There are many filesystem related errors that can occur with
MariaBackup. These already outputed to stderr with a good description of
the error. Many of these are permission or resource (file descriptor)
limits where the assertion and resulting core crash doesn't offer
developers anything more than the log message. To the user, assertions
and core crashes come across as poor error handling.

As such we return an error and handle this all the way up the stack.

log_t::create(): Return whether the initialisation succeeded.
It may fail if too large an innodb_log_buffer_size is specified.

- `mariadb-backup --backup` was fixed to fetch the value of the
   @@aria_log_dir_path server variable and copy aria_log* files
   from @@aria_log_dir_path directory to the backup directory.
   Absolute and relative (to --datadir) paths are supported.

   Before this change aria_log* files were copied to the backup
   only if they were in the default location in @@datadir.

- `mariadb-backup --copy-back` now understands a new my.cnf and command line
   parameter --aria-log-dir-path.

  `mariadb-backup --copy-back` in the main loop in copy_back()
   (when copying back from the backup directory to --datadir)
   was fixed to ignore all aria_log* files.

   A new function copy_back_aria_logs() was added.
   It consists of a separate loop copying back aria_log* files from
   the backup directory to the directory specified in --aria-log-dir-path.
   Absolute and relative (to --datadir) paths are supported.
   If --aria-log-dir-path is not specified,
   aria_log* files are copied to --datadir by default.

- The function is_absolute_path() was fixed to understand MTR style
  paths on Windows with forward slashes, e.g.
   --aria-log-dir-path=D:/Buildbot/amd64-windows/build/mysql-test/var/...

This is a non-functional change.

simplifying the code logic:
- removing global variables ds_data and ds_meta
- passing these variables as parameters to functions instead
- adding helper classes: Datasink_free_list and Backup_datasinks
- moving some function accepting a ds_ctxt parameter
  as methods to ds_ctxt.

MDEV-25887 "Got notification message from PID xxxx, but reception only permitted for main PID yyyy" in systemd during SST

server has systemd support and calls sd_notify() to communicate
the status to systemd.

mariabackup links the whole server in, but it should not notify
systemd, because it's not started or managed by systemd.

MDEV-29050 mariabackup issues error messages during InnoDB tablespaces export on partial backup preparing

The solution is to suppress error messages for missing tablespaces if
mariabackup is launched with "--prepare --export" options.

"mariabackup --prepare --export" invokes itself with --mysqld parameter.
If the parameter is set, then it starts server to feed "FLUSH TABLES ...
FOR EXPORT;" queries for exported tablespaces. This is "normal" server
start, that's why new srv_operation value is introduced.

Reviewed by Marko Makela.

fil_node_open_file_low() tries to close files from the top of
fil_system.space_list if the number of opened files is exceeded.

It invokes fil_space_t::try_to_close(), which iterates the list searching
for the first opened space. Then it just closes the space, leaving it in
the same position in fil_system.space_list.

On heavy files opening, like during 'SHOW TABLE STATUS ...' execution,
if the number of opened files limit is reached,
fil_space_t::try_to_close() iterates more and more closed spaces before
reaching any opened space for each fil_node_open_file_low() call. What
causes performance regression if the number of spaces is big enough.

The fix is to keep opened spaces at the top of fil_system.space_list,
and move closed files at the end of the list.

For this purpose fil_space_t::space_list_last_opened pointer is
introduced. It points to the last inserted opened space in
fil_space_t::space_list. When space is opened, it's inserted to the
position just after the pointer points to in fil_space_t::space_list to
preserve the logic, inroduced in MDEV-23855. Any closed space is added
to the end of fil_space_t::space_list.

As opened spaces are located at the top of fil_space_t::space_list,
fil_space_t::try_to_close() finds opened space faster.

There can be the case when opened and closed spaces are mixed in
fil_space_t::space_list if fil_system.freeze_space_list was set during
fil_node_open_file_low() execution. But this should not cause any error,
as fil_space_t::try_to_close() still iterates spaces in the list.

There is no need in any test case for the fix, as it does not change any
functionality, but just fixes performance regression.

Normalize innodb_flush_method, the same as the service, before
attempting to print it.

Changing the tool name in the "mariadb-backup --help" output
from "innobackupex" to "mariadb-backup".

Minimize unsafe C functions usage - replace strcat() and strcpy() (and strncat() and strncpy()) with custom safe_strcat() and safe_strcpy() functions

The MariaDB code base uses strcat() and strcpy() in several
places. These are known to have memory safety issues and their usage is
discouraged. Common security scanners like Flawfinder flags them. In MariaDB we
should start using modern and safer variants on these functions.

This is similar to memory issues fixes in 19af1890
and 9de9f105 but now replace use of strcat()
and strcpy() with safer options strncat() and strncpy().

However, add '\0' forcefully to make sure the result string is correct since
for these two functions it is not guaranteed what new string will be null-terminated.

Example:

    size_t dest_len = sizeof(g->Message);
    strncpy(g->Message, "Null json tree", dest_len); strncat(g->Message, ":",
    sizeof(g->Message) - strlen(g->Message)); size_t wrote_sz = strlen(g->Message);
    size_t cur_len = wrote_sz >= dest_len ? dest_len - 1 : wrote_sz;
    g->Message[cur_len] = '\0';

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the BSD-new
license. I am contributing on behalf of my employer Amazon Web Services

-- Reviewer and co-author Vicențiu Ciorbaru <vicentiu@mariadb.org>
-- Reviewer additions:
* The initial function implementation was flawed. Replaced with a simpler
  and also correct version.
* Simplified code by making use of snprintf instead of chaining strcat.
* Simplified code by removing dynamic string construction in the first
  place and using static strings if possible. See connect storage engine
  changes.

			to copy datafile

- Mariabackup fails to copy the undo log tablespace when it undergoes
truncation. So Mariabackup should detect the redo log which does
undo tablespace truncation and also backup should read the minimum
file size of the tablespace and ignore the error while reading.

- Throw error when innodb undo tablespace read failed, but backup
doesn't find the redo log for undo tablespace truncation

The variable was not really being used for anything. The parameters
innodb_read_io_threads, innodb_write_io_threads have replaced
innodb_file_io_threads.

- Mariabackup fails to open the undo tablespaces while applying delta
files to the corresponding data file. Mariabackup opens the
undo tablespaces first time in srv_undo_tablespaces_init() and does
tries to open the undo tablespaces in xtrabackup_apply_deltas() with
conflicting mode and leads to the failure.

- Mariabackup should close the undo tablespaces before applying
the incremental delta files.

- mariabackup fails to assign srv_undo_space_id_start when the
dedicated undo tablespaces are disabled

In commit 28325b08
a compile-time option was introduced to disable the macros
DBUG_ENTER and DBUG_RETURN or DBUG_VOID_RETURN.

The parameter name WITH_DBUG_TRACE would hint that it also
covers DBUG_PRINT statements. Let us do that: WITH_DBUG_TRACE=OFF
shall disable DBUG_PRINT() as well.

A few InnoDB recovery tests used to check that some output from
DBUG_PRINT("ib_log", ...) is present. We can live without those checks.

Reviewed by: Vladislav Vaintroub

xb_read_delta_metadata(): For ROW_FORMAT=COMPRESSED tables, initialize
the info.zip_size with the physical page size and let info.page_size
remain the logical page size, like xb_delta_open_matching_space()
expects it to be ever since
commit 0a1c3477 (MDEV-18493).

Since the 10.5 split of the privileges, the required GRANTs
for various mariabackup operations has changed.

In the addition of tests, a number of mappings where incorrect:

The option --lock-ddl-per-table didn't require connection admin.

The option --safe-slave-backup requires SLAVE MONITOR even without
the --no-lock option.

Avoid the loop with getting rid of back and forth jumping.

This reverts commit 17e0f522.

The solution is to initialize field_ref_zero in main_low() before
xtrabackup_backup_func() and xtrabackup_prepare_func() calls.

MDEV-28446 mariabackup prepare fails for incrementals if a new schema is created after full backup is taken

When "mariabackup --target-dir=$basedir --incremental-dir=$incremental_dir"
is running and is moving a new table file (e.g. `db1/t1.new`) from the
incremental directory to the base directory, it needs to verify that the base
backup database directory (e.g. `$basedir/db1`) really exists
(or create it otherwise).

The table `db1/t1` can come from a new database `db1` which
was created during the base mariabackup execution time.

In such case the directory `db1` exists only in the incremental directory,
but does not exist in the base directory.

MDEV-24317 Data race in LOGGER::init_error_log at sql/log.cc:1443 and in LOGGER::error_log_print at sql/log.cc:1181

don't initialize error_log_handler_list in set_handlers()
* error_log_handler_list is initialized to LOG_FILE early, in init_base()
* set_handlers always reinitializes it to LOG_FILE, so it's pointless
* after init_base() concurrent threads start using sql_log_warning,
  so following set_handlers() shouldn't modify error_log_handler_list
  without some protection

We will remove the parameter innodb_disallow_writes because it is badly
designed and implemented. The parameter was never allowed at startup.
It was only internally used by Galera snapshot transfer.
If a user executed
SET GLOBAL innodb_disallow_writes=ON;
the server could hang even on subsequent read operations.

During Galera snapshot transfer, we will block writes
to implement an rsync friendly snapshot, as follows:

sst_flush_tables() will acquire a global lock by executing
FLUSH TABLES WITH READ LOCK, which will block any writes
at the high level.

sst_disable_innodb_writes(), invoked via ha_disable_internal_writes(true),
will suspend or disable InnoDB background tasks or threads that could
initiate writes. As part of this, log_make_checkpoint() will be invoked
to ensure that anything in the InnoDB buf_pool.flush_list will be written
to the data files. This has the nice side effect that the Galera joiner
will avoid crash recovery.

The changes to sql/wsrep.cc and to the tests are based on a prototype
that was developed by Jan Lindström.

Reviewed by: Jan Lindström

This commit adds correct handling of binlogs for SST using rsync
or mariabackup. Before this fix, binlogs were handled incorrectly -
- only one (last) binary log file was transferred during SST, which
then led to various failures (for example, when trying to list all
events from the binary log). These bugs were long masked by flaws
in the primitive binlogs handling code in the SST scripts, which
causing binary logs files to be erased after transfer or not added
to the binlog index on the joiner node. Now the correct transfer
of all binary logs (not just the last of the binary log files) has
been implemented both for the rsync (at the script level) and for
the mariabackup (at the level of the main utility code).

This commit also adds a new sst_max_binlogs=<n> parameter, which
can be located in the [sst] section or in the [xtrabackup] section
(historically, supported for mariabackup only, not for rsync), or
in one of the server sections. This parameter specifies the number
of binary log files to be sent to the joiner node during SST. This
option is added for compatibility with old SST scripting behavior,
which can be emulated by setting the sst_max_binlogs=1 (although
in general this can cause problems for the reasons described above).
In addition, setting the sst_max_binlogs=0 can be used to suppress
the transmission of binary logs to the joiner nodes during SST
(although sometimes a single file with the current binary log can
still be transmitted to the joiner, even with sst_max_binlogs=0,
because this sometimes necessary in modes that involve the use of
GTIDs with Galera).

Also, this commit ensures correct handling of paths to various
innodb files and directories in the SST scripts, and fixes some
problems with this that existed in mariabackup utility (which
were associated with incorrect handling of the innodb_data_dir
parameter in some scenarios).

In addition, this commit contains the following enhancements:

 1) Added tests for mtr, which check the correct work with binlogs
    after SST (using rsync and mariabackup);
 2) Added correct handling of slashes at the end of all paths that
    the SST script receives as parameters;
 3) Improved parsing code for --mysqld-args parameters. Now it
    correctly processes the sequence "--" after the name of the
    one-letter option;
 4) Checking the secret signature during joiner authentication
    is made independent of presence of bash (as a unix shell)
    in the system and diff utility no longer needed to check
    certificates compliance;
 5) All directories that are necessary for the correct placement
    of various logs are automatically created by SST scripts in
    advance (before running mariabackup on the joiner node);
 6) Removal of old binary logs on joiner is done using the binlog
    index (if it exists) (not only by fixed pattern that based
    on the current binlog name, as before);
 7) Paths for placing binary logs are correctly processed if they
    are set as relative paths (to the datadir);
 8) SST scripts are made even more resistant to spaces in filenames
    (now for binlogs);
 9) In case of failure, SST scripts now always end with an exit
    code other than zero;
10) SST script for rsync now correctly create a tar file with
    the binlogs, even if the paths to them (in the binlog index
    file) are specified as a mix of absolute and relative paths,
    and even if they do not match with the datadir path specified
    in the current configuration settings.

because the name was misleading, it counts not threads, but THDs,
and as THD_count is the only way to increment/decrement it, it
could as well be declared inside THD_count.

It is implementation-defined whether alignment requirements
that are larger than std::max_align_t (typically 8 or 16 bytes)
will be honored by the compiler and linker.

It turns out that on IBM AIX, both alignas() and MY_ALIGNED()
only guarantees alignment up to 16 bytes.

For some data structures, specifying alignment to the CPU
cache line size (typically 64 or 128 bytes) is a mere performance
optimization, and we do not really care whether the requested
alignment is guaranteed.

But, for the correct operation of direct I/O, we do require that
the buffers be aligned at a block size boundary.

field_ref_zero: Define as a pointer, not an array.
For innochecksum, we can make this point to unaligned memory;
for anything else, we will allocate an aligned buffer from the heap.
This buffer will be used for overwriting freed data pages when
innodb_immediate_scrub_data_uncompressed=ON. And exactly that code
hit an assertion failure on AIX, in the test innodb.innodb_scrub.

log_sys.checkpoint_buf: Define as a pointer to aligned memory
that is allocated from heap.

log_t::file::write_header_durable(): Reuse log_sys.checkpoint_buf
instead of trying to allocate an aligned buffer from the stack.

Thanks to @shinguz for helping with this.
This a backport commit from 10.7

Fix regression (debug assertion or division by 0)
caused by cfd3d70c

The functions fil_file_readdir_next_file(), os_file_opendir(),
os_file_closedir() became dead code in the server in MariaDB 10.4.0
with commit 09af00cb (the removal of
the crash recovery logic for the TRUNCATE TABLE implementation that
was replaced in MDEV-13564).

os_file_opendir(), os_file_closedir(): Define as macros.

change after MDEV-24197)

This patch fixes an issue with launching mariabackup during SST
(when used with Galera), when during bootstrap mariabackup receives
the "--innodb" option, which is incorrectly interpreted as shortcut
for "--innodb-force-recovery". This patch does not require separate
test for mtr, as the problem is visible in general testing on
buildbot.

During the prepare phase of restoring backups, "mariabackup" does
not seem to allow (or recognize) the option "innodb_force_recovery"
for the embedded InnoDB server instance that it starts.

If page corruption observed during page recovery, the prepare step
fails. While this is indeed the correct behavior ideally, allowing
this option to be set in case of emergencies might be useful when
the current backup is the only copy available. Some error messages
during "--prepare" suggest to set "innodb_force_recovery" to 1:

  [ERROR] InnoDB: Set innodb_force_recovery=1 to ignore corruption.

For backwards compatibility, "mariabackup --innobackupex --apply-log"
should also have this option.
Signed-off-by: Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>