Re: [PATCH for-5.0 v3 2/3] block: Increase BB.in_flight for coroutine and sync interfaces

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

07.04.2020 17:42, Kevin Wolf wrote:
> Am 07.04.2020 um 16:22 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> 07.04.2020 15:12, Kevin Wolf wrote:
>>> External callers of blk_co_*() and of the synchronous blk_*() functions
>>> don't currently increase the BlockBackend.in_flight counter, but calls
>>> from blk_aio_*() do, so there is an inconsistency whether the counter
>>> has been increased or not.
>>>
>>> This patch moves the actual operations to static functions that can
>>> later know they will always be called with in_flight increased exactly
>>> once, even for external callers using the blk_co_*() coroutine
>>> interfaces.
>>>
>>> If the public blk_co_*() interface is unused, remove it.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>
>> side question:
>>
>> Should we inc/dec in blk_make_zero, blk_truncate?
> 
> I don't think it's necessary. They call into their bdrv_* counterpart
> immediately, so the node-level counter should be enough.
> 

bdrv_make_zero is not one request, it does block_status/pwrite_zeroes in a loop. So drained section may occur during bdrv_make_zero. Possibly, nothing bad in it?

blk_truncate may do coroutine_enter before incrementing node-level counter, which may only schedule it..



-- 
Best regards,
Vladimir