From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35642) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VLX7q-0006AC-UE for qemu-devel@nongnu.org; Mon, 16 Sep 2013 07:38:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VLX7k-0004kb-Ne for qemu-devel@nongnu.org; Mon, 16 Sep 2013 07:37:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55009) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VLX7k-0004jI-EN for qemu-devel@nongnu.org; Mon, 16 Sep 2013 07:37:48 -0400 Message-ID: <5236ED8E.1080008@redhat.com> Date: Mon, 16 Sep 2013 13:37:50 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1379067909-22984-1-git-send-email-pl@kamp.de> <1379067909-22984-6-git-send-email-pl@kamp.de> <5232EA41.3030607@redhat.com> <5232EC9C.2060301@kamp.de> <5232FAC7.7030001@redhat.com> <5236EBD1.3000506@kamp.de> In-Reply-To: <5236EBD1.3000506@kamp.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 05/12] block: add logical block provisioning information to BlockDriverInfo List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, stefanha@redhat.com, qemu-devel@nongnu.org, anthony@codemonkey.ws Il 16/09/2013 13:30, Peter Lieven ha scritto: > On 13.09.2013 13:45, Paolo Bonzini wrote: >> Il 13/09/2013 12:44, Peter Lieven ha scritto: >>> On 13.09.2013 12:34, Paolo Bonzini wrote: >>>> Il 13/09/2013 12:25, Peter Lieven ha scritto: >>>>> + /* maximum number of sectors that can be discarded at once */ >>>>> + int max_discard; >>>>> + /* maximum number of sectors that can zeroized at once */ >>>>> + int max_write_zeroes; >>>> These should not be needed outside the driver. >>>> >>>> If you want to make them private between block.c and block/iscsi.c, you >>>> can add them to BlockDriverState. >>> The question is, if the discard_zeroes or discard_write_zeroes is needed >>> outside the driver as well? >>> >>> I can put the max_* information in the block driver state. I also >>> thought >>> to add alignment and granularity information even if they are currently >>> not yet used. >> Yeah, in fact bdrv_write_zeroes and bdrv_discard can be taught to split >> requests according to these parameters instead of introducing a new >> function bdrv_zeroize. You don't need bdrv_zeroize I think; you can >> simply use bdrv_write_zeroes. This is why I don't like this information >> in BlockDriverInfo. >> >> On the contrary, discard_write_zeroes is useful to "generic" clients, >> and your qemu-img patch shows why. >> >> Discard_zeroes is somewhere in the middle. You only use it in >> bdrv_get_block_status, but it is not something that should be hidden to >> users of the high-level block.c API. So it is fine to leave it in >> BlockDriverInfo. > > Would you also be ok to introduce bdrv_has_discard_zeroes() > and bdrv_has_discard_write_zeroes() as Kevin suggested to avoid the need to > add the logic to return 0 if there is a bs->backing_hd everywhere. If Kevin says it, I agree. :) > This would also make the use of it easier as it avoids the steps > necessary to invoke bdrv_get_info(). Another possibility could be to put the "info" in a member of BlockDriverState, since it is static. Then bdrv_get_info() could be simply return &bs->info; which is faster and removes the need for a BlockDriverInfo temporary. Paolo