1 files changed, 62 insertions, 1 deletions

diff --git a/fs/pnode.c b/fs/pnode.c
index fbaca7df2eb0..53d411a371ce 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -24,6 +24,11 @@ static inline struct mount *first_slave(struct mount *p)
 	return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
 }
 
+static inline struct mount *last_slave(struct mount *p)
+{
+	return list_entry(p->mnt_slave_list.prev, struct mount, mnt_slave);
+}
+
 static inline struct mount *next_slave(struct mount *p)
 {
 	return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
@@ -162,6 +167,19 @@ static struct mount *propagation_next(struct mount *m,
 	}
 }
 
+static struct mount *skip_propagation_subtree(struct mount *m,
+						struct mount *origin)
+{
+	/*
+	 * Advance m such that propagation_next will not return
+	 * the slaves of m.
+	 */
+	if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
+		m = last_slave(m);
+
+	return m;
+}
+
 static struct mount *next_group(struct mount *m, struct mount *origin)
 {
 	while (1) {
@@ -505,6 +523,15 @@ static void restore_mounts(struct list_head *to_restore)
 	}
 }
 
+static void cleanup_umount_visitations(struct list_head *visited)
+{
+	while (!list_empty(visited)) {
+		struct mount *mnt =
+			list_first_entry(visited, struct mount, mnt_umounting);
+		list_del_init(&mnt->mnt_umounting);
+	}
+}
+
 /*
  * collect all mounts that receive propagation from the mount in @list,
  * and return these additional mounts in the same list.
@@ -517,11 +544,23 @@ int propagate_umount(struct list_head *list)
 	struct mount *mnt;
 	LIST_HEAD(to_restore);
 	LIST_HEAD(to_umount);
+	LIST_HEAD(visited);
 
-	list_for_each_entry(mnt, list, mnt_list) {
+	/* Find candidates for unmounting */
+	list_for_each_entry_reverse(mnt, list, mnt_list) {
 		struct mount *parent = mnt->mnt_parent;
 		struct mount *m;
 
+		/*
+		 * If this mount has already been visited it is known that it's
+		 * entire peer group and all of their slaves in the propagation
+		 * tree for the mountpoint has already been visited and there is
+		 * no need to visit them again.
+		 */
+		if (!list_empty(&mnt->mnt_umounting))
+			continue;
+
+		list_add_tail(&mnt->mnt_umounting, &visited);
 		for (m = propagation_next(parent, parent); m;
 		     m = propagation_next(m, parent)) {
 			struct mount *child = __lookup_mnt(&m->mnt,
@@ -529,6 +568,27 @@ int propagate_umount(struct list_head *list)
 			if (!child)
 				continue;
 
+			if (!list_empty(&child->mnt_umounting)) {
+				/*
+				 * If the child has already been visited it is
+				 * know that it's entire peer group and all of
+				 * their slaves in the propgation tree for the
+				 * mountpoint has already been visited and there
+				 * is no need to visit this subtree again.
+				 */
+				m = skip_propagation_subtree(m, parent);
+				continue;
+			} else if (child->mnt.mnt_flags & MNT_UMOUNT) {
+				/*
+				 * We have come accross an partially unmounted
+				 * mount in list that has not been visited yet.
+				 * Remember it has been visited and continue
+				 * about our merry way.
+				 */
+				list_add_tail(&child->mnt_umounting, &visited);
+				continue;
+			}
+
 			/* Check the child and parents while progress is made */
 			while (__propagate_umount(child,
 						  &to_umount, &to_restore)) {
@@ -542,6 +602,7 @@ int propagate_umount(struct list_head *list)
 
 	umount_list(&to_umount, &to_restore);
 	restore_mounts(&to_restore);
+	cleanup_umount_visitations(&visited);
 	list_splice_tail(&to_umount, list);
 
 	return 0;