fs/9p: xattr: add trusted and security namespaces

Allow requests for security.* and trusted.* xattr name spaces
to pass through to server.

The new files are 99% cut and paste from fs/9p/xattr_user.c with the
namespaces changed.  It has the intended effect in superficial testing.
I do not know much detail about how these namespaces are used, but passing
them through to the server, which can decide whether to handle them or not,
seems reasonable.

I want to support a use case where an ext4 file system is mounted via 9P,
then re-exported via samba to windows clients in a cluster.  Windows wants
to store xattrs such as security.NTACL.  This works when ext4 directly
backs samba, but not when 9P is inserted.  This use case is documented here:
   http://code.google.com/p/diod/issues/detail?id=95

Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/9p/Kconfig b/fs/9p/Kconfig
index 55abfd62654a..6489e1fc1afd 100644
--- a/fs/9p/Kconfig
+++ b/fs/9p/Kconfig
@@ -31,3 +31,16 @@ config 9P_FS_POSIX_ACL
           If you don't know what Access Control Lists are, say N
 
 endif
+
+
+config 9P_FS_SECURITY
+        bool "9P Security Labels"
+        depends on 9P_FS
+        help
+          Security labels support alternative access control models
+          implemented by security modules like SELinux.  This option
+          enables an extended attribute handler for file security
+          labels in the 9P filesystem.
+
+          If you are not using a security module that requires using
+          extended attributes for file security labels, say N.