NFS/pnfs: Separate NFSv3 DS and MDS traffic

If a NFSv3 server is being used as both a DS and as a regular NFSv3 server,
we may want to keep the IO traffic on a separate TCP connection, since
it will typically have very different timeout characteristics.

This patch therefore sets up a flag to separate the two modes of operation
for the nfs_client.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/client.c

@@ -312,6 +312,12 @@ again:
 		/* Match nfsv4 minorversion */
 		if (clp->cl_minorversion != data->minorversion)
 			continue;
+
+		/* Match request for a dedicated DS */
+		if (test_bit(NFS_CS_DS, &data->init_flags) !=
+		    test_bit(NFS_CS_DS, &clp->cl_flags))
+			continue;
+
 		/* Match the full socket address */
 		if (!rpc_cmp_addr_port(sap, clap))
 			/* Match all xprt_switch full socket addresses */