netdev - Re: [PATCH net-next 2/2] io_uring: ignore POLLIN for recvmsg on MSG

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Date:   Fri, 21 Aug 2020 17:08:43 -0700
From:   Luke Hsiao <lukehsiao@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Luke Hsiao <luke.w.hsiao@...il.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Arjun Roy <arjunroy@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 2/2] io_uring: ignore POLLIN for recvmsg on MSG_ERRQUEUE

Hi Jakub and Jens,

Thank you for both of your reviews. Some responses inline below.

On Fri, Aug 21, 2020 at 2:11 PM Jens Axboe <axboe@...nel.dk> wrote:
>
> On 8/21/20 2:41 PM, Jakub Kicinski wrote:
> > On Thu, 20 Aug 2020 16:49:54 -0700 Luke Hsiao wrote:
> >> +    /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
> >> +    if (req->opcode == IORING_OP_RECVMSG && (sqe->msg_flags & MSG_ERRQUEUE))
> >> +            mask &= ~(POLLIN);
> >
> > FWIW this adds another W=1 C=1 warnings to this code:
> >
> > fs/io_uring.c:4940:22: warning: invalid assignment: &=
> > fs/io_uring.c:4940:22:    left side has type restricted __poll_t
> > fs/io_uring.c:4940:22:    right side has type int
>
> Well, 8 or 9 of them don't really matter... This is something that should
> be cleaned up separately at some point.

In the spirit of not adding a warning, even if it doesn't really
matter, I'd like to fix this. But, I'm struggling to reproduce these
warnings using upstream net-next and make for x86_64. With my patches
on top of net-next/master, I'm running

$ make defconfig
$ make -j`nproc` W=1

I don't see the warning you mentioned in the logs. Could you tell me
how I can repro this warning?

> > And obviously the brackets around POLLIN are not necessary.
>
> Agree, would be cleaner without!

Thanks, I'll also remove these unnecessary parens in v2 of the patch series.

--
Luke