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

[Trond Myklebust <trondmy@hammerspace.com>]

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.

> 
> > > 
> > > > > > > +
> > > > > > > +     if (xprtdata.cred)
> > > > > > > +             put_cred(xprtdata.cred);
> > > > > > > +}
> > > > > > > +
> > > > > > > /**
> > > > > > > * nfs4_init_client - Initialise an NFS4 client record
> > > > > > > *
> > > > > > > @@ -434,6 +472,8 @@ struct nfs_client
> > > > > > > *nfs4_init_client(struct nfs_client *clp,
> > > > > > >               * won't try to use it.
> > > > > > >               */
> > > > > > >              nfs_mark_client_ready(clp, -EPERM);
> > > > > > > +             if (old->cl_mvops->session_trunk)
> > > > > > > +                     nfs4_add_trunk(clp, old);
> > > > > > >      }
> > > > > > >      clear_bit(NFS_CS_TSM_POSSIBLE, &clp->cl_flags);
> > > > > > >      nfs_put_client(clp);
> > > > > > > --
> > > > > > > 2.27.0
> > > > > > > 
> > > > > > 
> > > > > > --
> > > > > > Chuck Lever
> > > > 
> > > > --
> > > > Chuck Lever
> > > > 
> > > > 
> > > > 
> > 
> > --
> > Trond Myklebust
> > Linux NFS client maintainer, Hammerspace
> > trond.myklebust@hammerspace.com
> > 
> > 

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