Re: [PATCH 1/1] NFSv4.1+ add trunking when server trunking detected

Trond Myklebust
2021-06-08T22:58:07Z

On Tue, 2021-06-08 at 18:38 -0400, Olga Kornievskaia wrote:
> On Tue, Jun 8, 2021 at 6:28 PM Trond Myklebust <
> trondmy@hammerspace.com> wrote:
> >
> > On Tue, 2021-06-08 at 18:18 -0400, Olga Kornievskaia wrote:
> > > On Tue, Jun 8, 2021 at 6:13 PM Trond Myklebust <
> > > trondmy@hammerspace.com> wrote:
> > > >
> > > > On Tue, 2021-06-08 at 17:40 -0400, Olga Kornievskaia wrote:
> > > > > On Tue, Jun 8, 2021 at 5:06 PM Chuck Lever III <
> > > > > chuck.lever@oracle.com> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > > On Jun 8, 2021, at 4:56 PM, Olga Kornievskaia <
> > > > > > > olga.kornievskaia@gmail.com> wrote:
> > > > > > >
> > > > > > > On Tue, Jun 8, 2021 at 4:41 PM Chuck Lever III <
> > > > > > > chuck.lever@oracle.com> wrote:
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > > On Jun 8, 2021, at 2:45 PM, Olga Kornievskaia <
> > > > > > > > > olga.kornievskaia@gmail.com> wrote:
> > > > > > > > >
> > > > > > > > > From: Olga Kornievskaia <kolga@netapp.com>
> > > > > > > > >
> > > > > > > > > After trunking is discovered in
> > > > > > > > > nfs4_discover_server_trunking(),
> > > > > > > > > add the transport to the old client structure before
> > > > > > > > > destroying
> > > > > > > > > the new client structure (along with its transport).
> > > > > > > > >
> > > > > > > > > Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> > > > > > > > > ---
> > > > > > > > > fs/nfs/nfs4client.c | 40
> > > > > > > > > ++++++++++++++++++++++++++++++++++++++++
> > > > > > > > > 1 file changed, 40 insertions(+)
> > > > > > > > >
> > > > > > > > > diff --git a/fs/nfs/nfs4client.c
> > > > > > > > > b/fs/nfs/nfs4client.c
> > > > > > > > > index 42719384e25f..984c851844d8 100644
> > > > > > > > > --- a/fs/nfs/nfs4client.c
> > > > > > > > > +++ b/fs/nfs/nfs4client.c
> > > > > > > > > @@ -361,6 +361,44 @@ static int
> > > > > > > > > nfs4_init_client_minor_version(struct nfs_client
> > > > > > > > > *clp)
> > > > > > > > >      return nfs4_init_callback(clp);
> > > > > > > > > }
> > > > > > > > >
> > > > > > > > > +static void nfs4_add_trunk(struct nfs_client *clp,
> > > > > > > > > struct
> > > > > > > > > nfs_client *old)
> > > > > > > > > +{
> > > > > > > > > +     struct sockaddr_storage clp_addr, old_addr;
> > > > > > > > > +     struct sockaddr *clp_sap = (struct sockaddr
> > > > > > > > > *)&clp_addr;
> > > > > > > > > +     struct sockaddr *old_sap = (struct sockaddr
> > > > > > > > > *)&old_addr;
> > > > > > > > > +     size_t clp_salen, old_salen;
> > > > > > > > > +     struct xprt_create xprt_args = {
> > > > > > > > > +             .ident = old->cl_proto,
> > > > > > > > > +             .net = old->cl_net,
> > > > > > > > > +             .servername = old->cl_hostname,
> > > > > > > > > +     };
> > > > > > > > > +     struct nfs4_add_xprt_data xprtdata = {
> > > > > > > > > +             .clp = old,
> > > > > > > > > +     };
> > > > > > > > > +     struct rpc_add_xprt_test rpcdata = {
> > > > > > > > > +             .add_xprt_test = old->cl_mvops-
> > > > > > > > > > session_trunk,
> > > > > > > > > +             .data = &xprtdata,
> > > > > > > > > +     };
> > > > > > > > > +
> > > > > > > > > +     if (clp->cl_proto != old->cl_proto)
> > > > > > > > > +             return;
> > > > > > > > > +     clp_salen = rpc_peeraddr(clp->cl_rpcclient,
> > > > > > > > > clp_sap,
> > > > > > > > > sizeof(clp_addr));
> > > > > > > > > +     old_salen = rpc_peeraddr(old->cl_rpcclient,
> > > > > > > > > old_sap,
> > > > > > > > > sizeof(old_addr));
> > > > > > > > > +
> > > > > > > > > +     if (clp_addr.ss_family != old_addr.ss_family)
> > > > > > > > > +             return;
> > > > > > > > > +
> > > > > > > > > +     xprt_args.dstaddr = clp_sap;
> > > > > > > > > +     xprt_args.addrlen = clp_salen;
> > > > > > > > > +
> > > > > > > > > +     xprtdata.cred = nfs4_get_clid_cred(old);
> > > > > > > > > +     rpc_clnt_add_xprt(old->cl_rpcclient,
> > > > > > > > > &xprt_args,
> > > > > > > > > +
> > > > > > > > > rpc_clnt_setup_test_and_add_xprt,
> > > > > > > > > &rpcdata);
> > > > > > > >
> > > > > > > > Is there an upper bound on the number of transports
> > > > > > > > that
> > > > > > > > are added to the NFS client's switch?
> > > > > > >
> > > > > > > I don't believe any limits exist right now. Why should
> > > > > > > there
> > > > > > > be a
> > > > > > > limit? Are you saying that the client should limit
> > > > > > > trunking?
> > > > > > > While
> > > > > > > this is not what's happening here, but say FS_LOCATION
> > > > > > > returned
> > > > > > > 100
> > > > > > > ips for the server. Are you saying the client should be
> > > > > > > limiting
> > > > > > > how
> > > > > > > many trunkable connections it would be establishing and
> > > > > > > picking
> > > > > > > just a
> > > > > > > few addresses to try? What's happening with this patch is
> > > > > > > that
> > > > > > > say
> > > > > > > there are 100mounts to 100 ips (each representing the
> > > > > > > same
> > > > > > > server
> > > > > > > or
> > > > > > > trunkable server(s)), without this patch a single
> > > > > > > connection
> > > > > > > is
> > > > > > > kept,
> > > > > > > with this patch we'll have 100 connections.
> > > > > >
> > > > > > The patch description needs to make this behavior more
> > > > > > clear.
> > > > > > It
> > > > > > needs to explain "why" -- the body of the patch already
> > > > > > explains
> > > > > > "what". Can you include your last sentence in the
> > > > > > description
> > > > > > as
> > > > > > a use case?
> > > > >
> > > > > I sure can.
> > > > >
> > > > > > As for the behavior... Seems to me that there are going to
> > > > > > be
> > > > > > only
> > > > > > infinitesimal gains after the first few connections, and
> > > > > > after
> > > > > > that, it's going to be a lot for both sides to manage for
> > > > > > no
> > > > > > real
> > > > > > gain. I think you do want to cap the total number of
> > > > > > connections
> > > > > > at a reasonable number, even in the FS_LOCATIONS case.
> > > > >
> > > > > Do you want to cap it at 16 like we do for nconnect? I'm ok
> > > > > with
> > > > > that
> > > > > for now.
> > > > >
> > > > > I don't understand why a setup where there X NICs on each
> > > > > side
> > > > > (client/server) and X mounts are done, there won't be
> > > > > throughput
> > > > > of
> > > > > close to X * throughput of a single NIC.
> > > >
> > > > That still does not make the patch acceptable. There are
> > > > already
> > > > server
> > > > vendors seeing problems with supporting nconnect for various
> > > > reasons.
> > >
> > > Why are there servers presenting multiple IP addresses and
> > > returning
> > > the same server identity if they can not support trunking? That
> > > seems
> > > to be going against the spec?
> >
> > That's not a question I can answer, but I'm not thinking of our
> > server
> > or the Linux server.
> >
> > >
> > > > There needs to be a way to ensure that we can keep the current
> > > > client
> > > > behaviour without requiring changes to server DNS entries, etc.
> > >
> > > Ok, how about we introduce a mount option, "enable_trunking", and
> > > if
> > > that's present we would not collapse transports?
> >
> > I'd suggest making it 'max_connect=X' so that we can actually set a
> > limit like we do for nconnect. That limit probably needs to be
> > lower
> > bounded by the value of nconnect.
>
> Sure I can do that. But wouldn't that be confusing since we already
> have nconnect option? How about "max_trunking=X"? The lack of the
> setting or max_trunking=1, would result in all transports collapsed,
> other values would result in all additions of trunkable transports.
>
>

I'm not comfortable using the word 'trunking' in the mount API.

The NFS community uses 'trunking' to mean something very different from
what the networking community does. You're only talking about session
trunking here, and not clientid trunking, so I suggest we stick with a
terminology that reminds us this is connection related.

--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com