XUPT inclusion
category: feature
bugzilla: https://gitee.com/open_euler/dashboard?issue_id=I5WIS5
CVE: NA

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In the actual production environment, Overlayfs often occurs some
problems, such as continuous growth of quota statistics. There is no
good way to define this category for the current environment. Overlatfs
has many restrictions in the actual use process but it has not directly
restricted at the code level. Therefore, some strange problems
introduced in operation errors will occur during the use process. It is
time-consuming. Based on this background, Overlayfs's maintenance
function needs to be enhanced.

This patch add sysfs file for overlayfs to recording the mount
information. The sysfs file will be deleted only when overlayfs if truly
unloaded.

Mainly implementation:
Put a hook function in file_system_type, and register sysfs after do_add_mount().
Signed-off-by: hiyoyolumi <862127279@qq.com>