Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir

Andreas Gruenbacher
2016-12-06T13:18:31Z

On Tue, Dec 6, 2016 at 11:08 AM, Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org> wrote:
> On Tue, Dec 6, 2016 at 12:24 AM, Andreas Grünbacher
> <andreas.gruenbacher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> 2016-12-06 0:19 GMT+01:00 Andreas Grünbacher <andreas.gruenbacher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
>
>>> It's not hard to come up with a heuristic that determines if a
>>> system.nfs4_acl value is equivalent to a file mode, and to ignore the
>>> attribute in that case. (The file mode is transmitted in its own
>>> attribute already, so actually converting .) That way, overlayfs could
>>> still fail copying up files that have an actual ACL. It's still an
>>> ugly hack ...
>>
>> Actually, that kind of heuristic would make sense in the NFS client
>> which could then hide the "system.nfs4_acl" attribute.
>
> Even simpler would be if knfsd didn't send the attribute if not
> necessary. Looks like there's code actively creating the nfs4_acl on
> the wire even if the filesystem had none:
>
> pacl = get_acl(inode, ACL_TYPE_ACCESS);
> if (!pacl)
> pacl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
>
> What's the point?

That's how the protocol is specified. (I'm not saying that that's very helpful.)

Andreas
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