--- //depot/vendor/freebsd/src/sys/kern/vfs_lookup.c	2008/11/17 20:55:47
+++ //depot/user/attilio/attilio_vfs/sys/kern/vfs_lookup.c	2008/12/14 18:36:51
@@ -698,8 +698,10 @@
 	 */
 	while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
 	       (cnp->cn_flags & NOCROSSMOUNT) == 0) {
-		if (vfs_busy(mp, 0))
-			continue;
+		if (vfs_busy(mp, MBF_NOWAIT)) {
+			dpunlocked = 0;
+			goto bad2;
+		}
 		vput(dp);
 		VFS_UNLOCK_GIANT(vfslocked);
 		vfslocked = VFS_LOCK_GIANT(mp);
--- //depot/vendor/freebsd/src/sys/kern/vfs_mount.c	2008/12/01 03:05:24
+++ //depot/user/attilio/attilio_vfs/sys/kern/vfs_mount.c	2008/12/14 18:36:51
@@ -507,29 +507,20 @@
 {
 
 	MNT_ILOCK(mp);
+	mp->mnt_kern_flag |= MNTK_REFEXPIRE;
+	if (mp->mnt_kern_flag & MNTK_MWAIT) {
+		mp->mnt_kern_flag &= ~MNTK_MWAIT;
+		wakeup(mp);
+	}
 	while (mp->mnt_ref)
 		msleep(mp, MNT_MTX(mp), PVFS, "mntref", 0);
-	if (mp->mnt_writeopcount > 0) {
-		printf("Waiting for mount point write ops\n");
-		while (mp->mnt_writeopcount > 0) {
-			mp->mnt_kern_flag |= MNTK_SUSPEND;
-			msleep(&mp->mnt_writeopcount,
-			       MNT_MTX(mp),
-			       PZERO, "mntdestroy2", 0);
-		}
-		printf("mount point write ops completed\n");
-	}
-	if (mp->mnt_secondary_writes > 0) {
-		printf("Waiting for mount point secondary write ops\n");
-		while (mp->mnt_secondary_writes > 0) {
-			mp->mnt_kern_flag |= MNTK_SUSPEND;
-			msleep(&mp->mnt_secondary_writes,
-			       MNT_MTX(mp),
-			       PZERO, "mntdestroy3", 0);
-		}
-		printf("mount point secondary write ops completed\n");
-	}
-	MNT_IUNLOCK(mp);
+	KASSERT(mp->mnt_ref == 0,
+	    ("%s: invalid refcount in the drain path @ %s:%d", __func__,
+	    __FILE__, __LINE__));
+	if (mp->mnt_writeopcount != 0)
+		panic("vfs_mount_destroy: nonzero writeopcount");
+	if (mp->mnt_secondary_writes != 0)
+		panic("vfs_mount_destroy: nonzero secondary_writes");
 	mp->mnt_vfc->vfc_refcount--;
 	if (!TAILQ_EMPTY(&mp->mnt_nvnodelist)) {
 		struct vnode *vp;
@@ -538,18 +529,10 @@
 			vprint("", vp);
 		panic("unmount: dangling vnode");
 	}
-	MNT_ILOCK(mp);
-	if (mp->mnt_kern_flag & MNTK_MWAIT)
-		wakeup(mp);
-	if (mp->mnt_writeopcount != 0)
-		panic("vfs_mount_destroy: nonzero writeopcount");
-	if (mp->mnt_secondary_writes != 0)
-		panic("vfs_mount_destroy: nonzero secondary_writes");
 	if (mp->mnt_nvnodelistsize != 0)
 		panic("vfs_mount_destroy: nonzero nvnodelistsize");
-	mp->mnt_writeopcount = -1000;
-	mp->mnt_nvnodelistsize = -1000;
-	mp->mnt_secondary_writes = -1000;
+	if (mp->mnt_lockref != 0)
+		panic("vfs_mount_destroy: nonzero lock refcount");
 	MNT_IUNLOCK(mp);
 #ifdef MAC
 	mac_mount_destroy(mp);
@@ -1200,41 +1183,20 @@
 
 	mtx_assert(&Giant, MA_OWNED);
 
-	if ((coveredvp = mp->mnt_vnodecovered) != NULL) {
-		mnt_gen_r = mp->mnt_gen;
-		VI_LOCK(coveredvp);
-		vholdl(coveredvp);
-		vn_lock(coveredvp, LK_EXCLUSIVE | LK_INTERLOCK | LK_RETRY);
-		vdrop(coveredvp);
-		/*
-		 * Check for mp being unmounted while waiting for the
-		 * covered vnode lock.
-		 */
-		if (coveredvp->v_mountedhere != mp ||
-		    coveredvp->v_mountedhere->mnt_gen != mnt_gen_r) {
-			VOP_UNLOCK(coveredvp, 0);
-			return (EBUSY);
-		}
-	}
 	/*
 	 * Only privileged root, or (if MNT_USER is set) the user that did the
 	 * original mount is permitted to unmount this filesystem.
 	 */
 	error = vfs_suser(mp, td);
-	if (error) {
-		if (coveredvp)
-			VOP_UNLOCK(coveredvp, 0);
+	if (error)
 		return (error);
-	}
-
 	MNT_ILOCK(mp);
 	if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
 		MNT_IUNLOCK(mp);
-		if (coveredvp)
-			VOP_UNLOCK(coveredvp, 0);
 		return (EBUSY);
 	}
 	mp->mnt_kern_flag |= MNTK_UNMOUNT | MNTK_NOINSMNTQ;
+
 	/* Allow filesystems to detect that a forced unmount is in progress. */
 	if (flags & MNT_FORCE)
 		mp->mnt_kern_flag |= MNTK_UNMOUNTF;
@@ -1248,8 +1210,6 @@
 				wakeup(mp);
 			}
 			MNT_IUNLOCK(mp);
-			if (coveredvp)
-				VOP_UNLOCK(coveredvp, 0);
 			return (EBUSY);
 		}
 		mp->mnt_kern_flag |= MNTK_DRAINING;
@@ -1263,6 +1223,30 @@
 	KASSERT(error == 0,
 	    ("%s: invalid return value for msleep in the drain path @ %s:%d",
 	    __func__, __FILE__, __LINE__));
+	if ((coveredvp = mp->mnt_vnodecovered) != NULL) {
+		mnt_gen_r = mp->mnt_gen;
+		VI_LOCK(coveredvp);
+		vholdl(coveredvp);
+		vn_lock(coveredvp, LK_EXCLUSIVE | LK_INTERLOCK | LK_RETRY);
+		vdrop(coveredvp);
+		/*
+		 * Check for mp being unmounted while waiting for the
+		 * covered vnode lock.
+		 */
+		if (coveredvp->v_mountedhere != mp ||
+		    coveredvp->v_mountedhere->mnt_gen != mnt_gen_r) {
+			VOP_UNLOCK(coveredvp, 0);
+			MNT_ILOCK(mp);
+			mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_NOINSMNTQ |
+			    MNTK_UNMOUNTF);
+			if (mp->mnt_kern_flag & MNTK_MWAIT) {
+				mp->mnt_kern_flag &= ~MNTK_MWAIT;
+				wakeup(mp);
+			}
+			MNT_IUNLOCK(mp);
+			return (EBUSY);
+		}
+	}
 	vn_start_write(NULL, &mp, V_WAIT);
 
 	if (mp->mnt_flag & MNT_EXPUBLIC)
--- //depot/vendor/freebsd/src/sys/kern/vfs_subr.c	2008/11/29 13:37:40
+++ //depot/user/attilio/attilio_vfs/sys/kern/vfs_subr.c	2008/12/02 15:09:44
@@ -345,7 +345,7 @@
 	MNT_ILOCK(mp);
 	MNT_REF(mp);
 	if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
-		if (flags & MBF_NOWAIT) {
+		if (flags & MBF_NOWAIT || mp->mnt_kern_flag & MNTK_REFEXPIRE) {
 			MNT_REL(mp);
 			MNT_IUNLOCK(mp);
 			return (ENOENT);
--- //depot/vendor/freebsd/src/sys/kern/vfs_syscalls.c	2008/11/29 13:37:40
+++ //depot/user/attilio/attilio_vfs/sys/kern/vfs_syscalls.c	2008/12/14 18:36:51
@@ -751,8 +751,9 @@
 	error = change_dir(vp, td);
 	while (!error && (mp = vp->v_mountedhere) != NULL) {
 		int tvfslocked;
-		if (vfs_busy(mp, 0))
-			continue;
+		error = vfs_busy(mp, MBF_NOWAIT);
+		if (error != 0)
+			break;
 		tvfslocked = VFS_LOCK_GIANT(mp);
 		error = VFS_ROOT(mp, LK_EXCLUSIVE, &tdp, td);
 		vfs_unbusy(mp);
--- //depot/vendor/freebsd/src/sys/sys/mount.h	2008/11/29 13:37:40
+++ //depot/user/attilio/attilio_vfs/sys/sys/mount.h	2008/12/02 15:09:44
@@ -316,6 +316,7 @@
 #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_REFEXPIRE	0x00000020	/* refcount expiring 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 */