netdev - Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ, WRITE}

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Message-ID: <1b780dd4-227f-64c4-260d-9e819ba7081f@intel.com>
Date:   Mon, 26 Aug 2019 18:34:39 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Ilya Maximets <i.maximets@...sung.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Cc:     magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        bpf@...r.kernel.org, jonathan.lemon@...il.com,
        syzbot+c82697e3043781e08802@...kaller.appspotmail.com,
        hdanton@...a.com
Subject: Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ,
 WRITE}_ONCE-correctness for state

On 2019-08-26 17:24, Ilya Maximets wrote:
> This changes the error code a bit.
> Previously:
>     umem exists + xs unbound    --> EINVAL
>     no umem     + xs unbound    --> EBADF
>     xs bound to different dev/q --> EINVAL
> 
> With this change:
>     umem exists + xs unbound    --> EBADF
>     no umem     + xs unbound    --> EBADF
>     xs bound to different dev/q --> EINVAL
> 
> Just a note. Not sure if this is important.
> 

Note that this is for *shared* umem, so it's very seldom used. Still,
you're right, that strictly this is an uapi break, but I'd vote for the
change still. I find it hard to see that anyone relies on EINVAL/EBADF
for shared umem bind.

Opinions? :-)


Björn