diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -4061,7 +4061,7 @@
 vn_lock_pair(struct vnode *vp1, bool vp1_locked, int lkflags1,
     struct vnode *vp2, bool vp2_locked, int lkflags2)
 {
-	int error;
+	int error, locked1;
 
 	MPASS(((lkflags1 & LK_SHARED) != 0) ^ ((lkflags1 & LK_EXCLUSIVE) != 0));
 	MPASS((lkflags1 & ~(LK_SHARED | LK_EXCLUSIVE | LK_NODDLKTREAT)) == 0);
@@ -4071,6 +4071,29 @@
 	if (vp1 == NULL && vp2 == NULL)
 		return;
 
+	if (vp1 == vp2) {
+		MPASS(vp1_locked == vp2_locked);
+
+		/* Select the most exclusive mode for lock. */
+		if ((lkflags1 & LK_TYPE_MASK) != (lkflags2 & LK_TYPE_MASK))
+			lkflags1 = (lkflags1 & ~LK_SHARED) | LK_EXCLUSIVE;
+
+		if (vp1_locked) {
+			ASSERT_VOP_LOCKED(vp1, "vp1");
+			locked1 = VOP_ISLOCKED(vp1);
+			if (((lkflags1 & LK_SHARED) != 0 &&
+			    locked1 != LK_EXCLUSIVE) ||
+			    ((lkflags1 & LK_EXCLUSIVE) != 0 &&
+			    locked1 == LK_EXCLUSIVE))
+				return;
+			VOP_UNLOCK(vp1);
+		}
+
+		ASSERT_VOP_UNLOCKED(vp1, "vp1");
+		vn_lock(vp1, lkflags1 | LK_RETRY);
+		return;
+	}		
+
 	if (vp1 != NULL) {
 		if ((lkflags1 & LK_SHARED) != 0 &&
 		    (vp1->v_vnlock->lock_object.lo_flags & LK_NOSHARE) != 0)