linux-kernel - [PATCH 52/73] union-mount: Set opaque flag on new directories in unioned file systems [ver #2]

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Date:	Tue, 21 Feb 2012 18:03:58 +0000
From:	David Howells <dhowells@...hat.com>
To:	linux-fsdevel@...r.kernel.org, viro@...IV.linux.org.uk,
	valerie.aurora@...il.com
Cc:	linux-kernel@...r.kernel.org, Jan Blunck <jblunck@...e.de>,
	Valerie Aurora <vaurora@...hat.com>,
	David Howells <dhowells@...hat.com>
Subject: [PATCH 52/73] union-mount: Set opaque flag on new directories in
 unioned file systems [ver #2]

From: Valerie Aurora <vaurora@...hat.com>

If we mkdir() a directory on the top layer of a union, we don't want
entries from a matching directory on the lower layer to "show through"
suddenly.  To prevent this, we set the opaque flag on a directory in a
union mount if there is no matching directory on the lower layers.

Signed-off-by: Jan Blunck <jblunck@...e.de>
Signed-off-by: Valerie Aurora <vaurora@...hat.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/namei.c |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f9e0d68..d52377d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2946,8 +2946,17 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 		return error;
 
 	error = dir->i_op->mkdir(dir, dentry, mode);
-	if (!error)
-		fsnotify_mkdir(dir, dentry);
+	if (error)
+		return error;
+
+	/* XXX racy - crash now and dir isn't opaque */
+	if (IS_DIR_UNIONED(dentry->d_parent)) {
+		dentry->d_inode->i_flags |= S_OPAQUE;
+		mark_inode_dirty(dentry->d_inode);
+	}
+
+	fsnotify_mkdir(dir, dentry);
+
 	return error;
 }
 

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