MDEV-38833 Suboptimal or dead code at server startup

[dr-m]

The InnoDB bootstrap is creating unnecessary log checkpoints and even invalidating the buffer pool for no reason, making it necessary to read pages into the buffer pool during bootstrap.

Furthermore, the page cleaner thread attempts to invoke recv_sys.apply(true), even though most calls were unreachable starting with 685d958 (MDEV-14425) if not earlier.

buf_flush_sync(): Replaced with buf_flush_sync_batch(LSN_MAX), possibly preceded by recv_sys.apply(true).

buf_pool_t::assert_all_freed(): Assert that buf_pool.mutex is being held by the caller.

buf_dblwr_t::create(): Evict each doublewrite buffer pool page immediately from the buffer pool, so that there will be no need to invoke buf_pool_invalidate(). Also, remove the unnecessary call to buf_flush_wait_flushed(); there is nothing special about the doublewrite buffer creation ever since e2c63a7 (MDEV-38595) made the redo logging actually crash-safe.

buf_pool_invalidate(): Moved to the same compilation unit with the only remaining caller, recv_sys_t::apply().

srv_start(): Do not invoke buf_flush_sync(). We already created an initial checkpoint in log_t::create(lsn_t), and we will create the final one during shutdown. Together with the simplification of buf_dblwr_t::create(), this should noticeably speed up the server bootstrap. Also, simplify the log file rebuild by extending the critical section of log_sys.latch and buf_pool.flush_list_mutex.

create_log_file(): Assert and assume that both log_sys.latch and buf_pool.flush_list_mutex were acquired by the caller. This prevents any race condition with buf_flush_page_cleaner() when the log is being rebuilt.

srv_prepare_to_delete_redo_log_file(): Invoke recv_sys.apply(true) and mark the recovery as completed, before checking for one more precondition and invoking buf_flush_sync_batch(LSN_MAX). Remove some duplicated assertions as well as a redundant call to log_write_up_to() from the end. If we crash while rebuilding a latest_format log file, the subsequent startup will perform crash recovery normally. This avoids a redundant write to the old log file during log file resizing.

[CLAassistant]

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