netdev - Re: [PATCH 31/31] aio: implement io

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Date:   Tue, 9 Jan 2018 23:16:16 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Avi Kivity <avi@...lladb.com>,
        linux-aio@...ck.org,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>
Subject: Re: [PATCH 31/31] aio: implement io_pgetevents

On Thu, Jan 4, 2018 at 9:00 AM, Christoph Hellwig <hch@....de> wrote:

> +}
> +
> +SYSCALL_DEFINE6(io_pgetevents,
> +               aio_context_t, ctx_id,
> +               long, min_nr,
> +               long, nr,
> +               struct io_event __user *, events,
> +               struct timespec __user *, timeout,
> +               const sigset_t __user *, sigmask)
> +{

> +COMPAT_SYSCALL_DEFINE6(io_pgetevents,
> +               compat_aio_context_t, ctx_id,
> +               compat_long_t, min_nr,
> +               compat_long_t, nr,
> +               struct io_event __user *, events,
> +               struct compat_timespec __user *, timeout,
> +               const compat_sigset_t __user *, sigmask)
> +{

Hmm, these two new syscall entry points turn into four when we add in
support for 64-bit time_t, as we'd have to support all combinations of 32/64
bit aio_context_t and time_t.

Would it be better to start this interface out by defining it using a 64-bit
timeout structure? The downside would be that the user space syscall
wrappers have to start out with a conversion, if we don't do it, then
the opposite conversion would have to get added later.

      Arnd