[Gluster-devel] Problems about cache virtual glusterfs ACLs for ganesha in md-cache

[Kinglong Mee]

Cc nfs-ganesha,

Md-cache has option "cache-posix-acl" that controls caching of posix ACLs
("system.posix_acl_access"/"system.posix_acl_default") and virtual glusterfs ACLs
("glusterfs.posix.acl"/"glusterfs.posix.default_acl") now.

But, _posix_xattr_get_set does not fill virtual glusterfs ACLs when lookup requests.
So, md-cache caches bad virtual glusterfs ACLs.

After I turn on "cache-posix-acl" option to cache ACLs at md-cache, nfs client gets many EIO errors.

https://review.gerrithub.io/c/ffilz/nfs-ganesha/+/427305

There are two chooses for cache virtual glusterfs ACLs in md-cache,
1. Cache it separately as posix ACLs (a new option maybe "cache-glusterfs-acl" is added);
   And make sure _posix_xattr_get_set fills them when lookup requests.

2. Does not cache it, only cache posix ACLs;
   If gfapi request it, md-cache lookup according posix ACL at cache,
   if exist, make the virtual glusterfs ACL locally and return to gfapi;
   otherwise, send the request to glusterfsd.

Virtual glusterfs ACLs are another format of posix ACLs, there are larger than posix ACLs, 
and always exist no matter the really posix ACL exist or not.

So, I'd prefer #2.
Any comments are welcome.

thanks,
Kinglong Mee