Am 04.10.2017 um 04:00 hat Eric Blake geschrieben:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based. Convert another internal
> function (no semantic change), and rename it to is_zero() in the
> process.
>
> Signed-off-by: Eric Blake <[email protected]>
> Reviewed-by: Fam Zheng <[email protected]>
> Reviewed-by: John Snow <[email protected]>
>
> ---
> v3-v5: no change
> v2: rename function, rebase to upstream changes
> ---
> block/qcow2.c | 32 ++++++++++++++++++--------------
> 1 file changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index bcd5c4a34c..e0de46f530 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2972,21 +2972,28 @@ finish:
> }
>
>
> -static bool is_zero_sectors(BlockDriverState *bs, int64_t start,
> - uint32_t count)
> +static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes)
> {
> int nr;
> int64_t res;
> + int64_t start;
>
> - if (start + count > bs->total_sectors) {
> - count = bs->total_sectors - start;
> + /* Widen to sector boundaries, then clamp to image length, before
> + * checking status of underlying sectors */
> + start = QEMU_ALIGN_DOWN(offset, BDRV_SECTOR_SIZE);
> + bytes = QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE) - start;
Why do we still widen to sector boundaries after this series is fully
applied? Isn't the whole point that we don't have to do this any more?
> + if (start + bytes > bs->total_sectors * BDRV_SECTOR_SIZE) {
> + bytes = bs->total_sectors * BDRV_SECTOR_SIZE - start;
> }
>
> - if (!count) {
> + if (!bytes) {
> return true;
> }
> - res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL);
> - return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count;
> + res = bdrv_get_block_status_above(bs, NULL, start >> BDRV_SECTOR_BITS,
> + bytes >> BDRV_SECTOR_BITS, &nr, NULL);
> + return res >= 0 && (res & BDRV_BLOCK_ZERO) &&
> + nr * BDRV_SECTOR_SIZE == bytes;
> }
Kevin
