On Tue, 2018-05-22 at 10:34 -0600, Keith Busch wrote:
> On Tue, May 22, 2018 at 04:29:07PM +0000, Bart Van Assche wrote:
> > Please have another look at the current code that handles request timeouts
> > and completions. The current implementation guarantees that no double
> > completions can occur but your patch removes essential aspects of that
> > implementation.
>
> How does the current implementation guarantee a double completion doesn't
> happen when the request is allocated for a new command?
Hello Keith,
If a request is completes and is reused after the timeout handler has set
aborted_gstate and before blk_mq_terminate_expired() is called then the latter
function will skip the request because restarting a request causes the
generation number in rq->gstate to be incremented. From
blk_mq_rq_update_state():
if (state == MQ_RQ_IN_FLIGHT) {
WARN_ON_ONCE((old_val & MQ_RQ_STATE_MASK) != MQ_RQ_IDLE);
new_val += MQ_RQ_GEN_INC;
}
Bart.
