Re: [RFC PATCH 0/7] SUNRPC: Create sysfs files for changing IP

From: Anna Schumaker <schumaker.anna@gmail.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Chuck Lever <chuck.lever@oracle.com>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [RFC PATCH 0/7] SUNRPC: Create sysfs files for changing IP
Date: Wed, 13 Jan 2021 14:23:16 -0500	[thread overview]
Message-ID: <CAFX2JfmYrCSYfCCGgQ0eghU3WSqk=T38wxkJ7Q42ORw-NFeFQg@mail.gmail.com> (raw)
In-Reply-To: <20210112165911.GH9248@fieldses.org>

On Tue, Jan 12, 2021 at 11:59 AM J. Bruce Fields <bfields@fieldses.org> wrote:
>
> On Tue, Jan 12, 2021 at 08:09:09AM -0500, Chuck Lever wrote:
> > Hi Anna-
> >
> > > On Jan 11, 2021, at 4:41 PM, schumaker.anna@gmail.com wrote:
> > >
> > > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > >
> > > It's possible for an NFS server to go down but come back up with a
> > > different IP address. These patches provide a way for administrators to
> > > handle this issue by providing a new IP address for xprt sockets to
> > > connect to.
> > >
> > > This is a first draft of the code, so any thoughts or suggestions would
> > > be greatly appreciated!
> >
> > One implementation question, one future question.
> >
> > Would /sys/kernel/net be a little better? or /sys/kernel/sunrpc ?

Possibly! I was trying to match /sys/fs/nfs, but I can definitely
change this if another location is better.

> >
> > Do you have a plan to integrate support for fs_locations to probe
> > servers for alternate IP addresses? Would that be a userspace
> > utility that would plug values into this new /sys API?

Yeah, I would expect there to be a new utility to help with assigning
new values. I haven't given any thought to using fs_locations yet, but
it could probably work.
>
> We already have dns resolution for fs_locations, right?  Why can't we
> use that here?  Is it that the mount call doesn't give us a host name?
> Or we don't trust dns to have the updated IP address for some reason?

The mount call doesn't give us a host name (that I can find, at
least). By the time we get to the sunrpc layer we're dealing with just
the IP address anyway. I'd expect there to be a userland utility to
translate the dns name to the new IP address and pass it along to the
new API.

Anna
>
> --b.
>
> >
> >
> > > Anna
> > >
> > >
> > > Anna Schumaker (7):
> > >  net: Add a /sys/net directory to sysfs
> > >  sunrpc: Create a sunrpc directory under /sys/net/
> > >  sunrpc: Create a net/ subdirectory in the sunrpc sysfs
> > >  sunrpc: Create per-rpc_clnt sysfs kobjects
> > >  sunrpc: Create a per-rpc_clnt file for managing the IP address
> > >  sunrpc: Prepare xs_connect() for taking NULL tasks
> > >  sunrpc: Connect to a new IP address provided by the user
> > >
> > > include/linux/sunrpc/clnt.h |   1 +
> > > include/net/sock.h          |   4 +
> > > net/socket.c                |   8 ++
> > > net/sunrpc/Makefile         |   2 +-
> > > net/sunrpc/clnt.c           |   5 ++
> > > net/sunrpc/sunrpc_syms.c    |   8 ++
> > > net/sunrpc/sysfs.c          | 160 ++++++++++++++++++++++++++++++++++++
> > > net/sunrpc/sysfs.h          |  22 +++++
> > > net/sunrpc/xprtsock.c       |   3 +-
> > > 9 files changed, 211 insertions(+), 2 deletions(-)
> > > create mode 100644 net/sunrpc/sysfs.c
> > > create mode 100644 net/sunrpc/sysfs.h
> > >
> > > --
> > > 2.29.2
> > >
> >
> > --
> > Chuck Lever
> >
> >