nfsd: make client/ directory names small ints

We want clientid's on the wire to be randomized for reasons explained in
ebd7c72c "nfsd: randomize SETCLIENTID reply to help distinguish
servers".  But I'd rather have mostly small integers for the clients/
directory.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/netns.h

@@ -111,6 +111,7 @@ struct nfsd_net {
 	 */
 	unsigned int max_connections;
 
+	u32 clientid_base;
 	u32 clientid_counter;
 	u32 clverifier_counter;
 

fs/nfsd/nfs4state.c

@@ -2242,7 +2242,7 @@ static struct nfs4_client *create_client(struct xdr_netobj name,
 	clp->cl_cb_session = NULL;
 	clp->net = net;
 	clp->cl_nfsd_dentry = nfsd_client_mkdir(nn, &clp->cl_nfsdfs,
-						clp->cl_clientid.cl_id);
+			clp->cl_clientid.cl_id - nn->clientid_base);
 	if (!clp->cl_nfsd_dentry) {
 		free_client(clp);
 		return NULL;

fs/nfsd/nfsctl.c

@@ -1213,7 +1213,7 @@ struct dentry *nfsd_client_mkdir(struct nfsd_net *nn, struct nfsdfs_client *ncl,
 {
 	char name[11];
 
-	sprintf(name, "%d", id++);
+	sprintf(name, "%u", id);
 
 	return nfsd_mkdir(nn->nfsd_client_dir, ncl, name);
 }
@@ -1352,7 +1352,8 @@ static __net_init int nfsd_init_net(struct net *net)
 	nn->somebody_reclaimed = false;
 	nn->track_reclaim_completes = false;
 	nn->clverifier_counter = prandom_u32();
-	nn->clientid_counter = prandom_u32();
+	nn->clientid_base = prandom_u32();
+	nn->clientid_counter = nn->clientid_base + 1;
 	nn->s2s_cp_cl_id = nn->clientid_counter++;
 
 	atomic_set(&nn->ntf_refcnt, 0);