From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mx143.netapp.com ([216.240.21.24]:49526 "EHLO mx143.netapp.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751955AbdCGWIk (ORCPT <rfc822;linux-fsdevel@vger.kernel.org>);
        Tue, 7 Mar 2017 17:08:40 -0500
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0 (Mac OS X Mail 9.3 \(3124\))
Subject: Re: [PATCH v1 2/3] VFS permit cross device vfs_copy_file_range
From: Olga Kornievskaia <kolga@netapp.com>
In-Reply-To: <0ADCDD29-61BA-46CA-902C-06A6F7D06450@netapp.com>
Date: Tue, 7 Mar 2017 15:35:40 -0500
CC: <linux-fsdevel@vger.kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        ng-linux-team <ng-linux-team@netapp.com>
Content-Transfer-Encoding: quoted-printable
Message-ID: <0AA27980-5FDF-4C15-A583-9A2D22422A4B@netapp.com>
References: <20170302160211.30451-1-kolga@netapp.com>
 <20170302160211.30451-3-kolga@netapp.com> <20170302160714.GA4760@lst.de>
 <0ADCDD29-61BA-46CA-902C-06A6F7D06450@netapp.com>
To: Christoph Hellwig <hch@lst.de>, <viro@zeniv.linux.org.uk>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>


> On Mar 2, 2017, at 11:38 AM, Olga Kornievskaia <kolga@netapp.com> =
wrote:
>=20
>=20
>> On Mar 2, 2017, at 11:07 AM, Christoph Hellwig <hch@lst.de> wrote:
>>=20
>> On Thu, Mar 02, 2017 at 11:02:10AM -0500, Olga Kornievskaia wrote:
>>> Allow nfs_copy_file_range to copy across devices.
>>> NFSv4.2 inter server to server copy always copies across devices, =
and
>>> NFSv4.2 intra server to server copy can copy across devices on the =
same
>>> server.
>>>=20
>>> If a file system's fileoperations copy_file_range operation =
prohibits
>>> cross-device copies, fall back to do_splice_direct. This is needed =
for
>>> nfsd_copy_file_range() which is called by the inter server to server
>>> destination server acting as an NFS client, and reading the file =
from
>>> the source server.
>>=20
>> NAK, we really should not do operations between different =
superblocks.
>=20
> Can you provide some reasoning as to why? What would it break? The =
reasoning for including one is to allow for a file system to achieve =
better performance which seems like a feature that would be of great =
benefit.

Christoph, could you please elaborate on your objection.

Al, could you weigh in with regards to if and what would it take to =
allow for copy_file_range() to allow for copies between different =
superblocks.

We would appreciate the feedback of how can we enable this performance =
feature to be useful to users.

Thank you.