[INET]: Generalise tcp_tw_bucket, aka TIME_WAIT sockets

This paves the way to generalise the rest of the sock ID lookup
routines and saves some bytes in TCPv4 TIME_WAIT sockets on distro
kernels (where IPv6 is always built as a module):

[root@qemu ~]# grep tw_sock /proc/slabinfo
tw_sock_TCPv6  0  0  128  31  1
tw_sock_TCP    0  0   96  41  1
[root@qemu ~]#

Now if a protocol wants to use the TIME_WAIT generic infrastructure it
only has to set the sk_prot->twsk_obj_size field with the size of its
inet_timewait_sock derived sock and proto_register will create
sk_prot->twsk_slab, for now its only for INET sockets, but we can
introduce timewait_sock later if some non INET transport protocolo
wants to use this stuff.

Next changesets will take advantage of this new infrastructure to
generalise even more TCP code.

[acme@toy net-2.6.14]$ grep built-in /tmp/before.size /tmp/after.size
/tmp/before.size: 188646   11764    5068  205478   322a6 net/ipv4/built-in.o
/tmp/after.size:  188144   11764    5068  204976   320b0 net/ipv4/built-in.o
[acme@toy net-2.6.14]$

Tested with both IPv4 & IPv6 (::1 (localhost) & ::ffff:172.20.0.1
(qemu host)).

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 34 insertions, 1 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index a1a23be..aba31fe 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1378,7 +1378,8 @@ static LIST_HEAD(proto_list);
 
 int proto_register(struct proto *prot, int alloc_slab)
 {
-	char *request_sock_slab_name;
+	char *request_sock_slab_name = NULL;
+	char *timewait_sock_slab_name;
 	int rc = -ENOBUFS;
 
 	if (alloc_slab) {
@@ -1409,6 +1410,23 @@ int proto_register(struct proto *prot, int alloc_slab)
 				goto out_free_request_sock_slab_name;
 			}
 		}
+
+		if (prot->twsk_obj_size) {
+			static const char mask[] = "tw_sock_%s";
+
+			timewait_sock_slab_name = kmalloc(strlen(prot->name) + sizeof(mask) - 1, GFP_KERNEL);
+
+			if (timewait_sock_slab_name == NULL)
+				goto out_free_request_sock_slab;
+
+			sprintf(timewait_sock_slab_name, mask, prot->name);
+			prot->twsk_slab = kmem_cache_create(timewait_sock_slab_name,
+							    prot->twsk_obj_size,
+							    0, SLAB_HWCACHE_ALIGN,
+							    NULL, NULL);
+			if (prot->twsk_slab == NULL)
+				goto out_free_timewait_sock_slab_name;
+		}
 	}
 
 	write_lock(&proto_list_lock);
@@ -1417,6 +1435,13 @@ int proto_register(struct proto *prot, int alloc_slab)
 	rc = 0;
 out:
 	return rc;
+out_free_timewait_sock_slab_name:
+	kfree(timewait_sock_slab_name);
+out_free_request_sock_slab:
+	if (prot->rsk_prot && prot->rsk_prot->slab) {
+		kmem_cache_destroy(prot->rsk_prot->slab);
+		prot->rsk_prot->slab = NULL;
+	}
 out_free_request_sock_slab_name:
 	kfree(request_sock_slab_name);
 out_free_sock_slab:
@@ -1444,6 +1469,14 @@ void proto_unregister(struct proto *prot)
 		prot->rsk_prot->slab = NULL;
 	}
 
+	if (prot->twsk_slab != NULL) {
+		const char *name = kmem_cache_name(prot->twsk_slab);
+
+		kmem_cache_destroy(prot->twsk_slab);
+		kfree(name);
+		prot->twsk_slab = NULL;
+	}
+
 	list_del(&prot->node);
 	write_unlock(&proto_list_lock);
 }