diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index b4289060ebaf06c801438bc04972e6f37a3c515e..bf3a3575d060aeb67f5fc6305256332e30430abd 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -1264,6 +1264,22 @@ nfsd4_umh_cltrack_init(struct net *net)
 	return ret;
 }
 
+static void
+nfsd4_cltrack_upcall_lock(struct nfs4_client *clp)
+{
+	wait_on_bit_lock(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK,
+			 TASK_UNINTERRUPTIBLE);
+}
+
+static void
+nfsd4_cltrack_upcall_unlock(struct nfs4_client *clp)
+{
+	smp_mb__before_atomic();
+	clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags);
+	smp_mb__after_atomic();
+	wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK);
+}
+
 static void
 nfsd4_umh_cltrack_create(struct nfs4_client *clp)
 {
@@ -1275,9 +1291,14 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
 		dprintk("%s: can't allocate memory for upcall!\n", __func__);
 		return;
 	}
+
 	has_session = nfsd4_cltrack_client_has_session(clp);
 	grace_start = nfsd4_cltrack_grace_start(nn->boot_time);
+
+	nfsd4_cltrack_upcall_lock(clp);
 	nfsd4_umh_cltrack_upcall("create", hexid, has_session, grace_start);
+	nfsd4_cltrack_upcall_unlock(clp);
+
 	kfree(has_session);
 	kfree(grace_start);
 	kfree(hexid);
@@ -1293,7 +1314,11 @@ nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
 		dprintk("%s: can't allocate memory for upcall!\n", __func__);
 		return;
 	}
+
+	nfsd4_cltrack_upcall_lock(clp);
 	nfsd4_umh_cltrack_upcall("remove", hexid, NULL, NULL);
+	nfsd4_cltrack_upcall_unlock(clp);
+
 	kfree(hexid);
 }
 
@@ -1311,7 +1336,11 @@ nfsd4_umh_cltrack_check(struct nfs4_client *clp)
 
 	has_session = nfsd4_cltrack_client_has_session(clp);
 	legacy = nfsd4_cltrack_legacy_recdir(&clp->cl_name);
+
+	nfsd4_cltrack_upcall_lock(clp);
 	ret = nfsd4_umh_cltrack_upcall("check", hexid, has_session, legacy);
+	nfsd4_cltrack_upcall_unlock(clp);
+
 	kfree(has_session);
 	kfree(legacy);
 	kfree(hexid);
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 854f0c574ccf887ad1259c03dd319883a5762b71..62a82ab06cf1bba3ee102dcaf25f9637cef608eb 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -306,6 +306,7 @@ struct nfs4_client {
 #define NFSD4_CLIENT_STABLE		(2)	/* client on stable storage */
 #define NFSD4_CLIENT_RECLAIM_COMPLETE	(3)	/* reclaim_complete done */
 #define NFSD4_CLIENT_CONFIRMED		(4)	/* client is confirmed */
+#define NFSD4_CLIENT_UPCALL_LOCK	(5)	/* upcall serialization */
 #define NFSD4_CLIENT_CB_FLAG_MASK	(1 << NFSD4_CLIENT_CB_UPDATE | \
 					 1 << NFSD4_CLIENT_CB_KILL)
 	unsigned long		cl_flags;