Failed InnoDB initialization leaves garbage files behind

The following invocation will fail, leaving behind NUL-filled ibdata1 and ib_logfile0 in InnoDB initialization.

./mtr --mysqld=--innodb-log-file-size=1m --mysqld=--loose-innodb-log-files-in-group=1 innodb.innodb

Note: MDEV-12061 reduced the minimum value of innodb_log_files_in_group to 1. In MariaDB Server 10.5, that parameter was deprecated, and only a single ib_logfile0 can be created.

The actual minimum log file size limit is as follows:

MDEV-14425 would change the minimum (logically empty) redo log file size to 12288+16 bytes.

The log must be reasonably large to prevent overrun. Only once MDEV-14462 has been fixed, we could run with a smaller redo log without any fear of data loss. Also in that case, the log must be large enough for a single mini-transaction. A maximal mini-transaction could split a B-tree all way from the leaf to roof, modifying 2*height pages. The maximum height of a B-tree is somewhere around 32 pages when the tree is a binary tree. 2*32*innodb_page_size would be 1MiB at the default innodb_page_size=16k.

The immediate problem here is that if an attempt to initialize InnoDB with a too small log file is made, InnoDB will leave behind NUL-filled system tablespace and log files. That needs to be fixed, to avoid confusing messages like this:

innodb.innodb 'innodb'                   [ skipped ]  Test requires InnoDB with 16k Page size.

line

2021-12-15 13:36:15 140326778985536 [ERROR] InnoDB: Corrupted page [page id: space=0, page number=0] of datafile './ibdata1' could not be found in the doublewrite buffer.

2021-12-15 13:36:15 140326778985536 [ERROR] InnoDB: Plugin initialization aborted at srv0start.cc[1911] with error Data structure corruption

2021-12-15 13:36:15 140326778985536 [ERROR] Plugin 'InnoDB' init function returned error.

2021-12-15 13:36:15 140326778985536 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.

^ Found warnings in /dev/shm/10.2o/mysql-test/var/log/mysqld.1.err