net: ethtool: take rss_lock for all rxfh changes

Always take the rss_lock in ethtool_set_rxfh(). We will want to
make a similar change in ethtool_set_rxfh_fields() and some
drivers lock that callback regardless of rss context ID being set.
Having some callbacks locked unconditionally and some only if
context ID is set would be very confusing.

ethtool handling is under rtnl_lock, so rss_lock is very unlikely
to ever be congested.

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ethtool/ioctl.c

···
 	}
 
 	rxfh_dev.hfunc = ETH_RSS_HASH_NO_CHANGE;
+
+	mutex_lock(&dev->ethtool->rss_lock);
 	ret = ops->set_rxfh(dev, &rxfh_dev, extack);
 	if (ret)
-		goto out;
+		goto out_unlock;
 
 	/* indicate whether rxfh was set to default */
 	if (user_size == 0)
···
 	else
 		dev->priv_flags |= IFF_RXFH_CONFIGURED;
 
+out_unlock:
+	mutex_unlock(&dev->ethtool->rss_lock);
 out:
 	kfree(rxfh_dev.indir);
 	return ret;
···
 	struct netlink_ext_ack *extack = NULL;
 	struct ethtool_rxnfc rx_rings;
 	struct ethtool_rxfh rxfh;
-	bool locked = false; /* dev->ethtool->rss_lock taken */
 	bool create = false;
 	bool mod = false;
 	u8 *rss_config;
···
 	rx_rings.cmd = ETHTOOL_GRXRINGS;
 	ret = ops->get_rxnfc(dev, &rx_rings, NULL);
 	if (ret)
-		goto out;
+		goto out_free;
 
 	/* rxfh.indir_size == 0 means reset the indir table to default (master
 	 * context) or delete the context (other RSS contexts).
···
 						  &rx_rings,
 						  rxfh.indir_size);
 		if (ret)
-			goto out;
+			goto out_free;
 	} else if (rxfh.indir_size == 0) {
 		if (rxfh.rss_context == 0) {
 			u32 *indir;
···
 				   useraddr + rss_cfg_offset + user_indir_len,
 				   rxfh.key_size)) {
 			ret = -EFAULT;
-			goto out;
+			goto out_free;
 		}
 	}
 
-	if (rxfh.rss_context) {
-		mutex_lock(&dev->ethtool->rss_lock);
-		locked = true;
-	}
+	mutex_lock(&dev->ethtool->rss_lock);
 
 	if (rxfh.rss_context && rxfh_dev.rss_delete) {
 		ret = ethtool_check_rss_ctx_busy(dev, rxfh.rss_context);
 		if (ret)
-			goto out;
+			goto out_unlock;
 	}
 
 	if (create) {
 		if (rxfh_dev.rss_delete) {
 			ret = -EINVAL;
-			goto out;
+			goto out_unlock;
 		}
 		ctx = ethtool_rxfh_ctx_alloc(ops, dev_indir_size, dev_key_size);
 		if (!ctx) {
 			ret = -ENOMEM;
-			goto out;
+			goto out_unlock;
 		}
 
 		if (ops->create_rxfh_context) {
···
 				       GFP_KERNEL_ACCOUNT);
 			if (ret < 0) {
 				kfree(ctx);
-				goto out;
+				goto out_unlock;
 			}
 			WARN_ON(!ctx_id); /* can't happen */
 			rxfh.rss_context = ctx_id;
···
 		ctx = xa_load(&dev->ethtool->rss_ctx, rxfh.rss_context);
 		if (!ctx) {
 			ret = -ENOENT;
-			goto out;
+			goto out_unlock;
 		}
 	}
 	rxfh_dev.hfunc = rxfh.hfunc;
···
 				xa_erase(&dev->ethtool->rss_ctx, rxfh.rss_context);
 			kfree(ctx);
 		}
-		goto out;
+		goto out_unlock;
 	}
 	mod = !create && !rxfh_dev.rss_delete;
 
···
 		if (WARN_ON(xa_load(&dev->ethtool->rss_ctx, rxfh_dev.rss_context))) {
 			/* context ID reused, our tracking is screwed */
 			kfree(ctx);
-			goto out;
+			goto out_unlock;
 		}
 		/* Allocate the exact ID the driver gave us */
 		if (xa_is_err(xa_store(&dev->ethtool->rss_ctx, rxfh_dev.rss_context,
 				       ctx, GFP_KERNEL))) {
 			kfree(ctx);
-			goto out;
+			goto out_unlock;
 		}
 
 		/* Fetch the defaults for the old API, in the new API drivers
···
 		if (WARN_ON(ret)) {
 			xa_erase(&dev->ethtool->rss_ctx, rxfh.rss_context);
 			kfree(ctx);
-			goto out;
+			goto out_unlock;
 		}
 	}
 	if (rxfh_dev.rss_delete) {
···
 			ctx->input_xfrm = rxfh_dev.input_xfrm;
 	}
 
-out:
-	if (locked)
-		mutex_unlock(&dev->ethtool->rss_lock);
+out_unlock:
+	mutex_unlock(&dev->ethtool->rss_lock);
+out_free:
 	kfree(rss_config);
 	if (mod)
 		ethtool_rss_notify(dev, rxfh.rss_context);