Re: [1/8] readdir-plus system call - LSF/MM follow up

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On Tue, 28 May 2013 20:38:57 -0700
Frank S Filz <ffilz@xxxxxxxxxx> wrote:

> 
> Jim Lieb <jlieb@xxxxxxxxxxx> wrote on 05/28/2013 05:57:31 PM:
> > > Actually, ACLs are critical for Ganesha. Unless we decide to have
> separate
> > > attr validity bits for "stat" attributes and ACLs, Ganesha will have a
> > > difficult time knowing if the ACL attribute is up to date (or even
> > > available).
> >
> > True enough.  But one of the pushbacks was the amount of work neededto
> get to
> > xattrs where acls live.  One thing I heard that made not having acls on
> the
> > readdir+ pass was a status of some kind that indicated "I have acls..."
> The
> > readdir is a dir op and so 10k+ entries need to be minimal overhead.  we
> > already have the acls of the dir from the lookup.  we don't need an
> entry's
> > acls until we do the lookup on it.  at that time we can grab the acls.
> That
> > was the argument as I remember and I'm willing to accept it.  IIRC,
> > the client
> > is going to send us a getattrs later.  we can do it then.  Is this
> reasonable?
> 
> The ACL COULD be required on READDIR, though I would not expect any clients
> to ask for ACL on READDIR (though it sure would be handy if Ganesha's PROXY
> client could do so...).
> 
> Fortunately we don't enforce ACE4_READ_ATTR, otherwise we WOULD need ACL on
> any READDIR...
> 
> If there are times when we get attrs without getting ACL, then we will need
> a separate validity bit for ACL, otherwise we won't be able to tell if we
> have current ACL for an entry or not.
> 
> What would actually be helpful though, and make Ganesha a lot more
> efficient is if we could actually get all the ACLs for a directory in one
> fell swoop with some sort of "compression". Given that a large percentage
> of files actually have the same ACL, we could get a the 1-4 ACLs that
> apply, and then a bunch of entries, each indicating which of the 4 ACLs
> they have.
> 

Most NFS clients aren't going to need ACLs during a READDIR operation.
I'll go as so far to say that most NFS clients don't care *at all*
about ACLs. Those are things that are enforced by the server and the
client doesn't really care to know about them.

The exception is when a client gets an explicit request to either view
or change the ACL. For Linux clients (and most other POSIX-y ones),
that's never done in any sort of batch form. It's always an operation
done against a single dentry.

So, I'm not sure I understand the argument for adding ACLs here. It's
not likely to be something you're going to end up stuffing into a
READDIR reply.

-- 
Jeff Layton <jlayton@xxxxxxxxxx>
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