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From:   Brian Vazquez <brianvv@google.com>
Date:   Mon, 18 Nov 2019 21:26:17 -0800
Message-ID: <CAMzD94Rv2ysZuMOwMFtZqPVjnhYdx-t2N=ekZzgVNeRapd86Ow@mail.gmail.com>
Subject: Re: [PATCH bpf-next 5/9] bpf: add batch ops to all htab bpf map
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     Brian Vazquez <brianvv.kernel@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "David S . Miller" <davem@davemloft.net>,
        Yonghong Song <yhs@fb.com>,
        Stanislav Fomichev <sdf@google.com>,
        Petar Penkov <ppenkov@google.com>,
        Willem de Bruijn <willemb@google.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org
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On Mon, Nov 18, 2019 at 8:35 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, Nov 18, 2019 at 05:43:53PM -0800, Brian Vazquez wrote:
> > From: Yonghong Song <yhs@fb.com>
> >
> > htab can't use generic batch support due some problematic behaviours
> > inherent to the datastructre, i.e. while iterating the bpf map  a
> > concurrent program might delete the next entry that batch was about to
> > use, in this case there's no easy solution to retrieve the next entry
> > and the issua has been discussed multiple times (see [1] and [2]).
> > The only way hmap can be traversed without the problem previously
> > exposed is by making sure that the map is traversing entire buckets.
> > This commit implements those strict requirements for hmap, the
> > implementation follows the same interaction that generic support with
> > some exceptions:
> >
> >  - If keys/values buffer are not big enough to traverse a bucket,
> >    ENOSPC will be returned.
> >  - out_batch contains the value of the next bucket in the iteration, not
> >  the next key, but this is transparent for the user since the user
> >  should never use out_batch for other than bpf batch syscalls.
> >
> > Note that only lookup and lookup_and_delete batch ops require the hmap
> > specific implementation and update/delete batch ops can be the generic
> > ones.
> >
> > [1] https://lore.kernel.org/bpf/20190724165803.87470-1-brianvv@google.com/
> > [2] https://lore.kernel.org/bpf/20190906225434.3635421-1-yhs@fb.com/
> >
> > Co-authored-by: Brian Vazquez <brianvv@google.com>
> > Signed-off-by: Brian Vazquez <brianvv@google.com>
> > Signed-off-by: Yonghong Song <yhs@fb.com>
>
> SOB order is not quite correct.
> If the patch was mainly developed by Yonghong it should have his 'From:'
> then his SOB and then your SOB.
> You can drop Co-authored-by field.
>
Thanks for clarifying, will fix in v2.

> Patch 2 was also mainly done by Yonghong or not ?
> If so it should have his 'From:' field.6504484251

Generic support was done by me, but will double check the rest of the
patches and fix them if needed.