diff --git a/fs/nfsd/acl.h b/fs/nfsd/acl.h
index 8b186a4..5b7bf21 100644
--- a/fs/nfsd/acl.h
+++ b/fs/nfsd/acl.h
@@ -43,7 +43,7 @@
 
 struct nfs4_acl *nfs4_acl_new(int);
 int nfs4_acl_get_whotype(char *, u32);
-int nfs4_acl_write_who(int who, char *p);
+int nfs4_acl_write_who(int who, __be32 **p, int *len);
 
 #define NFS4_ACL_TYPE_DEFAULT	0x01
 #define NFS4_ACL_DIR		0x02
diff --git a/fs/nfsd/idmap.h b/fs/nfsd/idmap.h
index bf95f6b..66e58db 100644
--- a/fs/nfsd/idmap.h
+++ b/fs/nfsd/idmap.h
@@ -56,7 +56,7 @@ static inline void nfsd_idmap_shutdown(struct net *net)
 
 __be32 nfsd_map_name_to_uid(struct svc_rqst *, const char *, size_t, kuid_t *);
 __be32 nfsd_map_name_to_gid(struct svc_rqst *, const char *, size_t, kgid_t *);
-int nfsd_map_uid_to_name(struct svc_rqst *, kuid_t, char *);
-int nfsd_map_gid_to_name(struct svc_rqst *, kgid_t, char *);
+__be32 nfsd4_encode_user(struct svc_rqst *, kuid_t, __be32 **, int *);
+__be32 nfsd4_encode_group(struct svc_rqst *, kgid_t, __be32 **, int *);
 
 #endif /* LINUX_NFSD_IDMAP_H */
diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
index 8a50b3c..eea24c9 100644
--- a/fs/nfsd/nfs4acl.c
+++ b/fs/nfsd/nfs4acl.c
@@ -37,6 +37,7 @@
 #include <linux/slab.h>
 #include <linux/nfs_fs.h>
 #include <linux/export.h>
+#include "nfsd.h"
 #include "acl.h"
 
 
@@ -848,18 +849,23 @@ nfs4_acl_get_whotype(char *p, u32 len)
 	return NFS4_ACL_WHO_NAMED;
 }
 
-int
-nfs4_acl_write_who(int who, char *p)
+__be32 nfs4_acl_write_who(int who, __be32 **p, int *len)
 {
 	int i;
+	int bytes;
 
 	for (i = 0; i < ARRAY_SIZE(s2t_map); i++) {
-		if (s2t_map[i].type == who) {
-			memcpy(p, s2t_map[i].string, s2t_map[i].stringlen);
-			return s2t_map[i].stringlen;
-		}
+		if (s2t_map[i].type != who)
+			continue;
+		bytes = 4 + (XDR_QUADLEN(s2t_map[i].stringlen) << 2);
+		if (bytes > *len)
+			return nfserr_resource;
+		*p = xdr_encode_opaque(*p, s2t_map[i].string,
+					s2t_map[i].stringlen);
+		*len -= bytes;
+		return 0;
 	}
-	BUG();
+	WARN_ON_ONCE(1);
 	return -1;
 }
 
diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index 4832fd8..c0dfde6 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -551,27 +551,46 @@ idmap_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen
 	return 0;
 }
 
-static int
-idmap_id_to_name(struct svc_rqst *rqstp, int type, u32 id, char *name)
+static __be32 encode_ascii_id(u32 id, __be32 **p, int *buflen)
+{
+	char buf[11];
+	int len;
+	int bytes;
+
+	len = sprintf(buf, "%u", id);
+	bytes = 4 + (XDR_QUADLEN(len) << 2);
+	if (bytes > *buflen)
+		return nfserr_resource;
+	*p = xdr_encode_opaque(*p, buf, len);
+	*buflen -= bytes;
+	return 0;
+}
+
+static __be32 idmap_id_to_name(struct svc_rqst *rqstp, int type, u32 id, __be32 **p, int *buflen)
 {
 	struct ent *item, key = {
 		.id = id,
 		.type = type,
 	};
 	int ret;
+	int bytes;
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
 
 	strlcpy(key.authname, rqst_authname(rqstp), sizeof(key.authname));
 	ret = idmap_lookup(rqstp, idtoname_lookup, &key, nn->idtoname_cache, &item);
 	if (ret == -ENOENT)
-		return sprintf(name, "%u", id);
+		return encode_ascii_id(id, p, buflen);
 	if (ret)
-		return ret;
+		return nfserrno(ret);
 	ret = strlen(item->name);
-	BUG_ON(ret > IDMAP_NAMESZ);
-	memcpy(name, item->name, ret);
+	WARN_ON_ONCE(ret > IDMAP_NAMESZ);
+	bytes = 4 + (XDR_QUADLEN(ret) << 2);
+	if (bytes > *buflen)
+		return nfserr_resource;
+	*p = xdr_encode_opaque(*p, item->name, ret);
+	*buflen -= bytes;
 	cache_put(&item->h, nn->idtoname_cache);
-	return ret;
+	return 0;
 }
 
 static bool
@@ -603,12 +622,11 @@ do_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen, u
 	return idmap_name_to_id(rqstp, type, name, namelen, id);
 }
 
-static int
-do_id_to_name(struct svc_rqst *rqstp, int type, u32 id, char *name)
+static __be32 encode_name_from_id(struct svc_rqst *rqstp, int type, u32 id, __be32 **p, int *buflen)
 {
 	if (nfs4_disable_idmapping && rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS)
-		return sprintf(name, "%u", id);
-	return idmap_id_to_name(rqstp, type, id, name);
+		return encode_ascii_id(id, p, buflen);
+	return idmap_id_to_name(rqstp, type, id, p, buflen);
 }
 
 __be32
@@ -637,16 +655,14 @@ nfsd_map_name_to_gid(struct svc_rqst *rqstp, const char *name, size_t namelen,
 	return status;
 }
 
-int
-nfsd_map_uid_to_name(struct svc_rqst *rqstp, kuid_t uid, char *name)
+__be32 nfsd4_encode_user(struct svc_rqst *rqstp, kuid_t uid,  __be32 **p, int *buflen)
 {
 	u32 id = from_kuid(&init_user_ns, uid);
-	return do_id_to_name(rqstp, IDMAP_TYPE_USER, id, name);
+	return encode_name_from_id(rqstp, IDMAP_TYPE_USER, id, p, buflen);
 }
 
-int
-nfsd_map_gid_to_name(struct svc_rqst *rqstp, kgid_t gid, char *name)
+__be32 nfsd4_encode_group(struct svc_rqst *rqstp, kgid_t gid, __be32 **p, int *buflen)
 {
 	u32 id = from_kgid(&init_user_ns, gid);
-	return do_id_to_name(rqstp, IDMAP_TYPE_GROUP, id, name);
+	return encode_name_from_id(rqstp, IDMAP_TYPE_GROUP, id, p, buflen);
 }
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 67b4496..8198ecf 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1965,56 +1965,16 @@ static u32 nfs4_file_type(umode_t mode)
 	};
 }
 
-static __be32
-nfsd4_encode_name(struct svc_rqst *rqstp, int whotype, kuid_t uid, kgid_t gid,
-			__be32 **p, int *buflen)
-{
-	int status;
-
-	if (*buflen < (XDR_QUADLEN(IDMAP_NAMESZ) << 2) + 4)
-		return nfserr_resource;
-	if (whotype != NFS4_ACL_WHO_NAMED)
-		status = nfs4_acl_write_who(whotype, (u8 *)(*p + 1));
-	else if (gid_valid(gid))
-		status = nfsd_map_gid_to_name(rqstp, gid, (u8 *)(*p + 1));
-	else
-		status = nfsd_map_uid_to_name(rqstp, uid, (u8 *)(*p + 1));
-	if (status < 0)
-		return nfserrno(status);
-	*p = xdr_encode_opaque(*p, NULL, status);
-	*buflen -= (XDR_QUADLEN(status) << 2) + 4;
-	BUG_ON(*buflen < 0);
-	return 0;
-}
-
-static inline __be32
-nfsd4_encode_user(struct svc_rqst *rqstp, kuid_t user, __be32 **p, int *buflen)
-{
-	return nfsd4_encode_name(rqstp, NFS4_ACL_WHO_NAMED, user, INVALID_GID,
-				 p, buflen);
-}
-
-static inline __be32
-nfsd4_encode_group(struct svc_rqst *rqstp, kgid_t group, __be32 **p, int *buflen)
-{
-	return nfsd4_encode_name(rqstp, NFS4_ACL_WHO_NAMED, INVALID_UID, group,
-				 p, buflen);
-}
-
 static inline __be32
 nfsd4_encode_aclname(struct svc_rqst *rqstp, struct nfs4_ace *ace,
 		__be32 **p, int *buflen)
 {
-	kuid_t uid = INVALID_UID;
-	kgid_t gid = INVALID_GID;
-
-	if (ace->whotype == NFS4_ACL_WHO_NAMED) {
-		if (ace->flag & NFS4_ACE_IDENTIFIER_GROUP)
-			gid = ace->who_gid;
-		else
-			uid = ace->who_uid;
-	}
-	return nfsd4_encode_name(rqstp, ace->whotype, uid, gid, p, buflen);
+	if (ace->whotype != NFS4_ACL_WHO_NAMED)
+		return nfs4_acl_write_who(ace->whotype, p, buflen);
+	else if (ace->flag & NFS4_ACE_IDENTIFIER_GROUP)
+		return nfsd4_encode_group(rqstp, ace->who_gid, p, buflen);
+	else
+		return nfsd4_encode_user(rqstp, ace->who_uid, p, buflen);
 }
 
 #define WORD0_ABSENT_FS_ATTRS (FATTR4_WORD0_FS_LOCATIONS | FATTR4_WORD0_FSID | \
