Re: [PATCH v11 13/13] block: apply COR-filter to block-stream jobs

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

15.10.2020 20:16, Andrey Shinkevich wrote:
> On 14.10.2020 19:24, Max Reitz wrote:
>> On 12.10.20 19:43, Andrey Shinkevich wrote:
> 
> [...]
> 
>>> ---
>>>   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, 81 insertions(+), 88 deletions(-)
>>
>> Looks like stream_run() could be a bit streamlined now (the allocation
>> checking should be unnecessary, unconditionally calling
>> stream_populate() should be sufficient), but not necessary now.
>>
> 
> That is what I had kept in my mind when I tackled this patch. But there is an underwater reef to streamline. Namely, how the block-stream job gets known about a long unallocated tail to exit the loop earlier in the stream_run(). Shall we return the '-EOF' or another error code from the cor_co_preadv_part() to be handled by the stream_run()? Any other suggestions, if any, will be appreciated.

Just calling read CHUNK by CHUNK may be less efficient than is_allocated()-driven loop: you may end up with splitting regions unaligned to CHUNK-granularity, which would not be splitted with is_allocated()-driven loop. Current loop allows chunks unaligned to CHUNK.

So, I think, it's better to keep is_allocated() logic as is for now.



-- 
Best regards,
Vladimir