Index: kern/vfs_mount.c
===================================================================
--- kern/vfs_mount.c	(revision 184100)
+++ kern/vfs_mount.c	(working copy)
@@ -1245,19 +1245,16 @@
 	/* Allow filesystems to detect that a forced unmount is in progress. */
 	if (flags & MNT_FORCE)
 		mp->mnt_kern_flag |= MNTK_UNMOUNTF;
-	error = lockmgr(&mp->mnt_lock, LK_DRAIN | LK_INTERLOCK |
-	    ((flags & MNT_FORCE) ? 0 : LK_NOWAIT), MNT_MTX(mp));
-	if (error) {
-		MNT_ILOCK(mp);
-		mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_NOINSMNTQ |
-		    MNTK_UNMOUNTF);
-		if (mp->mnt_kern_flag & MNTK_MWAIT)
-			wakeup(mp);
+	error = 0;
+	if (mp->mnt_lockref) {
+		mp->mnt_kern_flag |= MNTK_DRAINING;
+		error = msleep(&mp->mnt_lockref, MNT_MTX(mp), PVFS,
+		    "mount drain", 0);
+	} else
 		MNT_IUNLOCK(mp);
-		if (coveredvp)
-			VOP_UNLOCK(coveredvp, 0);
-		return (error);
-	}
+	KASSERT(error == 0,
+	    ("%s: invalid return value for msleep in the drain path @ %s:%d",
+	    __func__, __FILE__, __LINE__));
 	vn_start_write(NULL, &mp, V_WAIT);
 
 	if (mp->mnt_flag & MNT_EXPUBLIC)
@@ -1321,7 +1318,6 @@
 		mp->mnt_flag |= async_flag;
 		if ((mp->mnt_flag & MNT_ASYNC) != 0 && mp->mnt_noasync == 0)
 			mp->mnt_kern_flag |= MNTK_ASYNC;
-		lockmgr(&mp->mnt_lock, LK_RELEASE, NULL);
 		if (mp->mnt_kern_flag & MNTK_MWAIT)
 			wakeup(mp);
 		MNT_IUNLOCK(mp);
@@ -1337,7 +1333,6 @@
 		vput(coveredvp);
 	}
 	vfs_event_signal(NULL, VQ_UNMOUNT, 0);
-	lockmgr(&mp->mnt_lock, LK_RELEASE, NULL);
 	vfs_mount_destroy(mp);
 	return (0);
 }
@@ -2070,7 +2065,6 @@
 			wakeup(&mp->mnt_holdcnt);
 		return (NULL);
 	}
-	mp->mnt_markercnt++;
 	(*mvp)->v_mount = mp;
 	TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
 	return (vp);
@@ -2093,7 +2087,6 @@
 	MNT_ILOCK(mp);
 	*mvp = NULL;
 
-	mp->mnt_markercnt--;
 	mp->mnt_holdcnt--;
 	if (mp->mnt_holdcnt == 0 && mp->mnt_holdcntwaiters != 0)
 		wakeup(&mp->mnt_holdcnt);
Index: kern/vfs_subr.c
===================================================================
--- kern/vfs_subr.c	(revision 184100)
+++ kern/vfs_subr.c	(working copy)
@@ -369,8 +369,16 @@
 	if (interlkp)
 		mtx_unlock(interlkp);
 	lkflags = LK_SHARED | LK_INTERLOCK | LK_NOWAIT;
-	if (lockmgr(&mp->mnt_lock, lkflags, MNT_MTX(mp)))
+	mp->mnt_lockref++;
+	if (lockmgr(&mp->mnt_lock, lkflags, MNT_MTX(mp))) {
+
+		/*
+		 * It does not matter that we modify lockcount while the
+		 * interlock is not held as long as we are going to panic.
+		 */
+		mp->mnt_lockref--;
 		panic("vfs_busy: unexpected lock failure");
+	}
 	return (0);
 }
 
@@ -380,9 +388,19 @@
 void
 vfs_unbusy(struct mount *mp)
 {
+	int wakedrainers;
 
-	lockmgr(&mp->mnt_lock, LK_RELEASE, NULL);
-	vfs_rel(mp);
+	wakedrainers = 0;
+	MNT_ILOCK(mp);
+	mp->mnt_lockref--;
+	if (mp->mnt_lockref == 0 && (mp->mnt_kern_flag & MNTK_DRAINING)) {
+		MPASS(mp->mnt_kern_flag & MNTK_UNMOUNT);
+		mp->mnt_kern_flag &= ~MNTK_DRAINING;
+		wakedrainers = 1;
+	}
+	lockmgr(&mp->mnt_lock, LK_RELEASE | LK_INTERLOCK, MNT_MTX(mp));
+	if (wakedrainers)
+		wakeup(&mp->mnt_lockref);
 }
 
 /*
@@ -2840,7 +2859,6 @@
 	db_printf("    mnt_maxsymlinklen = %d\n", mp->mnt_maxsymlinklen);
 	db_printf("    mnt_iosize_max = %d\n", mp->mnt_iosize_max);
 	db_printf("    mnt_hashseed = %u\n", mp->mnt_hashseed);
-	db_printf("    mnt_markercnt = %d\n", mp->mnt_markercnt);
 	db_printf("    mnt_holdcnt = %d\n", mp->mnt_holdcnt);
 	db_printf("    mnt_holdcntwaiters = %d\n", mp->mnt_holdcntwaiters);
 	db_printf("    mnt_secondary_writes = %d\n", mp->mnt_secondary_writes);
Index: sys/mount.h
===================================================================
--- sys/mount.h	(revision 184100)
+++ sys/mount.h	(working copy)
@@ -175,7 +175,7 @@
 	struct netexport *mnt_export;		/* export list */
 	struct label	*mnt_label;		/* MAC label for the fs */
 	u_int		mnt_hashseed;		/* Random seed for vfs_hash */
-	int		mnt_markercnt;		/* marker vnodes in use */
+	int		mnt_lockref;		/* (i) Lock reference count */
 	int		mnt_holdcnt;		/* hold count */
 	int		mnt_holdcntwaiters;	/* waits on hold count */
 	int		mnt_secondary_writes;   /* (i) # of secondary writes */
@@ -319,6 +319,7 @@
 #define MNTK_ASYNC	0x00000002	/* filtered async flag */
 #define MNTK_SOFTDEP	0x00000004	/* async disabled by softdep */
 #define MNTK_NOINSMNTQ	0x00000008	/* insmntque is not allowed */
+#define	MNTK_DRAINING	0x00000010	/* lock draining is happening */
 #define MNTK_UNMOUNT	0x01000000	/* unmount in progress */
 #define	MNTK_MWAIT	0x02000000	/* waiting for unmount to finish */
 #define	MNTK_SUSPEND	0x08000000	/* request write suspension */