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 <ishizaki.teru...@lab.ntt.co.jp> > >>--- > >>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? Thanks Yuan
