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

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

On 07.10.2020 20:27, Andrey Shinkevich wrote:
> 
> 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, BDRV_REQ_PREFETCH);

Sorry, with the only flag BDRV_REQ_PREFETCH set.
A change in the comment at the flag BDRV_REQ_PREFETCH is coming with a 
separate patch as Vladimir suggested.

Andrey

> +    return blk_co_preadv(blk, offset, bytes, NULL, 0);
>   }
> 
> Andrey