Re: [PATCHv3 1/3] Add support IORING_SETUP_SQE_MIXED

[Keith Busch <kbusch@kernel.org>]

On Wed, Sep 24, 2025 at 01:20:44PM -0700, Caleb Sander Mateos wrote:
> > index 052d6b56..66f1b990 100644
> > --- a/src/include/liburing.h
> > +++ b/src/include/liburing.h
> > @@ -575,6 +575,7 @@ IOURINGINLINE void io_uring_initialize_sqe(struct io_uring_sqe *sqe)
> >         sqe->buf_index = 0;
> >         sqe->personality = 0;
> >         sqe->file_index = 0;
> > +       sqe->addr2 = 0;
> 
> Why is this necessary for mixed SQE size support? It looks like this
> field is already initialized in io_uring_prep_rw() via the unioned off
> field. Though, to be honest, I can't say I understand why the
> initialization of the SQE fields is split between
> io_uring_initialize_sqe() and io_uring_prep_rw().

The nvme passthrough uring_cmd doesn't call io_uring_prep_rw(), so we'd
just get a stale value in that field if we don't clear it. But you're
right that many cases would end up setting the field twice when we don't
need that.
 
> > +       IOSQE_SQE_128B_BIT,
> 
> I thought we decided against using an SQE flag bit for this? Looks
> like this needs to be re-synced with the kernel uapi header.

We did, and this is a left over artifact that is not supposed to be
here. :( Nothing is depending on the bit in this series.