In trx_free() we used to declare the entire trx_t unaccessible
and then declare that some data members are accessible.
This involves a race condition with other threads that may concurrently
access the data members that must remain accessible.
One type of error is "AddressSanitizer: unknown-crash", whose
exact cause we have not determined.

Another type of error (reported in MDEV-23472) is "use-after-poison",
where the reported shadow bytes would in fact be 00, indicating that
the memory was no longer poisoned. The poison-access-unpoison race
condition was confirmed by "rr replay".

We eliminate the race condition by invoking MEM_NOACCESS on each
individual data member of trx_t before freeing the memory to the pool.
The memory would not be unpoisoned until the pool is freed
or the memory is being reused for another allocation.

trx_t::free(): Replaces trx_free().

trx_t::active_commit_ordered: Changed to bool, so that MEM_NOACCESS
can be invoked. Removed some accessor functions.

Pool: Remove all MEM_ instrumentation.

TrxFactory: Move the MEM_ instrumentation from Pool.

TrxFactory::debug(): Removed. Moved to trx_t::free(). Because
the memory was already marked unaccessible in trx_t::free(), the
Factory::debug() call in Pool::putl() would be unable to access it.

trx_allocate_for_background(): Replaces trx_create_low().

trx_t::free(): Perform all consistency checks while avoiding
duplication, and declare most data members unaccessible.

Shutdown of mtr tests may be too impatient, esp on CI environment where
10 seconds of `arg` of `shutdown_server arg` may not be enough for the clean
shutdown to complete.

This is fixed to remove explicit non-zero timeout argument to
`shutdown_server` from all mtr tests. mysqltest computes 60 seconds default
value for the timeout for the argless `shutdown_server` command.
This policy is additionally ensured with a compile time assert.

Leaks of some members of statically allocated objects are
not being reported by AddressSanitizer or Valgrind, but they
can be reported by implementing SAFEMALLOC instrumentation.

These leaks were identified and original fixes provided
by Michael Widenius and Vicențiu Ciorbaru.

A leak of the contents of fil_system.ssd that was introduced in
commit 10dd290b (MDEV-17380)
was caught by implementing SAFEMALLOC instrumentation of operator new.
I did not try to find out how to make AddressSanitizer or Valgrind
detect it.

fil_system_t::close(): Clear fil_system.ssd.

The leak was identified and a fix suggested by Michael Widenius
and Vicențiu Ciorbaru.

This reverts commit 57960211.

This was possible because we can create any missing aria files from
the aria transactional log

The 3 remaining syncs are:
- .frm file
- Directory where frm file is
- Aria log file

If WSREP was not initalized SHOW GLOBAL STATUS could have a random
value of "wsrep"

		in buf_page_set_sticky

- Adding os_thread_yield() in buf_page_create() to avoid the continuous
buffer pool mutex acquistions.

			in buf_page_set_sticky

commit a1f899a8 (MDEV-23233) added the
code to make page sticky. So that InnoDB can't allow the page to
be grabbed by other thread while doing lazy drop of ahi.

But the block could be in flush list and it could have io_fix value
as BUF_IO_WRITE. It could lead to the failure in buf_page_set_sticky().

buf_page_create(): If btr_search_drop_page_hash_index() must be invoked,
take x-latch on the block. If the block io_fix value is other than
BUF_IO_NONE, release the buffer pool mutex and page hash lock and
wait for I/O to complete.

Since commit 15093639 (MDEV-23484)
the rollback of InnoDB transactions is no longer protected by
dict_operation_lock. Removing that protection revealed a race
condition between transaction rollback and the rollback of an
online table-rebuilding operation (OPTIMIZE TABLE, or any online
ALTER TABLE that is rebuilding the table).

row_undo_mod_clust(): Re-check dict_index_is_online_ddl() after
acquiring index->lock, similar to how row_undo_ins_remove_clust_rec()
is doing it. Because innobase_online_rebuild_log_free() is holding
exclusive index->lock while invoking row_log_free(), this re-check
will ensure that row_log_table_low() will not be invoked when
index->online_log=NULL.

A different race condition is possible between the rollback of a
recovered transaction and the start of online secondary index creation.
Because prepare_inplace_alter_table_dict() is not acquiring an InnoDB
table lock in this case, and because recovered transactions are not
covered by metadata locks (MDL), the dict_table_t::indexes could be
modified by prepare_inplace_alter_table_dict() while the rollback of
a recovered transaction is being executed. Normal transactions would
be covered by MDL, and during prepare_inplace_alter_table_dict() we
do hold MDL_EXCLUSIVE, that is, an online ALTER TABLE operation may
not execute concurrently with other transactions that have accessed
the table.

row_undo(): To prevent a race condition with
prepare_inplace_alter_table_dict(), acquire dict_operation_lock
for all recovered transactions. Before MDEV-23484 we used to acquire
it for all transactions, not only recovered ones.

Note: row_merge_drop_indexes() would not invoke
dict_index_remove_from_cache() while transactional locks
exist on the table, or while any thread is holding an open table handle.
OK, it does that for FULLTEXT INDEX, but ADD FULLTEXT INDEX is not
supported as an online operation, and therefore
prepare_inplace_alter_table_dict() would acquire a table S lock,
which cannot succeed as long as recovered transactions on the table
exist, because they would hold a conflicting IX lock on the table.

Ever since MDEV-15053 changed something in the page flushing,
we are occasionally observing pending I/O for a data file that
is about to be deleted.

fil_check_pending_io(): Change the Warning to a note.

This message was already made less frequent in
commit dcc0baf5 (10.5.4)
and commit 65f831d1 (10.3.24, 10.4.14).

SELECT WSREP_LAST_SEEN_GTID aborts the server if no provider is
loaded.

Some invalid wsrep_provider paths may be interpreted as a valid
directory. For example '/invalid/libgalera_smm.so' with UTF character
set is interpreted as '/', which is a valid directory. A early check
that wsrep_provider should not be a directory fixes it.

This happens with global wsrep_on disabled and local wsrep_on enabled.
The fix consists in avoiding sync wait when global wsrep_on is
disabled.

In commit fe39d02f (MDEV-20638)
we removed some wake-up signaling of the master thread that should
have been there, to ensure a steady log checkpointing workload.

Common sense suggests that the commit omitted some necessary calls
to srv_inc_activity_count(). But, an attempt to add the call to
trx_flush_log_if_needed_low() as well as to reinstate the function
innobase_active_small() did not restore the performance for the
case where sync_binlog=1 is set.

Therefore, we will revert the entire commit in MariaDB Server 10.2.
In MariaDB Server 10.5, adding a srv_inc_activity_count() call to
trx_flush_log_if_needed_low() did restore the performance, so we
will not revert MDEV-20638 across all versions.

InnoDB transaction rollback includes an unnecessary work-around for
a data corruption bug that was fixed by me in MySQL 5.6.12
mysql/mysql-server@935ba09d52c1908bde273ad1940b5ab919d9763d
and ported to MariaDB 10.0.8 by
commit c291ddfd
in 2013 and 2014, respectively.

By acquiring and releasing dict_operation_lock in shared mode,
row_undo() hopes to prevent the table from being dropped while
the undo log record is being rolled back. But, thanks to mentioned fix,
debug assertions (that we are adding) show that the rollback is
protected by transactional locks (table IX lock, in addition to
implicit or explicit exclusive locks on the records that had been modified).

Because row_drop_table_for_mysql() would invoke
row_add_table_to_background_drop_list() if any locks exist on the table,
the mere existence of locks (which is guaranteed during ROLLBACK) is
enough to protect the table from disappearing. Hence, acquiring and
releasing dict_operation_lock for every row that is being rolled back is
unnecessary.

row_undo(): Remove the unnecessary acquisition and release of
dict_operation_lock.

Note: row_add_table_to_background_drop_list() is mostly working around
bugs outside InnoDB:
MDEV-21175 (insufficient MDL protection of FOREIGN KEY operations)
MDEV-21602 (incorrect error handling of CREATE TABLE...SELECT).

Regretfully, the parameter innodb_log_checksums was introduced
in MySQL 5.7.9 (the first GA release of that series) by
mysql/mysql-server@af0acedd885eb7103e319f79d25fda7386ef1506
which partly replaced a parameter that had been introduced in 5.7.8
mysql/mysql-server@22ba38218e1d76c24f69b5a5595ad3bf5933acb0
as innodb_log_checksum_algorithm.

Given that the CRC-32C operations are accelerated on many processor
implementations (AMD64 with SSE4.2; since MDEV-22669 also on IA-32
with SSE4.2, POWER 8 and later, ARMv8 with some extensions)
and by lookup tables when only generic SISD instructions are available,
there should be no valid reason to disable checksums.

In MariaDB 10.5.2, as a preparation for MDEV-12353, MDEV-19543 deprecated
and ignored the parameter innodb_log_checksums altogether. This should
imply that after a clean shutdown with innodb_log_checksums=OFF one
cannot upgrade to MariaDB Server 10.5 at all.

Due to these problems, let us deprecate the parameter innodb_log_checksums
and honor it only during server startup.
The command SET GLOBAL innodb_log_checksums will always set the
parameter to ON.

dict_col_t::same_encoding(), dict_col_t::same_format(): Allow
an instantaneous change of a column to a compatible encoding,
just like ha_innobase::can_convert_string() and similar functions do.

Problem:
=======
InnoDB drops the column which has foreign key relations on it. So it
tries to load the foreign key during rename process of copy algorithm
even though the foreign_key_check is disabled.

Solution:
========
During alter copy algorithm, InnoDB ignores the error while loading
the foreign key constraint if foreign key check is disabled. It
should throw the warning about failure of the foreign key constraint
when foreign key check is disabled.

This problem is caused by 6697135c
(MDEV-21572). During recovery, InnoDB prefetches the siblings of
change buffer index leaf page. It does asynchronous page read
and recovery scenario wasn't handled in buf_read_page_background().
It leads to the refusal of startup of the server.

Solution:
=========
  InnoDB shouldn't allow the change buffer index page siblings
to be prefetched.

Remove __bss_start & Co, because systen call "write" check buffer address and return EFAULT if it is wrong.

Adding any unknown option to the "[mysqld_safe]" section makes
mysqld impossible to start with mysqld_multi. For example, after
adding the unknown option "numa_interleave" to the "[mysqld_safe]"
section, mysqld_multi exits with the following diagnostics:

[ERROR] /usr/local/mysql/bin/mysqld: unknown option '--numa_interleave'

To get rid of this behavior, this patch by default adds the "--loose-"
prefix to all unknown (for mysqld_safe) options. This behavior can be
enabled explicitly with the --ignore-unknown option and disabled with
the --no-ignore-unknown option.