mariabackup silently ended during xtrabackup_copy_logfile()

) log_sys.log.read_log_seg() returned true, but lsn == start_lsn. If we look into log_t::files::read_log_seg(), we will see that the function can silently return true and do not advance lsn on the following condition:

=== log_t::files::read_log_seg()

if (block_number != log_block_convert_lsn_to_no(*start_lsn)) {

/* Garbage or an incompletely written log block.

We will not report any error, because this can

happen when InnoDB was killed while it was

writing redo log. We simply treat this as an

abrupt end of the redo log. */

end_lsn = *start_lsn;

break;

}

=== log_t::files::read_log_seg()

if (dl < LOG_BLOCK_HDR_SIZE

|| (dl > OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE

&& dl != OS_FILE_LOG_BLOCK_SIZE)) {

recv_sys->found_corrupt_log = true;

end_lsn = *start_lsn;

break;

}

=== log_t::files::read_log_seg()

===

--- a/extra/mariabackup/xtrabackup.cc

+++ b/extra/mariabackup/xtrabackup.cc

@@ -2728,13 +2728,19 @@ static bool xtrabackup_copy_logfile(bool last = false)

lsn_t lsn= start_lsn;

for (int retries= 0; retries < 100; retries++) {

if (log_sys.log.read_log_seg(&lsn, end_lsn)

- || lsn != start_lsn) {

+ && lsn != start_lsn) {

break;

}

msg("Retrying read of log at LSN=" LSN_PF "\n", lsn);

my_sleep(1000);

}

+ if (recv_sys->found_corrupt_log) {

+ msg("mariabackup: Error: xtrabackup_copy_logfile()"

+ " found corrupted log.\n");

+ exit(EXIT_FAILURE);

+ }

+

start_lsn = (lsn == start_lsn)

? 0 : xtrabackup_copy_log(start_lsn, lsn, last);

===