[PATCH bpf-next v4 5/5] selftests/bpf: Add test for open coded dmabuf_iter

[T.J. Mercier]

On Fri, May 9, 2025 at 2:58 PM Song Liu <song at kernel.org> wrote:
>
> On Fri, May 9, 2025 at 2:43 PM T.J. Mercier <tjmercier at google.com> wrote:
> >
> [...]
> > >
> > > Personally, I would prefer we just merge all the logic of
> > > create_udmabuf() and create_sys_heap_dmabuf()
> > > into create_test_buffers().
> >
> > That's a lot of different stuff to put in one place. How about
> > returning file descriptors from the buffer create functions while
> > having them clean up after themselves:
>
> I do like this version better. Some nitpicks though.
>
> >
> > -static int memfd, udmabuf;
> > +static int udmabuf;
>
> About this, and ...
>
> >  static const char udmabuf_test_buffer_name[DMA_BUF_NAME_LEN] =
> > "udmabuf_test_buffer_for_iter";
> >  static size_t udmabuf_test_buffer_size;
> >  static int sysheap_dmabuf;
> >  static const char sysheap_test_buffer_name[DMA_BUF_NAME_LEN] =
> > "sysheap_test_buffer_for_iter";
> >  static size_t sysheap_test_buffer_size;
> >
> > -static int create_udmabuf(int map_fd)
> > +static int create_udmabuf(void)
> >  {
> >         struct udmabuf_create create;
> > -       int dev_udmabuf;
> > -       bool f = false;
> > +       int dev_udmabuf, memfd, udmabuf;
> .. here.
>
> It is not ideal to have a global udmabuf and a local udmabuf.
> If we want the global version, let's rename the local one.

Ok let me change up the name of the aliasing variable to local_udmabuf.

> [...]
>
> >
> >  static int create_test_buffers(int map_fd)
> >  {
> > -       int ret;
> > +       bool f = false;
> > +
> > +       udmabuf = create_udmabuf();
> > +       sysheap_dmabuf = create_sys_heap_dmabuf();
> >
> > -       ret = create_udmabuf(map_fd);
> > -       if (ret)
> > -               return ret;
> > +       if (udmabuf < 0 || sysheap_dmabuf < 0)
> > +               return -1;
>
> We also need destroy_test_buffers() on the error path here,
> or at the caller.

The caller does currently check to decide if it should bother running
the tests or not, and calls destroy_test_buffers() if not.

> > -       return create_sys_heap_dmabuf(map_fd);
> > +       return bpf_map_update_elem(map_fd, udmabuf_test_buffer_name,
> > &f, BPF_ANY) ||
> > +              bpf_map_update_elem(map_fd, sysheap_test_buffer_name,
> > &f, BPF_ANY);
> >  }
> >
> >  static void destroy_test_buffers(void)
> >  {
> >         close(udmabuf);
> > -       close(memfd);
> >         close(sysheap_dmabuf);
>
> For the two global fds, let's reset them to -1 right after close().
>
> Thanks,
> Song

Will do, thanks.