nfs4_get_state_owner
extern struct nfs4_state_owner *nfs4_get_state_owner(struct nfs_server *, const struct cred *, gfp_t);
sp = nfs4_get_state_owner(server, ctx->cred, GFP_KERNEL);
sp = nfs4_get_state_owner(server, cred, GFP_KERNEL);