mnt: Add MNT_UMOUNT flag

In some instances it is necessary to know if the the unmounting
process has begun on a mount.  Add MNT_UMOUNT to make that reliably
testable.

This fix gets used in fixing locked mounts in MNT_DETACH

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/pnode.c b/fs/pnode.c
index bf012af709dd..ac3aa0d43b90 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -384,6 +384,7 @@ static void __propagate_umount(struct mount *mnt)
                 if (child && list_empty(&child->mnt_mounts)) {
                         list_del_init(&child->mnt_child);
                         hlist_del_init_rcu(&child->mnt_hash);
+                        child->mnt.mnt_flags |= MNT_UMOUNT;
                         list_move_tail(&child->mnt_list, &mnt->mnt_list);
                 }
         }