Re: [Qemu-block] [Qemu-devel] [PATCH v4 11/20] qcow2: Switch to .bdrv_co_block_status()

[Vladimir Sementsov-Ogievskiy]

12.10.2017 21:59, Eric Blake wrote:
> We are gradually moving away from sector-based interfaces, towards
> byte-based.  Update the qcow2 driver accordingly.
>
> For now, we are ignoring the 'want_zero' hint.  However, it should
> be relatively straightforward to honor the hint as a way to return
> larger *pnum values when we have consecutive clusters with the same
> data/zero status but which differ only in having non-consecutive
> mappings.

useful thing (for example, to get several compressed clusters in one chunk,
but do not include following zero clusters). but should not the hint be 
called want_mapping for it?
or may be we will move to "int hint_flags", which will include status flags
we a interested in?

> Signed-off-by: Eric Blake <address@hidden>

Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

> ---
> v4: update to interface tweak
> v3: no change
> v2: rebase to mapping flag
> ---
>   block/qcow2.c | 24 +++++++++++++-----------
>   1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 92cb9f9bfa..a84e50a6e6 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1625,32 +1625,34 @@ static void qcow2_join_options(QDict *options, QDict 
> *old_options)
>       }
>   }
>
> -static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
> -        int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file)
> +static int coroutine_fn qcow2_co_block_status(BlockDriverState *bs,
> +                                              bool want_zero,
> +                                              int64_t offset, int64_t count,

'count' is used instead of 'bytes' because of qcow2_get_cluster_offset 
which wants int*..

> +                                              int64_t *pnum, int64_t *map,
> +                                              BlockDriverState **file)
>   {
>       BDRVQcow2State *s = bs->opaque;
>       uint64_t cluster_offset;
>       int index_in_cluster, ret;
>       unsigned int bytes;
> -    int64_t status = 0;
> +    int status = 0;
>
> -    bytes = MIN(INT_MAX, nb_sectors * BDRV_SECTOR_SIZE);
> +    bytes = MIN(INT_MAX, count);
>       qemu_co_mutex_lock(&s->lock);
> -    ret = qcow2_get_cluster_offset(bs, sector_num << BDRV_SECTOR_BITS, &bytes,
> -                                   &cluster_offset);
> +    ret = qcow2_get_cluster_offset(bs, offset, &bytes, &cluster_offset);
>       qemu_co_mutex_unlock(&s->lock);
>       if (ret < 0) {
>           return ret;
>       }
>
> -    *pnum = bytes >> BDRV_SECTOR_BITS;
> +    *pnum = bytes;
>
>       if (cluster_offset != 0 && ret != QCOW2_CLUSTER_COMPRESSED &&
>           !s->crypto) {
> -        index_in_cluster = sector_num & (s->cluster_sectors - 1);
> -        cluster_offset |= (index_in_cluster << BDRV_SECTOR_BITS);
> +        index_in_cluster = offset & (s->cluster_size - 1);
> +        *map = cluster_offset | index_in_cluster;
>           *file = bs->file->bs;
> -        status |= BDRV_BLOCK_OFFSET_VALID | cluster_offset;
> +        status |= BDRV_BLOCK_OFFSET_VALID;
>       }
>       if (ret == QCOW2_CLUSTER_ZERO_PLAIN || ret == QCOW2_CLUSTER_ZERO_ALLOC) {
>           status |= BDRV_BLOCK_ZERO;
> @@ -4333,7 +4335,7 @@ BlockDriver bdrv_qcow2 = {
>       .bdrv_child_perm      = bdrv_format_default_perms,
>       .bdrv_create        = qcow2_create,
>       .bdrv_has_zero_init = bdrv_has_zero_init_1,
> -    .bdrv_co_get_block_status = qcow2_co_get_block_status,
> +    .bdrv_co_block_status = qcow2_co_block_status,
>
>       .bdrv_co_preadv         = qcow2_co_preadv,
>       .bdrv_co_pwritev        = qcow2_co_pwritev,


--
Best regards,
Vladimir