netdev-dpdk: fix management of pre-existing mempools.

Fix an issue on reconfiguration of pre-existing mempools.
This patch avoids to call dpdk_mp_put() - and erroneously
release the mempool - when it already exists.

CC: Mark B Kavanagh <mark.b.kavanagh@intel.com>
CC: Aaron Conole <aconole@redhat.com>
CC: Darrell Ball <dlu998@gmail.com>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Reported-by: Ciara Loftus <ciara.loftus@intel.com>
Tested-by: Ciara Loftus <ciara.loftus@intel.com>
Reported-by: Róbert Mulik <robert.mulik@ericsson.com>
Fixes: d555d9bded ("netdev-dpdk: Create separate memory pool for each port.")
Signed-off-by: Antonio Fischetti <antonio.fischetti@intel.com>
Acked-by: Mark Kavanagh <mark.b.kavanagh@intel.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>

lib/netdev-dpdk.c

@@ -508,12 +508,13 @@ dpdk_mp_name(struct dpdk_mp *dmp)
 }
 
 static struct dpdk_mp *
-dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
+dpdk_mp_create(struct netdev_dpdk *dev, int mtu, bool *mp_exists)
 {
     struct dpdk_mp *dmp = dpdk_rte_mzalloc(sizeof *dmp);
     if (!dmp) {
         return NULL;
     }
+    *mp_exists = false;
     dmp->socket_id = dev->requested_socket_id;
     dmp->mtu = mtu;
     ovs_strzcpy(dmp->if_name, dev->up.name, IFNAMSIZ);
@@ -530,8 +531,6 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
             + MIN(RTE_MAX_LCORE, dev->requested_n_rxq) * NETDEV_MAX_BURST
             + MIN_NB_MBUF;
 
-    bool mp_exists = false;
-
     do {
         char *mp_name = dpdk_mp_name(dmp);
 
@@ -559,7 +558,7 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
             /* As the mempool create returned EEXIST we can expect the
              * lookup has returned a valid pointer.  If for some reason
              * that's not the case we keep track of it. */
-            mp_exists = true;
+            *mp_exists = true;
         } else {
             VLOG_ERR("Failed mempool \"%s\" create request of %u mbufs",
                      mp_name, dmp->mp_size);
@@ -573,20 +572,23 @@ dpdk_mp_create(struct netdev_dpdk *dev, int mtu)
             rte_mempool_obj_iter(dmp->mp, ovs_rte_pktmbuf_init, NULL);
             return dmp;
         }
-    } while (!mp_exists &&
+    } while (!(*mp_exists) &&
             (rte_errno == ENOMEM && (dmp->mp_size /= 2) >= MIN_NB_MBUF));
 
     rte_free(dmp);
     return NULL;
 }
 
+/* Returns a valid pointer when either of the following is true:
+ *  - a new mempool was just created;
+ *  - a matching mempool already exists. */
 static struct dpdk_mp *
-dpdk_mp_get(struct netdev_dpdk *dev, int mtu)
+dpdk_mp_get(struct netdev_dpdk *dev, int mtu, bool *mp_exists)
 {
     struct dpdk_mp *dmp;
 
     ovs_mutex_lock(&dpdk_mp_mutex);
-    dmp = dpdk_mp_create(dev, mtu);
+    dmp = dpdk_mp_create(dev, mtu, mp_exists);
     ovs_mutex_unlock(&dpdk_mp_mutex);
 
     return dmp;
@@ -610,9 +612,11 @@ dpdk_mp_put(struct dpdk_mp *dmp)
     ovs_mutex_unlock(&dpdk_mp_mutex);
 }
 
-/* Tries to allocate new mempool on requested_socket_id with
- * mbuf size corresponding to requested_mtu.
- * On success new configuration will be applied.
+/* Tries to allocate a new mempool - or re-use an existing one where
+ * appropriate - on requested_socket_id with a size determined by
+ * requested_mtu and requested Rx/Tx queues.
+ * On success - or when re-using an existing mempool - the new configuration
+ * will be applied.
  * On error, device will be left unchanged. */
 static int
 netdev_dpdk_mempool_configure(struct netdev_dpdk *dev)
@@ -620,14 +624,22 @@ netdev_dpdk_mempool_configure(struct netdev_dpdk *dev)
 {
     uint32_t buf_size = dpdk_buf_size(dev->requested_mtu);
     struct dpdk_mp *mp;
+    bool mp_exists;
 
-    mp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size));
+    mp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size), &mp_exists);
     if (!mp) {
         VLOG_ERR("Failed to create memory pool for netdev "
                  "%s, with MTU %d on socket %d: %s\n",
                  dev->up.name, dev->requested_mtu, dev->requested_socket_id,
                  rte_strerror(rte_errno));
         return rte_errno;
+    } else if (mp_exists) {
+        /* If a new MTU was requested and its rounded value equals the one
+         * that is currently used, then the existing mempool is returned.
+         * Update dev with the new values. */
+        dev->mtu = dev->requested_mtu;
+        dev->max_packet_len = MTU_TO_FRAME_LEN(dev->mtu);
+        return EEXIST;
     } else {
         dpdk_mp_put(dev->dpdk_mp);
         dev->dpdk_mp = mp;
@@ -3207,7 +3219,7 @@ netdev_dpdk_reconfigure(struct netdev *netdev)
     rte_eth_dev_stop(dev->port_id);
 
     err = netdev_dpdk_mempool_configure(dev);
-    if (err) {
+    if (err && err != EEXIST) {
         goto out;
     }
 
@@ -3247,12 +3259,12 @@ dpdk_vhost_reconfigure_helper(struct netdev_dpdk *dev)
     netdev_dpdk_remap_txqs(dev);
 
     err = netdev_dpdk_mempool_configure(dev);
-    if (err) {
-        return err;
-    } else {
+    if (!err) {
+        /* A new mempool was created. */
         netdev_change_seq_changed(&dev->up);
+    } else if (err != EEXIST){
+        return err;
     }
-
     if (netdev_dpdk_get_vid(dev) >= 0) {
         if (dev->vhost_reconfigured == false) {
             dev->vhost_reconfigured = true;