Re: [PATCH 4/4] io_uring/uring_cmd: implement ->sqe_copy() to avoid unnecessary copies

[Caleb Sander Mateos <csander@purestorage.com>]

On Fri, Jun 6, 2025 at 3:08 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 6/6/25 3:05 PM, Jens Axboe wrote:
> >> Is it necessary to pass the sqe? Wouldn't it always be ioucmd->sqe?
> >> Presumably any other opcode that implements ->sqe_copy() would also
> >> have the sqe pointer stashed somewhere. Seems like it would simplify
> >> the core io_uring code a bit not to have to thread the sqe through
> >> several function calls.
> >
> > It's not necessary, but I would rather get rid of needing to store an
> > SQE since that is a bit iffy than get rid of passing the SQE. When it
> > comes from the core, you _know_ it's going to be valid. I feel like you
> > need a fairly intimate understanding of io_uring issue flow to make any
> > judgement on this, if you were adding an opcode and defining this type
> > of handler.
>
> Actually did go that route anyway, because we still need to stash it.
> And if we do go that route, then we can keep all the checking in the
> core and leave the handler just a basic copy with a void return. Which
> is pretty nice.
>
> Anyway, checkout v3 and see what you thing.

From a quick glance it looks good to me. Let me give it a more
detailed look with a fresh pair of eyes.

Best,
Caleb