On 2013年11月27日 18:03, Peter Lieven wrote:
Am 27.11.2013 07:40, schrieb Fam Zheng:
On 2013年11月27日 14:01, Hu Tao wrote:
On Wed, Nov 27, 2013 at 11:01:23AM +0800, Fam Zheng wrote:
On 2013年11月27日 10:15, Hu Tao wrote:
Signed-off-by: Hu Tao <hu...@cn.fujitsu.com>
---
block/qcow2.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/block/qcow2.c b/block/qcow2.c
index b054a01..a23fade 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2180,6 +2180,12 @@ static int qcow2_amend_options(BlockDriverState *bs,
return 0;
}
+static int qcow2_preallocate(BlockDriverState *bs, int64_t offset,
+ int64_t length)
+{
+ return bdrv_preallocate(bs->file, offset, length);
+}
+
What's the semantics of .bdrv_preallocate? I think you should map
[offset, offset + length) to clusters in image file, and then
forward to bs->file, rather than this direct wrapper.
E.g. bdrv_preallocate(qcow2_bs, 0, cluster_size) should call
bdrv_preallocate(qcow2_bs->file, offset_off_first_cluster,
cluster_size).
You mean data clusters here, right? Is there a single function to get
the offset of the first data cluster?
There is a function, qcow2_get_cluster_offset.
This should return no valid offset as long as the cluster is not allocated.
I think you actually have to "write" all clusters of a qcow2 one by one.
Eventually this write could be an fallocate call instead of a zero write.
Yes, I was wrong about qcow2_get_cluster_offset. The logic here is more
like cluster allocation in qcow2_alloc_cluster_offset. Maybe we can
reuse that.
Fam
