From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33655) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1addCy-0004Oy-Ao for qemu-devel@nongnu.org; Wed, 09 Mar 2016 07:27:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1addCx-0002zy-GN for qemu-devel@nongnu.org; Wed, 09 Mar 2016 07:27:20 -0500 Date: Wed, 9 Mar 2016 13:27:09 +0100 From: Kevin Wolf Message-ID: <20160309122709.GF5205@noname.redhat.com> References: <1457454872-12183-1-git-send-email-kwolf@redhat.com> <1457454872-12183-2-git-send-email-kwolf@redhat.com> <56E013BA.8010606@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56E013BA.8010606@redhat.com> Subject: Re: [Qemu-devel] [PATCH 01/11] block: Use writeback in .bdrv_create() implementations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org Am 09.03.2016 um 13:14 hat Paolo Bonzini geschrieben: > > > On 08/03/2016 17:34, Kevin Wolf wrote: > > There's no reason to use a writethrough cache mode while creating an > > image. > > There's no reason to do flushes in fact, so you could use > BDRV_O_NO_FLUSH too. :) That's true. On the other hand, we don't issue flushes anyway, so there's little reason to ignore non-existing flushes. :-) The only part where it might make sense is where image formats don't open the raw image file, but actually open the image with themselves and allocate things. qcow2 at least already sets BDRV_O_NO_FLUSH for that part. In fact, the only bdrv_open() touched in this patch that doesn't have BDRV_O_PROTOCOL set, is one instance in VMDK where it opens the backing file to read some ID from the header. So no flush involved there. Kevin