From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [PATCH 1/3] fs: Document the reflink(2) system call. Date: Tue, 5 May 2009 23:12:36 +0100 Message-ID: <20090505221236.GE7574@shareable.org> References: <20090505071608.GB10258@mail.oracle.com> <20090505130114.GD17486@mit.edu> <20090505131907.GF25328@shareable.org> <1241530798.7244.65.camel@think.oraclecorp.com> <20090505153629.GB31100@shareable.org> <1241538102.7244.72.camel@think.oraclecorp.com> <20090505160313.GF31100@shareable.org> <4A00A634.4020008@hp.com> <20090505215711.GA7574@shareable.org> <20090505220459.GN7835@mail.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: jim owens , Chris Mason , Theodore Tso , linux-fsdevel@vger.kernel.org, jmorris@namei.org, ocfs2-devel@oss.oracle.com, viro@zeniv Return-path: Received: from mail2.shareable.org ([80.68.89.115]:49831 "EHLO mail2.shareable.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753808AbZEEWMi (ORCPT ); Tue, 5 May 2009 18:12:38 -0400 Content-Disposition: inline In-Reply-To: <20090505220459.GN7835@mail.oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Joel Becker wrote: > On Tue, May 05, 2009 at 10:57:11PM +0100, Jamie Lokier wrote: > > jim owens wrote: > > > 3) the granularity of the COW (1-byte write may cause > > > 1-block up through whole file copy) is fs-dependent. > > > > And yet ENOSYS if the fs cannot implement any COW, and it isn't > > possible for userspace to duplicate the semantics by explicit copying? > > The point-in-time of the snapshot is what's important here. Don't we have a slight problem that useful point-in-time snapshots really need to snapshot whole directory trees? Otherwise you get the same inter-file inconsistency issues that you get intra-file from old fashioned copying. -- Jamie