On Mon, 11 Mar 2013 15:36:38 -0400
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> On Mon, Mar 11, 2013 at 03:05:40PM -0400, Jeff Layton wrote:
> > knfsd has some code already to handle share reservations internally.
> > Nothing outside of knfsd is aware of these reservations, of course so
> > moving to a vfs-level object for it would be a marked improvement.
> >
> > It doesn't look like this patch removes any of that old code though. I
> > think it probably should, or there ought to be some consideration of
> > how this new stuff will mesh with it.
> >
> > I think you have 2 choices here:
> >
> > 1/ rip out the old share reservation code altogether and require that
> > filesystems mount with -o sharemand or whatever if they want to allow
> > their enforcement
> >
> > 2/ make knfsd fall back to using the internal share reservation code
> > when the mount option isn't enabled
> >
> > Personally, I think #1 would be fine, but Bruce may want to weigh in on
> > what he'd prefer.
>
> #1 sounds good. Clients that use deny bits are few. My preference
> would be to return an error to such clients in the case share locks
> aren't available.
>
> (We're a little out of spec there, so I'm not sure which error. I think
> the goal is to notify a human there's a problem with minimal collateral
> damange.
>
> NFS4ERR_SERVERFAULT ("I'm a buggy server, sorry about that!") would
> probably result in an IO error to the application.
>
> SHARE_DENIED strikes me as unsafe: an application would be in its rights
> not to even check for that e.g. in the case of an exclusive create.
>
> Maybe DELAY? Kind of ridiculous, but blocking the application
> indefinitely would probably get someone's attention quickly enough
> without doing any damnage.)
>
I agree that we should return an error, but hadn't considered what
error. Given that hardly any NFS clients use them, I'd probably just go
with NFS4ERR_SERVERFAULT, and maybe throw a printk or something on the
server about enabling share reservations for superblock x:y.
Pavel, as a side note, you may want to consider adding a patch to hook
this stuff up in the NFS client as well.
--
Jeff Layton <jlayton@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
