From: David P. Quigley on
On Wed, 2010-07-07 at 13:49 -0400, Chuck Lever wrote:
> On 07/ 7/10 12:22 PM, David P. Quigley wrote:
> > Hello Chuck,
> > Thank you for the comments. I'll go through and address them inline
> > (Sorry for the top post).
> >
> > On Wed, 2010-07-07 at 12:01 -0400, Chuck Lever wrote:
> >> My comments below apply to the other NFS client patches as well. This
> >> seemed like the right one to use for code examples.
> >>
> >> On 07/ 7/10 10:31 AM, David P. Quigley wrote:
> [ ... snipped ... ]
> >> It seems to me you want something more generic, just like nfs_fh or
> >> nfs_fattr, to represent these. Over time, I'm guessing label support
> >> won't be tied to a specific NFS version. And, you are passing these
> >> around in the generic NFS functions (for post-op updates and inode
> >> revalidation, and what not).
> >>
> >> Can I recommend "struct nfs_seclabel" instead? Then have
> >> nfs_seclabel_alloc() and nfs_seclabel_free().
> >
> > I can definitely rename them to be more generic. I don't see anything
> > else besides NFSv4 using them but its fine with me to rename them. The
> > reason we call them nfs4_label is because we modeled it after the NFSv4
> > acl support code. I spoke with Christoph a long time ago and he
> > suggested that it should be handled the same way that the NFSv4 ACLs are
> > handled as opposed to the iattr thing we were trying.
> >
> >>
> >> Does it make sense to deduplicate these in the client's memory? It
> >> seems to me that you could have hundreds or thousands that all contain
> >> the same label information.
> >
> > I don't think it is worth the effort. We are only using these structures
> > until the security label is crammed into the inode. Once that happens
> > they get freed. You shouldn't have them sitting around for very long.
> OK, the lifetime of these things wasn't clear.
> > They will be pulled again when the inode attributes expire and need to
> > be revalidated. For things like SELinux you could argue that the LSM
> > might benefit from this (and it might already do it but I'm not sure)
> > but I think that is something to be handled by the LSM itself or the
> > credentials code (since it already supports COW credentials it should be
> > possible).
> I think the lifetime of the label structure then is about the same as
> the lifetime of an nfs_attr, and not at all the same as an ACL. I'm
> just guessing here.

Intersting I figured that the ACL structure was just to get it to a
point where you could convert the NFS ACL into a posixacl and set it in
the inode. I didn't realize they were hanging around for a while.

> Would it then make sense to add a field that refers to the security
> label to struct nfs_fattr instead? That might simplify or eliminate all
> of the internal API changes.

I want to say that we had it in there at one point and then we endedup
running into a problem and having to change it. I'll ask Matt about what
problems we had sticking it in the nfs_fattr initially.


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