This performance regression was introduced in the MariaDB 10.1
file format incompatibility bug fix MDEV-11623 (MariaDB 10.1.21
and MariaDB 10.2.4) and partially fixed in MariaDB 10.1.25 in
MDEV-12610 without adding a regression test case.

On a normal startup (without crash recovery), InnoDB should not read
every .ibd data file, because this is slow. Like in MySQL, for now,
InnoDB will still open every data file (without reading), and it
will read every .ibd file for which an .isl file exists, or the
DATA DIRECTORY attribute has been specified for the table.

The test case shuts down InnoDB, moves data files, replaces them
with garbage, and then restarts InnoDB, expecting no messages to
be issued for the garbage files. (Some messages will for now be
issued for the table that uses the DATA DIRECTORY attribute.)
Finally, the test shuts down the server, restores the old data files,
and restarts again to drop the tables.

fil_open_single_table_tablespace(): Remove the condition on flags,
and only call fsp_flags_try_adjust() if validate==true
(reading the first page has been requested). The only caller with
validate==false is at server startup when we are processing all
records from SYS_TABLES. The flags passed to this function are
actually derived from SYS_TABLES.TYPE and SYS_TABLES.N_COLS,
and there never was any problem with SYS_TABLES in MariaDB 10.1.
The problem that MDEV-11623 was that incorrect tablespace flags
were computed and written to FSP_SPACE_FLAGS.

MDEV-9962: encryption.innodb_encryption_filekeys stalled waiting for key encryption threads to decrypt all required spaces

Test changes.

MDEV-14814: encryption.innodb_encryption-page-compression failed in buildbot with timeout on wait condition

Problem is that if pages are in buffer pool there is no need for
decrypt or page decompression operations.

GAL-506 breaks galera_defaults MTR test by upping repl.proto_max again. Fix this once and for all by overwriting it with constant string since it makes little sense to check for it in this test.

lock_trx_release_locks(): Relax a debug assertion to allow
recovered TRX_STATE_COMMITTED_IN_MEMORY transactions.

trx_commit_in_memory(): Add DEBUG_SYNC instrumentation.

trx_undo_insert_cleanup(): Skip persistent changes if innodb_read_only
is set. This should only happen when a recovered committed transaction
would be cleaned up at shutdown.

        When table is renamed, the InnoDB's dictionary cache didn't
        change the ib_table->data_dir_path accordingly.
        Now it's set to NULL.

Before that line there is call to buf_page_get_gen that could
return block = NULL when decrypting a page fails. However,
we should set error to be != DB_SUCCESS also. In error log
there was error about decompression but in that code there
is one case where error is not set correctly.

add a test that restores the data from a binlog

Fix reinit_io_cache(WRITE_CACHE) with non-zero seek_offset.
Run encryption.tempfiles with and without binlog checksums.

The update was lost during merge.

Timing problem as sometimes table is marked as encrypted but
sometimes we are not sure and table is just marked missing.

Before killing the server, we have to FLUSH TABLES in order to
prevent the corruption of any MyISAM system tables.

PageConverter::adjust_cluster_record(): Instead of writing
the invalid value DB_ROLL_PTR=0, write a value that indicates
a fresh insert, that is, prevents the DB_ROLL_PTR from being
dereferenced in any circumstances.

It can be argued that IMPORT TABLESPACE should actually
update the dict_index_t::trx_id to prevent older transactions
from accessing the table, similar to what I did on table
rebuild in MySQL 5.6.6 in
https://github.com/mysql/mysql-server/commit/03f81a55f221095d397c375afe8a10c8038da339

Use unsigned comparison.

in gcc `-Wno-unsupported-something` will not be an error or even a warning,
so cmake will think the flag is supported. But if there's any other
warning during compilation, for any reason, unknown option will
be a warning too. Or an error when -Werror, even if that "other warning"
would not be an error on itself.

So we need to detect whether `-Wno-unsupported-something` is *really*
supported. Luckily, `-Wunsupported-something` will always fail with an
error.

So, whenever there's a need to detect if -Wno-something is supported,
test -Wsomething instead.

Suppress some messages that are emitted rarely
(when the FIL_PAGE_FILE_FLUSH_LSN of the first page of ibdata1
does not match the latest redo log checkpoint).

Previously, the function could theoretically return an uninitialized
value if the system tablespace contained no data files. It should be
impossible for InnoDB to start up in such scenario.

xtrabackup_init_temp_log(): Remove a redundant variable and limit scope.

The merge omitted some InnoDB and XtraDB conflict resolutions,
most notably, failing to merge the fix of MDEV-12173.

ibuf_merge_or_delete_for_page(), lock_rec_block_validate():
Invoke fil_space_acquire_silent() instead of fil_space_acquire().
This fixes MDEV-12173.

wsrep_debug, wsrep_trx_is_aborting(): Removed unused declarations.

_fil_io(): Remove. Instead, declare default parameters for the XtraDB
fil_io().

buf_read_page_low(): Declare default parameters, and clean up some
callers.

os_aio(): Correct the macro that is defined when !UNIV_PFS_IO.

* use a longer timeout, 10ms is not always enough
* stop waiting as long as the data is read, do not unconditionally
  wait for timeout every time

mysqltest cannot free all memory on exit by design,
so there's no need to check.

mysql frees memory in mysql_end(), so enable memory-leak-on-exit check
only after it was initialized enough to use  mysql_end() - early exits
use my_end().