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References: <20210215174002.2376333-1-dan@kernelim.com>
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From:   Olga Kornievskaia <aglo@umich.edu>
Date:   Mon, 1 Mar 2021 22:56:22 -0500
Message-ID: <CAN-5tyGw3D-+emeQhu31agom9yuZ9=PL6YUVyEKiR-n2q9uE3A@mail.gmail.com>
Subject: Re: [PATCH v1 0/8] sysfs files for multipath transport control
To:     Dan Aloni <dan@kernelim.com>
Cc:     linux-nfs <linux-nfs@vger.kernel.org>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>
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Hi Dan,

On Mon, Feb 15, 2021 at 12:43 PM Dan Aloni <dan@kernelim.com> wrote:
>
> Hi Anna,
>
> This patchset builds ontop v2 of your 'sysfs files for changing IP' changeset.
>
> - The patchset adds two more sysfs objects, for one for transport and another
>   for multipath.
> - Also, `net` renamed to `client`, and `client` now has symlink to its principal
>   transport. A client also has a symlink to its `multipath` object.
> - The transport interface lets you change `dstaddr` of individual transports,
>   when `nconnect` is used (or if it wasn't used and these were added with the
>   new interface).
> - The interface to add a transport is using a single string written to 'add',
>   for example:
>
>        echo 'dstaddr 192.168.40.8 kind rdma' \
>                > /sys/kernel/sunrpc/client/0/multipath/add
>
> These changes are independent of the method used to obtain a sunrpc ID for a
> mountpoint. For that I've sent a concept patch showing an fspick-based
> implementation: https://marc.info/?l=linux-nfs&m=161332454821849&w=4

I'm confused: does this allow adding arbitrary connections between a
client and some server IP to an existing RPC client? Given the above
description, that's how it reads to me, can you clarify please. I
thought it was something specifically for v3 (because it has no
concept of trunking). As for NFSv4 there is a notion of getting server
locations via FS_LOCATION and doing trunking (ie multipathing)? I
don't see how this code restricts the addition of transports to v3.

>
> Thanks
>
> Dan Aloni (8):
>   sunrpc: rename 'net' to 'client'
>   sunrpc: add xprt id
>   sunrpc: add a directory per sunrpc xprt
>   sunrpc: have client directory a symlink to the root transport
>   sunrpc: add IDs to multipath
>   sunrpc: add multipath directory and symlink from client
>   sunrpc: change rpc_clnt_add_xprt() to rpc_add_xprt()
>   sunrpc: introduce an 'add' node to 'multipath' sysfs directory
>
>  fs/nfs/pnfs_nfs.c                    |  12 +-
>  include/linux/sunrpc/clnt.h          |  12 +-
>  include/linux/sunrpc/xprt.h          |   3 +
>  include/linux/sunrpc/xprtmultipath.h |   6 +
>  net/sunrpc/clnt.c                    |  39 +--
>  net/sunrpc/sunrpc_syms.c             |   2 +
>  net/sunrpc/sysfs.c                   | 403 +++++++++++++++++++++++----
>  net/sunrpc/sysfs.h                   |  21 +-
>  net/sunrpc/xprt.c                    |  29 ++
>  net/sunrpc/xprtmultipath.c           |  37 +++
>  10 files changed, 487 insertions(+), 77 deletions(-)
>
> --
> 2.26.2
>