--- fs/nfsserver/nfs_nfsdstate.c.nodstsess	2018-05-29 18:15:02.777775000 -0400
+++ fs/nfsserver/nfs_nfsdstate.c	2018-05-29 18:49:21.903599000 -0400
@@ -710,8 +710,10 @@ nfsrv_destroyclient(nfsquad_t clientid, 
 {
 	struct nfsclient *clp;
 	struct nfsclienthashhead *hp;
-	int error = 0, i, igotlock;
+	struct nfsdsession *sep;
+	int error, i, igotlock;
 
+	error = 0;
 	if (nfsrvboottime != clientid.lval[0]) {
 		error = NFSERR_STALECLIENTID;
 		goto out;
@@ -740,19 +742,24 @@ nfsrv_destroyclient(nfsquad_t clientid, 
 	}
 
 	/* Scan for state on the clientid. */
-	for (i = 0; i < nfsrv_statehashsize; i++)
-		if (!LIST_EMPTY(&clp->lc_stateid[i])) {
-			NFSLOCKV4ROOTMUTEX();
-			nfsv4_unlock(&nfsv4rootfs_lock, 1);
-			NFSUNLOCKV4ROOTMUTEX();
+	if (!LIST_EMPTY(&clp->lc_deleg))
+		error = NFSERR_CLIENTIDBUSY;
+	for (i = 0; i < nfsrv_statehashsize && error == 0; i++)
+		if (!LIST_EMPTY(&clp->lc_stateid[i]))
 			error = NFSERR_CLIENTIDBUSY;
-			goto out;
+	if (error == 0) {
+		LIST_FOREACH(sep, &clp->lc_session, sess_list) {
+			if ((sep->sess_crflags & NFSV4CRSESS_DEFUNCT) == 0) {
+				error = NFSERR_CLIENTIDBUSY;
+				break;
+			}
 		}
-	if (!LIST_EMPTY(&clp->lc_session) || !LIST_EMPTY(&clp->lc_deleg)) {
+	}
+
+	if (error != 0) {
 		NFSLOCKV4ROOTMUTEX();
 		nfsv4_unlock(&nfsv4rootfs_lock, 1);
 		NFSUNLOCKV4ROOTMUTEX();
-		error = NFSERR_CLIENTIDBUSY;
 		goto out;
 	}
 
@@ -5993,7 +6000,8 @@ nfsrv_findsession(uint8_t *sessionid)
 
 	shp = NFSSESSIONHASH(sessionid);
 	LIST_FOREACH(sep, &shp->list, sess_hash) {
-		if (!NFSBCMP(sessionid, sep->sess_sessionid, NFSX_V4SESSIONID))
+		if (NFSBCMP(sessionid, sep->sess_sessionid, NFSX_V4SESSIONID) ==
+		    0 && (sep->sess_crflags & NFSV4CRSESS_DEFUNCT) == 0)
 			break;
 	}
 	return (sep);
@@ -6005,15 +6013,25 @@ nfsrv_findsession(uint8_t *sessionid)
 int
 nfsrv_destroysession(struct nfsrv_descript *nd, uint8_t *sessionid)
 {
+	struct nfssessionhash *shp;
+	struct nfsdsession *sep;
 	int error, samesess;
 
 	samesess = 0;
+	error = 0;
 	if (!NFSBCMP(sessionid, nd->nd_sessionid, NFSX_V4SESSIONID)) {
 		samesess = 1;
 		if ((nd->nd_flag & ND_LASTOP) == 0)
 			return (NFSERR_BADSESSION);
 	}
-	error = nfsrv_freesession(NULL, sessionid);
+	shp = NFSSESSIONHASH(sessionid);
+	NFSLOCKSESSION(shp);
+	sep = nfsrv_findsession(sessionid);
+	if (sep != NULL)
+		sep->sess_crflags |= NFSV4CRSESS_DEFUNCT;
+	NFSUNLOCKSESSION(shp);
+	if (sep == NULL)
+		error = NFSERR_BADSESSION;
 	if (error == 0 && samesess != 0)
 		nd->nd_flag &= ~ND_HASSEQUENCE;
 	return (error);
--- fs/nfs/nfsproto.h.nodstsess	2018-05-29 18:33:37.179826000 -0400
+++ fs/nfs/nfsproto.h	2018-05-29 18:34:43.509040000 -0400
@@ -616,6 +616,9 @@
 #define	NFSV4CRSESS_CONNBACKCHAN	0x00000002
 #define	NFSV4CRSESS_CONNRDMA		0x00000004
 
+/* Fake flag for Create Session used internally. */
+#define	NFSV4CRSESS_DEFUNCT		0x80000000
+
 /* Flags for Sequence */
 #define	NFSV4SEQ_CBPATHDOWN		0x00000001
 #define	NFSV4SEQ_CBGSSCONTEXPIRING	0x00000002