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([2a01:e0a:e10:ef90:343a:68f:2e91:95c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f25913eb6sm14385035f8f.51.2025.02.18.00.01.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 00:01:31 -0800 (PST) Message-ID: <53e1b351-da19-4491-b438-1e77e0dc836c@redhat.com> Date: Tue, 18 Feb 2025 09:01:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tcp_vu: head_cnt need not be global To: David Gibson , Stefano Brivio , passt-dev@passt.top References: <20250218025013.1035148-1-david@gibson.dropbear.id.au> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: <20250218025013.1035148-1-david@gibson.dropbear.id.au> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: PaIzWP2WxPKuHeUaybjAHd3NsjK_SA8MXUca9e7MAfA_1739865692 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: VLCW326NLKIMTAQXGZH7UO7BDIA22N4B X-Message-ID-Hash: VLCW326NLKIMTAQXGZH7UO7BDIA22N4B X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 18/02/2025 03:50, David Gibson wrote: > head_cnt is a global variable which tracks how many entries in head[] are > currently used. The fact that it's global obscures the fact that the > lifetime over which it has a meaningful value is quite short: a single > call to of tcp_vu_data_from_sock(). > > Make it a local to tcp_vu_data_from_sock() to make that lifetime clearer. > We keep the head[] array global for now - although technically it has the > same valid lifetime - because it's large enough we might not want to put > it on the stack. We can make the array local but on the heap using a static declaration in the function. Reviewed-by: Laurent Vivier > > Cc: Laurent Vivier > > Signed-off-by: David Gibson > --- > tcp_vu.c | 21 +++++++++++---------- > 1 file changed, 11 insertions(+), 10 deletions(-) > > diff --git a/tcp_vu.c b/tcp_vu.c > index 0622f173..6891ed13 100644 > --- a/tcp_vu.c > +++ b/tcp_vu.c > @@ -38,7 +38,6 @@ > static struct iovec iov_vu[VIRTQUEUE_MAX_SIZE + 1]; > static struct vu_virtq_element elem[VIRTQUEUE_MAX_SIZE]; > static int head[VIRTQUEUE_MAX_SIZE + 1]; > -static int head_cnt; > > /** > * tcp_vu_hdrlen() - return the size of the header in level 2 frame (TCP) > @@ -183,7 +182,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) > static ssize_t tcp_vu_sock_recv(const struct ctx *c, > const struct tcp_tap_conn *conn, bool v6, > uint32_t already_sent, size_t fillsize, > - int *iov_cnt) > + int *iov_cnt, int *head_cnt) > { > struct vu_dev *vdev = c->vdev; > struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; > @@ -202,7 +201,7 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, > vu_init_elem(elem, &iov_vu[1], VIRTQUEUE_MAX_SIZE); > > elem_cnt = 0; > - head_cnt = 0; > + *head_cnt = 0; > while (fillsize > 0 && elem_cnt < VIRTQUEUE_MAX_SIZE) { > struct iovec *iov; > size_t frame_size, dlen; > @@ -221,7 +220,7 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, > ASSERT(iov->iov_len >= hdrlen); > iov->iov_base = (char *)iov->iov_base + hdrlen; > iov->iov_len -= hdrlen; > - head[head_cnt++] = elem_cnt; > + head[(*head_cnt)++] = elem_cnt; > > fillsize -= dlen; > elem_cnt += cnt; > @@ -261,17 +260,18 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, > len -= iov->iov_len; > } > /* adjust head count */ > - while (head_cnt > 0 && head[head_cnt - 1] >= i) > - head_cnt--; > + while (*head_cnt > 0 && head[*head_cnt - 1] >= i) > + (*head_cnt)--; > + > /* mark end of array */ > - head[head_cnt] = i; > + head[*head_cnt] = i; > *iov_cnt = i; > > /* release unused buffers */ > vu_queue_rewind(vq, elem_cnt - i); > > /* restore space for headers in iov */ > - for (i = 0; i < head_cnt; i++) { > + for (i = 0; i < *head_cnt; i++) { > struct iovec *iov = &elem[head[i]].in_sg[0]; > > iov->iov_base = (char *)iov->iov_base - hdrlen; > @@ -357,11 +357,11 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn) > struct vu_dev *vdev = c->vdev; > struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE]; > ssize_t len, previous_dlen; > + int i, iov_cnt, head_cnt; > size_t hdrlen, fillsize; > int v6 = CONN_V6(conn); > uint32_t already_sent; > const uint16_t *check; > - int i, iov_cnt; > > if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) { > debug("Got packet, but RX virtqueue not usable yet"); > @@ -396,7 +396,8 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn) > /* collect the buffers from vhost-user and fill them with the > * data from the socket > */ > - len = tcp_vu_sock_recv(c, conn, v6, already_sent, fillsize, &iov_cnt); > + len = tcp_vu_sock_recv(c, conn, v6, already_sent, fillsize, > + &iov_cnt, &head_cnt); > if (len < 0) { > if (len != -EAGAIN && len != -EWOULDBLOCK) { > tcp_rst(c, conn);