On Wed, 27 Jan 2010, Chuck Lever wrote: > I haven't followed this closely, but two questions come to mind when reading > this: > > a) why would a distro (or admin building their own kernels) want to disable > this? iow why not leave the capability always built in? Some people may want to save memory, and it's in keeping with config options for similar features such as ACLs. > > b) why is the side protocol not compatible with IRIX? wouldn't the IRIX > protocol be a de facto standard? did you mention before whether there were > other implementations we _should_ be wire compatible with? I started out hoping to make it compatible with IRIX, but there are a couple of issues: - They use a cursor-based scheme for listxattr, which we don't support at the xattr API level. If we want wire-compatibility, we could ignore the cursor field, or try and detect that the client is using it and return an error. - We use arbitrary text namespaces, whereas they indicate xattr types via flags. Technically, we could try and use only the IRIX format: e.g. only use their flags when talking to an IRIX box, and otherwise concatenate our xattr namespace and names on the wire. In both cases, we need to detect that we're talking to an IRIX system and then alter the way we handle the protocol. It also makes our implementation more complicated than necessary, and it's not clear to me what level of demand there is for IRIX and Linux interop for NFSv3. So, my suggestion would be to implement the protocol in a way which is optimized for Linux, and then look at adding a separate IRIX compatibility option which: - uses a distinct protocol number (the existing IRIX one); - is wire-compatible; - handles the cursor field somehow; and - only supports actual IRIX xattr types. i.e. an option to support legacy IRIX clients. I don't think there's any point in trying to support IRIX servers. It keeps the overall code cleaner, and avoids optimizing for what might be a marginal use case. I don't know of any other open implementations of xattrs for NFSv3. - James -- James Morris <jmorris@xxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
