linux-kernel - Re: [PATCH v3 bpf-next 05/11] bpf: add generic_batch_ops to lpm

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Date:   Tue, 7 Jan 2020 00:39:07 -0600
From:   Brian Vazquez <brianvv.kernel@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Brian Vazquez <brianvv@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S . Miller" <davem@...emloft.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Petar Penkov <ppenkov@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 05/11] bpf: add generic_batch_ops to lpm_trie map

Hi Yonghong, thanks for reviewing it and sorry for the late reply I
had been traveling.

On Fri, Dec 13, 2019 at 11:46 AM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 12/11/19 2:33 PM, Brian Vazquez wrote:
> > This adds the generic batch ops functionality to bpf lpm_trie.
> >
> > Signed-off-by: Brian Vazquez <brianvv@...gle.com>
> > ---
> >   kernel/bpf/lpm_trie.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
> > index 56e6c75d354d9..92c47b4f03337 100644
> > --- a/kernel/bpf/lpm_trie.c
> > +++ b/kernel/bpf/lpm_trie.c
> > @@ -743,4 +743,8 @@ const struct bpf_map_ops trie_map_ops = {
> >       .map_update_elem = trie_update_elem,
> >       .map_delete_elem = trie_delete_elem,
> >       .map_check_btf = trie_check_btf,
> > +     .map_lookup_batch = generic_map_lookup_batch,
> > +     .map_lookup_and_delete_batch = generic_map_lookup_and_delete_batch,
>
> Not 100% sure whether trie should use generic map
> lookup/lookup_and_delete or not. If the key is not available,
> the get_next_key will return the 'leftmost' node which roughly
> corresponding to the first node in the hash table.
>

I think you're right, we shouldn't use generic
lookup/lookup_and_delete for lpm_trie. That being said, would you be
ok, if we don't add lpm_trie support in this patch series? Also we can
drop the generic_map_lookup_and_delete implementation in this patch
series and add it in the future, if needed. What do you think?

> > +     .map_delete_batch = generic_map_delete_batch,
> > +     .map_update_batch = generic_map_update_batch,with efault
> >   };
> >