On Wed, May 25, 2016 at 05:29:35PM +0000, Adamson, Andy wrote: > Anna Schumaker who reviewed my client side session trunking patchset, wants a full featured version of both the client and the server session trunking pieces before accepting the session trunking feature upstream. To that end, I want to implement the server mountd V4ROOT processing of an fs_locations configuration to satisfy an fs_locations request on the pseudo fs. > > The forwarded message is from an email stream between Bruce, Chuck and I concerning the server pseufo fs fs_locations configuration that I’m now sharing with the list. > > Some background: > > The recent "NFSV4.1,2 session trunking” Version-5 patch set sent to the list notes (in patch 00/10): > > The pseudo-fs GETATTR(fs_locations) probe session trunking > was tested against a Linux server with a pseudo-fs > export stanza (e.g. a stanza with the fsid=0 or fsid=root > export option) and a replicas= export option > (replicas=<path1>@<server1>:<path2>@<server2>..) > Note that this configuration is for testing only. A future > patchset will add the replicas= configuration to the > NFSEXP_V4ROOT nfsd and mountd processing. > > > There are several ideas on how to accomplish mountd/V4ROOT fs_locations configuration in the forwarded message. See inline. > > > > Begin forwarded message: > > > > From: Chuck Lever <chuck.lever@xxxxxxxxxx> > > Subject: Re: Configuring fs_locations on Linux upstream server > > Date: May 6, 2016 at 4:31:00 PM EDT > > To: "J. Bruce Fields" <bfields@xxxxxxxxxxxx> > > Cc: "Adamson, Andy" <William.Adamson@xxxxxxxxxx> > > > > > >> On May 6, 2016, at 4:16 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > >> > >> On Fri, May 06, 2016 at 02:20:12PM -0400, Chuck Lever wrote: > >>> Seems like when a server does not return a list, that is > >>> information the client can use: basically, there is no > >>> ability to do any session trunking. It has to be set up > >>> explicitly; is that a bad thing, operationally? > >> > >> I like the idea of it being opt in on the server. > >> > >> Suppose the server transparently starts advertising all available > >> addresses for session trunking. It's not hard to imagine cases where > >> that would go wrong. E.g., maybe the server has the odd wireless or > >> 100Mb or other interface that happens to work but that's slow. Then > >> somebody upgrades their server and performance goes down and it may take > >> them a while to figure out why. Whereas if they'd had to opt in they'd > >> probably have avoided advertising an inappropriate interface. Or at > >> least they'd have a better chance of figuring out that turning on > >> trunking was what caused the problem. > >> > >> I'd rather not force people to export "/" explicitly, though. It's fine > >> for testing, but: > >> > >> - I don't think we give a way to do an explicit V4ROOT export, > >> so they'd be exposing their entire root partition. We could > >> fix that, but > >> - the pseudofs just seems to me like something people shouldn't > >> normally have to think about. It's a protocol implementation > >> detail, I'd rather hide it. It'd be to easy to configure it a > >> little wrong, I think. > >> > >> We can still do this by adding a replicas= option to the / export, but > >> we can let rpc.mountd do that internally instead of making the admin add > >> it to /etc/exports. > >> > >> But then you still need a way for the admin to tell rpc.mountd to cook > >> up the replicas= option..... I'm not sure what that should look like. > > Idea 1: extra syntax in /etc/exports It's not really export-specific information. I wonder if it'd be better to pass it on the rpc.nfsd commandline? rpc.nfsd --multipath-set="192.168.0.1,192.168.0.2" (and then that can be configured in /etc/sysconfig/nfs or whatever)? > >> Maybe some extra syntax in /etc/exports, but what do they need to give > >> us--just one list of IP addresses? Chuck, any ideas? > > Idea 2: xattr attached to “/" > > > > > How about using the same approach used for junctions: > > put the list in an xattr attached to / ? mountd can > > extract that when the kernel asks for help satisfying > > a GETATTR(fs_locations) on V4ROOT. I don't think that works. "/" isn't a good place to put configuration. It could be read-only, among other things. > Idea 3: new /etc/ config file > > > > Or it could be put in a separate config file in /etc. > > You might want to specify more than just the i/f list > > here; for instance, the security policy for the > > pseudofs, or a constant fsid UUID, among other things. > > > API to update the i/f list. This is not about where to hold fs_locations config info, but rather how to insert the (changed) info into the running system. > > > > > Also, I suggested to Andy earlier: > > > >> I find myself leaning towards mechanisms that are easy > >> both for admins and for programs (ie, an API). Perhaps > >> one day you might want to add a command that updates the > >> i/f list from the scripts in /etc/sysconfig/network-scripts, > >> for instance. > >> > >> As part of an ifup: > >> > >> nfspfs add <addr> > >> > >> and ifdown: > >> > >> nfspfs remove <addr> > >> > >> I wrote some Python code to manipulate entries in > >> /etc/exports, now found in fedfs-utils. It's icky. > > > > I think we should move away from "edit this file > > and save it, then restart rpc.xyzpdq". Build some > > command line interfaces for this. I'm OK with that. (Note do have that for information in /etc/exports--we have exportfs. Is there a reason that didn't work for fedfs-utils?) --b. > > > > And as you have suggested many times: separate > > policy from mechanism. /etc/exports is the > > mechanism. > > > > -- > > Chuck Lever > > Bruce - do you have a preference between #1 and #2 or #3 (or another idea?) > > Thanks > > —>Andy -- 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
