From: Constantine Gavrilov <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: Jens Axboe <[email protected]>,
[email protected], [email protected]
Subject: Re: [PATCH 1/2] io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly
Date: Wed, 23 Mar 2022 22:45:02 +0200 [thread overview]
Message-ID: <CAAL3td3_VFmOH1mNXiG6geFeONSm066Xba5ePqPwkMr-zxkDGg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
On Wed, Mar 23, 2022 at 10:14 PM Pavel Begunkov <[email protected]> wrote:
>
> On 3/23/22 15:39, Jens Axboe wrote:
> > We currently don't attempt to get the full asked for length even if
> > MSG_WAITALL is set, if we get a partial receive. If we do see a partial
> > receive, then just note how many bytes we did and return -EAGAIN to
> > get it retried.
> >
> > The iov is advanced appropriately for the vector based case, and we
> > manually bump the buffer and remainder for the non-vector case.
>
> How datagrams work with MSG_WAITALL? I highly doubt it coalesces 2+
> packets to satisfy the length requirement (e.g. because it may move
> the address back into the userspace). I'm mainly afraid about
> breaking io_uring users who are using the flag just to fail links
> when there is not enough data in a packet.
>
> --
> Pavel Begunkov
Pavel:
Datagrams have message boundaries and the MSG_WAITALL flag does not
make sense there. I believe it is ignored by receive code on daragram
sockets. MSG_WAITALL makes sends only on stream sockets, like TCP. The
manual page says "This flag has no effect for datagram sockets.".
--
----------------------------------------
Constantine Gavrilov
Storage Architect
Master Inventor
Tel-Aviv IBM Storage Lab
1 Azrieli Center, Tel-Aviv
----------------------------------------
next prev parent reply other threads:[~2022-03-23 20:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 15:39 [PATCHSET 0/2] Fix MSG_WAITALL for IORING_OP_RECV/RECVMSG Jens Axboe
2022-03-23 15:39 ` [PATCH 1/2] io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly Jens Axboe
2022-03-23 20:13 ` Pavel Begunkov
2022-03-23 20:15 ` Jens Axboe
2022-03-23 20:45 ` Constantine Gavrilov [this message]
2022-03-23 20:52 ` Pavel Begunkov
2022-03-23 21:24 ` Jens Axboe
2022-03-23 15:39 ` [PATCH 2/2] io_uring: add flag for disabling provided buffer recycling Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2022-03-23 22:41 [PATCHSET v2 0/2] Fix MSG_WAITALL for IORING_OP_RECV/RECVMSG Jens Axboe
2022-03-23 22:41 ` [PATCH 1/2] io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly Jens Axboe
2022-03-24 0:32 ` Stefan Metzmacher
2022-03-24 0:35 ` Jens Axboe
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