On Fri, Mar 13, 2020 at 01:50:38PM +0000, Trond Myklebust wrote: > 'xattr_support' seems like a protocol hack to allow the client to > determine whether or not the xattr operations are supported. > > The reason why it is a hack is that 'supported_attrs' is also a per- > filesystem attribute, and there is no value in advertising > 'xattr_support' there unless your filesystem also supports xattrs. > > IOW: the protocol forces you to do 2 round trips to the server in order > to figure out something that really should be obvious with 1 round > trip. Right, that's the annoying part. I mean, theoretically, a server can legally reject a GETATTR because you're asking for an unknown attribute (e.g. xattr_support in this case). So then what I have in my current patch (asking for both the supported_attrs and xattr_support at once) might fail, and the mount would fail. Which means I should split it up and have nfs4_do_fsinfo do the 2nd part, just in case. - Frank
