From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konstantinos Skarlatos Subject: Re: [PATCH 0/2] btrfs: allow cross-subvolume BTRFS_IOC_CLONE Date: Fri, 06 Jan 2012 14:04:12 +0200 Message-ID: <4F06E33C.8090104@gmail.com> References: <20110401133405.GA17956@infradead.org> <1301665083-sup-3969@think> <201112222324.16871.chris@csamuel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Cc: linux-btrfs@vger.kernel.org, Christoph Hellwig , Chris Mason To: Chris Samuel Return-path: In-Reply-To: <201112222324.16871.chris@csamuel.org> List-ID: On 22/12/2011 2:24 =CE=BC=CE=BC, Chris Samuel wrote: > Christoph, > > On Sat, 2 Apr 2011 12:40:11 AM Chris Mason wrote: > >> Excerpts from Christoph Hellwig's message of 2011-04-01 09:34:05 > -0400: >> >>> I don't think it's a good idea to introduce any user visible >>> operations over subvolume boundaries. Currently we don't have >>> any operations over mount boundaries, which is pretty >>> fumdamental to the unix filesystem semantics. If you want to >>> change this please come up with a clear description of the >>> semantics and post it to linux-fsdevel for discussion. That of >>> course requires a clear description of the btrfs subvolumes, >>> which is still completely missing. >> >> The subvolume is just a directory tree that can be snapshotted, and >> has it's own private inode number space. >> >> reflink across subvolumes is no different from copying a file from >> one subvolume to another at the VFS level. The src and >> destination are different files and different inodes, they just >> happen to share data extents. > > Were Chris Mason's points above enough to sway your opposition to thi= s > functionality/patch? > > There is demand for the ability to move data between subvolumes > without needing to copy the extents themselves, it's cropped up again > on the list in recent days. > > It seems a little hard (and counterintuitive) to enforce a wasteful > use of resources to copy data between different parts of the same > filesystem which happen to be a on a different subvolume when it's > permitted& functional to the same filesystem on the same subvolume. > > I don't dispute the comment about documentation on subvolumes though, > there is a short discussion of them on the btrfs wiki in the sysadmin= s > guide, but not really a lot of detail. :-) > > All the best, > Chris Me too wants cp --reflink across subvolumes. Please make this feature=20 available to us, as its a "poor man's dedupe" and would give big space=20 savings for many use cases. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html