Am 08.03.2012 18:15, schrieb Paolo Bonzini:
> In the next patches we will declare the guest's semantics for discard
> to be "always zero the data". We need to know whether the operation
> need to be emulated or can be passed down. For this purpose we need
> to know the semantics of the operation and its granularity.
>
> The granularity may not be related to the cluster size (for example
> "raw" does not have a cluster size), so add it separately.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block.h | 4 ++++
> block/qcow2.c | 2 ++
> qemu-io.c | 5 ++++-
> 3 files changed, 10 insertions(+), 1 deletions(-)
>
> diff --git a/block.h b/block.h
> index 48d0bf3..7feda73 100644
> --- a/block.h
> +++ b/block.h
> @@ -15,6 +15,10 @@ typedef struct BlockDriverInfo {
> int cluster_size;
> /* offset at which the VM state can be saved (0 if not possible) */
> int64_t vm_state_offset;
> + /* whether discard is guaranteed to zero bytes */
> + bool discard_zeroes_data;
> + /* discard granularity in sectors */
> + int discard_granularity;
Why not in bytes? The arbitrary 512 byte units used in the block layer
were probably not the best idea ever and we shouldn't spread it further.
Kevin
