linux-kernel - Re: [PATCH v11 1/8] fork: Make IO worker options flag based

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Message-ID: <CAHk-=wjTzdQr7xNm53ZUJT0jxaxSYLkf8XT2S1CoxnyFgVafKg@mail.gmail.com>
Date:   Thu, 2 Feb 2023 16:14:15 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, brauner@...nel.org,
        ebiederm@...ssion.com, konrad.wilk@...cle.com,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v11 1/8] fork: Make IO worker options flag based

On Thu, Feb 2, 2023 at 3:25 PM Mike Christie
<michael.christie@...cle.com> wrote:
>
>  struct kernel_clone_args {
>         u64 flags;
> +       u32 worker_flags;
>         int __user *pidfd;
>         int __user *child_tid;
>         int __user *parent_tid;

Minor nit: please put this next to "exit_signal".

As it is, you've put a new 32-bit field in between two 64-bit fields
and are generating extra pointless padding.

We have that padding by "exit_signal" already, so let's just use it.

Also, I like moving those flags to a "flags" field, but can we please
make it consistent? We have that "args->kthread" field too, which is
100% analogous to args->io_thread.

So don't make a bit field for io_thread, and then not do the same for kthread.

Finally, why isn't this all just a bitfield - every single case would
seem to prefer something like

     if (args->user_worker) ..

instead of

    if (args->worker_flags & USER_WORKER)

which would seem to make everything simpler still?

            Linus