Hi,
On 2016/10/20 23:34, Eric Blake wrote:
On 10/20/2016 08:57 AM, zhanghailiang wrote:
Without this callback, there will be an error reports in the primary side:
"qemu-system-x86_64: Couldn't determine the cluster size of the target image,
which has no backing file: Operation not supported
Aborting, since this may create an unusable destination image"
For nbd driver, it doesn't have cluster size, so here we return
a fake value for it.
Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
---
block/nbd.c | 12 ++++++++++++
block/replication.c | 6 ++++++
2 files changed, 18 insertions(+)
diff --git a/block/nbd.c b/block/nbd.c
index 6bc06d6..96d7023 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -40,6 +40,8 @@
#define EN_OPTSTR ":exportname="
+#define NBD_FAKE_CLUSTER_SIZE 512
Why 512? NBD allows byte-addressable operations (even if it is more
efficient on aligned I/O); and I've been working hard to convert things
to the point that NBD does not enforce alignment on other layers.
Wouldn't 1 be better?
Yes, that makes no difference for block replication driver. :)
+static int nbd_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
+{
+ bdi->cluster_size = NBD_FAKE_CLUSTER_SIZE;
I also have patches written (but waiting for NBD write zeroes support to
be reviewed first) that add support for the experimental NBD block info,
that lets a server advertise actual sizes to the client rather than
having to guess. Here's the last time I posted a preview of it:
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg03567.html
It would be nice to use that instead of just faking things.
That's great, that's what we really want, here it is just a
temporary solution, I'll drop this patch after you nbd patch been merged.
Thanks,
Hailiang
