Re: [Qemu-devel] [PATCH 2/4] block: vhdx - update PAYLOAD_BLOCK_UNMAPPED value to match 1.00 spec

[Max Reitz <mreitz@redhat.com>]

On 2014-12-08 at 07:07, Jeff Cody wrote:
> The 0.95 VHDX spec defined PAYLOAD_BLOCK_UNMAPPED to be 5.  The 1.00
> VHDX spec redefines PAYLOAD_BLOCK_UNMAPPED to be 3 instead.
>
> The original value of 5 is now an undefined state in the spec, but it
> should be safe to treat it the same and return zeros for data read.
> This way, we can maintain compatibility with any images out in the wild
> that may have been created in accordance to the 0.95 spec.
>
> Reported-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>   block/vhdx.c | 3 ++-
>   block/vhdx.h | 3 ++-
>   2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/block/vhdx.c b/block/vhdx.c
> index f1e1e2e..bec10bd 100644
> --- a/block/vhdx.c
> +++ b/block/vhdx.c
> @@ -1111,6 +1111,7 @@ static coroutine_fn int vhdx_co_readv(BlockDriverState *bs, int64_t sector_num,
>               case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
>               case PAYLOAD_BLOCK_UNDEFINED:
>               case PAYLOAD_BLOCK_UNMAPPED:
> +            case PAYLOAD_BLOCK_UNMAPPED_v095:
>               case PAYLOAD_BLOCK_ZERO:
>                   /* return zero */
>                   qemu_iovec_memset(&hd_qiov, 0, 0, sinfo.bytes_avail);
> @@ -1277,10 +1278,10 @@ static coroutine_fn int vhdx_co_writev(BlockDriverState *bs, int64_t sector_num,
>                           sectors_to_write += iov2.iov_len >> BDRV_SECTOR_BITS;
>                       }
>                   }
> -

Was this line removal intended?

Anyway:

Reviewed-by: Max Reitz <mreitz@redhat.com>

>                   /* fall through */
>               case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
>               case PAYLOAD_BLOCK_UNMAPPED:
> +            case PAYLOAD_BLOCK_UNMAPPED_v095:
>               case PAYLOAD_BLOCK_UNDEFINED:
>                   bat_prior_offset = sinfo.file_offset;
>                   ret = vhdx_allocate_block(bs, s, &sinfo.file_offset);
> diff --git a/block/vhdx.h b/block/vhdx.h
> index b4a12a0..7003ab7 100644
> --- a/block/vhdx.h
> +++ b/block/vhdx.h
> @@ -226,7 +226,8 @@ typedef struct QEMU_PACKED VHDXLogDataSector {
>   #define PAYLOAD_BLOCK_NOT_PRESENT       0
>   #define PAYLOAD_BLOCK_UNDEFINED         1
>   #define PAYLOAD_BLOCK_ZERO              2
> -#define PAYLOAD_BLOCK_UNMAPPED          5
> +#define PAYLOAD_BLOCK_UNMAPPED          3
> +#define PAYLOAD_BLOCK_UNMAPPED_v095     5
>   #define PAYLOAD_BLOCK_FULLY_PRESENT     6
>   #define PAYLOAD_BLOCK_PARTIALLY_PRESENT 7