netns: make struct pernet_operations::id unsigned int

Make struct pernet_operations::id unsigned.

There are 2 reasons to do so:

1)
This field is really an index into an zero based array and
thus is unsigned entity. Using negative value is out-of-bound
access by definition.

2)
On x86_64 unsigned 32-bit data which are mixed with pointers
via array indexing or offsets added or subtracted to pointers
are preffered to signed 32-bit data.

"int" being used as an array index needs to be sign-extended
to 64-bit before being used.

	void f(long *p, int i)
	{
		g(p[i]);
	}

  roughly translates to

	movsx	rsi, esi
	mov	rdi, [rsi+...]
	call 	g

MOVSX is 3 byte instruction which isn't necessary if the variable is
unsigned because x86_64 is zero extending by default.

Now, there is net_generic() function which, you guessed it right, uses
"int" as an array index:

	static inline void *net_generic(const struct net *net, int id)
	{
		...
		ptr = ng->ptr[id - 1];
		...
	}

And this function is used a lot, so those sign extensions add up.

Patch snipes ~1730 bytes on allyesconfig kernel (without all junk
messing with code generation):

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)

Unfortunately some functions actually grow bigger.
This is a semmingly random artefact of code generation with register
allocator being used differently. gcc decides that some variable
needs to live in new r8+ registers and every access now requires REX
prefix. Or it is shifted into r12, so [r12+0] addressing mode has to be
used which is longer than [r8]

However, overall balance is in negative direction:

	add/remove: 0/0 grow/shrink: 70/598 up/down: 396/-2126 (-1730)
	function                                     old     new   delta
	nfsd4_lock                                  3886    3959     +73
	tipc_link_build_proto_msg                   1096    1140     +44
	mac80211_hwsim_new_radio                    2776    2808     +32
	tipc_mon_rcv                                1032    1058     +26
	svcauth_gss_legacy_init                     1413    1429     +16
	tipc_bcbase_select_primary                   379     392     +13
	nfsd4_exchange_id                           1247    1260     +13
	nfsd4_setclientid_confirm                    782     793     +11
		...
	put_client_renew_locked                      494     480     -14
	ip_set_sockfn_get                            730     716     -14
	geneve_sock_add                              829     813     -16
	nfsd4_sequence_done                          721     703     -18
	nlmclnt_lookup_host                          708     686     -22
	nfsd4_lockt                                 1085    1063     -22
	nfs_get_client                              1077    1050     -27
	tcf_bpf_init                                1106    1076     -30
	nfsd4_encode_fattr                          5997    5930     -67
	Total: Before=154856051, After=154854321, chg -0.00%

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 5 insertions, 5 deletions

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 710bc79..75b6108 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -64,7 +64,7 @@ MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");
 #define IP6_GRE_HASH_SIZE_SHIFT  5
 #define IP6_GRE_HASH_SIZE (1 << IP6_GRE_HASH_SIZE_SHIFT)
 
-static int ip6gre_net_id __read_mostly;
+static unsigned int ip6gre_net_id __read_mostly;
 struct ip6gre_net {
 	struct ip6_tnl __rcu *tunnels[4][IP6_GRE_HASH_SIZE];
 
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 259e850..d3c619e 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -83,7 +83,7 @@ static int ip6_tnl_dev_init(struct net_device *dev);
 static void ip6_tnl_dev_setup(struct net_device *dev);
 static struct rtnl_link_ops ip6_link_ops __read_mostly;
 
-static int ip6_tnl_net_id __read_mostly;
+static unsigned int ip6_tnl_net_id __read_mostly;
 struct ip6_tnl_net {
 	/* the IPv6 tunnel fallback device */
 	struct net_device *fb_tnl_dev;
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index af3f0e0..c476bb8 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -64,7 +64,7 @@ static int vti6_dev_init(struct net_device *dev);
 static void vti6_dev_setup(struct net_device *dev);
 static struct rtnl_link_ops vti6_link_ops __read_mostly;
 
-static int vti6_net_id __read_mostly;
+static unsigned int vti6_net_id __read_mostly;
 struct vti6_net {
 	/* the vti6 tunnel fallback device */
 	struct net_device *fb_tnl_dev;
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index dc7a344..0355231 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -76,7 +76,7 @@ static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst,
 		      __be32 *v4dst);
 static struct rtnl_link_ops sit_link_ops __read_mostly;
 
-static int sit_net_id __read_mostly;
+static unsigned int sit_net_id __read_mostly;
 struct sit_net {
 	struct ip_tunnel __rcu *tunnels_r_l[IP6_SIT_HASH_SIZE];
 	struct ip_tunnel __rcu *tunnels_r[IP6_SIT_HASH_SIZE];
diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index e1c0bbe..d7b731a 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -44,7 +44,7 @@ struct xfrm6_tunnel_net {
 	u32 spi;
 };
 
-static int xfrm6_tunnel_net_id __read_mostly;
+static unsigned int xfrm6_tunnel_net_id __read_mostly;
 static inline struct xfrm6_tunnel_net *xfrm6_tunnel_pernet(struct net *net)
 {
 	return net_generic(net, xfrm6_tunnel_net_id);