Re: [PATCH v7 4/4] block: apply COR-filter to block-stream jobs

[Andrey Shinkevich]

On 24.08.2020 14:30, Vladimir Sementsov-Ogievskiy wrote:
> 24.08.2020 11:31, Andrey Shinkevich wrote:
> > This patch completes the series with the COR-filter insertion for
> > block-stream operations. Adding the filter makes it possible for copied
> > regions to be discarded in backing files during the block-stream job,
> > what will reduce the disk overuse.
> > The COR-filter insertion incurs changes in the iotests case
> > 245:test_block_stream_4 that reopens the backing chain during a
> > block-stream job. There are changes in the iotests #030 as well.
> > The iotests case 030:test_stream_parallel was deleted due to multiple
> > conflicts between the concurrent job operations over the same backing
> > chain. The base backing node for one job is the top node for another
> > job. It may change due to the filter node inserted into the backing
> > chain while both jobs are running. Another issue is that the parts of
> > the backing chain are being frozen by the running job and may not be
> > changed by the concurrent job when needed. The concept of the parallel
> > jobs with common nodes is considered vital no more.
> >
> > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> > ---
> >   block/stream.c             | 58 
> > +++++++++++++++++++++++++++++++++++-----------
> >   tests/qemu-iotests/030     | 50 
> > ++++-----------------------------------
> >   tests/qemu-iotests/030.out |  4 ++--
> >   tests/qemu-iotests/245     | 19 +++++++++++----
> >   4 files changed, 65 insertions(+), 66 deletions(-)
> >
> > diff --git a/block/stream.c b/block/stream.c
> > index 8bf6b6d..e927fed 100644
> > --- a/block/stream.c
> > +++ b/block/stream.c
...
> > @@ -307,5 +332,10 @@ fail:
> >       if (bs_read_only) {
> >           bdrv_reopen_set_read_only(bs, true, NULL);
> >       }
> > -    bdrv_unfreeze_backing_chain(bs, above_base);
> > +    if () {
> > +        bdrv_unfreeze_backing_chain(cor_filter_bs, above_base);
> > +        bdrv_cor_filter_drop(cor_filter_bs);
> > +    } else {
> > +        bdrv_unfreeze_backing_chain(bs, above_base);
>
> as I see, in this case chain is not yet frozen

When cor_filter_bs is NULL, only bs - above_base chain is frozen at this 
point.

Andrey


> > +    }
> >   }
> > diff --git a/tests/qemu-iotests/030 b/tests/qemu-iotests/030
> > index 1cdd7e2..fec9d89 100755
> > --- a/tests/qemu-iotests/030
> > +++ b/tests/qemu-iotests/030
...