From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48148) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fYvYF-0006ce-NH for qemu-devel@nongnu.org; Fri, 29 Jun 2018 11:43:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fYvYE-0004Mk-MZ for qemu-devel@nongnu.org; Fri, 29 Jun 2018 11:43:11 -0400 Date: Fri, 29 Jun 2018 16:43:00 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180629154300.GX27016@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20180628190723.276458-1-eblake@redhat.com> <20180628190723.276458-4-eblake@redhat.com> <20180629084444.GC15588@localhost.localdomain> <41be61a0-9048-c08f-1a9a-1c213f5103ef@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <41be61a0-9048-c08f-1a9a-1c213f5103ef@redhat.com> Subject: Re: [Qemu-devel] [PATCH v7 3/6] qcow2: Reduce REFT_OFFSET_MASK List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Kevin Wolf , berto@igalia.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com On Fri, Jun 29, 2018 at 10:22:22AM -0500, Eric Blake wrote: > On 06/29/2018 03:44 AM, Kevin Wolf wrote: > > Am 28.06.2018 um 21:07 hat Eric Blake geschrieben: > > > Match our code to the spec change in the previous patch - there's > > > no reason for the refcount table to allow larger offsets than the > > > L1/L2 tables. > > > > What about internal snapshots? And anyway, because of the metadata > > overhead, the physical image size of a fully allocated image is always > > going to be at least minimally larger than the virtual disk size. > > > > I'm not necessarily opposed to making the change if there is a good > > reason to make it, but I don't see a real need for it and the > > justification used here and also in the previous patch is incorrect. > > The fact that ext4 cannot hold an image this large is already an indication > that setting this limit on the refcount table is NOT going to bite real > users. NB, RHEL-7 defaults to xfs and this supports file sizes way larger than ext4 does, so not sure we should consider ext4 as representative of real world limits anymore. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|