diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 882c01a64498..126529ec7ca9 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1027,6 +1027,7 @@ void ceph_mdsc_release_request(struct kref *kref)
 	if (req->r_pagelist)
 		ceph_pagelist_release(req->r_pagelist);
 	kfree(req->r_fscrypt_auth);
+	kfree(req->r_altname);
 	put_request_session(req);
 	ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
 	WARN_ON_ONCE(!list_empty(&req->r_wait));
@@ -2435,6 +2436,64 @@ static inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
 	return mdsc->oldest_tid;
 }
 
+#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
+static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
+{
+	struct inode *dir = req->r_parent;
+	struct dentry *dentry = req->r_dentry;
+	u8 *cryptbuf = NULL;
+	u32 len = 0;
+	int ret = 0;
+
+	/* only encode if we have parent and dentry */
+	if (!dir || !dentry)
+		goto success;
+
+	/* No-op unless this is encrypted */
+	if (!IS_ENCRYPTED(dir))
+		goto success;
+
+	ret = __fscrypt_prepare_readdir(dir);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/* No key? Just ignore it. */
+	if (!fscrypt_has_encryption_key(dir))
+		goto success;
+
+	if (!fscrypt_fname_encrypted_size(dir, dentry->d_name.len, NAME_MAX,
+					  &len)) {
+		WARN_ON_ONCE(1);
+		return ERR_PTR(-ENAMETOOLONG);
+	}
+
+	/* No need to append altname if name is short enough */
+	if (len <= CEPH_NOHASH_NAME_MAX) {
+		len = 0;
+		goto success;
+	}
+
+	cryptbuf = kmalloc(len, GFP_KERNEL);
+	if (!cryptbuf)
+		return ERR_PTR(-ENOMEM);
+
+	ret = fscrypt_fname_encrypt(dir, &dentry->d_name, cryptbuf, len);
+	if (ret) {
+		kfree(cryptbuf);
+		return ERR_PTR(ret);
+	}
+success:
+	*plen = len;
+	return cryptbuf;
+}
+#else
+static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
+{
+	*plen = 0;
+	return NULL;
+}
+#endif
+
 /**
  * ceph_mdsc_build_path - build a path string to a given dentry
  * @dentry: dentry to which path should be built
@@ -2662,14 +2721,15 @@ static void encode_mclientrequest_tail(void **p,
 	ceph_encode_timespec64(&ts, &req->r_stamp);
 	ceph_encode_copy(p, &ts, sizeof(ts));
 
-	/* gid_list */
+	/* v4: gid_list */
 	ceph_encode_32(p, req->r_cred->group_info->ngroups);
 	for (i = 0; i < req->r_cred->group_info->ngroups; i++)
 		ceph_encode_64(p, from_kgid(&init_user_ns,
 					    req->r_cred->group_info->gid[i]));
 
-	/* v5: altname (TODO: skip for now) */
-	ceph_encode_32(p, 0);
+	/* v5: altname */
+	ceph_encode_32(p, req->r_altname_len);
+	ceph_encode_copy(p, req->r_altname, req->r_altname_len);
 
 	/* v6: fscrypt_auth and fscrypt_file */
 	if (req->r_fscrypt_auth) {
@@ -2729,7 +2789,13 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
 		goto out_free1;
 	}
 
-	/* head */
+	req->r_altname = get_fscrypt_altname(req, &req->r_altname_len);
+	if (IS_ERR(req->r_altname)) {
+		msg = ERR_CAST(req->r_altname);
+		req->r_altname = NULL;
+		goto out_free2;
+	}
+
 	len = legacy ? sizeof(*head) : sizeof(struct ceph_mds_request_head);
 
 	/* filepaths */
@@ -2755,7 +2821,7 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
 	len += sizeof(u32) + (sizeof(u64) * req->r_cred->group_info->ngroups);
 
 	/* alternate name */
-	len += sizeof(u32);	// TODO
+	len += sizeof(u32) + req->r_altname_len;
 
 	/* fscrypt_auth */
 	len += sizeof(u32); // fscrypt_auth
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 1105baa97d49..3cf874925519 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -285,6 +285,9 @@ struct ceph_mds_request {
 
 	struct ceph_fscrypt_auth *r_fscrypt_auth;
 
+	u8 *r_altname;		    /* fscrypt binary crypttext for long filenames */
+	u32 r_altname_len;	    /* length of r_altname */
+
 	int r_fmode;        /* file mode, if expecting cap */
 	int r_request_release_offset;
 	const struct cred *r_cred;