On Wed, May 09, 2018 at 10:58:09PM +0800, Fam Zheng wrote:
> +static int qcow2_co_copy_range_from(BlockDriverState *bs,
> + BdrvChild *src, uint64_t src_offset,
> + BdrvChild *dst, uint64_t dst_offset,
> + uint64_t bytes, BdrvRequestFlags flags)
> +{
> + BDRVQcow2State *s = bs->opaque;
> + int offset_in_cluster;
> + int ret;
> + unsigned int cur_bytes; /* number of bytes in current iteration */
> + uint64_t cluster_offset = 0;
> + BdrvChild *child = NULL;
> +
> + assert(!bs->encrypted);
> + qemu_co_mutex_lock(&s->lock);
> +
> + while (bytes != 0) {
> +
> + /* prepare next request */
> + cur_bytes = MIN(bytes, INT_MAX);
> +
> + ret = qcow2_get_cluster_offset(bs, src_offset, &cur_bytes,
> &cluster_offset);
> + if (ret < 0) {
> + goto out;
> + }
> +
> + offset_in_cluster = offset_into_cluster(s, src_offset);
> +
> + switch (ret) {
> + case QCOW2_CLUSTER_UNALLOCATED:
> + if (bs->backing) {
> + child = bs->backing;
> + } else {
> + flags |= BDRV_REQ_ZERO_WRITE;
> + }
> + break;Do we need a special case if the backing file is shorter than this image?
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