On Fri, 2018-06-22 at 18:31 -0400, Trond Myklebust wrote:
> On Fri, 2018-06-22 at 17:49 -0400, Chuck Lever wrote:
> > Hi Bruce-
> >
> >
> > > On Jun 22, 2018, at 1:54 PM, J. Bruce Fields <bfields@xxxxxxxxxxx
> > > g>
> > > wrote:
> > >
> > > On Thu, Jun 21, 2018 at 04:35:33PM +0000, Manjunath Patil wrote:
> > > > Presently nfserr_jukebox is being returned by nfsd for
> > > > create_session
> > > > request if server is unable to allocate a session slot. This
> > > > may
> > > > be
> > > > treated as NFS4ERR_DELAY by the clients and which may continue
> > > > to
> > > > re-try
> > > > create_session in loop leading NFSv4.1+ mounts in hung state.
> > > > nfsd
> > > > should return nfserr_nospc in this case as per rfc5661(section-
> > > > 18.36.4
> > > > subpoint 4. Session creation).
> > >
> > > I don't think the spec actually gives us an error that we can use
> > > to say
> > > a CREATE_SESSION failed permanently for lack of resources.
> >
> > The current situation is that the server replies NFS4ERR_DELAY,
> > and the client retries indefinitely. The goal is to let the
> > client choose whether it wants to try the CREATE_SESSION again,
> > try a different NFS version, or fail the mount request.
> >
> > Bill and I both looked at this section of RFC 5661. It seems to
> > us that the use of NFS4ERR_NOSPC is appropriate and unambiguous
> > in this situation, and it is an allowed status for the
> > CREATE_SESSION operation. NFS4ERR_DELAY OTOH is not helpful.
>
> There are a range of errors which we may need to handle by destroying
> the session, and then creating a new one (mainly the ones where the
> client and server slot handling get out of sync). That's why
> returning
> NFS4ERR_NOSPC in response to CREATE_SESSION is unhelpful, and is why
> the only sane response by the client will be to treat is as a
> temporary
> error.
>
> IOW: these patches will not be acceptable, even with a rewrite, as
> they
> are based on a flawed assumption.
The one use case for NFS4ERR_NOSPC for which it would appear to make
sense to treat it as a more or less permanent error, is if the client
is engaging in client ID trunking, and it tries to set up too many
sessions. If that happens, then the server needs a way to tell the
client to stop creating new sessions. However I'm not aware of any
clients out there that do client id trunking...
--
Trond Myklebust
CTO, Hammerspace Inc
4300 El Camino Real, Suite 105
Los Altos, CA 94022
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