On Fri, Dec 23, 2016 at 05:28:51PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> In case of full backup we can skip unallocated clusters if the target
> disk is already zero-initialized.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> block/backup.c | 8 ++++++--
> tests/qemu-iotests/055 | 2 ++
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/block/backup.c b/block/backup.c
> index 2afd1b6..4ef8daf 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -562,9 +562,13 @@ static void coroutine_fn backup_run(void *opaque)
> if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
> backup_incremental_init_copy_bitmap(job);
> } else {
> + /* top or full mode */
> + bool is_top = job->sync_mode == MIRROR_SYNC_MODE_TOP;
> + BlockDriverState *base =
> + is_top ? backing_bs(blk_bs(job->common.blk)) : NULL;
> hbitmap_set(job->copy_bitmap, 0, end);
> - if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
> - backup_skip_loop(job, backing_bs(blk_bs(job->common.blk)));
> + if (is_top || bdrv_has_zero_init(blk_bs(job->target))) {
> + backup_skip_loop(job, base);
> }
An alternative that I find easier to read:
hbitmap_set(job->copy_bitmap, 0, end);
if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
backup_skip_loop(job, backing_bs(blk_bs(job->common.blk)));
} else if (bdrv_has_zero_init(blk_bs(job->target))) {
backup_skip_loop(job, NULL);
}
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