From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754143AbcIOPZQ (ORCPT ); Thu, 15 Sep 2016 11:25:16 -0400 Received: from mail.avalus.com ([89.16.176.221]:53430 "EHLO mail.avalus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751519AbcIOPZO (ORCPT ); Thu, 15 Sep 2016 11:25:14 -0400 Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Content-Type: multipart/signed; boundary="Apple-Mail=_57A0BD0F-1162-4E60-A11A-9FA1634DE77E"; protocol="application/pgp-signature"; micalg=pgp-sha512 X-Pgp-Agent: GPGMail 2.6b2 From: Alex Bligh In-Reply-To: <8dd28f8b-0a3c-4112-ca6d-a9ad080d5920@redhat.com> Date: Thu, 15 Sep 2016 16:25:12 +0100 Cc: Alex Bligh , Wouter Verhelst , Josef Bacik , linux-block@vger.kernel.org, Markus Pargmann , kernel-team@fb.com, "nbd-general@lists.sourceforge.net" , "linux-kernel@vger.kernel.org" , Paolo Bonzini Message-Id: <2DFDFFC6-F682-4127-8684-76CB7AF43494@alex.org.uk> References: <1473369130-22986-1-git-send-email-jbacik@fb.com> <20160909200203.phhvodsfs7ymukfp@grep.be> <20160915104935.ohuwgq2chsedz6fl@grep.be> <27B346AF-F144-4770-BE38-446A66E71326@alex.org.uk> <8dd28f8b-0a3c-4112-ca6d-a9ad080d5920@redhat.com> To: Eric Blake X-Mailer: Apple Mail (2.3124) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Apple-Mail=_57A0BD0F-1162-4E60-A11A-9FA1634DE77E Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Eric, > I doubt that qemu-nbd would ever want to support the situation with more > than one client connection writing to the same image at the same time; > the implications of sorting out data consistency between multiple > writers is rather complex and not worth coding into qemu. So I think > qemu would probably prefer to just prohibit the multiple writer > situation. Yeah, I was thinking about a 'no multiple connection' flag. > And while multiple readers with no writer should be fine, > I'm not even sure if multiple readers plus one writer can always be made > to appear sane (if there is no coordination between the different > connections, on an image where the writer changes AA to BA then flushes > then changes to BB, it is still feasible that a reader could see AB > (pre-flush state of the first sector, post-flush changes to the second > sector, even though the writer never flushed that particular content to > disk). Agree -- Alex Bligh --Apple-Mail=_57A0BD0F-1162-4E60-A11A-9FA1634DE77E Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJX2r1YAAoJEBPm5K7i9iORlaEP/iZS+5oqbOPZftPV4eKNPfBr WDx4QUtsfXeygRY3TMm0ipNJ98v08zRYl6grWtxOJLkSteYj838wy71ACQFWAyBG ZseTvxhw3bkl/+DHHu08tVxhUqiHi3iCHKUuOyT+Na3Bi2dpyNN+KM35+gLo6GpI 4FQFgf4jBRIa5lmRv7/auEKPcJ8fGewaVjj7kD2b+X0xJ0wXUUdwsrnJ90hhIgqQ rlifGsAmbxM2qeLgujRCC3id5q0yixtYpJE7PbJRVqJNVoetirPG/T9Ded9AVb2q KY9HyW1o1u773DVbLXLcHK1A/IVY2bVk29uhgfh/a2rsycnaNxLNJFm2+Xspc5tN P7oiJ/Ywi+g57jmQX6S+n3PjPrkRgMxJhhlWwt36v8OxgCXPhf1bxo8NdzI0bzx5 En74/1C+fFBWFCleeruc+HeX/5+mRN4Qvae1xusIQca/wol7qsX9VQ7DEYJubtk6 f9+ixN9Y7NhAAhyjU5V3UqvjOIDrQZKGP4KztQVxxEfD1vZ4nRn+NoUylS/Evk1+ VUvMWaDuvoFcvjXjxbcqjYmwDBAEjZGRx+BvxN/An6XdLtfxrn8O9vwmddTO2JgA nqnlPbz9HiF8wNe1bqfDizGX/HLbDpZwOgtJge3Hol8aMeBvsipGv1I8OTzllPUq uEX9mnje2RNC9EAfmPa1 =ZpeU -----END PGP SIGNATURE----- --Apple-Mail=_57A0BD0F-1162-4E60-A11A-9FA1634DE77E--