Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive

[Andrey Konovalov]

On Mon, Mar 18, 2019 at 3:45 PM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Mon, Mar 18, 2019 at 6:17 AM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> >
>
> > Looking at the code, what's the point of this address != zc->address
> > check? Should I just remove it?
>
> No you must not remove it.
>
> The test detects if a u64 ->unsigned long  conversion might have truncated bits.
>
> Quite surprisingly some people still use 32bit kernels.
>
> The ABI is 64bit only, because we did not want to have yet another compat layer.
>
> struct tcp_zerocopy_receive {
>     __u64 address; /* in: address of mapping */
>     __u32 length; /* in/out: number of bytes to map/mapped */
>     __u32 recv_skip_hint; /* out: amount of bytes to skip */
> };

Ah, got it, thanks! I'll add a comment here then, otherwise this looks
confusing.