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>

7 files changed, 7 insertions, 7 deletions

diff --git a/fs/lockd/netns.h b/fs/lockd/netns.h
index 5426189406c1..fb8cac88251a 100644
--- a/fs/lockd/netns.h
+++ b/fs/lockd/netns.h
@@ -15,6 +15,6 @@ struct lockd_net {
 	struct list_head nsm_handles;
 };
 
-extern int lockd_net_id;
+extern unsigned int lockd_net_id;
 
 #endif
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index fc4084ef4736..1c13dd80744f 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -57,7 +57,7 @@ static struct task_struct	*nlmsvc_task;
 static struct svc_rqst		*nlmsvc_rqst;
 unsigned long			nlmsvc_timeout;
 
-int lockd_net_id;
+unsigned int lockd_net_id;
 
 /*
  * These can be set at insmod time (useful for NFS as root filesystem),
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index bf4ec5ecc97e..ce42dd00e4ee 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -2015,7 +2015,7 @@ static void nfsiod_stop(void)
 	destroy_workqueue(wq);
 }
 
-int nfs_net_id;
+unsigned int nfs_net_id;
 EXPORT_SYMBOL_GPL(nfs_net_id);
 
 static int nfs_net_init(struct net *net)
diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h
index fbce0d885d4c..5fbd2bde91ba 100644
--- a/fs/nfs/netns.h
+++ b/fs/nfs/netns.h
@@ -35,6 +35,6 @@ struct nfs_net {
 #endif
 };
 
-extern int nfs_net_id;
+extern unsigned int nfs_net_id;
 
 #endif
diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
index fd8c9a5bcac4..420d3a0ab258 100644
--- a/fs/nfs_common/grace.c
+++ b/fs/nfs_common/grace.c
@@ -9,7 +9,7 @@
 #include <net/netns/generic.h>
 #include <linux/fs.h>
 
-static int grace_net_id;
+static unsigned int grace_net_id;
 static DEFINE_SPINLOCK(grace_lock);
 
 /**
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index ee36efd5aece..3714231a9d0f 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -124,5 +124,5 @@ struct nfsd_net {
 /* Simple check to find out if a given net was properly initialized */
 #define nfsd_netns_ready(nn) ((nn)->sessionid_hashtbl)
 
-extern int nfsd_net_id;
+extern unsigned int nfsd_net_id;
 #endif /* __NFSD_NETNS_H__ */
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 36b2af931e06..2857e46d5cc5 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1201,7 +1201,7 @@ static int create_proc_exports_entry(void)
 }
 #endif
 
-int nfsd_net_id;
+unsigned int nfsd_net_id;
 
 static __net_init int nfsd_init_net(struct net *net)
 {