Received-SPF: pass (google.com: best guess record for domain of linux-nfs-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Content-Type: text/plain;
        charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\))
Subject: Re: [PATCH 11/14] nfsd: add user xattr RPC XDR encoding/decoding
 logic
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20200325234455.GA742@dev-dsk-fllinden-2c-c1893d73.us-west-2.amazon.com>
Date:   Thu, 26 Mar 2020 10:12:50 -0400
Cc:     Bruce Fields <bfields@fieldses.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <25531EEE-A41C-45B0-AB34-5638E4910E2D@oracle.com>
References: <20200311195954.27117-1-fllinden@amazon.com>
 <20200311195954.27117-12-fllinden@amazon.com>
 <17D7709F-2FE0-4B84-A9AF-4D6C2B36A4E7@oracle.com>
 <20200325234455.GA742@dev-dsk-fllinden-2c-c1893d73.us-west-2.amazon.com>
To:     Frank van der Linden <fllinden@amazon.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


> On Mar 25, 2020, at 7:44 PM, Frank van der Linden =
<fllinden@amazon.com> wrote:
>=20
> 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.
>>> +      */
>>=20
>> 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.
>=20
> I missed this comment initially, sorry about the slow reply.
>=20
> I'll copy this one to -fsdevel for v2.
>=20
> 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