nfs(5): Clarify behavior of the mountproto= and proto= options

Document the interaction between the mountproto= and the proto= mount
options in a new subsection of nfs(5).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man
index 433e73a1527c361784c6d6c66df46f951b5403c0..0c86559f5d08e00009f72e25de87f391e71ebde3 100644 (file)
--- a/utils/mount/nfs.man
+++ b/utils/mount/nfs.man
@@ -507,6 +507,11 @@ option, different transports for mountd requests and NFS requests
 can be specified.
 If the server's mountd service is not available via the specified
 transport, the mount request fails.
 can be specified.
 If the server's mountd service is not available via the specified
 transport, the mount request fails.

+Refer to the TRANSPORT METHODS section for more on how the
+.B mountproto
+mount option interacts with the
+.B proto
+mount option.

 .TP 1.5i
 .BI mounthost= name
 The hostname of the host running mountd.
 .TP 1.5i
 .BI mounthost= name
 The hostname of the host running mountd.


@@ -831,6 +836,84 @@ 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.
 .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 "Using the mountproto mount option"
+This section applies only to NFS version 2 and version 3 mounts
+since NFS version 4 does not use a separate protocol for mount
+requests.
+.P
+The Linux NFS client can use a different transport for
+contacting an NFS server's rpcbind service, its mountd service,
+its Network Lock Manager (NLM) service, and its NFS service.
+The exact transports employed by the Linux NFS client for
+each mount point depends on the settings of the transport
+mount options, which include
+.BR proto ,
+.BR mountproto ,
+.BR udp ", and " tcp .
+.P
+The client sends Network Status Manager (NSM) notifications
+via UDP no matter what transport options are specified, but
+listens for server NSM notifications on both UDP and TCP.
+The NFS Access Control List (NFSACL) protocol shares the same
+transport as the main NFS service.
+.P
+If no transport 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
+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 transports.
+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.

 .SH "DATA AND METADATA COHERENCE"
 Some modern cluster file systems provide
 perfect cache coherence among their clients.
 .SH "DATA AND METADATA COHERENCE"
 Some modern cluster file systems provide
 perfect cache coherence among their clients.


@@ -1234,6 +1317,8 @@ such as security negotiation, server referrals, and named attributes.
 .BR umount.nfs (5),
 .BR exports (5),
 .BR nfsd (8),
 .BR umount.nfs (5),
 .BR exports (5),
 .BR nfsd (8),

+.BR sm-notify (8),
+.BR rpc.statd (8),

 .BR rpc.idmapd (8),
 .BR rpc.gssd (8),
 .BR rpc.svcgssd (8),
 .BR rpc.idmapd (8),
 .BR rpc.gssd (8),
 .BR rpc.svcgssd (8),