From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: What to do about subvolumes? Date: Thu, 02 Dec 2010 21:43:08 -0500 Message-ID: <4CF8593C.3080100@cfl.rr.com> References: <20101201142136.GD427@dhcp231-156.rdu.redhat.com> <4CF76BB3.3020705@gmx.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Josef Bacik , linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, chris.mason@oracle.com, hch@lst.de, ssorce@redhat.com To: Arne Jansen Return-path: In-Reply-To: <4CF76BB3.3020705@gmx.net> Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 12/02/2010 04:49 AM, Arne Jansen wrote: > What about the alternative and allocating inode numbers globally? The only > problem would be with snapshots as they share the inum with the source, but > one could just remap inode numbers in snapshots by sparing some bits at the > top of this 64 bit field. I was wondering this as well. Why give each subvol its own inode number space? To avoid breaking assumptions of various programs, if they each have their own inode space, they must each have a unique st_dev. How are inode numbers currently allocated, and why wouldn't it be simple to just have a single pool of inode numbers for all subvols? It seems obvious to me that snapshots start out inheriting the inode numbers of the original subvol, but must be given a new st_dev.