Received: by 2002:a05:6a10:206:0:0:0:0 with SMTP id 6csp3969873pxj; Tue, 8 Jun 2021 03:22:05 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzUV/jDtWQakVn+4PDS3qNIMWtpPXpmli6C2micJc13tNolQbmgXvpfCfk60tsKLdoS/Bmr X-Received: by 2002:aa7:ce86:: with SMTP id y6mr932236edv.309.1623147725297; Tue, 08 Jun 2021 03:22:05 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1623147725; cv=none; d=google.com; s=arc-20160816; b=jGg6iy/yWaRvE6ocxMcaShjBOn7rA8VDjDZRQ6UekYqrd7wG1JsP55L97mZW/TJ3nh 9eOozGNZdWPIIydZUbu4D81zyZkxyT9ZmbcGgN2VVaXTqB0H4KHtqmcExkhQxSUtlXxQ WOM6iLtvO1VjkXVvkTskqRWrklOXCg1UI1tcTwczK7qzD94prep0p8ZcZEv2YVbrhOFu RW6xdZPrlhtIITsqTFQAtHY5ni8uBvCngAYhEwD8Yg61TMwRoYdnHj+vibx1fzHlBOkp Yr0oUjWY5qzEjYIG7PDjeJhVS01RwTK95UkQglg1IOdFXN/At3wFdZrtV0Ptd/ysXAGy x/TQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date:dkim-signature; bh=LXIgbsKcwmgL9PLadPLYMZ2Gr+lpa7CAtfsyCgK+hX8=; b=ldGB2eXqQrWxxP/AJJiwZOpKouKH5QKvKsSw4mBQOGL+6EPgJuojEHCFpDTExDFuKD N7ec1jkuogYaRNaqh17yPR4cAyU8Q+l26hpGmA/31uHUPfOHKFEEUlpTjFTbSYpozzQs hqmX6tr1hrpf+dBeeFvsr2HLl6fsdwRA/BDa0qlIzsMj1WAq+SzZT8PNLAkILjB3GatJ kcxUN5XhJa+Y/AkPBDz0TrvBwIi4EHBO+q42P9NiaakWM90AljP792YRAnRgsVKlA15j cISo9JtKx4QPcqHiZOj5EnMSMnFaQ9w8qzldXq5RWAPu5lm/aBkq9bXSejmSR91wG/cw W1mw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=HtK7dgyy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id m13si9274025edv.357.2021.06.08.03.21.42; Tue, 08 Jun 2021 03:22:05 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=HtK7dgyy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231228AbhFHKVz (ORCPT + 99 others); Tue, 8 Jun 2021 06:21:55 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42679 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229937AbhFHKVw (ORCPT ); Tue, 8 Jun 2021 06:21:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623147599; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=LXIgbsKcwmgL9PLadPLYMZ2Gr+lpa7CAtfsyCgK+hX8=; b=HtK7dgyy8kT70un37ipB8JbHT28SxcIuaCOjRVlSMeX9xsZIY2Tc4DJ8+wMk1YPaDP+dIP zYSAPj8v5HIBTOhioPcVJA7B76yh8wmfu+8qqvVZE6/LbShgHIEDEXMVHhsDVKm0zbFVTk 0ml49qTzY+d3/tWymQ7RnoTG8RhjIQs= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-85-aIuvd811PuuaQWJNmmBRkQ-1; Tue, 08 Jun 2021 06:19:57 -0400 X-MC-Unique: aIuvd811PuuaQWJNmmBRkQ-1 Received: by mail-ej1-f72.google.com with SMTP id e11-20020a170906080bb02903f9c27ad9f5so6539652ejd.6 for ; Tue, 08 Jun 2021 03:19:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=LXIgbsKcwmgL9PLadPLYMZ2Gr+lpa7CAtfsyCgK+hX8=; b=rMUHh4rLbSgtFtat6PiohXnp7FZXj+5eA/rLVApn1u2fUlGWdFAWBJ5Wwm936Ns83T Oi10SlXfs6mihT3ek+u/ZLJIFfgp6YiJz3a8bcUlmYna9h8p7pM/gxfwehupImHyarPP Io18xsfTkzizzUTzjl4/H1X2IHhjuAbyGs+5bbxi0iAiFeKYk6gWwHFM51GnenzJ6ZGp uK7q233MBT9/hH3yep2DIaTjz1VMS8e+ILymYVjywJiYTlDuQitzEOa9PafZ88S2s63g CyNlFzLVrYa3TnLFn8UGJiydpdHqZbnKl5EIdOI4aB5ghfln2doTWafTVOBHl076RBtc P2aQ== X-Gm-Message-State: AOAM531s2m/VuvrmPSiIQehus/AH+D2GqUnHCwADHhbR981mYuD+QW6N FScn2kxPUXiJ8GnkyAzzKEcw33/12XGwzDiDWXQJB5KGVvVnlgu4Bv26vQ7RtRakYRZCSIf18HO lHbmAs5dUW0eaKQjH5pCIAbmD X-Received: by 2002:a17:906:95c8:: with SMTP id n8mr23089767ejy.357.1623147596543; Tue, 08 Jun 2021 03:19:56 -0700 (PDT) X-Received: by 2002:a17:906:95c8:: with SMTP id n8mr23089743ejy.357.1623147596314; Tue, 08 Jun 2021 03:19:56 -0700 (PDT) Received: from steredhat (host-79-18-148-79.retail.telecomitalia.it. [79.18.148.79]) by smtp.gmail.com with ESMTPSA id f6sm7548251eja.108.2021.06.08.03.19.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Jun 2021 03:19:55 -0700 (PDT) Date: Tue, 8 Jun 2021 12:19:52 +0200 From: Stefano Garzarella To: Arseny Krasnov Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jorgen Hansen , Norbert Slusarek , Colin Ian King , Andra Paraschiv , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "oxffffaa@gmail.com" Subject: Re: [PATCH v10 11/18] virtio/vsock: dequeue callback for SOCK_SEQPACKET Message-ID: <20210608101952.6meiasy7zqp474sf@steredhat> References: <20210520191357.1270473-1-arseny.krasnov@kaspersky.com> <20210520191801.1272027-1-arseny.krasnov@kaspersky.com> <20210603144513.ryjzauq7abnjogu3@steredhat> <6b833ccf-ea93-db6a-4743-463ac1cfe817@kaspersky.com> <20210604150324.winiikx5h3p6gsyy@steredhat> <20210607110421.wkx4dj7wipwsqztj@steredhat> <8e2eb802-7c5d-70b0-82b5-ec8de4fdc046@kaspersky.com> <20210608082320.vs2tzgpxgr2dhxye@steredhat> <3c35f04a-8406-d26f-27d0-becbd3c43c1b@kaspersky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <3c35f04a-8406-d26f-27d0-becbd3c43c1b@kaspersky.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 08, 2021 at 12:40:39PM +0300, Arseny Krasnov wrote: > >On 08.06.2021 11:23, Stefano Garzarella wrote: >> On Mon, Jun 07, 2021 at 04:18:38PM +0300, Arseny Krasnov wrote: >>> On 07.06.2021 14:04, Stefano Garzarella wrote: >>>> On Fri, Jun 04, 2021 at 09:03:26PM +0300, Arseny Krasnov wrote: >>>>> On 04.06.2021 18:03, Stefano Garzarella wrote: >>>>>> On Fri, Jun 04, 2021 at 04:12:23PM +0300, Arseny Krasnov wrote: >>>>>>> On 03.06.2021 17:45, Stefano Garzarella wrote: >>>>>>>> On Thu, May 20, 2021 at 10:17:58PM +0300, Arseny Krasnov wrote: >>>>>>>>> Callback fetches RW packets from rx queue of socket until whole record >>>>>>>>> is copied(if user's buffer is full, user is not woken up). This is done >>>>>>>>> to not stall sender, because if we wake up user and it leaves syscall, >>>>>>>>> nobody will send credit update for rest of record, and sender will wait >>>>>>>>> for next enter of read syscall at receiver's side. So if user buffer is >>>>>>>>> full, we just send credit update and drop data. >>>>>>>>> >>>>>>>>> Signed-off-by: Arseny Krasnov >>>>>>>>> --- >>>>>>>>> v9 -> v10: >>>>>>>>> 1) Number of dequeued bytes incremented even in case when >>>>>>>>> user's buffer is full. >>>>>>>>> 2) Use 'msg_data_left()' instead of direct access to 'msg_hdr'. >>>>>>>>> 3) Rename variable 'err' to 'dequeued_len', in case of error >>>>>>>>> it has negative value. >>>>>>>>> >>>>>>>>> include/linux/virtio_vsock.h | 5 ++ >>>>>>>>> net/vmw_vsock/virtio_transport_common.c | 65 +++++++++++++++++++++++++ >>>>>>>>> 2 files changed, 70 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h >>>>>>>>> index dc636b727179..02acf6e9ae04 100644 >>>>>>>>> --- a/include/linux/virtio_vsock.h >>>>>>>>> +++ b/include/linux/virtio_vsock.h >>>>>>>>> @@ -80,6 +80,11 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk, >>>>>>>>> struct msghdr *msg, >>>>>>>>> size_t len, int flags); >>>>>>>>> >>>>>>>>> +ssize_t >>>>>>>>> +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk, >>>>>>>>> + struct msghdr *msg, >>>>>>>>> + int flags, >>>>>>>>> + bool *msg_ready); >>>>>>>>> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk); >>>>>>>>> s64 virtio_transport_stream_has_space(struct vsock_sock *vsk); >>>>>>>>> >>>>>>>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >>>>>>>>> index ad0d34d41444..61349b2ea7fe 100644 >>>>>>>>> --- a/net/vmw_vsock/virtio_transport_common.c >>>>>>>>> +++ b/net/vmw_vsock/virtio_transport_common.c >>>>>>>>> @@ -393,6 +393,59 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, >>>>>>>>> return err; >>>>>>>>> } >>>>>>>>> >>>>>>>>> +static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, >>>>>>>>> + struct msghdr *msg, >>>>>>>>> + int flags, >>>>>>>>> + bool *msg_ready) >>>>>>>>> +{ >>>>>>>>> + struct virtio_vsock_sock *vvs = vsk->trans; >>>>>>>>> + struct virtio_vsock_pkt *pkt; >>>>>>>>> + int dequeued_len = 0; >>>>>>>>> + size_t user_buf_len = msg_data_left(msg); >>>>>>>>> + >>>>>>>>> + *msg_ready = false; >>>>>>>>> + spin_lock_bh(&vvs->rx_lock); >>>>>>>>> + >>>>>>>>> + while (!*msg_ready && !list_empty(&vvs->rx_queue) && dequeued_len >= 0) { >>>>>>>> I' >>>>>>>> >>>>>>>>> + size_t bytes_to_copy; >>>>>>>>> + size_t pkt_len; >>>>>>>>> + >>>>>>>>> + pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list); >>>>>>>>> + pkt_len = (size_t)le32_to_cpu(pkt->hdr.len); >>>>>>>>> + bytes_to_copy = min(user_buf_len, pkt_len); >>>>>>>>> + >>>>>>>>> + if (bytes_to_copy) { >>>>>>>>> + /* sk_lock is held by caller so no one else can dequeue. >>>>>>>>> + * Unlock rx_lock since memcpy_to_msg() may sleep. >>>>>>>>> + */ >>>>>>>>> + spin_unlock_bh(&vvs->rx_lock); >>>>>>>>> + >>>>>>>>> + if (memcpy_to_msg(msg, pkt->buf, bytes_to_copy)) >>>>>>>>> + dequeued_len = -EINVAL; >>>>>>>> I think here is better to return the error returned by memcpy_to_msg(), >>>>>>>> as we do in the other place where we use memcpy_to_msg(). >>>>>>>> >>>>>>>> I mean something like this: >>>>>>>> err = memcpy_to_msgmsg, pkt->buf, bytes_to_copy); >>>>>>>> if (err) >>>>>>>> dequeued_len = err; >>>>>>> Ack >>>>>>>>> + else >>>>>>>>> + user_buf_len -= bytes_to_copy; >>>>>>>>> + >>>>>>>>> + spin_lock_bh(&vvs->rx_lock); >>>>>>>>> + } >>>>>>>>> + >>>>>>>> Maybe here we can simply break the cycle if we have an error: >>>>>>>> if (dequeued_len < 0) >>>>>>>> break; >>>>>>>> >>>>>>>> Or we can refactor a bit, simplifying the while() condition and also the >>>>>>>> code in this way (not tested): >>>>>>>> >>>>>>>> while (!*msg_ready && !list_empty(&vvs->rx_queue)) { >>>>>>>> ... >>>>>>>> >>>>>>>> if (bytes_to_copy) { >>>>>>>> int err; >>>>>>>> >>>>>>>> /* ... >>>>>>>> */ >>>>>>>> spin_unlock_bh(&vvs->rx_lock); >>>>>>>> err = memcpy_to_msgmsg, pkt->buf, bytes_to_copy); >>>>>>>> if (err) { >>>>>>>> dequeued_len = err; >>>>>>>> goto out; >>>>>>>> } >>>>>>>> spin_lock_bh(&vvs->rx_lock); >>>>>>>> >>>>>>>> user_buf_len -= bytes_to_copy; >>>>>>>> } >>>>>>>> >>>>>>>> dequeued_len += pkt_len; >>>>>>>> >>>>>>>> if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) >>>>>>>> *msg_ready = true; >>>>>>>> >>>>>>>> virtio_transport_dec_rx_pkt(vvs, pkt); >>>>>>>> list_del(&pkt->list); >>>>>>>> virtio_transport_free_pkt(pkt); >>>>>>>> } >>>>>>>> >>>>>>>> out: >>>>>>>> spin_unlock_bh(&vvs->rx_lock); >>>>>>>> >>>>>>>> virtio_transport_send_credit_update(vsk); >>>>>>>> >>>>>>>> return dequeued_len; >>>>>>>> } >>>>>>> I think we can't do 'goto out' or break, because in case of error, >>>>>>> we still need >>>>>>> to free packet. >>>>>> Didn't we have code that remove packets from a previous message? >>>>>> I don't see it anymore. >>>>>> >>>>>> For example if we have 10 packets queued for a message (the 10th >>>>>> packet >>>>>> has the EOR flag) and the memcpy_to_msg() fails on the 2nd packet, with >>>>>> you proposal we are freeing only the first 2 packets, the rest is there >>>>>> and should be freed when reading the next message, but I don't see that >>>>>> code. >>>>>> >>>>>> The same can happen if the recvmsg syscall is interrupted. In that case >>>>>> we report that nothing was copied, but we freed the first N packets, so >>>>>> they are lost but the other packets are still in the queue. >>>>>> >>>>>> Please check also the patch where we implemented >>>>>> __vsock_seqpacket_recvmsg(). >>>>>> >>>>>> I thinks we should free packets only when we are sure we copied them to >>>>>> the user space. >>>>> Hm, yes, this is problem. To solve it i can restore previous approach >>>>> with seqbegin/seqend. In that case i can detect unfinished record and >>>>> drop it's packets. Seems seqbegin will be a bit like >>>>> VIRTIO_VSOCK_SEQ_EOR in flags >>>>> field of header(e.g. VIRTIO_VSOCK_SEQ_BEGIN). Message id and length are >>>>> unneeded, >>>>> as channel considedered lossless. What do You think? >>>>> >>>> I think VIRTIO_VSOCK_SEQ_BEGIN is redundant, using only EOR should be >>>> fine. >>>> >>>> When we receive EOR we know that this is the last packet on this message >>>> and the next packet will be the first of a new message. >>>> >>>> What we should do is check that we have all the fragments of a packet >>>> and return them all together, otherwise we have to say we have nothing. >>>> >>>> For example as we process packets from the vitqueue and queue them in >>>> the rx_queue we could use a counter of how many EORs are in the >>>> rx_queue, which we decrease in virtio_transport_seqpacket_do_dequeue() >>>> when we copied all the fragments. >>>> >>>> If the counter is 0, we don't remove anything from the queue and >>>> virtio_transport_seqpacket_do_dequeue() returns 0. >>>> >>>> So .seqpacket_dequeue should return 0 if there is not at least one >>>> complete message, or return the entire message. A partial message should >>>> never return. >>>> >>>> What do you think? >>> I like it, i've implemented this approach in some early pre v1 versions. >>> >>> But in this case, credit update logic will be changed - in current implementation >>> >>> (both seqpacket and stream) credit update reply is sent when data is copied >>> >>> to user's buffer(e.g. we copy data somewhere, free packet and ready to process >>> >>> new packet). But if we don't touch user's buffer and keeping incoming packet in rx queue >>> >>> until whole record is ready, when to send credit update? >> I think the best approach could be to send credit updates when we remove >> them from the rx_queue. > >In that case, it will be impossible to send message bigger than size of rx buffer > >(e.g. credit allowed size), because packet will be queued without credit update > >reply until credit allowed reach 0. > Yep, but I think it is a reasonable limit for a datagram socket. Maybe we can add a check on the TX side, since we know this value and return an error to the user. Thanks, Stefano