On 25/05/2015 16:36, Paolo Bonzini wrote:
>
>
> On 22/05/2015 05:40, Fam Zheng wrote:
>> + ret = bdrv_get_block_status(source, NULL, sector_num, nb_sectors,
>> &pnum);
>> + if (ret < 0 || pnum < nb_sectors ||
>> + (ret & BDRV_BLOCK_ALLOCATED && !(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_ALLOCATED));
>> + bdrv_aio_discard(s->target, sector_num, op->nb_sectors,
>> + mirror_write_complete, op);
>> + }
>
> This doesn't work if you have a backing file. You want to test
> BDRV_BLOCK_DATA, not BDRV_BLOCK_ALLOCATED.
>
> On the other hand, if BDRV_BLOCK_ALLOCATED is nonzero, you need to
> recurse on bs->backing_hd. The logic is very similar to
> bdrv_is_allocated_above, but you need to write bdrv_get_block_status_above.
Oops, I totally missed the "NULL" in the first line. Still, I think
BDRV_BLOCK_DATA is a better check than BDRV_BLOCK_ALLOCATED.
Paolo
