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>

2 files changed, 4 insertions, 1 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 54cbef129f4a..d1708147eb45 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1331,8 +1331,10 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
         struct mount *p;
 
         /* Gather the mounts to umount */
-        for (p = mnt; p; p = next_mnt(p, mnt))
+        for (p = mnt; p; p = next_mnt(p, mnt)) {
+                p->mnt.mnt_flags |= MNT_UMOUNT;
                 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) {
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);
                 }
         }