ethtool: refactor checking max channels

Currently ethtool_set_channel calls separate functions to check whether
the new channel number violates rss configuration or flow steering
configuration.

Very soon we need to check whether the new channel number violates
memory provider configuration as well.

To do all 3 checks cleanly, add a wrapper around
ethtool_get_max_rxnfc_channel() and ethtool_get_max_rxfh_channel(),
which does both checks. We can later extend this wrapper to add the
memory provider check in one place.

Note that in the current code, we put a descriptive genl error message
when we run into issues. To preserve the error message, we pass the
genl_info* to the common helper. The ioctl calls can pass NULL instead.
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20240808205345.2141858-1-almasrymina@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ethtool/channels.c

@@ -114,8 +114,7 @@ ethnl_set_channels(struct ethnl_req_info *req_info, struct genl_info *info)
 	struct net_device *dev = req_info->dev;
 	struct ethtool_channels channels = {};
 	struct nlattr **tb = info->attrs;
-	u32 err_attr, max_rxfh_in_use;
-	u64 max_rxnfc_in_use;
+	u32 err_attr;
 	int ret;
 
 	dev->ethtool_ops->get_channels(dev, &channels);
@@ -166,20 +165,9 @@ ethnl_set_channels(struct ethnl_req_info *req_info, struct genl_info *info)
 		return -EINVAL;
 	}
 
-	/* ensure the new Rx count fits within the configured Rx flow
-	 * indirection table/rxnfc settings
-	 */
-	if (ethtool_get_max_rxnfc_channel(dev, &max_rxnfc_in_use))
-		max_rxnfc_in_use = 0;
-	max_rxfh_in_use = ethtool_get_max_rxfh_channel(dev);
-	if (channels.combined_count + channels.rx_count <= max_rxfh_in_use) {
-		GENL_SET_ERR_MSG_FMT(info, "requested channel counts are too low for existing indirection table (%d)", max_rxfh_in_use);
-		return -EINVAL;
-	}
-	if (channels.combined_count + channels.rx_count <= max_rxnfc_in_use) {
-		GENL_SET_ERR_MSG(info, "requested channel counts are too low for existing ntuple filter settings");
-		return -EINVAL;
-	}
+	ret = ethtool_check_max_channel(dev, channels, info);
+	if (ret)
+		return ret;
 
 	/* Disabling channels, query zero-copy AF_XDP sockets */
 	from_channel = channels.combined_count +

net/ethtool/common.c

@@ -6,6 +6,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/ptp_clock_kernel.h>
 
+#include "netlink.h"
 #include "common.h"
 
 const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
@@ -539,7 +540,7 @@ static int ethtool_get_rxnfc_rule_count(struct net_device *dev)
 	return info.rule_cnt;
 }
 
-int ethtool_get_max_rxnfc_channel(struct net_device *dev, u64 *max)
+static int ethtool_get_max_rxnfc_channel(struct net_device *dev, u64 *max)
 {
 	const struct ethtool_ops *ops = dev->ethtool_ops;
 	struct ethtool_rxnfc *info;
@@ -609,7 +610,7 @@ static u32 ethtool_get_max_rss_ctx_channel(struct net_device *dev)
 	return max_ring;
 }
 
-u32 ethtool_get_max_rxfh_channel(struct net_device *dev)
+static u32 ethtool_get_max_rxfh_channel(struct net_device *dev)
 {
 	struct ethtool_rxfh_param rxfh = {};
 	u32 dev_size, current_max;
@@ -650,6 +651,33 @@ u32 ethtool_get_max_rxfh_channel(struct net_device *dev)
 	return current_max;
 }
 
+int ethtool_check_max_channel(struct net_device *dev,
+			      struct ethtool_channels channels,
+			      struct genl_info *info)
+{
+	u64 max_rxnfc_in_use;
+	u32 max_rxfh_in_use;
+
+	/* ensure the new Rx count fits within the configured Rx flow
+	 * indirection table/rxnfc settings
+	 */
+	if (ethtool_get_max_rxnfc_channel(dev, &max_rxnfc_in_use))
+		max_rxnfc_in_use = 0;
+	max_rxfh_in_use = ethtool_get_max_rxfh_channel(dev);
+	if (channels.combined_count + channels.rx_count <= max_rxfh_in_use) {
+		if (info)
+			GENL_SET_ERR_MSG_FMT(info, "requested channel counts are too low for existing indirection table (%d)", max_rxfh_in_use);
+		return -EINVAL;
+	}
+	if (channels.combined_count + channels.rx_count <= max_rxnfc_in_use) {
+		if (info)
+			GENL_SET_ERR_MSG(info, "requested channel counts are too low for existing ntuple filter settings");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 int ethtool_check_ops(const struct ethtool_ops *ops)
 {
 	if (WARN_ON(ops->set_coalesce && !ops->supported_coalesce_params))

net/ethtool/common.h

@@ -20,6 +20,8 @@ struct link_mode_info {
 	u8				duplex;
 };
 
+struct genl_info;
+
 extern const char
 netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN];
 extern const char
@@ -42,8 +44,9 @@ int __ethtool_get_link(struct net_device *dev);
 bool convert_legacy_settings_to_link_ksettings(
 	struct ethtool_link_ksettings *link_ksettings,
 	const struct ethtool_cmd *legacy_settings);
-u32 ethtool_get_max_rxfh_channel(struct net_device *dev);
-int ethtool_get_max_rxnfc_channel(struct net_device *dev, u64 *max);
+int ethtool_check_max_channel(struct net_device *dev,
+			      struct ethtool_channels channels,
+			      struct genl_info *info);
 int __ethtool_get_ts_info(struct net_device *dev, struct kernel_ethtool_ts_info *info);
 
 extern const struct ethtool_phy_ops *ethtool_phy_ops;

net/ethtool/ioctl.c

@@ -2069,8 +2069,6 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 {
 	struct ethtool_channels channels, curr = { .cmd = ETHTOOL_GCHANNELS };
 	u16 from_channel, to_channel;
-	u64 max_rxnfc_in_use;
-	u32 max_rxfh_in_use;
 	unsigned int i;
 	int ret;
 
@@ -2100,14 +2098,9 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 	    (!channels.rx_count || !channels.tx_count))
 		return -EINVAL;
 
-	/* ensure the new Rx count fits within the configured Rx flow
-	 * indirection table/rxnfc settings */
-	if (ethtool_get_max_rxnfc_channel(dev, &max_rxnfc_in_use))
-		max_rxnfc_in_use = 0;
-	max_rxfh_in_use = ethtool_get_max_rxfh_channel(dev);
-	if (channels.combined_count + channels.rx_count <=
-	    max_t(u64, max_rxnfc_in_use, max_rxfh_in_use))
-		return -EINVAL;
+	ret = ethtool_check_max_channel(dev, channels, NULL);
+	if (ret)
+		return ret;
 
 	/* Disabling channels, query zero-copy AF_XDP sockets */
 	from_channel = channels.combined_count +