[PATCH 43/74] union-mount: Implement union mount

[Valerie Aurora <valerie.aurora@gmail.com>]

From: Valerie Aurora <vaurora@redhat.com>

Up till this commit, mount with MS_UNION flag succeeded but didn't
actually union the file systems.  Now call the functions to check
the source mounts and create/destroy the per-vfsmount union structures.

Signed-off-by: Valerie Aurora <valerie.aurora@gmail.com>
---
 fs/namespace.c |   13 ++++++++++++-
 fs/super.c     |    1 +
 2 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 1581411..11677d4 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1675,9 +1675,17 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
 		if (err)
 			goto out;
 	}
+
+	/* parent_path means we are moving an existing unioned mount */
+	if (!parent_path && IS_MNT_UNION(source_mnt)) {
+		err = prepare_mnt_union(source_mnt, path);
+		if (err)
+			goto out_cleanup_ids;
+	}
+
 	err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
 	if (err)
-		goto out_cleanup_ids;
+		goto out_cleanup_union;
 
 	br_write_lock(vfsmount_lock);
 
@@ -1702,6 +1710,9 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
 
 	return 0;
 
+ out_cleanup_union:
+	if (!parent_path && IS_MNT_UNION(source_mnt))
+		cleanup_mnt_union(source_mnt);
  out_cleanup_ids:
 	if (IS_MNT_SHARED(dest_mnt))
 		cleanup_group_ids(source_mnt, NULL);
diff --git a/fs/super.c b/fs/super.c
index d02a4d6..78232d2 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -178,6 +178,7 @@ void deactivate_locked_super(struct super_block *s)
 	if (atomic_dec_and_test(&s->s_active)) {
 		fs->kill_sb(s);
 		put_filesystem(fs);
+		put_union_sb(s);
 		put_super(s);
 	} else {
 		up_write(&s->s_umount);
-- 
1.7.0.4