linux-kernel - Re: [PATCH bpf] libbpf: unmap rings when umem deleted

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Message-ID: <CAEf4BzYm=3Awdz2H32JC6bB4anCY40=+_LWF6E57CbR8a9TFxg@mail.gmail.com>
Date:   Mon, 7 Mar 2022 22:03:09 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     lic121 <lic121@...natelecom.cn>
Cc:     bpf <bpf@...r.kernel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] libbpf: unmap rings when umem deleted

On Tue, Mar 1, 2022 at 5:26 AM lic121 <lic121@...natelecom.cn> wrote:
>
> xsk_umem__create() does mmap for fill/comp rings, but xsk_umem__delete()
> doesn't do the unmap. This works fine for regular cases, because
> xsk_socket__delete() does unmap for the rings. But for the case that
> xsk_socket__create_shared() fails, umem rings are not unmapped.
>
> fill_save/comp_save are checked to determine if rings have already be
> unmapped by xsk. If fill_save and comp_save are NULL, it means that the
> rings have already been used by xsk. Then they are supposed to be
> unmapped by xsk_socket__delete(). Otherwise, xsk_umem__delete() does the
> unmap.
>
> Fixes: 2f6324a3937f ("libbpf: Support shared umems between queues and devices")
> Signed-off-by: lic121 <lic121@...natelecom.cn>
> ---

Applied to bpf-next as well. Changed the name to Cheng Li while
applying. Thanks.

>  tools/lib/bpf/xsk.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index edafe56..32a2f57 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -1193,12 +1193,23 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>
>  int xsk_umem__delete(struct xsk_umem *umem)
>  {
> +       struct xdp_mmap_offsets off;
> +       int err;
> +
>         if (!umem)
>                 return 0;
>
>         if (umem->refcount)
>                 return -EBUSY;
>
> +       err = xsk_get_mmap_offsets(umem->fd, &off);
> +       if (!err && umem->fill_save && umem->comp_save) {
> +               munmap(umem->fill_save->ring - off.fr.desc,
> +                      off.fr.desc + umem->config.fill_size * sizeof(__u64));
> +               munmap(umem->comp_save->ring - off.cr.desc,
> +                      off.cr.desc + umem->config.comp_size * sizeof(__u64));
> +       }
> +
>         close(umem->fd);
>         free(umem);
>
> --
> 1.8.3.1
>