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

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Date:   Fri, 21 Aug 2020 19:17:46 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Luke Hsiao <lukehsiao@...gle.com>
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

On 8/21/20 6:08 PM, Luke Hsiao wrote:
> 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?

You should see them with C=1. But as I said, don't worry about it, as that's
a class of warnings and several exist already. It needs to get cleaned up
separately.

>>> 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.

Please do, thanks!

-- 
Jens Axboe