On Tue, 7 Feb 2006, Bill Nottingham wrote:
The way xattrs appear to work on tmpfs is that the VFS tries the
getxattr
op of tmpfs (which fails, as it doesn't exist), and then does an end-run
around in the selinux code to get an attribute, as long as you're only
looking for the security xattr.
What it's doing is checking if the fs can supply a security xattr, and if
not, allows the kernel to supply one.
This means that anything on tmpfs can have a xattr retrieved from
userspace
just fine with getxattr(2), but if you try and get it in the kernel via
'normal' means (such as the inode's getxattr method), it will fail. This
breaks tmpfs as part of a unionfs branch pretty badly.
Why was xattrs-on-tmpfs done this way? It seems somewhat hackish.
So xattrs do not have to be implemented for every type of psudo fs.
What is the upstream status of unionfs?
I could theoretically patch unionfs to call the vfs method, but...
ew.
--
James Morris
<jmorris(a)namei.org>