On Wed, 2012-07-11 at 16:31 -0400, Chuck Lever wrote:
> "Server trunking" is a fancy named for a multi-homed NFS server.
> Trunking might occur if a client sends NFS requests for a single
> workload to multiple network interfaces on the same server. There
> are some implications for NFSv4 state management that make it useful
> for a client to know if a single NFSv4 server instance is
> multi-homed. (Note this is only a consideration for NFSv4, not for
> legacy versions of NFS, which are stateless).
>
> If a client cares about server trunking, no NFSv4 operations can
> proceed until that client determines who it is talking to. Thus
> server IP trunking discovery must be done when the client first
> encounters an unfamiliar server IP address.
>
> The nfs_get_client() function walks the nfs_client_list and matches
> on server IP address. The outcome of that walk tells us immediately
> if we have an unfamiliar server IP address. It invokes
> nfs_init_client() in this case. Thus, nfs4_init_client() is a good
> spot to perform trunking discovery.
>
> Discovery requires a client to establish a fresh client ID, so our
> client will now send SETCLIENTID or EXCHANGE_ID as the first NFS
> operation after a successful ping, rather than waiting for an
> application to perform an operation that requires NFSv4 state.
>
> The exact process for detecting trunking is different for NFSv4.0 and
> NFSv4.1, so a minorversion-specific init_client callout method is
> introduced.
>
> CLID_INUSE recovery is important for the trunking discovery process.
> CLID_INUSE is a sign the server recognizes the client's nfs_client_id4
> id string, but the client is using the wrong principal this time for
> the SETCLIENTID operation. The SETCLIENTID must be retried with a
> series of different principals until one works, and the rest of
> trunking discovery can proceed.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
>
> fs/nfs/client.c | 237 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/nfs/internal.h | 6 +
> fs/nfs/nfs4_fs.h | 8 ++
> fs/nfs/nfs4proc.c | 2
> fs/nfs/nfs4state.c | 186 ++++++++++++++++++++++++++++++++++++++++-
> 5 files changed, 433 insertions(+), 6 deletions(-)
Applying: NFS: Discover NFSv4 server trunking when mounting
error: patch failed: fs/nfs/nfs4state.c:1656
error: fs/nfs/nfs4state.c: patch does not apply
Patch failed at 0001 NFS: Discover NFSv4 server trunking when mounting
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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