MSAN use-of-uninitialized-value in pagecache_fwrite()

diff --git a/storage/maria/ma_pagecache.c b/storage/maria/ma_pagecache.c

index 119b5310f49..12e88f2535c 100644

--- a/storage/maria/ma_pagecache.c

+++ b/storage/maria/ma_pagecache.c

@@ -681,10 +681,6 @@ static my_bool pagecache_fwrite(PAGECACHE *pagecache,

     DBUG_PRINT("error", ("write callback problem"));

     DBUG_RETURN(1);

   }

-#if __has_feature(memory_sanitizer) /* FIXME: encryption.aria_tiny etc. fail */

-  /* FIXME: ENGINE=Aria occasionally writes uninitialized data */

-  __msan_unpoison(args.page, pagecache->block_size);

-#endif

   res= (int)my_pwrite(filedesc->file, args.page, pagecache->block_size,

                  ((my_off_t) pageno << pagecache->shift), flags);

   (*filedesc->post_write_hook)(res, &args);

CURRENT_TEST: encryption.aria_tiny

mysqltest: At line 10: query 'drop table t1' failed: 2013: Lost connection to MySQL server during query

…

Uninitialized bytes in __interceptor_pwrite64 at offset 31 inside [0x725000043818, 8192)

==40014==WARNING: MemorySanitizer: use-of-uninitialized-value

    #0 0x5565a0801827 in my_pwrite /mariadb/10.5m/mysys/my_pread.c:159:19

    #1 0x55659ee8e355 in pagecache_fwrite /mariadb/10.5m/storage/maria/ma_pagecache.c:684:13

    #2 0x55659ee9e23c in flush_cached_blocks /mariadb/10.5m/storage/maria/ma_pagecache.c:4745:12

    #3 0x55659ee90bcb in flush_pagecache_blocks_int /mariadb/10.5m/storage/maria/ma_pagecache.c:5041:17

    #4 0x55659ee90bcb in flush_pagecache_blocks_with_filter /mariadb/10.5m/storage/maria/ma_pagecache.c:5156:8

    #5 0x55659ed991d7 in maria_close /mariadb/10.5m/storage/maria/ma_close.c:51:9

    #6 0x55659edbb468 in ha_maria::close() /mariadb/10.5m/storage/maria/ha_maria.cc:1240:10

    #7 0x55659e3432dd in handler::ha_close() /mariadb/10.5m/sql/handler.cc:2975:3

    #8 0x55659db6f30c in closefrm(TABLE*) /mariadb/10.5m/sql/table.cc:4271:24

    #9 0x55659dff35d2 in intern_close_table(TABLE*) /mariadb/10.5m/sql/table_cache.cc:220:3

    #10 0x55659dffff00 in TDC_element::flush_unused(bool) /mariadb/10.5m/sql/table_cache.cc:1292:5

    #11 0x55659dfff2de in tdc_remove_referenced_share(THD*, TABLE_SHARE*) /mariadb/10.5m/sql/table_cache.cc:1004:15

    #12 0x55659e0006e2 in tdc_remove_table(THD*, char const*, char const*) /mariadb/10.5m/sql/table_cache.cc:1061:3

    #13 0x55659da25e25 in mysql_rm_table_no_locks(THD*, TABLE_LIST*, bool, bool, bool, bool, bool, bool) /mariadb/10.5m/sql/sql_table.cc:2481:9

    #14 0x55659da220cc in mysql_rm_table(THD*, TABLE_LIST*, bool, bool, bool, bool) /mariadb/10.5m/sql/sql_table.cc:2137:10

    #15 0x55659d6b6874 in mysql_execute_command(THD*) /mariadb/10.5m/sql/sql_parse.cc:4927:10

    #16 0x55659d6922f5 in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) /mariadb/10.5m/sql/sql_parse.cc:7991:18

    #17 0x55659d682c79 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) /mariadb/10.5m/sql/sql_parse.cc:1874:7

    #18 0x55659d6941ba in do_command(THD*) /mariadb/10.5m/sql/sql_parse.cc:1355:17

    #19 0x55659dcb02be in do_handle_one_connection(CONNECT*, bool) /mariadb/10.5m/sql/sql_connect.cc:1411:11

    #20 0x55659dcafaa4 in handle_one_connection /mariadb/10.5m/sql/sql_connect.cc:1313:5

    #21 0x55659f15a277 in pfs_spawn_thread /mariadb/10.5m/storage/perfschema/pfs.cc:2201:3

    #22 0x7fcd55afaf26 in start_thread nptl/pthread_create.c:479:8

    #23 0x7fcd555d931e in clone misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

  Memory was marked as uninitialized

    #0 0x55659d14028e in __msan_allocated_memory (/dev/shm/10.5-msan/sql/mariadbd+0x70928e)

    #1 0x5565a07fc1e7 in my_malloc /mariadb/10.5m/mysys/my_malloc.c:111:7