revalidator: Defer stats push to end of validation.

To make more of the core revalidate() functions do just one thing and
not modify state on the way, refactor them to prepare the xcache then
defer the ukey modification and stats/side effects execution to the end
of successful revalidation.

If revalidation causes deletion, then the xcache will be prepared and
attached to the ukey, but the actual execution will be skipped since it
will be executed on flow_delete very soon anyway with final stats.

Signed-off-by: Joe Stringer <joe@ovn.org>
Acked-by: Daniele Di Proietto <diproiettod@vmware.com>

ofproto/ofproto-dpif-upcall.c

@@ -1890,16 +1890,41 @@ xlate_key(struct udpif *udpif, const struct nlattr *key, unsigned int len,
 
 static int
 xlate_ukey(struct udpif *udpif, const struct udpif_key *ukey,
-           const struct dpif_flow_stats *push, struct reval_context *ctx)
+           uint16_t tcp_flags, struct reval_context *ctx)
 {
-    return xlate_key(udpif, ukey->key, ukey->key_len, push, ctx);
+    struct dpif_flow_stats push = {
+        .tcp_flags = tcp_flags,
+    };
+    return xlate_key(udpif, ukey->key, ukey->key_len, &push, ctx);
+}
+
+static int
+populate_xcache(struct udpif *udpif, struct udpif_key *ukey,
+                uint16_t tcp_flags)
+    OVS_REQUIRES(ukey->mutex)
+{
+    struct reval_context ctx = {
+        .odp_actions = NULL,
+        .netflow = NULL,
+        .wc = NULL,
+    };
+    int error;
+
+    ovs_assert(!ukey->xcache);
+    ukey->xcache = ctx.xcache = xlate_cache_new();
+    error = xlate_ukey(udpif, ukey, tcp_flags, &ctx);
+    if (error) {
+        return error;
+    }
+    xlate_out_uninit(&ctx.xout);
+
+    return 0;
 }
 
 static enum reval_result
 revalidate_ukey__(struct udpif *udpif, struct udpif_key *ukey,
-                  const struct dpif_flow_stats *push,
-                  struct ofpbuf *odp_actions, uint64_t reval_seq,
-                  struct recirc_refs *recircs)
+                  uint16_t tcp_flags, struct ofpbuf *odp_actions,
+                  uint64_t reval_seq, struct recirc_refs *recircs)
     OVS_REQUIRES(ukey->mutex)
 {
     bool need_revalidate = (ukey->reval_seq != reval_seq);
@@ -1924,7 +1949,7 @@ revalidate_ukey__(struct udpif *udpif, struct udpif_key *ukey,
         ukey->xcache = xlate_cache_new();
     }
     ctx.xcache = ukey->xcache;
-    if (xlate_ukey(udpif, ukey, push, &ctx)) {
+    if (xlate_ukey(udpif, ukey, tcp_flags, &ctx)) {
         goto exit;
     }
     xoutp = &ctx.xout;
@@ -2019,24 +2044,21 @@ revalidate_ukey(struct udpif *udpif, struct udpif_key *ukey,
         goto exit;
     }
 
-    /* We will push the stats, so update the ukey stats cache. */
-    ukey->stats = *stats;
-    if (!push.n_packets && !need_revalidate) {
-        result = UKEY_KEEP;
-        goto exit;
-    }
-
-    if (ukey->xcache && !need_revalidate) {
-        xlate_push_stats(ukey->xcache, &push);
-        result = UKEY_KEEP;
-        goto exit;
+    if (!need_revalidate) {
+        if (!push.n_packets || ukey->xcache
+            || !populate_xcache(udpif, ukey, push.tcp_flags)) {
+            result = UKEY_KEEP;
+            goto exit;
+        }
     }
 
-    result = revalidate_ukey__(udpif, ukey, &push, odp_actions, reval_seq,
-                               recircs);
-
+    result = revalidate_ukey__(udpif, ukey, push.tcp_flags, odp_actions,
+                               reval_seq, recircs);
 exit:
+    /* Stats for deleted flows will be attributed upon flow deletion. Skip. */
     if (result != UKEY_DELETE) {
+        xlate_push_stats(ukey->xcache, &push);
+        ukey->stats = *stats;
         ukey->reval_seq = reval_seq;
     }
     return result;