Re: [PATCH v1 22/30] io_uring/rsrc: refactor io_buffer_register_bvec()/io_buffer_unregister_bvec()

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

On Fri, Dec 12, 2025 at 9:11 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> On Sun, Dec 7, 2025 at 5:33 PM Caleb Sander Mateos
> <csander@purestorage.com> wrote:
> >
> > On Tue, Dec 2, 2025 at 4:37 PM Joanne Koong <joannelkoong@gmail.com> wrote:
> > >
> > > +int io_uring_cmd_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
> > > +                                  unsigned int issue_flags)
> > > +{
> > > +       struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
> > > +
> > > +       return io_buffer_unregister(ctx, index, issue_flags);
> > > +}
> > > +EXPORT_SYMBOL_GPL(io_uring_cmd_buffer_unregister);
> >
> > It would be nice to avoid these additional function calls that can't
> > be inlined. I guess we probably don't want to include the
> > io_uring-internal header io_uring/rsrc.h in the external header
> > linux/io_uring/cmd.h, which is probably why the functions were
> > declared in linux/io_uring/cmd.h but defined in io_uring/rsrc.c
> > previously. Maybe it would make sense to move the definitions of
> > io_uring_cmd_buffer_register_request() and
> > io_uring_cmd_buffer_unregister() to io_uring/rsrc.c so
> > io_buffer_register_request()/io_buffer_unregister() can be inlined
> > into them?
>
> imo I think having the code organized more logically outweighs the
> minimal improvement we would get from inlining (especially as
> io_buffer_register_request() is not a small function), but I'm happy
> to make this change if you feel strongly about it.

Yes, io_buffer_register_request() is a large function, but this
io_uring_cmd_buffer_unregister() wrapper is small. It would be nice to
either inline it into its caller or have io_buffer_register_request()
inlined into it. I don't feel that strongly, but this is in the ublk
zero-copy I/O path. You make a good point that this organization is a
cleaner abstraction. And I guess there are already plenty of thin
wrapper functions in io_uring/uring_cmd.c. Let's hope LTO comes to the
rescue!

Thanks,
Caleb

>
> Thanks,
> Joanne
>
> >
> > Best,
> > Caleb
> >
> > > +
> > >  /*
> > >   * Return true if this multishot uring_cmd needs to be completed, otherwise
> > >   * the event CQE is posted successfully.
> > > --
> > > 2.47.3
> > >