Re: [PATCH v2] block: Factor out bdrv_run_co()

[Kevin Wolf <kwolf@redhat.com>]

Am 20.05.2020 um 16:05 hat Kevin Wolf geschrieben:
> Am 19.05.2020 um 19:56 hat Vladimir Sementsov-Ogievskiy geschrieben:
> > We have a few bdrv_*() functions that can either spawn a new coroutine
> > and wait for it with BDRV_POLL_WHILE() or use a fastpath if they are
> > alreeady running in a coroutine. All of them duplicate basically the
> > same code.
> > 
> > Factor the common code into a new function bdrv_run_co().
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> >    [Factor out bdrv_run_co_entry too]
> > ---
> > 
> > Hi!
> > 
> > I'm a bit lost on rebasing "block/io: safer inc/dec in_flight sections"
> > (is it needed or not?), so, I decided to send just this one patch:
> > 
> > I suggest to go a bit further, and refactor that bdrv_run_co don't need
> > additional *ret argument neither NOT_DONE logic.
> 
> Hm, this approach adds another indirection and bdrv_pread/pwrite still
> seems to be on some hot paths. But maybe this is just the right
> motivation to clean up qcow2 a bit and use explicit bdrv_co_*() where it
> is possible. I might take a look later.

Still not easily possible it seems. We can add a few coroutine_fn
markers here and there (and probably should do that), but the
interesting I/O is in the Qcow2Cache, which is used from basically
everywhere.

Kevin