Re: unsharing tcp connections from different NFS mounts

[Bruce Fields <bfields@fieldses.org>]

On Wed, Oct 07, 2020 at 10:15:39AM -0400, Chuck Lever wrote:
> 
> 
> > On Oct 7, 2020, at 10:05 AM, Bruce Fields <bfields@fieldses.org> wrote:
> > 
> > On Wed, Oct 07, 2020 at 09:45:50AM -0400, Chuck Lever wrote:
> >> 
> >> 
> >>> On Oct 7, 2020, at 8:55 AM, Benjamin Coddington <bcodding@redhat.com> wrote:
> >>> 
> >>> On 7 Oct 2020, at 7:27, Benjamin Coddington wrote:
> >>> 
> >>>> On 6 Oct 2020, at 20:18, J. Bruce Fields wrote:
> >>>> 
> >>>>> On Tue, Oct 06, 2020 at 05:46:11PM -0400, Olga Kornievskaia wrote:
> >>>>>> On Tue, Oct 6, 2020 at 3:38 PM Benjamin Coddington <bcodding@redhat.com> wrote:
> >>>>>>> 
> >>>>>>> On 6 Oct 2020, at 11:13, J. Bruce Fields wrote:
> >>> 
> >>>>> Looks like nfs4_init_{non}uniform_client_string() stores it in
> >>>>> cl_owner_id, and I was thinking that meant cl_owner_id would be used
> >>>>> from then on....
> >>>>> 
> >>>>> But actually, I think it may run that again on recovery, yes, so I bet
> >>>>> changing the nfs4_unique_id parameter midway like this could cause bugs
> >>>>> on recovery.
> >>>> 
> >>>> Ah, that's what I thought as well.  Thanks for looking closer Olga!
> >>> 
> >>> Well, no -- it does indeed continue to use the original cl_owner_id.  We
> >>> only jump through nfs4_init_uniquifier_client_string() if cl_owner_id is
> >>> NULL:
> >>> 
> >>> 6087 static int
> >>> 6088 nfs4_init_uniform_client_string(struct nfs_client *clp)
> >>> 6089 {
> >>> 6090     size_t len;
> >>> 6091     char *str;
> >>> 6092
> >>> 6093     if (clp->cl_owner_id != NULL)
> >>> 6094         return 0;
> >>> 6095
> >>> 6096     if (nfs4_client_id_uniquifier[0] != '\0')
> >>> 6097         return nfs4_init_uniquifier_client_string(clp);
> >>> 6098
> >>> 
> >>> 
> >>> Testing proves this out as well for both EXCHANGE_ID and SETCLIENTID.
> >>> 
> >>> Is there any precedent for stabilizing module parameters as part of a
> >>> supported interface?  Maybe this ought to be a mount option, so client can
> >>> set a uniquifier per-mount.
> >> 
> >> The protocol is designed as one client-ID per client. FreeBSD is
> >> the only client I know of that uses one client-ID per mount, fwiw.
> >> 
> >> You are suggesting each mount point would have its own lease. There
> >> would likely be deeper implementation changes needed than just
> >> specifying a unique client-ID for each mount point.
> > 
> > Huh, I thought that should do it.
> > 
> > Do you have something specific in mind?
> 
> The relationship between nfs_client and nfs_server structs comes to
> mind.

I'm not following.  Do you have a specific problem in mind?

--b.

> 
> Trunking discovery has been around for several years. This is the
> first report I've heard of a performance regression.
> 
> We do know that nconnect helps relieve head-of-line blocking on TCP.
> I think adding a second socket would be a very easy thing to try and
> wouldn't have any NFSv4 state recovery ramifications.
> 
> 
> --
> Chuck Lever
> 
>