Re: [Qemu-devel] [PATCH v3 18/25] rbd: use BlockDriverState's AioContext

[Paolo Bonzini]

Il 09/05/2014 02:04, Josh Durgin ha scritto:
> On 05/08/2014 07:34 AM, Stefan Hajnoczi wrote:
> > Drop the assumption that we're using the main AioContext.  Convert
> > qemu_bh_new() to aio_bh_new() and qemu_aio_wait() to aio_poll().
> >
> > The .bdrv_detach_aio_context() and .bdrv_attach_aio_context() interfaces
> > are not needed since no fd handlers, timers, or BHs stay registered when
> > requests have been drained.
> >
> > Cc: Josh Durgin <address@hidden>
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> >   block/rbd.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/block/rbd.c b/block/rbd.c
> > index dbc79f4..41f7bdc 100644
> > --- a/block/rbd.c
> > +++ b/block/rbd.c
> > @@ -548,7 +548,7 @@ static void qemu_rbd_aio_cancel(BlockDriverAIOCB
> > *blockacb)
> >       acb->cancelled = 1;
> >
> >       while (acb->status == -EINPROGRESS) {
> > -        qemu_aio_wait();
> > +        aio_poll(bdrv_get_aio_context(acb->common.bs), true);
> >       }
> >
> >       qemu_aio_release(acb);
> > @@ -581,7 +581,8 @@ static void rbd_finish_aiocb(rbd_completion_t c,
> > RADOSCB *rcb)
> >       rcb->ret = rbd_aio_get_return_value(c);
> >       rbd_aio_release(c);
> >
> > -    acb->bh = qemu_bh_new(rbd_finish_bh, rcb);
> > +    acb->bh = aio_bh_new(bdrv_get_aio_context(acb->common.bs),
> > +                         rbd_finish_bh, rcb);
> >       qemu_bh_schedule(acb->bh);
> >   }
>
> Assuming bdrv_get_aio_context() continues to be safe to call from a
> non-qemu thread:
>
> Reviewed-by: Josh Durgin <address@hidden>

bdrv_get_aio_context()/bdrv_set_aio_context() are safe if called from 
the AioContext's own iothread.  This is the case here, in fact 
aio_bh_new has the same requirement (qemu_bh_schedule instead does not).

Paolo