL 5.7.9).
While generating page-change redo log records is strictly out of the
question during tat certain parts of crash recovery, the
fil_names_clear() is only emitting informational MLOG_FILE_NAME
and MLOG_CHECKPOINT records to guarantee that if the server is killed
during or soon after the crash recovery, subsequent crash recovery
will be possible.
The metadata buffer that fil_names_clear() is flushing to the redo log
is being filled by recv_init_crash_recovery_spaces(), right before
starting to apply redo log, by invoking fil_names_dirty() on every
discovered tablespace for which there are changes to apply.
When it comes to Mariabackup (xtrabackup --prepare), it is strictly out
of the question to generate any redo log whatsoever, because that could
break the restore of incremental backups by causing LSN deviation.
So, the fil_names_dirty() call must be skipped when restoring backups.
recv_recovery_from_checkpoint_start(): Do not invoke fil_names_clear()
when restoring a backup.
mtr_t::commit_checkpoint(): Remove the failing assertion. The only
caller is fil_names_clear(), and it must be called by
recv_recovery_from_checkpoint_start() for normal server startup to be
crash-safe. The debug assertion in mtr_t::commit() will still
catch rogue redo log writes.
42f657cd2f