ethtool: reduce stack usage with clang

clang inlines the dev_ethtool() more aggressively than gcc does, leading
to a larger amount of used stack space:

net/core/ethtool.c:2536:24: error: stack frame size of 1216 bytes in function 'dev_ethtool' [-Werror,-Wframe-larger-than=]

Marking the sub-functions that require the most stack space as
noinline_for_stack gives us reasonable behavior on all compilers.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/ethtool.c

@@ -2319,7 +2319,8 @@ static int ethtool_set_tunable(struct net_device *dev, void __user *useraddr)
 	return ret;
 }
 
-static int ethtool_get_per_queue_coalesce(struct net_device *dev,
+static noinline_for_stack int
+ethtool_get_per_queue_coalesce(struct net_device *dev,
 			       void __user *useraddr,
 			       struct ethtool_per_queue_op *per_queue_opt)
 {
@@ -2349,7 +2350,8 @@ static int ethtool_get_per_queue_coalesce(struct net_device *dev,
 	return 0;
 }
 
-static int ethtool_set_per_queue_coalesce(struct net_device *dev,
+static noinline_for_stack int
+ethtool_set_per_queue_coalesce(struct net_device *dev,
 			       void __user *useraddr,
 			       struct ethtool_per_queue_op *per_queue_opt)
 {
@@ -2405,7 +2407,7 @@ static int ethtool_set_per_queue_coalesce(struct net_device *dev,
 	return ret;
 }
 
-static int ethtool_set_per_queue(struct net_device *dev,
+static int noinline_for_stack ethtool_set_per_queue(struct net_device *dev,
 				 void __user *useraddr, u32 sub_cmd)
 {
 	struct ethtool_per_queue_op per_queue_opt;