MDEV-38968 Redundant FILE_CHECKPOINT writes

[dr-m]

• The Jira issue number for this PR is: MDEV-38968

Description

Concurrent calls to log_checkpoint_low() were possible from multiple threads, and they could cause redundant writes of FILE_CHECKPOINT records. Let us simplify the logic by making the dedicated buf_flush_page_cleaner() thread responsible for checkpoints.

log_t::write_checkpoint(lsn_t end_lsn): Add the parameter checkpoint, which replaces log_sys.next_checkpoint_lsn.

log_sys.checkpoint_pending: Remove. Only the buf_flush_page_cleaner thread will write checkpoints, hence there is no possibility of a race condition.

log_checkpoint_low(), log_checkpoint(): Remove the return value, because there cannot be any concurrent log checkpoint in progress.

buf_flush_wait(): Add special handling for log_sys.check_for_checkpoint() as well as shutdown.

buf_flush_wait_flushed(): Assert that buf_flush_page_cleaner() is available.

log_make_checkpoint(): Delegate all work to the page cleaner.

buf_flush_sync_for_checkpoint(): Update the systemd watchdog. On shutdown, keep flushing until a checkpoint has been written.

buf_flush_page_cleaner(): Revise the shutdown logic so that all changes will be written out.

buf_flush_buffer_pool(): Remove.

buf_flush_wait_flushed(): Require the caller to acquire buf_pool.flush_list_mutex.

logs_empty_and_mark_files_at_shutdown(): Simplify the logic.

fil_names_clear(): Fix an off-by-one error that would prevent removal from fil_system.named_spaces.

Release Notes

InnoDB shutdown was simplified.

How can this PR be tested?

rm -fr mysql-test/var
mkdir /tmp/var
ln -s /tmp/var mysql-test/var
mysql-test/mtr --repeat=10 --parallel=auto innodb.log_corruption_recovery{,,,,,}{,,,}
mysql-test/mtr --force --parallel=auto --big-test

This ensures that despite cmake -DWITH_INNODB_PMEM=ON the pwrite based log write code path will be used.

Basing the PR against the correct MariaDB version

• This is a new feature or a refactoring, and the PR is based against the main branch.
• This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

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[dr-m]

Apparently there are some problems with shutdown that make the tests innodb.table_flags and innodb_zip.restart fail. On i686, many --suite=mariabackup tests are failing.