Re: [PATCH v10 9/9] block: apply COR-filter to block-stream jobs

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

On 29.09.2020 15:38, 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             | 93 ++++++++++++++++++++++++++++++----------------
>   tests/qemu-iotests/030     | 51 +++----------------------
>   tests/qemu-iotests/030.out |  4 +-
>   tests/qemu-iotests/141.out |  2 +-
>   tests/qemu-iotests/245     | 19 +++++++---
>   5 files changed, 83 insertions(+), 86 deletions(-)
> 
> diff --git a/block/stream.c b/block/stream.c
> index fe2663f..240b3dc 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -17,8 +17,10 @@


One more change missed, as we use the COR-filter:

@@ -47,8 +47,7 @@ static int coroutine_fn stream_populate(BlockBackend *blk,
  {
      assert(bytes < SIZE_MAX);

-    return blk_co_preadv(blk, offset, bytes, NULL,
-                         BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
+    return blk_co_preadv(blk, offset, bytes, NULL, 0);
  }

Andrey