On 18/02/19 17:18, Kevin Wolf wrote:
> + /* aio_ctx_switch is only supposed to be set if we're sitting in
> + * the qio_channel_yield() below. */
> + assert(!*aio_ctx_switch);
> bdrv_dec_in_flight(bs);
> qio_channel_yield(ioc, G_IO_IN);
> - bdrv_inc_in_flight(bs);
> + if (*aio_ctx_switch) {
> + /* nbd_client_attach_aio_context() already increased
> in_flight
> + * when scheduling this coroutine for reentry */
> + *aio_ctx_switch = false;
> + } else {
> + bdrv_inc_in_flight(bs);
> + }
Hmm, my first thought would have been to do the bdrv_inc_in_flight(bs);
unconditionally here, and in nbd_connection_entry do the opposite, like
if (s->aio_ctx_switch) {
s->aio_ctx_switch = false;
bdrv_dec_in_flight(bs);
}
but I guess the problem is that then bdrv_drain could hang.
So my question is:
1) is there a testcase that shows the problem with this "obvious"
refactoring;
2) maybe instead of aio_co_schedul-ing client->connection_co and having
the s->aio_ctx_switch flag, you could go through a bottom half that does
the bdrv_inc_in_flight and then enters client->connection_co?
Paolo
