Re: [Qemu-devel] [PATCH v3 09/19] block drivers: expose requirement for write same alignment from formats

[Peter Lieven]

On 22.11.2013 13:39, Paolo Bonzini wrote:
> This will let misaligned but large requests use zero clusters.  This
> is important because the cluster size is not guest visible.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>   block/qcow2.c | 1 +
>   block/qed.c   | 1 +
>   block/vmdk.c  | 4 ++++
>   3 files changed, 6 insertions(+)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 1542750..81c4dad 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -718,6 +718,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, 
> int flags,
>       }
>   
>       qemu_opts_del(opts);
> +    bs->bl.write_zeroes_alignment = s->cluster_sectors;
please add a patch that sets

bs->bl.discard_alignment = s->cluster_sectors;

>   
>       if (s->use_lazy_refcounts && s->qcow_version < 3) {
>           error_setg(errp, "Lazy refcounts require a qcow2 image with at least "
> diff --git a/block/qed.c b/block/qed.c
> index 59516a5..450a1fa 100644
> --- a/block/qed.c
> +++ b/block/qed.c
> @@ -495,6 +495,7 @@ static int bdrv_qed_open(BlockDriverState *bs, QDict 
> *options, int flags,
>           }
>       }
>   
> +    bs->bl.write_zeroes_alignment = s->header.cluster_size >> BDRV_SECTOR_BITS;
>       s->need_check_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
>                                               qed_need_check_timer_cb, s);
>   
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 6555663..63ea7ff 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -428,6 +428,10 @@ static int vmdk_add_extent(BlockDriverState *bs,
>       extent->l2_size = l2_size;
>       extent->cluster_sectors = flat ? sectors : cluster_sectors;
>   
> +    if (!flat) {
> +        bs->bl.write_zeroes_alignment =
> +            MAX(bs->bl.write_zeroes_alignment, cluster_sectors);
> +    }
>       if (s->num_extents > 1) {
>           extent->end_sector = (*(extent - 1)).end_sector + extent->sectors;
>       } else {

Reviewed-by: Peter Lieven <address@hidden>