From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37398) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1am5em-0006vT-Dn for qemu-devel@nongnu.org; Fri, 01 Apr 2016 16:27:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1am5ej-0006Cw-7e for qemu-devel@nongnu.org; Fri, 01 Apr 2016 16:27:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55871) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1am5ej-0006Cs-25 for qemu-devel@nongnu.org; Fri, 01 Apr 2016 16:26:57 -0400 References: <1459429325-16350-1-git-send-email-den@openvz.org> <20160401083702.GD25514@grep.be> From: Eric Blake Message-ID: <56FED98E.2050204@redhat.com> Date: Fri, 1 Apr 2016 14:26:54 -0600 MIME-Version: 1.0 In-Reply-To: <20160401083702.GD25514@grep.be> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="5ll8RvEeAxkkVexkEhOjgqpxJQ6v73vTB" Subject: Re: [Qemu-devel] [Nbd] [PATCH v2 1/1] NBD proto: add WRITE_ZEROES extension List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wouter Verhelst , "Denis V. Lunev" Cc: nbd-general@lists.sourceforge.net, Kevin Wolf , qemu-devel@nongnu.org, Pavel Borzenkov , Stefan Hajnoczi , Paolo Bonzini This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --5ll8RvEeAxkkVexkEhOjgqpxJQ6v73vTB Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 04/01/2016 02:37 AM, Wouter Verhelst wrote: > Hi, >=20 > Thanks, applied. >=20 > On Thu, Mar 31, 2016 at 04:02:05PM +0300, Denis V. Lunev wrote: >> From: Pavel Borzenkov >> >> There exist some cases when a client knows that the data it is going t= o >> write is all zeroes. Such cases include mirroring or backing up a devi= ce >> implemented by a sparse file. >> >> With current NBD command set, the client has to issue NBD_CMD_WRITE >> command with zeroed payload and transfer these zero bytes through the >> wire. The server has to write the data onto disk, effectively denying >> the sparseness. >> >> + >> +- bit 1, `NBD_CMD_MAY_TRIM`; defined by the experimental `WRITE_ZEROE= S` >> + extension; see below. Hmm, we had an unfinished conversation about whether the default sense of this bit should be reversed. I'll propose a followup patch, now that the original has been merged. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --5ll8RvEeAxkkVexkEhOjgqpxJQ6v73vTB Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJW/tmOAAoJEKeha0olJ0NqKsoH/2ieUPJuzJj++qX2PkM+tmhL 1AsxGji1ILnHtAqSl5ovg2gUgmPYYIzEZTSXaxrPMRrXf9xXrJVJ6Lpv/Dq3ba1k 3ixKn1UpK1+q/320d6goUqxVfyphGuo5PlZgQ59VM4ahOc0hio4Bv4jumc1ne6C/ pGKoXl4++RdJ75v4ClW9wjto6xSaDi2FwEXV4uPRrdznBdXBYeIemFWJRI7QoaQg Y3d5QQ28ZEkQUGkHjmIC6bSgws/M7szpRmM7GFsb/g1B9/r6scrL8K5+1/kqzbH7 qAJbgXNg0I3W6tTWLvPCecBXvQF2MqgUQC+NNT/vdXAYjHi0b9cpAgSXlKgExZI= =AKAj -----END PGP SIGNATURE----- --5ll8RvEeAxkkVexkEhOjgqpxJQ6v73vTB--