NFS: Move cl_delegations to the nfs_server struct

Delegations are per-inode, not per-nfs_client.  When a server file
system is migrated, delegations on the client must be moved from the
source to the destination nfs_server.  Make it easier to manage a
mount point's delegation list across a migration event by moving the
list to the nfs_server struct.

Clean up: I added documenting comments to public functions I changed
in this patch.  For consistency I added comments to all the other
public functions in fs/nfs/delegation.c.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -172,7 +172,6 @@ static struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_
 	if (err)
 		goto error_cleanup;
 
-	INIT_LIST_HEAD(&clp->cl_delegations);
 	spin_lock_init(&clp->cl_lock);
 	INIT_DELAYED_WORK(&clp->cl_renewd, nfs4_renew_state);
 	rpc_init_wait_queue(&clp->cl_rpcwaitq, "NFS client");
@@ -1040,6 +1039,7 @@ static struct nfs_server *nfs_alloc_server(void)
 	/* Zero out the NFS state stuff */
 	INIT_LIST_HEAD(&server->client_link);
 	INIT_LIST_HEAD(&server->master_link);
+	INIT_LIST_HEAD(&server->delegations);
 
 	atomic_set(&server->active, 0);