On 4/12/22 17:46, Jens Axboe wrote:
On 4/12/22 10:41 AM, Jens Axboe wrote:
On 4/12/22 10:24 AM, Pavel Begunkov wrote:
If all completed requests in io_do_iopoll() were marked with
REQ_F_CQE_SKIP, we'll not only skip CQE posting but also
io_free_batch_list() leaking memory and resources.
Move @nr_events increment before REQ_F_CQE_SKIP check. We'll potentially
return the value greater than the real one, but iopolling will deal with
it and the userspace will re-iopoll if needed. In anyway, I don't think
there are many use cases for REQ_F_CQE_SKIP + IOPOLL.
Ah good catch - yes probably not much practical concern, as the lack of
ordering for file IO means that CQE_SKIP isn't really useful for that
scenario.
One potential snag is with the change we're now doing
io_cqring_ev_posted_iopoll() even if didn't post an event. Again
probably not a practical concern, but it is theoretically a violation
if an eventfd is used.
Looks this didn't get applied. Are you concerned about eventfd?
Is there any good reason why the userspace can't tolerate spurious
eventfd events? Because I don't think we should care this case
--
Pavel Begunkov
