linux-kernel - Re: [PATCH bpf-next v4 4/5] selftests/bpf: Add test for dmabuf

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Message-ID: <CABdmKX1A0Ard1yoV9SAV4jZfrD3tvMz2cftcuFPhQgkAKDk58w@mail.gmail.com>
Date: Fri, 9 May 2025 10:13:56 -0700
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Song Liu <song@...nel.org>
Cc: sumit.semwal@...aro.org, christian.koenig@....com, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	skhan@...uxfoundation.org, alexei.starovoitov@...il.com, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
	bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, android-mm@...gle.com, 
	simona@...ll.ch, eddyz87@...il.com, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	jolsa@...nel.org, mykolal@...com, shuah@...nel.org
Subject: Re: [PATCH bpf-next v4 4/5] selftests/bpf: Add test for dmabuf_iter

On Thu, May 8, 2025 at 5:36 PM Song Liu <song@...nel.org> wrote:
>
> On Thu, May 8, 2025 at 11:20 AM T.J. Mercier <tjmercier@...gle.com> wrote:
> [...]
> > diff --git a/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
> > new file mode 100644
> > index 000000000000..35745f4ce0f8
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
> > @@ -0,0 +1,224 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2025 Google */
> > +
> > +#include <test_progs.h>
> > +#include <bpf/libbpf.h>
> > +#include <bpf/btf.h>
> > +#include "dmabuf_iter.skel.h"
> > +
> > +#include <fcntl.h>
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <sys/ioctl.h>
> > +#include <sys/mman.h>
> > +#include <unistd.h>
> > +
> > +#include <linux/dma-buf.h>
> > +#include <linux/dma-heap.h>
> > +#include <linux/udmabuf.h>
> > +
> > +static int memfd, udmabuf;
>
> Global fds are weird. AFAICT, we don't really need them
> to be global? If we really need them to be global, please
> initialize them to -1, just in case we close(0) by accident.

Hmm, no we don't really need them to be global but I didn't really
want to pass all these variables around to all the setup and test
functions. The fd lifetimes are nearly the whole program lifetime
anyways, and just need to exist without actually being used for
anything. I'll add the -1 initialization as you suggest. If udmabuf
creation failed, we would have done a close(0) in
destroy_test_buffers() on the sysheap_dmabuf fd.


> > +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;