On 28/05/2015 07:29, Fam Zheng wrote:
> If guest discards a source cluster, mirroring with bdrv_aio_readv is overkill.
> Some protocols do zero upon discard, where it's best to use
> bdrv_aio_write_zeroes, otherwise, bdrv_aio_discard will be enough.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block/mirror.c | 20 ++++++++++++++++++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 85995b2..ba33254 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -164,6 +164,8 @@ static uint64_t coroutine_fn
> mirror_iteration(MirrorBlockJob *s)
> int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
> uint64_t delay_ns = 0;
> MirrorOp *op;
> + int pnum;
> + int64_t ret;
>
> s->sector_num = hbitmap_iter_next(&s->hbi);
> if (s->sector_num < 0) {
> @@ -290,8 +292,22 @@ static uint64_t coroutine_fn
> mirror_iteration(MirrorBlockJob *s)
> s->in_flight++;
> s->sectors_in_flight += nb_sectors;
> trace_mirror_one_iteration(s, sector_num, nb_sectors);
> - bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
> - mirror_read_complete, op);
> +
> + ret = bdrv_get_block_status_above(source, NULL, sector_num,
> + nb_sectors, &pnum);
> + if (ret < 0 || pnum < nb_sectors ||
> + (ret & BDRV_BLOCK_DATA && !(ret & BDRV_BLOCK_ZERO))) {
> + bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
> + mirror_read_complete, op);
> + } else if (ret & BDRV_BLOCK_ZERO) {
> + bdrv_aio_write_zeroes(s->target, sector_num, op->nb_sectors,
> + s->unmap ? BDRV_REQ_MAY_UNMAP : 0,
> + mirror_write_complete, op);
> + } else {
> + assert(!(ret & BDRV_BLOCK_DATA));
> + bdrv_aio_discard(s->target, sector_num, op->nb_sectors,
> + mirror_write_complete, op);
> + }
> return delay_ns;
> }
>
>
