From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH v5 9/9] btrfs: btrfs_copy_file_range() only supports reflinks Date: Sun, 11 Oct 2015 07:29:39 -0700 Message-ID: <20151011142939.GA30905@infradead.org> References: <1443634014-3026-1-git-send-email-Anna.Schumaker@Netapp.com> <1443634014-3026-10-git-send-email-Anna.Schumaker@Netapp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1443634014-3026-10-git-send-email-Anna.Schumaker-ZwjVKphTwtPQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Anna Schumaker Cc: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, zab-ugsP4Wv/S6ZeoWH0uzbU5w@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, clm-b10kYP2dOMg@public.gmane.org, darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, andros-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org List-Id: linux-api@vger.kernel.org On Wed, Sep 30, 2015 at 01:26:53PM -0400, Anna Schumaker wrote: > Reject copies that don't have the COPY_FR_REFLINK flag set. I think a reflink actually is a perfectly valid copy, and I don't buy the duplicate arguments in earlier threads. We really need to think more in terms of how this impacts a user and now how it's implemented internally. How does a user notice it's a reflink? They don't as implemented in btrfs and co. Now on filesystem that don't always do copy on write but might support reflinks (ocfs2, XFS in the future) this becomes a bit more interesting - the difference he is that we get an implicit fallocate when doing a real copy. But if that's something we have actual requests for that's how we should specify it rather than in terms of arcane implementation details.