filesystems/nfs/localio.rst

10 host. Select "NFS client and server support for LOCALIO auxiliary
14 Once an NFS client and server handshake as "local", the client will
23 clients local to their servers. In a private implementation that
25 address based match against all local network interfaces was attempted.
26 But unlike the LOCALIO protocol, the sockaddr-based matching didn't
29 The robust handshake between local client and server is just the
35 (e.g. kubernetes) where it is possible to run an IO job local to the
42   - With LOCALIO:
48   - Without LOCALIO:
55   - With LOCALIO:
61   - Without LOCALIO:
72    a. Workloads where the NFS client and server are on the same host
75       running on the same host as the knfsd server being used for
84       running local to each other without making any assumptions about
85       the local network topology.
93    deciding if the NFS client and server are co-located on the same
94    host?
101    same host. The handshake uses a secret that is sent over the wire,
103    in shared kernel memory if they are truly co-located.
115    onus on the server to somehow discover that the client is co-located
122 6. Why is having the client perform a server-side file OPEN, without
131    client perform a server-side file open, without using RPC, is ideal.
151    as they do for non-LOCALIO.
162 RPC method that allows the Linux NFS client to verify the local Linux
163 NFS server can see the nonce (single-use UUID) the client generated and
165 standard, nor does it need to be considering it is Linux-to-Linux
174 by IANA, see https://www.iana.org/assignments/rpc-program-numbers/ ):
200 to generate a nonce (single-use UUID) and associated short-lived
204 transfer the nfs_uuid_t from its nfs_uuids to the nn->nfsd_serv
211 access nn->nfsd_serv with proper rcu read access). It is this client
213 objects to span from the host kernel's nfsd to per-container knfsd
214 instances that are connected to nfs client's running on the same local
215 host.
221 allow proper network namespace (net-ns) and NFSD object refcounting.
225 each net-ns is not destroyed while in use by nfsd_open_local_fh(), and
230     reference for the nfsd_file and associated net-ns using
235     NFSD's net-ns (and nfsd_net by association) may have been destroyed
244 NFSD's net-ns.
255 focused use of select nfs server objects to allow a client local to a
260 both the associated nfsd network namespace and nn->nfsd_serv in terms of
262 nfsd objects (be it struct net or nn->nfsd_serv) it returns -ENXIO
269 writes and commits directly to the underlying local filesystem (normally
271 is issuing IO to the underlying local filesystem that it is sharing with
280 can be configured to use end-to-end O_DIRECT semantics from the NFS
281 client to the underlying local filesystem, that it is sharing with
287 Once enabled, it will cause LOCALIO to use end-to-end O_DIRECT semantics
294 LOCALIO is only supported when UNIX-style authentication (AUTH_UNIX, aka
304 the server's per-namespace nfsd_net struct. With traditional NFS, the
314 local but 'localio_enabled' is set to N then LOCALIO will not be used.
324 (disabled). Must be power-of-2, admin keeps all the pieces if they
325 misconfigure (too low a value or non-power-of-2).
333 - Client and server both on the same host.
335 - All permutations of client and server support enablement for both
336   local and remote client and server.
338 - Testing against NFS storage products that don't support the LOCALIO
341 - Client on host, server within a container (for both v3 and v4.2).
345 - Formalizing these test scenarios in terms of existing test
346   infrastructure is on-going. Initial regular coverage is provided in
347   terms of ktest running xfstests against a LOCALIO-enabled NFS loopback
349   https://evilpiepirate.org/~testdashboard/ci?user=snitzer&branch=snitm-nfs-next
352 - Various kdevops testing (in terms of "Chuck's BuildBot") has been
354   regressions to non-LOCALIO NFS use cases.
356 - All of Hammerspace's various sanity tests pass with LOCALIO enabled