On Tue, Jun 27, 2017 at 02:24:48PM -0500, Eric Blake wrote:
> 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 add mirror_clip_bytes() as a
> counterpart to mirror_clip_sectors(). Some of the conversion is
> a bit tricky, requiring temporaries to convert between units; it
> will be cleared up in a following patch.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
> Reviewed-by: John Snow <js...@redhat.com>
>
Reviewed-by: Jeff Cody <jc...@redhat.com>
> ---
> v2: tweak mirror_clip_bytes() signature to match previous patch
> ---
> block/mirror.c | 64
> ++++++++++++++++++++++++++++++++++------------------------
> 1 file changed, 38 insertions(+), 26 deletions(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 1a43304..1a4602a 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -176,6 +176,15 @@ static void mirror_read_complete(void *opaque, int ret)
> aio_context_release(blk_get_aio_context(s->common.blk));
> }
>
> +/* Clip bytes relative to offset to not exceed end-of-file */
> +static inline int64_t mirror_clip_bytes(MirrorBlockJob *s,
> + int64_t offset,
> + int64_t bytes)
> +{
> + return MIN(bytes, s->bdev_length - offset);
> +}
> +
> +/* Clip nb_sectors relative to sector_num to not exceed end-of-file */
> static inline int mirror_clip_sectors(MirrorBlockJob *s,
> int64_t sector_num,
> int nb_sectors)
> @@ -184,44 +193,39 @@ static inline int mirror_clip_sectors(MirrorBlockJob *s,
> s->bdev_length / BDRV_SECTOR_SIZE - sector_num);
> }
>
> -/* Round sector_num and/or nb_sectors to target cluster if COW is needed, and
> - * return the offset of the adjusted tail sector against original. */
> -static int mirror_cow_align(MirrorBlockJob *s,
> - int64_t *sector_num,
> - int *nb_sectors)
> +/* Round offset and/or bytes to target cluster if COW is needed, and
> + * return the offset of the adjusted tail against original. */
> +static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
> + unsigned int *bytes)
> {
> bool need_cow;
> int ret = 0;
> - int chunk_sectors = s->granularity >> BDRV_SECTOR_BITS;
> - int64_t align_sector_num = *sector_num;
> - int align_nb_sectors = *nb_sectors;
> - int max_sectors = chunk_sectors * s->max_iov;
> + int64_t align_offset = *offset;
> + unsigned int align_bytes = *bytes;
> + int max_bytes = s->granularity * s->max_iov;
>
> - need_cow = !test_bit(*sector_num / chunk_sectors, s->cow_bitmap);
> - need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors,
> + need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
> + need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
> s->cow_bitmap);
> if (need_cow) {
> - bdrv_round_sectors_to_clusters(blk_bs(s->target), *sector_num,
> - *nb_sectors, &align_sector_num,
> - &align_nb_sectors);
> + bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes,
> + &align_offset, &align_bytes);
> }
>
> - if (align_nb_sectors > max_sectors) {
> - align_nb_sectors = max_sectors;
> + if (align_bytes > max_bytes) {
> + align_bytes = max_bytes;
> if (need_cow) {
> - align_nb_sectors = QEMU_ALIGN_DOWN(align_nb_sectors,
> - s->target_cluster_size >>
> - BDRV_SECTOR_BITS);
> + align_bytes = QEMU_ALIGN_DOWN(align_bytes,
> + s->target_cluster_size);
> }
> }
> - /* Clipping may result in align_nb_sectors unaligned to chunk boundary,
> but
> + /* Clipping may result in align_bytes unaligned to chunk boundary, but
> * that doesn't matter because it's already the end of source image. */
> - align_nb_sectors = mirror_clip_sectors(s, align_sector_num,
> - align_nb_sectors);
> + align_bytes = mirror_clip_bytes(s, align_offset, align_bytes);
>
> - ret = align_sector_num + align_nb_sectors - (*sector_num + *nb_sectors);
> - *sector_num = align_sector_num;
> - *nb_sectors = align_nb_sectors;
> + ret = align_offset + align_bytes - (*offset + *bytes);
> + *offset = align_offset;
> + *bytes = align_bytes;
> assert(ret >= 0);
> return ret;
> }
> @@ -257,10 +261,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t
> sector_num,
> nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
> nb_sectors = MIN(max_sectors, nb_sectors);
> assert(nb_sectors);
> + assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS);
> ret = nb_sectors;
>
> if (s->cow_bitmap) {
> - ret += mirror_cow_align(s, §or_num, &nb_sectors);
> + int64_t offset = sector_num * BDRV_SECTOR_SIZE;
> + unsigned int bytes = nb_sectors * BDRV_SECTOR_SIZE;
> + int gap;
> +
> + gap = mirror_cow_align(s, &offset, &bytes);
> + sector_num = offset / BDRV_SECTOR_SIZE;
> + nb_sectors = bytes / BDRV_SECTOR_SIZE;
> + ret += gap / BDRV_SECTOR_SIZE;
> }
> assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size);
> /* The sector range must meet granularity because:
> --
> 2.9.4
>
