From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56602) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YLjaz-0003Rn-Sm for qemu-devel@nongnu.org; Wed, 11 Feb 2015 21:33:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YLjau-0000ik-ND for qemu-devel@nongnu.org; Wed, 11 Feb 2015 21:33:37 -0500 Received: from tama50.ecl.ntt.co.jp ([129.60.39.147]:52435) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YLjau-0000ib-8Q for qemu-devel@nongnu.org; Wed, 11 Feb 2015 21:33:32 -0500 Message-ID: <54DC10EC.3050502@lab.ntt.co.jp> Date: Thu, 12 Feb 2015 11:33:16 +0900 From: Teruaki Ishizaki MIME-Version: 1.0 References: <1422347727-13006-1-git-send-email-ishizaki.teruaki@lab.ntt.co.jp> <20150210111256.GG18727@ubuntu-trusty> <54DC071D.40503@lab.ntt.co.jp> <20150212021928.GI7801@ubuntu-trusty> In-Reply-To: <20150212021928.GI7801@ubuntu-trusty> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4] sheepdog: selectable object size support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Liu Yuan Cc: kwolf@redhat.com, mitake.hitoshi@lab.ntt.co.jp, sheepdog@lists.wpkg.org, qemu-devel@nongnu.org, stefanha@redhat.com (2015/02/12 11:19), Liu Yuan wrote: > On Thu, Feb 12, 2015 at 10:51:25AM +0900, Teruaki Ishizaki wrote: >> (2015/02/10 20:12), Liu Yuan wrote: >>> On Tue, Jan 27, 2015 at 05:35:27PM +0900, Teruaki Ishizaki wrote: >>>> Previously, qemu block driver of sheepdog used hard-coded VDI object size. >>>> This patch enables users to handle "block_size_shift" value for >>>> calculating VDI object size. >>>> >>>> When you start qemu, you don't need to specify additional command option. >>>> >>>> But when you create the VDI which doesn't have default object size >>>> with qemu-img command, you specify block_size_shift option. >>>> >>>> If you want to create a VDI of 8MB(1 << 23) object size, >>>> you need to specify following command option. >>>> >>>> # qemu-img create -o block_size_shift=23 sheepdog:test1 100M >>>> >>>> In addition, when you don't specify qemu-img command option, >>>> a default value of sheepdog cluster is used for creating VDI. >>>> >>>> # qemu-img create sheepdog:test2 100M >>>> >>>> Signed-off-by: Teruaki Ishizaki >>>> --- >>>> V4: >>>> - Limit a read/write buffer size for creating a preallocated VDI. >>>> - Replace a parse function for the block_size_shift option. >>>> - Fix an error message. >>>> >>>> V3: >>>> - Delete the needless operation of buffer. >>>> - Delete the needless operations of request header. >>>> for SD_OP_GET_CLUSTER_DEFAULT. >>>> - Fix coding style problems. >>>> >>>> V2: >>>> - Fix coding style problem (white space). >>>> - Add members, store_policy and block_size_shift to struct SheepdogVdiReq. >>>> - Initialize request header to use block_size_shift specified by user. >>>> --- >>>> block/sheepdog.c | 138 ++++++++++++++++++++++++++++++++++++++------- >>>> include/block/block_int.h | 1 + >>>> 2 files changed, 119 insertions(+), 20 deletions(-) >>>> >>>> diff --git a/block/sheepdog.c b/block/sheepdog.c >>>> index be3176f..a43b947 100644 >>>> --- a/block/sheepdog.c >>>> +++ b/block/sheepdog.c >>>> @@ -37,6 +37,7 @@ >>>> #define SD_OP_READ_VDIS 0x15 >>>> #define SD_OP_FLUSH_VDI 0x16 >>>> #define SD_OP_DEL_VDI 0x17 >>>> +#define SD_OP_GET_CLUSTER_DEFAULT 0x18 >>> >>> This might not be necessary. For old qemu or the qemu-img without setting >>> option, the block_size_shift will be 0. >>> >>> If we make 0 to represent 4MB object, then we don't need to get the default >>> cluster object size. >>> >>> We migth even get rid of the idea of cluster default size. The downsize is that, >>> if we want to create a vdi with different size not the default 4MB, >>> we have to write it every time for qemu-img or dog. >>> >>> If we choose to keep the idea of cluster default size, I think we'd also try to >>> avoid call this request from QEMU to make backward compatibility easier. In this >>> scenario, 0 might be used to ask new sheep to decide to use cluster default size. >>> >>> Both old qemu and new QEMU will send 0 to sheep and both old and new sheep can >>> handle 0 though it has different meanings. >>> >>> Table for this bit as 0: >>> Qe: qemu >>> SD: Sheep daemon >>> CDS: Cluster Default Size >>> Ign: Ignored by the sheep daemon >>> >>> Qe/sd new old >>> new CDS Ign >>> old CDS NULL >> Does Ign mean that VDI is handled as 4MB object size? > > Yes, old sheep can only handle 4MB object and doesn't check this field at all. > >> >>> >>> I think this approach is acceptable. The difference to your patch is that >>> we don't send SD_OP_GET_CLUSTER_DEFAULT to sheep daemon and >>> SD_OP_GET_CLUSTER_DEFAULT can be removed. >> When users create a new VDI with qemu-img, qemu's Sheepdog backend >> driver calculates max limit VDI size. > >> But if block_size_shift option is not specified, qemu's Sheepdog backend >> driver can't calculate max limit VDI size. > > If block_size_shift not specified, this means > > 1 for old sheep, use 4MB size > 2 for new sheep, use cluster wide default value. > > And sheep then can calculate it on its own, no? > Dog command(client) calculate max size, so I think that qemu's Sheepdog backend driver should calculate it like dog command. Is that policy changeable? Is there no policy? Thanks, Teruaki