MSAN/Valgrind uninitialised value warnings in translog_buffer_flush

--source include/have_partition.inc

CREATE TABLE t1 (a INT, b INT, c VARCHAR(64), KEY(b)) ENGINE=Aria

PARTITION BY RANGE (a) (

  PARTITION p0 VALUES LESS THAN (5),

  PARTITION pn VALUES LESS THAN (MAXVALUE)

);

INSERT INTO t1 VALUES (5,9,'foo'),(3,7,'qux'),(1,9,'x');

CREATE TABLE t2 (c INT) ENGINE=Aria;

INSERT INTO t2 VALUES (1),(2);

UPDATE t1 LEFT JOIN t2 ON (t2.c != t1.a) SET t1.a = 0 WHERE t1.b = 9;

DROP TABLE t1, t2;

Uninitialized bytes in __interceptor_pwrite64 at offset 307 inside [0x55d9746c77fa, 3486)

==53031==WARNING: MemorySanitizer: use-of-uninitialized-value

    #0 0x55d97138bc1c in my_pwrite /data/bld/10.6-msan/mysys/my_pread.c:159:19

    #1 0x55d96feff2f7 in translog_buffer_flush /data/bld/10.6-msan/storage/maria/ma_loghandler.c:2698:7

    #2 0x55d96fefc38d in translog_flush_buffers /data/bld/10.6-msan/storage/maria/ma_loghandler.c:8048:9

    #3 0x55d96ff00bdb in translog_flush /data/bld/10.6-msan/storage/maria/ma_loghandler.c:8167:5

    #4 0x55d96ff71327 in ma_commit /data/bld/10.6-msan/storage/maria/ma_commit.c:66:9

    #5 0x55d96febe4d2 in maria_commit(handlerton*, THD*, bool) /data/bld/10.6-msan/storage/maria/ha_maria.cc:3569:7

    #6 0x55d96f4a53aa in commit_one_phase_2(THD*, bool, THD_TRANS*, bool) /data/bld/10.6-msan/sql/handler.cc:2157:17

    #7 0x55d96f4a6c4d in ha_commit_one_phase(THD*, bool) /data/bld/10.6-msan/sql/handler.cc:2110:8

    #8 0x55d96f4a103f in ha_commit_trans(THD*, bool) /data/bld/10.6-msan/sql/handler.cc:1904:12

    #9 0x55d96eeab976 in trans_commit_stmt(THD*) /data/bld/10.6-msan/sql/transaction.cc:501:10

    #10 0x55d96e87c6cf in mysql_execute_command(THD*, bool) /data/bld/10.6-msan/sql/sql_parse.cc:6225:7

    #11 0x55d96e856049 in mysql_parse(THD*, char*, unsigned int, Parser_state*) /data/bld/10.6-msan/sql/sql_parse.cc:8200:18

    #12 0x55d96e84d080 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool) /data/bld/10.6-msan/sql/sql_parse.cc:1908:7

    #13 0x55d96e8577a6 in do_command(THD*, bool) /data/bld/10.6-msan/sql/sql_parse.cc:1421:17

    #14 0x55d96ee4f4ce in do_handle_one_connection(CONNECT*, bool) /data/bld/10.6-msan/sql/sql_connect.cc:1386:11

    #15 0x55d96ee4eab7 in handle_one_connection /data/bld/10.6-msan/sql/sql_connect.cc:1298:5

    #16 0x55d97019af5e in pfs_spawn_thread /data/bld/10.6-msan/storage/perfschema/pfs.cc:2201:3

    #17 0x7f6d6dfc91c3 in start_thread nptl/pthread_create.c:442:8

    #18 0x7f6d6e04985b in clone3 misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

  Uninitialized value was stored to memory at

    #0 0x55d96e3979a9 in __msan_memcpy (/share8t/bld/10.6-msan/sql/mariadbd+0x8699a9) (BuildId: 3b19f3214393035d506f50bd9507111e980e0f7d)

    #1 0x55d96ff12b1b in translog_write_parts_on_page /data/bld/10.6-msan/storage/maria/ma_loghandler.c:4511:7

  Uninitialized value was stored to memory at

    #0 0x55d96e3979a9 in __msan_memcpy (/share8t/bld/10.6-msan/sql/mariadbd+0x8699a9) (BuildId: 3b19f3214393035d506f50bd9507111e980e0f7d)

    #1 0x55d96ecd8d6f in multi_update::send_data(List<Item>&) /data/bld/10.6-msan/sql/sql_update.cc:2613:7

  Uninitialized value was stored to memory at

    #0 0x55d96e3979a9 in __msan_memcpy (/share8t/bld/10.6-msan/sql/mariadbd+0x8699a9) (BuildId: 3b19f3214393035d506f50bd9507111e980e0f7d)

    #1 0x55d97016e207 in ha_partition::return_top_record(unsigned char*) /data/bld/10.6-msan/sql/ha_partition.cc:8108:3

  Memory was marked as uninitialized

    #0 0x55d96e39e62d in __msan_allocated_memory (/share8t/bld/10.6-msan/sql/mariadbd+0x87062d) (BuildId: 3b19f3214393035d506f50bd9507111e980e0f7d)

    #1 0x55d96fffe422 in _ma_read_block_record2 /data/bld/10.6-msan/storage/maria/ma_blockrec.c:4953:7

SUMMARY: MemorySanitizer: use-of-uninitialized-value /data/bld/10.6-msan/mysys/my_pread.c:159:19 in my_pwrite

 ==52970== Thread 6:

==52970== Syscall param pwrite64(buf) points to uninitialised byte(s)

==52970==    at 0x4E0E437: __libc_pwrite64 (pwrite64.c:25)

==52970==    by 0x4E0E437: pwrite (pwrite64.c:23)

==52970==    by 0x183992D: my_pwrite (my_pread.c:159)

==52970==    by 0x1132BC7: translog_buffer_flush (ma_loghandler.c:2695)

==52970==    by 0x1143FE6: translog_flush_buffers (ma_loghandler.c:8046)

==52970==    by 0x11443CB: translog_flush (ma_loghandler.c:8165)

==52970==    by 0x11648A4: ma_commit (ma_commit.c:66)

==52970==    by 0x1122C34: maria_commit(handlerton*, THD*, bool) (ha_maria.cc:3584)

==52970==    by 0xEC2585: commit_one_phase_2(THD*, bool, THD_TRANS*, bool) (handler.cc:2118)

==52970==    by 0xEC2328: ha_commit_one_phase(THD*, bool) (handler.cc:2071)

==52970==    by 0xEC1325: ha_commit_trans(THD*, bool) (handler.cc:1865)

==52970==    by 0xCD95F4: trans_commit_stmt(THD*) (transaction.cc:472)

==52970==    by 0xAD7089: mysql_execute_command(THD*, bool) (sql_parse.cc:6090)

==52970==    by 0xADCFCF: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:8063)

==52970==    by 0xAC86D4: dispatch_command(enum_server_command, THD*, char*, unsigned int, bool) (sql_parse.cc:1903)

==52970==    by 0xAC6FD6: do_command(THD*, bool) (sql_parse.cc:1416)

==52970==    by 0xCB9963: do_handle_one_connection(CONNECT*, bool) (sql_connect.cc:1416)

==52970==  Address 0x2c04fad is 5251213 bytes inside data symbol "log_descriptor"

^ Found warnings in /share8t/bld/10.6.14-9-valgrind/mysql-test/var/log/mysqld.1.err