On 3/18/25 12:43 PM, Uday Shankar wrote:
> On Tue, Mar 18, 2025 at 12:22:57PM -0600, Jens Axboe wrote:
>>> struct ublk_rq_data {
>>> - struct llist_node node;
>>> -
>>> struct kref ref;
>>> };
>>
>> Can we get rid of ublk_rq_data then? If it's just a ref thing, I'm sure
>> we can find an atomic_t of space in struct request and avoid it. Not a
>> pressing thing, just tossing it out there...
>
> Yeah probably - we do need a ref since one could complete a request
> concurrently with another code path which references it (user copy and
> zero copy). I see that struct request has a refcount in it already,
Right, at least with the current usage, we still do need that kref, or
something similar. I would've probably made it just use refcount_t
though, rather than rely on the indirect calls. kref doesn't really
bring us anything here in terms of API.
> though I don't see any examples of drivers using it. Would it be a bad
> idea to try and reuse that?
We can't reuse that one, and it's not for driver use - purely internal.
But I _think_ you could easily grab space in the union that has the hash
and ipi_list for it. And then you could dump needing this extra data per
request.
--
Jens Axboe
