2008-09-29 11:41:11

by Steve Dickson

[permalink] [raw]
Subject: Re: [PATCH 2/2] nfs(5): Clarify behavior of the mountproto= and proto= options

Is this ready to go??


Chuck Lever wrote:
> Document the interaction between the mountproto= and the proto= mount
> options in a new subsection of nfs(5).
> Signed-off-by: Chuck Lever <[email protected]>
> ---
> utils/mount/nfs.man | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 81 insertions(+), 0 deletions(-)
> diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man
> index b1037a8..48f2153 100644
> --- a/utils/mount/nfs.man
> +++ b/utils/mount/nfs.man
> @@ -831,6 +831,87 @@ and
> .B wsize
> can safely be allowed to default to the largest values supported by
> both client and server, independent of the network's MTU size.
> +.SS "Interaction between the proto and mountproto options"
> +The Linux NFS client can use a different transport protocol for
> +contacting an NFS server's rpcbind service, its mountd service,
> +its NLM service, and its NFS service.
> +The exact transport protocols employed by the Linux NFS client for
> +each mount point depends on the settings of the transport protocol
> +mount options, which include
> +.BR proto ,
> +.BR mountproto ,
> +.BR udp ", and " tcp .
> +.P
> +The NSM protocol uses the UDP transport
> +no matter what transport specific options are specified.
> +The NFSACL protocol shares the same RPC transport as the main NFS
> +service.
> +.P
> +If no transport protocol options are specified, the Linux NFS client
> +uses UDP to contact the server's mountd service, and TCP to
> +contact its NLM and NFS services by default.
> +.P
> +UDP is a good choice for contacting the mountd server since most
> +common NFS servers support UDP for mountd, UDP generates less network
> +traffic, and UDP does not leave extra ports in TIME_WAIT after the
> +mountd request is complete.
> +However, a reliable stream transport such as TCP is a good choice for
> +NFS and NLM because these must handle large requests and must be
> +immune to network problems that might cause RPC requests to be lost.
> +.P
> +If the server does not support these transports for these services, the
> +.BR mount (8)
> +command attempts to discover what the server supports, and then retries
> +the mount request once using the discovered transport protocols.
> +If the server does not advertise any transport supported by the client
> +or is misconfigured, the mount request fails.
> +If the
> +.B bg
> +option is in effect, the mount command backgrounds itself and continues
> +to attempt the specified mount request.
> +.P
> +When the
> +.B proto
> +option, the
> +.B udp
> +option, or the
> +.B tcp
> +option is specified but the
> +.B mountproto
> +option is not, the specified transport is used to contact
> +both the server's mountd service and for the NLM and NFS services.
> +.P
> +If the
> +.B mountproto
> +option is specified but none of the
> +.BR proto ", " udp " or " tcp
> +options are specified, then the specified transport is used for the
> +initial mountd request, but the mount command attempts to discover
> +what the server supports for the NFS protocol, preferring TCP if
> +both transports are supported.
> +.P
> +If both the
> +.BR mountproto " and " proto
> +(or
> +.BR udp " or " tcp )
> +options are specified, then the transport specified by the
> +.B mountproto
> +option is used for the initial mountd request, and the transport
> +specified by the
> +.B proto
> +option (or the
> +.BR udp " or " tcp " options)"
> +is used for NFS, no matter what order these options appear.
> +No automatic service discovery is performed if these options are
> +specified.
> +.P
> +If any of the
> +.BR proto ", " udp ", " tcp ", "
> +or
> +.B mountproto
> +options are specified more than once on the same mount command line,
> +then the value of the rightmost instance of each of these options
> +takes effect.
> Some modern cluster file systems provide
> perfect cache coherence among their clients.