From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97F7AC678D4 for ; Fri, 3 Mar 2023 12:49:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229812AbjCCMtM (ORCPT ); Fri, 3 Mar 2023 07:49:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229895AbjCCMtJ (ORCPT ); Fri, 3 Mar 2023 07:49:09 -0500 Received: from mx.sberdevices.ru (mx.sberdevices.ru [45.89.227.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82CEA521DD; Fri, 3 Mar 2023 04:48:31 -0800 (PST) Received: from s-lin-edge02.sberdevices.ru (localhost [127.0.0.1]) by mx.sberdevices.ru (Postfix) with ESMTP id 2D2FE5FD18; Fri, 3 Mar 2023 15:48:12 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sberdevices.ru; s=mail; t=1677847692; bh=MO1GnWU4C+xASTFO4rCaIII7Du6k8rnPC00/+OtTNNw=; h=Message-ID:Date:MIME-Version:Subject:From:To:Content-Type; b=CewRtiS/Hm5DaPF4AiNQajYZUUA/FIB0X5Gbg9++ZiPEL1+Ja3TSz/pS0ZPowtx4H SJkT+UOdtyAl1SVLSDHyCfuLxZ0g3jxyyFlemq2oSFHeT3iuqfvWaairocrd4PH22U K+Yg2XgTZHWlYcWALJicn6z5esZc14hlfWPicOtPie0R05b6555qRMOnJR/5XxCzOt 60MsOcuzv790n1TWwhltCX7soarxquTULBB2DOJN10w3yoMHvu5seGgjFiykC0OvEP 1MBFBiyh532udjR+/FnObGAbm0Sq89b038llsfCV/Ae2xOeY6v36nzyozJ82TPBnNV 5pk6ksSVGboJw== Received: from S-MS-EXCH01.sberdevices.ru (S-MS-EXCH01.sberdevices.ru [172.16.1.4]) by mx.sberdevices.ru (Postfix) with ESMTP; Fri, 3 Mar 2023 15:48:08 +0300 (MSK) Message-ID: <3d5df796-3ff7-0b9f-efbd-cd33370442f9@sberdevices.ru> Date: Fri, 3 Mar 2023 15:45:18 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [RFC PATCH v1] vsock: check error queue to set EPOLLERR Content-Language: en-US From: Arseniy Krasnov To: Stefano Garzarella CC: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , , , , , , Bobby Eshleman References: <76e7698d-890b-d14d-fa34-da5dd7dd13d8@sberdevices.ru> <20230302100621.gk45unegjbqjgpxh@sgarzare-redhat> <3b38870c-7606-bf2e-8b17-21a75a1ed751@sberdevices.ru> <20230302133845.hglm4uregjsvrcrc@sgarzare-redhat> <63035ec9-6546-0881-353a-502b68daaada@sberdevices.ru> In-Reply-To: <63035ec9-6546-0881-353a-502b68daaada@sberdevices.ru> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH02.sberdevices.ru (172.16.1.5) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2023/03/03 09:42:00 #20911747 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02.03.2023 18:06, Arseniy Krasnov wrote: > > > On 02.03.2023 16:38, Stefano Garzarella wrote: >> On Thu, Mar 02, 2023 at 02:41:29PM +0300, Arseniy Krasnov wrote: >>> Hello! >>> >>> On 02.03.2023 13:06, Stefano Garzarella wrote: >>>> On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote: >>>>> EPOLLERR must be set not only when there is error on the socket, but also >>>>> when error queue of it is not empty (may be it contains some control >>>>> messages). Without this patch 'poll()' won't detect data in error queue. >>>> >>>> Do you have a reproducer? >>>> >>> Dedicated reproducer - no:) >>> To reproduce this issue, i used last MSG_ZEROCOPY patches. Completion was inserted to >>> error queue, and 'poll()' didn't report about it. That was the reason, why this patch >>> was included to MSG_ZEROCOPY patchset. But also i think it is better to reduce number >>> of patches in it(i'm working on v2), so it is good to handle this patch separately. >> >> Yep, absolutely! >> >>> May be one way to reproduce it is use SO_TIMESTAMP(time info about skbuff will be queued >>> to the error queue). IIUC this feature is implemented at socket layer and may work in >>> vsock (but i'm not sure). Ok, i'll check it and try to implement reproducer. >>> >>> IIUC, for future, policy for fixes is "for each fix implement reproducer in vsock_test"? >> >> Nope, but for each fix we should have a Fixes tag. >> >> Usually we use vsock_test to check regressions on features and also the >> behaviour of different transports. >> My question was more about whether this problem was there before >> supporting sk_buff or not, to figure out which Fixes tag to use. >> > Ok i see >>> >>>>> This patch is based on 'tcp_poll()'. >>>> >>>> LGTM but we should add a Fixes tag. >>>> It's not clear to me whether the problem depends on when we switched to using sk_buff or was pre-existing. >>>> >>>> Do you have any idea when we introduced this issue? >>> git blame shows, that this code exists since first commit to vsock: >> >> Okay, but did we use sk_error_queue before supporting sk_buff? >> > No I think, sk_error_queue was unavailable to user(and still unavailable today), > because we don't have check for MSG_ERRQUEUE flag in recv logic in af_vsock.c > (i've added it in MSG_ZEROCOPY). So even if some subsystem of the kernel inserts > skb to sk_error_queue in AF_VSOCK case, user won't dequeue it. > >> Anyway, if we are not sure I think we can use the following Fixes tag, >> I don't see any issue if we backport this patch also before supporting >> sk_buff. >> > Ok, i'll try to prepare reproducer(may be in vsock_test) and add Fixes tag with the > commit "VSOCK: Introduce VM Sockets." Hm, seems there is no way to reproduce it with AF_VSOCK in the current kernel: 1) I can't find test case how to use sk_error_queue(SO_TIMESTAMPXXX doesn't work on vsock - web says that it depends on NIC driver). And i don't see any generic socket layer features which uses sk_error_queue. 2) Anyway, as i mentioned above - user can't read data from sk_error_queue, because MSG_ERRQUEUE flag is not handled in af_vsock.c. So i'll resend this patch in MSG_ZEROCOPY v2 patchset - in this case, new MSG_ZEROCOPY logic will use this patch: it will be the "reproducer" Thanks, Arseniy > > Thanks, Arseniy >> Thanks, >> Stefano >> >>> >>> commit d021c344051af91f42c5ba9fdedc176740cbd238 >>> Author: Andy King >>> Date:   Wed Feb 6 14:23:56 2013 +0000 >>> >>>    VSOCK: Introduce VM Sockets >>> >>> For TCP same logic was added by: >>> >>> commit 4ed2d765dfaccff5ebdac68e2064b59125033a3b >>> Author: Willem de Bruijn >>> Date:   Mon Aug 4 22:11:49 2014 -0400 >>> >>>    net-timestamp: TCP timestamping >>> >>> >>>> >>>> Thanks, >>>> Stefano >>>> >>> >>> Thanks Arseniy >>> >>>>> >>>>> Signed-off-by: Arseniy Krasnov >>>>> --- >>>>> net/vmw_vsock/af_vsock.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>>>> index 19aea7cba26e..b5e51ef4a74c 100644 >>>>> --- a/net/vmw_vsock/af_vsock.c >>>>> +++ b/net/vmw_vsock/af_vsock.c >>>>> @@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock, >>>>>     poll_wait(file, sk_sleep(sk), wait); >>>>>     mask = 0; >>>>> >>>>> -    if (sk->sk_err) >>>>> +    if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) >>>>>         /* Signify that there has been an error on this socket. */ >>>>>         mask |= EPOLLERR; >>>>> >>>>> --  >>>>> 2.25.1 >>>>> >>>> >>> >>