On 6/16/21 8:01 AM, Pavel Begunkov wrote:
> On 6/16/21 2:42 PM, Olivier Langlois wrote:
>> On Tue, 2021-06-15 at 15:51 -0600, Jens Axboe wrote:
>>> Ditto for this one, don't see it in my email nor on the list.
>>>
>> I can resend you a private copy of this one but as Pavel pointed out,
>> it contains fatal flaws.
>>
>> So unless someone can tell me that the idea is interesting and has
>> potential and can give me some a hint or 2 about how to address the
>> challenges to fix the current flaws, it is pretty much a show stopper
>> to me and I think that I am going to let it go...
>
> It'd need to go through some other context, e.g. task context.
> task_work_add() + custom handler would work, either buf-select
> synchronisation can be reworked, but both would rather be
> bulky and not great.
Indeed - that'd solve both the passing around of locking state which
I really don't like, and make it much simpler. Just use task work for
the re-insert, and you can grab the ring lock unconditionally from
there.
--
Jens Axboe
On 6/16/21 3:44 PM, Jens Axboe wrote:
> On 6/16/21 8:01 AM, Pavel Begunkov wrote:
>> On 6/16/21 2:42 PM, Olivier Langlois wrote:
>>> On Tue, 2021-06-15 at 15:51 -0600, Jens Axboe wrote:
>>>> Ditto for this one, don't see it in my email nor on the list.
>>>>
>>> I can resend you a private copy of this one but as Pavel pointed out,
>>> it contains fatal flaws.
>>>
>>> So unless someone can tell me that the idea is interesting and has
>>> potential and can give me some a hint or 2 about how to address the
>>> challenges to fix the current flaws, it is pretty much a show stopper
>>> to me and I think that I am going to let it go...
>>
>> It'd need to go through some other context, e.g. task context.
>> task_work_add() + custom handler would work, either buf-select
>> synchronisation can be reworked, but both would rather be
>> bulky and not great.
>
> Indeed - that'd solve both the passing around of locking state which
> I really don't like, and make it much simpler. Just use task work for
> the re-insert, and you can grab the ring lock unconditionally from
> there.
Hmm, it might be much simpler than I thought if we allocate
a separate struct callback_head, i.e. task_work, queued it
with exactly task_work_add() but not io_req_task_work_add(),
and continue with the request handler.
--
Pavel Begunkov
On Wed, 2021-06-16 at 16:37 +0100, Pavel Begunkov wrote:
> On 6/16/21 3:44 PM, Jens Axboe wrote:
> > On 6/16/21 8:01 AM, Pavel Begunkov wrote:
> > > On 6/16/21 2:42 PM, Olivier Langlois wrote:
> > > > On Tue, 2021-06-15 at 15:51 -0600, Jens Axboe wrote:
> > > > > Ditto for this one, don't see it in my email nor on the list.
> > > > >
> > > > I can resend you a private copy of this one but as Pavel
> > > > pointed out,
> > > > it contains fatal flaws.
> > > >
> > > > So unless someone can tell me that the idea is interesting and
> > > > has
> > > > potential and can give me some a hint or 2 about how to address
> > > > the
> > > > challenges to fix the current flaws, it is pretty much a show
> > > > stopper
> > > > to me and I think that I am going to let it go...
> > >
> > > It'd need to go through some other context, e.g. task context.
> > > task_work_add() + custom handler would work, either buf-select
> > > synchronisation can be reworked, but both would rather be
> > > bulky and not great.
> >
> > Indeed - that'd solve both the passing around of locking state
> > which
> > I really don't like, and make it much simpler. Just use task work
> > for
> > the re-insert, and you can grab the ring lock unconditionally from
> > there.
>
> Hmm, it might be much simpler than I thought if we allocate
> a separate struct callback_head, i.e. task_work, queued it
> with exactly task_work_add() but not io_req_task_work_add(),
> and continue with the request handler.
>
ok thx a lot for the excellent suggestions! I think that you have
provided me everything that I need to give a shot for a second version
of this patch.