NFSv4.x: Remove hard coded slotids in callback channel

Instead, use the values encoded in the slot table itself.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/callback_proc.c

@@ -361,7 +361,7 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
 	dprintk("%s enter. slotid %u seqid %u\n",
 		__func__, args->csa_slotid, args->csa_sequenceid);
 
-	if (args->csa_slotid >= NFS41_BC_MAX_CALLBACKS)
+	if (args->csa_slotid > tbl->server_highest_slotid)
 		return htonl(NFS4ERR_BADSLOT);
 
 	slot = tbl->slots + args->csa_slotid;
@@ -489,8 +489,8 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 	       sizeof(res->csr_sessionid));
 	res->csr_sequenceid = args->csa_sequenceid;
 	res->csr_slotid = args->csa_slotid;
-	res->csr_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
-	res->csr_target_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
+	res->csr_highestslotid = tbl->server_highest_slotid;
+	res->csr_target_highestslotid = tbl->target_highest_slotid;
 
 	status = validate_seqid(tbl, args);
 	if (status)

fs/nfs/nfs4proc.c

@@ -7319,7 +7319,7 @@ static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args)
 	args->bc_attrs.max_resp_sz = PAGE_SIZE;
 	args->bc_attrs.max_resp_sz_cached = 0;
 	args->bc_attrs.max_ops = NFS4_MAX_BACK_CHANNEL_OPS;
-	args->bc_attrs.max_reqs = 1;
+	args->bc_attrs.max_reqs = NFS41_BC_MAX_CALLBACKS;
 
 	dprintk("%s: Back Channel : max_rqst_sz=%u max_resp_sz=%u "
 		"max_resp_sz_cached=%u max_ops=%u max_reqs=%u\n",