09.08.2019 19:13, Max Reitz wrote:
> This includes some permission limiting (for example, we only need to
> take the RESIZE permission for active commits where the base is smaller
> than the top).
>
> Signed-off-by: Max Reitz <mre...@redhat.com>
> ---
> block/mirror.c | 117 ++++++++++++++++++++++++++++++++++++++-----------
> blockdev.c | 47 +++++++++++++++++---
> 2 files changed, 131 insertions(+), 33 deletions(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 54bafdf176..6ddbfb9708 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
[..]
> @@ -1693,15 +1734,39 @@ static BlockJob *mirror_start_job(
> /* In commit_active_start() all intermediate nodes disappear, so
> * any jobs in them must be blocked */
> if (target_is_backing) {
> - BlockDriverState *iter;
> - for (iter = backing_bs(bs); iter != target; iter = backing_bs(iter))
> {
> - /* XXX BLK_PERM_WRITE needs to be allowed so we don't block
> - * ourselves at s->base (if writes are blocked for a node, they
> are
> - * also blocked for its backing file). The other options would
> be a
> - * second filter driver above s->base (== target). */
> + BlockDriverState *iter, *filtered_target;
> + uint64_t iter_shared_perms;
> +
> + /*
> + * The topmost node with
> + * bdrv_skip_rw_filters(filtered_target) ==
> bdrv_skip_rw_filters(target)
> + */
> + filtered_target = bdrv_filtered_cow_bs(bdrv_find_overlay(bs,
> target));
> +
> + assert(bdrv_skip_rw_filters(filtered_target) ==
> + bdrv_skip_rw_filters(target));
> +
> + /*
> + * XXX BLK_PERM_WRITE needs to be allowed so we don't block
> + * ourselves at s->base (if writes are blocked for a node, they are
> + * also blocked for its backing file). The other options would be a
> + * second filter driver above s->base (== target).
> + */
> + iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
> +
> + for (iter = bdrv_filtered_bs(bs); iter != target;
> + iter = bdrv_filtered_bs(iter))
> + {
> + if (iter == filtered_target) {
> + /*
> + * From here on, all nodes are filters on the base.
> + * This allows us to share BLK_PERM_CONSISTENT_READ.
> + */
> + iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
Hmm, I don't understand, why read from upper nodes is not shared?
> + }
> +
> ret = block_job_add_bdrv(&s->common, "intermediate node", iter,
> 0,
> - BLK_PERM_WRITE_UNCHANGED |
> BLK_PERM_WRITE,
> - errp);
> + iter_shared_perms, errp);
> if (ret < 0) {
> goto fail;
> }
[..]
--
Best regards,
Vladimir
