get rid of propagate_umount() mistakenly treating slaves as busy.

The check in __propagate_umount() ("has somebody explicitly mounted
something on that slave?") is done *before* taking the already doomed
victims out of the child lists.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 4 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index a01c7730e9af..3273177873f0 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1253,6 +1253,9 @@ void umount_tree(struct mount *mnt, int how)
                 hlist_add_head(&p->mnt_hash, &tmp_list);
         }
 
+        hlist_for_each_entry(p, &tmp_list, mnt_hash)
+                list_del_init(&p->mnt_child);
+
         if (how)
                 propagate_umount(&tmp_list);
 
@@ -1263,7 +1266,6 @@ void umount_tree(struct mount *mnt, int how)
                 p->mnt_ns = NULL;
                 if (how < 2)
                         p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
-                list_del_init(&p->mnt_child);
                 if (mnt_has_parent(p)) {
                         put_mountpoint(p->mnt_mp);
                         /* move the reference to mountpoint into ->mnt_ex_mountpoint */
diff --git a/fs/pnode.c b/fs/pnode.c
index 302bf22c4a30..aae331a5d03b 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -381,6 +381,7 @@ static void __propagate_umount(struct mount *mnt)
                  * other children
                  */
                 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);
                 }