Return-Path: Received: from fieldses.org ([173.255.197.46]:41842 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751416AbdCOSJq (ORCPT ); Wed, 15 Mar 2017 14:09:46 -0400 Date: Wed, 15 Mar 2017 14:09:13 -0400 To: Olga Kornievskaia Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, Linux NFS Mailing List , ng-linux-team Subject: Re: [PATCH v1 2/3] VFS permit cross device vfs_copy_file_range Message-ID: <20170315180913.GB18135@fieldses.org> References: <20170302160211.30451-1-kolga@netapp.com> <20170302160211.30451-3-kolga@netapp.com> <20170302160714.GA4760@lst.de> <0ADCDD29-61BA-46CA-902C-06A6F7D06450@netapp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <0ADCDD29-61BA-46CA-902C-06A6F7D06450@netapp.com> From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Mar 02, 2017 at 11:38:03AM -0500, Olga Kornievskaia wrote: > > On Mar 2, 2017, at 11:07 AM, Christoph Hellwig wrote: > > NAK, we really should not do operations between different > > superblocks. > > 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. -- Yes, this has come up a few times. What's going on?: - There was an explanation, and I missed it. - The explanation is complicated and Christoph hasn't had time to write it up. - Christoph has a strong suspicion there are issues without being sure exactly where they are. - Something else? I mean, the whole enterprise is dead in the water without this, as far as I can tell, so I'd really like to understand the answer one way or the other. --b.