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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id w1sm2452811edt.89.2021.04.21.01.56.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Apr 2021 01:56:47 -0700 (PDT) Date: Wed, 21 Apr 2021 10:56:45 +0200 From: Stefano Garzarella To: Arseny Krasnov Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jorgen Hansen , Andra Paraschiv , Colin Ian King , Norbert Slusarek , Jeff Vander Stoep , Alexander Popov , kvm , Linux Virtualization , netdev , kernel list , stsp , Krasnov Arseniy Subject: Re: [RFC PATCH v8 11/19] virtio/vsock: dequeue callback for SOCK_SEQPACKET Message-ID: References: <20210413123954.3396314-1-arseny.krasnov@kaspersky.com> <20210413124443.3403382-1-arseny.krasnov@kaspersky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210413124443.3403382-1-arseny.krasnov@kaspersky.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 13, 2021 at 03:44:40PM +0300, Arseny Krasnov wrote: >This adds transport callback and it's logic for SEQPACKET dequeue. >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 >--- >v7 -> v8: > - Things like SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id' now removed. > This callback fetches and copies RW packets to user's buffer, until > last packet of message found(this packet is marked in 'flags' field > of header). > > include/linux/virtio_vsock.h | 5 ++ > net/vmw_vsock/virtio_transport_common.c | 73 +++++++++++++++++++++++++ > 2 files changed, 78 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 833104b71a1c..8492b8bd5df5 100644 >--- a/net/vmw_vsock/virtio_transport_common.c >+++ b/net/vmw_vsock/virtio_transport_common.c >@@ -393,6 +393,67 @@ 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 err = 0; >+ size_t user_buf_len = msg->msg_iter.count; >+ >+ *msg_ready = false; >+ spin_lock_bh(&vvs->rx_lock); >+ >+ while (!*msg_ready && !list_empty(&vvs->rx_queue) && err >= 0) { >+ pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list); >+ >+ if (le16_to_cpu(pkt->hdr.op) == VIRTIO_VSOCK_OP_RW) { Is this check still necessary, should they all be RW? >+ size_t bytes_to_copy; >+ size_t pkt_len; >+ >+ pkt_len = (size_t)le32_to_cpu(pkt->hdr.len); >+ bytes_to_copy = min(user_buf_len, pkt_len); >+ If bytes_to_copy == 0, we can avoid the next steps (release the lock try to copy 0 bytes, reacquire the lock) >+ /* 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)) { >+ err = -EINVAL; Here we should reacquire the lock or prevent it from being released out of cycle. >+ break; >+ } >+ >+ spin_lock_bh(&vvs->rx_lock); >+ As mentioned before, I think we could move this part into the core and here always return the real dimension. >+ /* If user sets 'MSG_TRUNC' we return real >length >+ * of message. >+ */ >+ if (flags & MSG_TRUNC) >+ err += pkt_len; >+ else >+ err += bytes_to_copy; >+ >+ user_buf_len -= bytes_to_copy; >+ >+ if (pkt->hdr.flags & VIRTIO_VSOCK_SEQ_EOR) ^ We should use le32_to_cpu() to read the flags. >+ *msg_ready = true; >+ } >+ >+ virtio_transport_dec_rx_pkt(vvs, pkt); >+ list_del(&pkt->list); >+ virtio_transport_free_pkt(pkt); >+ } >+ >+ spin_unlock_bh(&vvs->rx_lock); >+ >+ virtio_transport_send_credit_update(vsk); >+ >+ return err; >+} >+ > ssize_t > virtio_transport_stream_dequeue(struct vsock_sock *vsk, > struct msghdr *msg, >@@ -405,6 +466,18 @@ virtio_transport_stream_dequeue(struct vsock_sock *vsk, > } > EXPORT_SYMBOL_GPL(virtio_transport_stream_dequeue); > >+ssize_t >+virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk, >+ struct msghdr *msg, >+ int flags, bool *msg_ready) >+{ >+ if (flags & MSG_PEEK) >+ return -EOPNOTSUPP; >+ >+ return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags, >msg_ready); >+} >+EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue); >+ > int > virtio_transport_dgram_dequeue(struct vsock_sock *vsk, > struct msghdr *msg, >-- >2.25.1 >