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

Chuck Lever
2020-03-26T14:13:03Z

> On Mar 25, 2020, at 7:44 PM, Frank van der Linden <fllinden@amazon.com> wrote:
>
> 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.

Yep, I recognize it would be a substantial chunk of work. Passing
it by -fsdevel is the right thing to do, IMO. Thanks!

--
Chuck Lever