MySQL reports an error: Can't find file: './mysql/plugin.frm' solution

2017-09-15 16:01:01 2420 [Warning] Using unique option prefix myisam-recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
2017-09-15 16:01:01 2420 [Note] Plugin 'FEDERATED' is disabled.
^G/usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13 - Permission denied)
2017-09-15 16:01:01 2420 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
2017-09-15 16:01:01 2420 [Note] InnoDB: Using atomics to ref count buffer pool pages
2017-09-15 16:01:01 2420 [Note] InnoDB: The InnoDB memory heap is disabled
2017-09-15 16:01:01 2420 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-09-15 16:01:01 2420 [Note] InnoDB: Memory barrier is not used
2017-09-15 16:01:01 2420 [Note] InnoDB: Compressed tables use zlib 1.2.8
2017-09-15 16:01:01 2420 [Note] InnoDB: Using Linux native AIO
2017-09-15 16:01:01 2420 [Note] InnoDB: Using CPU crc32 instructions
2017-09-15 16:01:01 2420 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2017-09-15 16:01:02 2420 [Note] InnoDB: Completed initialization of buffer pool
2017-09-15 16:01:02 2420 [ERROR] InnoDB: ./ibdata1 can't be opened in read-write mode
2017-09-15 16:01:02 2420 [ERROR] InnoDB: The system tablespace must be writable!
2017-09-15 16:01:02 2420 [ERROR] Plugin 'InnoDB' init function returned error.
2017-09-15 16:01:02 2420 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2017-09-15 16:01:02 2420 [ERROR] Unknown/unsupported storage engine: InnoDB
2017-09-15 16:01:02 2420 [ERROR] Aborting

root@hutaojie-1-pdd-sh:/data1/mysql/mysql# ll plugin.*
-rwxrwxrwx 1 mysql mysql 8586 Mar 6 2016 plugin.frm*
-rwxrwx--x 1 mysql mysql 116 Mar 6 2016 plugin.MYD*
-rwxrwx--x 1 mysql mysql 2048 Mar 6 2016 plugin.MYI*
root@hutaojie-1-pdd-sh:/data1/mysql/mysql#

/usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13 - Permission denied)

root@huayuan:/var/lib# vim /etc/apparmor.d/usr.sbin.mysqld 

# vim:syntax=apparmor
# Last Modified: Tue Jun 19 17:37:30 2007
#include <tunables/global>

/usr/sbin/mysqld {
 #include <abstractions/base>
 #include <abstractions/nameservice>
 #include <abstractions/user-tmp>
 #include <abstractions/mysql>
 #include <abstractions/winbind>

 capability dac_override,
 capability sys_resource,
 capability setgid,
 capability setuid,

 network tcp,

 /run/mysqld/mysqld.pid rw,
 /run/mysqld/mysqld.sock w,

 /sys/devices/system/cpu/ r,
 #.........Write the new datadir directory here, write 2 lines, one line of r, and one line of rwk.
 /data3/mysql/ r,
 /data3/mysql/** rwk,
 # Site-specific additions and overrides. See local/README for details.
 #include <local/usr.sbin.mysqld>
}