mnt: Move the clear of MNT_LOCKED from copy_tree to it's callers.

Clear MNT_LOCKED in the callers of copy_tree except copy_mnt_ns, and
collect_mounts.  In copy_mnt_ns it is necessary to create an exact
copy of a mount tree, so not clearing MNT_LOCKED is important.
Similarly collect_mounts is used to take a snapshot of the mount tree
for audit logging purposes and auditing using a faithful copy of the
tree is important.

This becomes particularly significant when we start setting MNT_LOCKED
on rootfs to prevent it from being unmounted.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

fs/namespace.c

@@ -1613,7 +1613,6 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
 	if (IS_ERR(q))
 		return q;
 
-	q->mnt.mnt_flags &= ~MNT_LOCKED;
 	q->mnt_mountpoint = mnt->mnt_mountpoint;
 
 	p = mnt;

fs/pnode.c

@@ -242,6 +242,7 @@ static int propagate_one(struct mount *m)
 	child = copy_tree(last_source, last_source->mnt.mnt_root, type);
 	if (IS_ERR(child))
 		return PTR_ERR(child);
+	child->mnt.mnt_flags &= ~MNT_LOCKED;
 	mnt_set_mountpoint(m, mp, child);
 	last_dest = m;
 	last_source = child;