Re: [PATCH for-5.0 v2 2/3] block: Increase BB.in_flight for coroutine interfaces

[Kevin Wolf <kwolf@redhat.com>]

Am 07.04.2020 um 08:41 hat Vladimir Sementsov-Ogievskiy geschrieben:
> 06.04.2020 20:14, Kevin Wolf wrote:
> > External callers of blk_co_*() 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>
> 
> Still, did you consider instead just move inc/dec to _co_ functions, like
> [...]
> (and same for write, ioctl, flush, discard). It seems more
> consistent.. Should it work?

No, it would be wrong because it would be too late. The main purpose of
blk_inc_in_flight() is to keep the request covered during the first and
the last phase outside of blk_co_*(), which can potentially involve BHs
like blk_aio_complete_bh().

Kevin