Return-Path: Received: from bombadil.infradead.org ([198.137.202.9]:60703 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751514AbbJPMWB (ORCPT ); Fri, 16 Oct 2015 08:22:01 -0400 Date: Fri, 16 Oct 2015 05:21:51 -0700 From: Christoph Hellwig To: Austin S Hemmelgarn Cc: Christoph Hellwig , Andy Lutomirski , Anna Schumaker , "Darrick J. Wong" , linux-nfs@vger.kernel.org, Linux btrfs Developers List , Linux FS Devel , Linux API , Zach Brown , Al Viro , Chris Mason , Michael Kerrisk-manpages , andros@netapp.com Subject: Re: [PATCH v5 8/9] vfs: Add vfs_copy_file_range() support for pagecache copies Message-ID: <20151016122151.GA5889@infradead.org> References: <20151011142203.GA31867@infradead.org> <20151012231749.GC11398@birch.djwong.org> <561E980C.9010509@Netapp.com> <20151014182701.GC31225@infradead.org> <561EA83E.8080000@gmail.com> <20151015063621.GA3025@infradead.org> <561F9B13.7020804@gmail.com> <20151016053808.GA29510@infradead.org> <5620E3A1.90408@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <5620E3A1.90408@gmail.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Oct 16, 2015 at 07:46:41AM -0400, Austin S Hemmelgarn wrote: > I should have been specific, what I meant was that some people will assume > that it actually creates a physical, on-disk byte-for-byte copy of the data. > There are many people out there (and sadly I have to deal with some at work) > who are absolutely terrified of the concept of data deduplication, and will > likely refuse to use this syscall for _anything_ if it reflinks by default > on filesystems that support it. If they use a file system that supports COW or dedup they are toast already. It's not the system call that does the 'dedup', it's the file system or storage device, that's where they need to set their preferences.