linux-kernel - [PATCH 25/34] union-mount: Implement union mount

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Date:	Thu, 16 Sep 2010 15:12:16 -0700
From:	Valerie Aurora <vaurora@...hat.com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Andreas Gruenbacher <agruen@...e.de>,
	Nick Piggin <npiggin@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Valerie Aurora <vaurora@...hat.com>
Subject: [PATCH 25/34] union-mount: Implement union mount

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 <vaurora@...hat.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 e3629dd..6bbeb49 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1632,9 +1632,17 @@ 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;
 
 	spin_lock(&vfsmount_lock);
 
@@ -1658,6 +1666,9 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
 	spin_unlock(&vfsmount_lock);
 	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 3f2df09..c376147 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -160,6 +160,7 @@ 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);
-- 
1.6.3.3

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