On 05.09.19 15:11, Kevin Wolf wrote: > Am 09.08.2019 um 18:13 hat Max Reitz geschrieben: >> Filters cannot compress data themselves but they have to implement >> .bdrv_co_pwritev_compressed() still (or they cannot forward compressed >> writes). Therefore, checking whether >> bs->drv->bdrv_co_pwritev_compressed is non-NULL is not sufficient to >> know whether the node can actually handle compressed writes. This >> function looks down the filter chain to see whether there is a >> non-filter that can actually convert the compressed writes into >> compressed data (and thus normal writes). >> >> Signed-off-by: Max Reitz <mre...@redhat.com> >> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > > Should patches 2 and 3 that add the .bdrv_co_pwritev_compressed() > callback to filter drivers come only after this one?
Why not. > And should we also > support it in the mirror filter? Hm. AFAIU, compressed writes have very limited use. You can basically only use them when writing to a new image (where you’d never write anywhere you’ve already written something to), i.e. for qemu-img convert or the backup target. It makes sense to blockdev-backup to throttle, so that’s why it should be implemented there. I don’t really see how it would make sense for mirror. OTOH, it doesn’t make sense for COR either. And it isn’t that hard. Now I don’t have a strong preference for either dropping the COR patch or adding it to mirror as well... Max
signature.asc
Description: OpenPGP digital signature
