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

[Fam Zheng <famz@redhat.com>]

On 2013年11月27日 10:15, Hu Tao wrote:
> Signed-off-by: Hu Tao <hutao@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).

Fam

>   static QEMUOptionParameter qcow2_create_options[] = {
>       {
>           .name = BLOCK_OPT_SIZE,
> @@ -2234,6 +2240,7 @@ static BlockDriver bdrv_qcow2 = {
>       .bdrv_reopen_prepare  = qcow2_reopen_prepare,
>       .bdrv_create        = qcow2_create,
>       .bdrv_has_zero_init = bdrv_has_zero_init_1,
> +    .bdrv_preallocate   = qcow2_preallocate,
>       .bdrv_co_get_block_status = qcow2_co_get_block_status,
>       .bdrv_set_key       = qcow2_set_key,
>       .bdrv_make_empty    = qcow2_make_empty,
>