From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38632) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1anREU-00013Z-Hd for qemu-devel@nongnu.org; Tue, 05 Apr 2016 09:41:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1anRER-0003e0-AE for qemu-devel@nongnu.org; Tue, 05 Apr 2016 09:41:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49847) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1anRER-0003dv-3Y for qemu-devel@nongnu.org; Tue, 05 Apr 2016 09:41:23 -0400 References: <1459787950-15286-1-git-send-email-eblake@redhat.com> <20160404224039.GB32049@grep.be> <5702F2B5.8060206@redhat.com> From: Paolo Bonzini Message-ID: <5703C07A.7090000@redhat.com> Date: Tue, 5 Apr 2016 15:41:14 +0200 MIME-Version: 1.0 In-Reply-To: <5702F2B5.8060206@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Oeo6lJvBJA68mPVnEir3oagqtXSafE7ec" Subject: Re: [Qemu-devel] [Nbd] [PATCH v2] doc: Add NBD_CMD_BLOCK_STATUS extension List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , Wouter Verhelst Cc: nbd-general@lists.sourceforge.net, Kevin Wolf , qemu-devel@nongnu.org, Pavel Borzenkov , Stefan Hajnoczi , "Denis V. Lunev" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Oeo6lJvBJA68mPVnEir3oagqtXSafE7ec Content-Type: multipart/mixed; boundary="Wsl1BbFTt1MtFqGn4ob5HvAcXKko54HHi" From: Paolo Bonzini To: Eric Blake , Wouter Verhelst Cc: nbd-general@lists.sourceforge.net, Kevin Wolf , qemu-devel@nongnu.org, Pavel Borzenkov , Stefan Hajnoczi , "Denis V. Lunev" Message-ID: <5703C07A.7090000@redhat.com> Subject: Re: [Nbd] [PATCH v2] doc: Add NBD_CMD_BLOCK_STATUS extension References: <1459787950-15286-1-git-send-email-eblake@redhat.com> <20160404224039.GB32049@grep.be> <5702F2B5.8060206@redhat.com> In-Reply-To: <5702F2B5.8060206@redhat.com> --Wsl1BbFTt1MtFqGn4ob5HvAcXKko54HHi Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 05/04/2016 01:03, Eric Blake wrote: >=20 > But while Alex and Denis were arguing that no one would ever query both= > things at once (and therefore, it might be better to make > NBD_STATUS_HOLE and NBD_STATUS_CLEAN both be bit 0), your approach of > having two separate request flags and allowing both at once would mean > we do need to keep the status information separate (NBD_STATUS_HOLE is > bit 0, NBD_STATUS_CLEAN is bit 2). I agree that querying both is messy. It would add complication to the implementation and the usecases are separate enough. Usually you would first query for dirtiness, and then perhaps ask for allocation status on the dirty areas. Getting back the allocation status on the clean areas would make the request unnecessarily larger. In addition, querying the dirtiness status should be extremely cheap, while querying the allocation status might be expensive depending on the underlying storage. Paolo --Wsl1BbFTt1MtFqGn4ob5HvAcXKko54HHi-- --Oeo6lJvBJA68mPVnEir3oagqtXSafE7ec 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 iQEcBAEBCAAGBQJXA8B6AAoJEL/70l94x66DIAEH/i4uPTM7nKdrGKCkeVmJvkg6 8a5OJNtBkANuULcexw2fUlJlmNSFcuAlC1E73kzokDnmo+jDvz3EPLvUKSHheZZe K0aQl7ntDOO7Ne1JoBMxBg45qTY8sbobnUHMkEnSgwHLF1+D6R5si6Tf9/d/3hSS FD+HR6kgSPQfk+q2s7ugDBIj8iRlkpzBi+LlcIjidCCgwKDTO/SI83SycpAdeDP/ s2v+aUIL9XocjeMsHJHO9Si5agp3pyMIh8PMsFQFpdxVlT5fusyGlQ7TaH8uVmaL nDpIa0boBOoxIUidNQAu9xGGKrVwHe8pPgkXqRoCl4aHb6yPfWZgcmme2wzRxp4= =IK3Q -----END PGP SIGNATURE----- --Oeo6lJvBJA68mPVnEir3oagqtXSafE7ec--