Re: [Qemu-devel] [RFC PATCH v2 5/6] qcow2: implement bdrv_preallocate

[Hu Tao]

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 <address@hidden>
> >---
> >  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?