Re: [PATCH 11/14] nfsd: add user xattr RPC XDR encoding/decoding logic

Frank van der Linden
2020-03-25T23:45:01Z

On Thu, Mar 12, 2020 at 12:24:18PM -0400, Chuck Lever wrote:
> > On Mar 11, 2020, at 3:59 PM, Frank van der Linden <fllinden@amazon.com> wrote:
> > + /*
> > + * Unfortunately, there is no interface to only list xattrs for
> > + * one prefix. So there is no good way to convert maxcount to
> > + * a maximum value to pass to vfs_listxattr, as we don't know
> > + * how many of the returned attributes will be user attributes.
> > + *
> > + * So, always ask vfs_listxattr for the maximum size, and encode
> > + * as many as possible.
> > + */
>
> Well, this approach worries me a little bit. Wouldn't it be better if the
> VFS provided the APIs? Review by linux-fsdevel might help here.

I missed this comment initially, sorry about the slow reply.

I'll copy this one to -fsdevel for v2.

It would require a modified or new entry point to all filesystems to
support this properly, so I didn't touch it. It's not a complex
task, it just would lead to quite a bit of code churn.

- Frank