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Date: Mon, 1 Aug 2022 16:16:48 -0700 From: Andrii Nakryiko <andrii.nakryiko@...il.com> To: Yafang Shao <laoar.shao@...il.com> Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org, hannes@...xchg.org, mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com, songmuchun@...edance.com, akpm@...ux-foundation.org, netdev@...r.kernel.org, bpf@...r.kernel.org, linux-mm@...ck.org Subject: Re: [RFC PATCH bpf-next 10/15] bpf: Use bpf_map_pages_alloc in ringbuf On Fri, Jul 29, 2022 at 8:23 AM Yafang Shao <laoar.shao@...il.com> wrote: > > Introduce new helper bpf_map_pages_alloc() for this memory allocation. > > Signed-off-by: Yafang Shao <laoar.shao@...il.com> > --- > include/linux/bpf.h | 4 ++++ > kernel/bpf/ringbuf.c | 27 +++++++++------------------ > kernel/bpf/syscall.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+), 18 deletions(-) > [...] > /* Each data page is mapped twice to allow "virtual" > * continuous read of samples wrapping around the end of ring > @@ -95,16 +95,10 @@ static struct bpf_ringbuf *bpf_ringbuf_area_alloc(struct bpf_map *map, > if (!pages) > return NULL; > > - for (i = 0; i < nr_pages; i++) { > - page = alloc_pages_node(numa_node, flags, 0); > - if (!page) { > - nr_pages = i; > - goto err_free_pages; > - } > - pages[i] = page; > - if (i >= nr_meta_pages) > - pages[nr_data_pages + i] = page; > - } > + ptr = bpf_map_pages_alloc(map, pages, nr_meta_pages, nr_data_pages, > + numa_node, flags, 0); > + if (!ptr) bpf_map_pages_alloc() has some weird and confusing interface. It fills out pages (second argument) and also returns pages as void *. Why not just return int error (0 or -ENOMEM)? You are discarding this ptr anyways. But also thinking some more, bpf_map_pages_alloc() is very ringbuf specific (which other map will have exactly the same meaning for nr_meta_pages and nr_data_pages, where we also allocate 2 * nr_data_pages, etc). I don't think it makes sense to expose it as a generic internal API. Why not keep all that inside kernel/bpf/ringbuf.c instead? > + goto err_free_pages; > > rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages, > VM_MAP | VM_USERMAP, PAGE_KERNEL); [...]
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