mnt: In umount_tree reuse mnt_list instead of mnt_hash umount_tree builds a list of mounts that need to be unmounted. Utilize mnt_list for this purpose instead of mnt_hash. This begins to allow keeping a mount on the mnt_hash after it is unmounted, which is necessary for a properly functioning MNT_LOCKED implementation. The fact that mnt_list is an ordinary list makding available list_move is nice bonus. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/fs/namespace.c b/fs/namespace.c
index c68d9fc..54cbef1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c

@@ -1327,23 +1327,25 @@
  */
 static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 {
-	HLIST_HEAD(tmp_list);
+	LIST_HEAD(tmp_list);
 	struct mount *p;
 
-	for (p = mnt; p; p = next_mnt(p, mnt)) {
+	/* Gather the mounts to umount */
+	for (p = mnt; p; p = next_mnt(p, mnt))
+		list_move(&p->mnt_list, &tmp_list);
+
+	/* Hide the mounts from lookup_mnt and mnt_mounts */
+	list_for_each_entry(p, &tmp_list, mnt_list) {
 		hlist_del_init_rcu(&p->mnt_hash);
-		hlist_add_head(&p->mnt_hash, &tmp_list);
+		list_del_init(&p->mnt_child);
 	}
 
-	hlist_for_each_entry(p, &tmp_list, mnt_hash)
-		list_del_init(&p->mnt_child);
-
+	/* Add propogated mounts to the tmp_list */
 	if (how & UMOUNT_PROPAGATE)
 		propagate_umount(&tmp_list);
 
-	while (!hlist_empty(&tmp_list)) {
-		p = hlist_entry(tmp_list.first, struct mount, mnt_hash);
-		hlist_del_init_rcu(&p->mnt_hash);
+	while (!list_empty(&tmp_list)) {
+		p = list_first_entry(&tmp_list, struct mount, mnt_list);
 		list_del_init(&p->mnt_expire);
 		list_del_init(&p->mnt_list);
 		__touch_mnt_namespace(p->mnt_ns);

diff --git a/fs/pnode.c b/fs/pnode.c
index 260ac8f..bf012af 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c

@@ -384,7 +384,7 @@
 		if (child && list_empty(&child->mnt_mounts)) {
 			list_del_init(&child->mnt_child);
 			hlist_del_init_rcu(&child->mnt_hash);
-			hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
+			list_move_tail(&child->mnt_list, &mnt->mnt_list);
 		}
 	}
 }
@@ -396,11 +396,11 @@
  *
  * vfsmount lock must be held for write
  */
-int propagate_umount(struct hlist_head *list)
+int propagate_umount(struct list_head *list)
 {
 	struct mount *mnt;
 
-	hlist_for_each_entry(mnt, list, mnt_hash)
+	list_for_each_entry(mnt, list, mnt_list)
 		__propagate_umount(mnt);
 	return 0;
 }

diff --git a/fs/pnode.h b/fs/pnode.h
index 16afc3d..aa6d65d 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h

@@ -40,7 +40,7 @@
 void change_mnt_propagation(struct mount *, int);
 int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
 		struct hlist_head *);
-int propagate_umount(struct hlist_head *);
+int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
 void mnt_release_group_id(struct mount *);
 int get_dominating_id(struct mount *mnt, const struct path *root);