mlxsw: spectrum_router: Use one LPM tree for all virtual routers

The number of LPM trees available for lookup is much smaller than the
number of virtual routers, which are used to implement VRFs. In
addition, an LPM tree can only be used by one protocol - either IPv4 or
IPv6.

Therefore, in order to increase the number of supported virtual routers
to the maximum we need to be able to share LPM trees across virtual
routers instead of trying to find an optimized tree for each.

Do that by allocating one LPM tree for each protocol, but make sure it
will only include prefixes that are actually used, so as to not perform
unnecessary lookups.

Since changing the structure of a bound tree isn't recommended, whenever
a new tree it required, it's first created and then bound to each
virtual router, replacing the old one.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -320,19 +320,6 @@ struct mlxsw_sp_prefix_usage {
 #define mlxsw_sp_prefix_usage_for_each(prefix, prefix_usage) \
 	for_each_set_bit(prefix, (prefix_usage)->b, MLXSW_SP_PREFIX_COUNT)
 
-static bool
-mlxsw_sp_prefix_usage_subset(struct mlxsw_sp_prefix_usage *prefix_usage1,
-			     struct mlxsw_sp_prefix_usage *prefix_usage2)
-{
-	unsigned char prefix;
-
-	mlxsw_sp_prefix_usage_for_each(prefix, prefix_usage1) {
-		if (!test_bit(prefix, prefix_usage2->b))
-			return false;
-	}
-	return true;
-}
-
 static bool
 mlxsw_sp_prefix_usage_eq(struct mlxsw_sp_prefix_usage *prefix_usage1,
 			 struct mlxsw_sp_prefix_usage *prefix_usage2)
@@ -589,16 +576,14 @@ mlxsw_sp_lpm_tree_get(struct mlxsw_sp *mlxsw_sp,
 		    lpm_tree->proto == proto &&
 		    mlxsw_sp_prefix_usage_eq(&lpm_tree->prefix_usage,
 					     prefix_usage))
-			goto inc_ref_count;
+			return lpm_tree;
 	}
-	lpm_tree = mlxsw_sp_lpm_tree_create(mlxsw_sp, prefix_usage,
-					    proto);
-	if (IS_ERR(lpm_tree))
-		return lpm_tree;
+	return mlxsw_sp_lpm_tree_create(mlxsw_sp, prefix_usage, proto);
+}
 
-inc_ref_count:
+static void mlxsw_sp_lpm_tree_hold(struct mlxsw_sp_lpm_tree *lpm_tree)
+{
 	lpm_tree->ref_count++;
-	return lpm_tree;
 }
 
 static void mlxsw_sp_lpm_tree_put(struct mlxsw_sp *mlxsw_sp,
@@ -750,46 +735,6 @@ static void mlxsw_sp_vr_destroy(struct mlxsw_sp_vr *vr)
 	vr->fib4 = NULL;
 }
 
-static int
-mlxsw_sp_vr_lpm_tree_check(struct mlxsw_sp *mlxsw_sp, struct mlxsw_sp_fib *fib,
-			   struct mlxsw_sp_prefix_usage *req_prefix_usage)
-{
-	struct mlxsw_sp_lpm_tree *lpm_tree = fib->lpm_tree;
-	struct mlxsw_sp_lpm_tree *new_tree;
-	int err;
-
-	if (mlxsw_sp_prefix_usage_eq(req_prefix_usage, &lpm_tree->prefix_usage))
-		return 0;
-
-	new_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, req_prefix_usage,
-					 fib->proto);
-	if (IS_ERR(new_tree)) {
-		/* We failed to get a tree according to the required
-		 * prefix usage. However, the current tree might be still good
-		 * for us if our requirement is subset of the prefixes used
-		 * in the tree.
-		 */
-		if (mlxsw_sp_prefix_usage_subset(req_prefix_usage,
-						 &lpm_tree->prefix_usage))
-			return 0;
-		return PTR_ERR(new_tree);
-	}
-
-	/* Prevent packet loss by overwriting existing binding */
-	fib->lpm_tree = new_tree;
-	err = mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, fib, new_tree->id);
-	if (err)
-		goto err_tree_bind;
-	mlxsw_sp_lpm_tree_put(mlxsw_sp, lpm_tree);
-
-	return 0;
-
-err_tree_bind:
-	fib->lpm_tree = lpm_tree;
-	mlxsw_sp_lpm_tree_put(mlxsw_sp, new_tree);
-	return err;
-}
-
 static struct mlxsw_sp_vr *mlxsw_sp_vr_get(struct mlxsw_sp *mlxsw_sp, u32 tb_id)
 {
 	struct mlxsw_sp_vr *vr;
@@ -808,6 +753,100 @@ static void mlxsw_sp_vr_put(struct mlxsw_sp_vr *vr)
 		mlxsw_sp_vr_destroy(vr);
 }
 
+static bool
+mlxsw_sp_vr_lpm_tree_should_replace(struct mlxsw_sp_vr *vr,
+				    enum mlxsw_sp_l3proto proto, u8 tree_id)
+{
+	struct mlxsw_sp_fib *fib = mlxsw_sp_vr_fib(vr, proto);
+
+	if (!mlxsw_sp_vr_is_used(vr))
+		return false;
+	if (fib->lpm_tree && fib->lpm_tree->id == tree_id)
+		return true;
+	return false;
+}
+
+static int mlxsw_sp_vr_lpm_tree_replace(struct mlxsw_sp *mlxsw_sp,
+					struct mlxsw_sp_fib *fib,
+					struct mlxsw_sp_lpm_tree *new_tree)
+{
+	struct mlxsw_sp_lpm_tree *old_tree = fib->lpm_tree;
+	int err;
+
+	err = mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, fib, new_tree->id);
+	if (err)
+		return err;
+	fib->lpm_tree = new_tree;
+	mlxsw_sp_lpm_tree_hold(new_tree);
+	mlxsw_sp_lpm_tree_put(mlxsw_sp, old_tree);
+	return 0;
+}
+
+static int mlxsw_sp_vrs_lpm_tree_replace(struct mlxsw_sp *mlxsw_sp,
+					 struct mlxsw_sp_fib *fib,
+					 struct mlxsw_sp_lpm_tree *new_tree)
+{
+	struct mlxsw_sp_lpm_tree *old_tree = fib->lpm_tree;
+	enum mlxsw_sp_l3proto proto = fib->proto;
+	u8 old_id, new_id = new_tree->id;
+	struct mlxsw_sp_vr *vr;
+	int i, err;
+
+	if (!old_tree)
+		goto no_replace;
+	old_id = old_tree->id;
+
+	for (i = 0; i < MLXSW_CORE_RES_GET(mlxsw_sp->core, MAX_VRS); i++) {
+		vr = &mlxsw_sp->router->vrs[i];
+		if (!mlxsw_sp_vr_lpm_tree_should_replace(vr, proto, old_id))
+			continue;
+		err = mlxsw_sp_vr_lpm_tree_replace(mlxsw_sp,
+						   mlxsw_sp_vr_fib(vr, proto),
+						   new_tree);
+		if (err)
+			goto err_tree_replace;
+	}
+
+	return 0;
+
+err_tree_replace:
+	for (i--; i >= 0; i--) {
+		if (!mlxsw_sp_vr_lpm_tree_should_replace(vr, proto, new_id))
+			continue;
+		mlxsw_sp_vr_lpm_tree_replace(mlxsw_sp,
+					     mlxsw_sp_vr_fib(vr, proto),
+					     old_tree);
+	}
+	return err;
+
+no_replace:
+	err = mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, fib, new_tree->id);
+	if (err)
+		return err;
+	fib->lpm_tree = new_tree;
+	mlxsw_sp_lpm_tree_hold(new_tree);
+	return 0;
+}
+
+static void
+mlxsw_sp_vrs_prefixes(struct mlxsw_sp *mlxsw_sp,
+		      enum mlxsw_sp_l3proto proto,
+		      struct mlxsw_sp_prefix_usage *req_prefix_usage)
+{
+	int i;
+
+	for (i = 0; i < MLXSW_CORE_RES_GET(mlxsw_sp->core, MAX_VRS); i++) {
+		struct mlxsw_sp_vr *vr = &mlxsw_sp->router->vrs[i];
+		struct mlxsw_sp_fib *fib = mlxsw_sp_vr_fib(vr, proto);
+		unsigned char prefix;
+
+		if (!mlxsw_sp_vr_is_used(vr))
+			continue;
+		mlxsw_sp_prefix_usage_for_each(prefix, &fib->prefix_usage)
+			mlxsw_sp_prefix_usage_set(req_prefix_usage, prefix);
+	}
+}
+
 static int mlxsw_sp_vrs_init(struct mlxsw_sp *mlxsw_sp)
 {
 	struct mlxsw_sp_vr *vr;
@@ -2586,6 +2625,67 @@ mlxsw_sp_fib_node_entry_is_first(const struct mlxsw_sp_fib_node *fib_node,
 				struct mlxsw_sp_fib_entry, list) == fib_entry;
 }
 
+static int mlxsw_sp_fib_lpm_tree_link(struct mlxsw_sp *mlxsw_sp,
+				      struct mlxsw_sp_fib *fib,
+				      struct mlxsw_sp_fib_node *fib_node)
+{
+	struct mlxsw_sp_prefix_usage req_prefix_usage = {{ 0 } };
+	struct mlxsw_sp_lpm_tree *lpm_tree;
+	int err;
+
+	/* Since the tree is shared between all virtual routers we must
+	 * make sure it contains all the required prefix lengths. This
+	 * can be computed by either adding the new prefix length to the
+	 * existing prefix usage of a bound tree, or by aggregating the
+	 * prefix lengths across all virtual routers and adding the new
+	 * one as well.
+	 */
+	if (fib->lpm_tree)
+		mlxsw_sp_prefix_usage_cpy(&req_prefix_usage,
+					  &fib->lpm_tree->prefix_usage);
+	else
+		mlxsw_sp_vrs_prefixes(mlxsw_sp, fib->proto, &req_prefix_usage);
+	mlxsw_sp_prefix_usage_set(&req_prefix_usage, fib_node->key.prefix_len);
+
+	lpm_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, &req_prefix_usage,
+					 fib->proto);
+	if (IS_ERR(lpm_tree))
+		return PTR_ERR(lpm_tree);
+
+	if (fib->lpm_tree && fib->lpm_tree->id == lpm_tree->id)
+		return 0;
+
+	err = mlxsw_sp_vrs_lpm_tree_replace(mlxsw_sp, fib, lpm_tree);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static void mlxsw_sp_fib_lpm_tree_unlink(struct mlxsw_sp *mlxsw_sp,
+					 struct mlxsw_sp_fib *fib)
+{
+	struct mlxsw_sp_prefix_usage req_prefix_usage = {{ 0 } };
+	struct mlxsw_sp_lpm_tree *lpm_tree;
+
+	/* Aggregate prefix lengths across all virtual routers to make
+	 * sure we only have used prefix lengths in the LPM tree.
+	 */
+	mlxsw_sp_vrs_prefixes(mlxsw_sp, fib->proto, &req_prefix_usage);
+	lpm_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, &req_prefix_usage,
+					 fib->proto);
+	if (IS_ERR(lpm_tree))
+		goto err_tree_get;
+	mlxsw_sp_vrs_lpm_tree_replace(mlxsw_sp, fib, lpm_tree);
+
+err_tree_get:
+	if (!mlxsw_sp_prefix_usage_none(&fib->prefix_usage))
+		return;
+	mlxsw_sp_vr_lpm_tree_unbind(mlxsw_sp, fib);
+	mlxsw_sp_lpm_tree_put(mlxsw_sp, fib->lpm_tree);
+	fib->lpm_tree = NULL;
+}
+
 static void mlxsw_sp_fib_node_prefix_inc(struct mlxsw_sp_fib_node *fib_node)
 {
 	unsigned char prefix_len = fib_node->key.prefix_len;
@@ -2608,8 +2708,6 @@ static int mlxsw_sp_fib_node_init(struct mlxsw_sp *mlxsw_sp,
 				  struct mlxsw_sp_fib_node *fib_node,
 				  struct mlxsw_sp_fib *fib)
 {
-	struct mlxsw_sp_prefix_usage req_prefix_usage;
-	struct mlxsw_sp_lpm_tree *lpm_tree;
 	int err;
 
 	err = mlxsw_sp_fib_node_insert(fib, fib_node);
@@ -2617,33 +2715,15 @@ static int mlxsw_sp_fib_node_init(struct mlxsw_sp *mlxsw_sp,
 		return err;
 	fib_node->fib = fib;
 
-	mlxsw_sp_prefix_usage_cpy(&req_prefix_usage, &fib->prefix_usage);
-	mlxsw_sp_prefix_usage_set(&req_prefix_usage, fib_node->key.prefix_len);
-
-	if (!mlxsw_sp_prefix_usage_none(&fib->prefix_usage)) {
-		err = mlxsw_sp_vr_lpm_tree_check(mlxsw_sp, fib,
-						 &req_prefix_usage);
-		if (err)
-			goto err_tree_check;
-	} else {
-		lpm_tree = mlxsw_sp_lpm_tree_get(mlxsw_sp, &req_prefix_usage,
-						 fib->proto);
-		if (IS_ERR(lpm_tree))
-			return PTR_ERR(lpm_tree);
-		fib->lpm_tree = lpm_tree;
-		err = mlxsw_sp_vr_lpm_tree_bind(mlxsw_sp, fib, lpm_tree->id);
-		if (err)
-			goto err_tree_bind;
-	}
+	err = mlxsw_sp_fib_lpm_tree_link(mlxsw_sp, fib, fib_node);
+	if (err)
+		goto err_fib_lpm_tree_link;
 
 	mlxsw_sp_fib_node_prefix_inc(fib_node);
 
 	return 0;
 
-err_tree_bind:
-	fib->lpm_tree = NULL;
-	mlxsw_sp_lpm_tree_put(mlxsw_sp, lpm_tree);
-err_tree_check:
+err_fib_lpm_tree_link:
 	fib_node->fib = NULL;
 	mlxsw_sp_fib_node_remove(fib, fib_node);
 	return err;
@@ -2652,19 +2732,10 @@ static int mlxsw_sp_fib_node_init(struct mlxsw_sp *mlxsw_sp,
 static void mlxsw_sp_fib_node_fini(struct mlxsw_sp *mlxsw_sp,
 				   struct mlxsw_sp_fib_node *fib_node)
 {
-	struct mlxsw_sp_lpm_tree *lpm_tree = fib_node->fib->lpm_tree;
 	struct mlxsw_sp_fib *fib = fib_node->fib;
 
 	mlxsw_sp_fib_node_prefix_dec(fib_node);
-
-	if (mlxsw_sp_prefix_usage_none(&fib->prefix_usage)) {
-		mlxsw_sp_vr_lpm_tree_unbind(mlxsw_sp, fib);
-		fib->lpm_tree = NULL;
-		mlxsw_sp_lpm_tree_put(mlxsw_sp, lpm_tree);
-	} else {
-		mlxsw_sp_vr_lpm_tree_check(mlxsw_sp, fib, &fib->prefix_usage);
-	}
-
+	mlxsw_sp_fib_lpm_tree_unlink(mlxsw_sp, fib);
 	fib_node->fib = NULL;
 	mlxsw_sp_fib_node_remove(fib, fib_node);
 }