On 05.08.19 13:49, Max Reitz wrote: > In write-blocking mode, all writes to the top node directly go to the > target. We must only mirror chunks of data that are aligned to the > job's granularity, because that is how the dirty bitmap works. > Therefore, the request alignment for writes must be the job's > granularity (in write-blocking mode). > > Unfortunately, this forces all reads and writes to have the same > granularity (we only need this alignment for writes to the target, not > the source), but that is something to be fixed another time. > > Signed-off-by: Max Reitz <[email protected]> > --- > This is an alternative to Vladimir's "util/hbitmap: fix unaligned reset" > patch. I don't mind much either way, both of pros and cons. Comparing
I don’t know why I can’t write (especially lately). s/of/have/, of course.
Max
> this patch to Vladimir's:
>
> + Makes copy-mode=write-blocking really work (unless I'm mistaken)
> - Lowers performance with copy-mode=write-blocking unnecessarily
> ---
> block/mirror.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 8cb75fb409..3f9c5a178a 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -1481,6 +1481,15 @@ static void
> bdrv_mirror_top_child_perm(BlockDriverState *bs, BdrvChild *c,
> *nshared = BLK_PERM_ALL;
> }
>
> +static void bdrv_mirror_top_refresh_limits(BlockDriverState *bs, Error
> **errp)
> +{
> + MirrorBDSOpaque *s = bs->opaque;
> +
> + if (s && s->job && s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING)
> {
> + bs->bl.request_alignment = s->job->granularity;
> + }
> +}
> +
> /* Dummy node that provides consistent read to its users without requiring it
> * from its backing file and that allows writes on the backing file chain. */
> static BlockDriver bdrv_mirror_top = {
> @@ -1493,6 +1502,7 @@ static BlockDriver bdrv_mirror_top = {
> .bdrv_co_block_status = bdrv_co_block_status_from_backing,
> .bdrv_refresh_filename = bdrv_mirror_top_refresh_filename,
> .bdrv_child_perm = bdrv_mirror_top_child_perm,
> + .bdrv_refresh_limits = bdrv_mirror_top_refresh_limits,
> };
>
> static BlockJob *mirror_start_job(
> @@ -1678,6 +1688,8 @@ static BlockJob *mirror_start_job(
>
> QTAILQ_INIT(&s->ops_in_flight);
>
> + bdrv_refresh_limits(mirror_top_bs, &error_abort);
> +
> trace_mirror_start(bs, s, opaque);
> job_start(&s->common.job);
>
>
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