[NET] Generalise TCP's struct open_request minisock infrastructure

Kept this first changeset minimal, without changing existing names to
ease peer review.

Basicaly tcp_openreq_alloc now receives the or_calltable, that in turn
has two new members:

->slab, that replaces tcp_openreq_cachep
->obj_size, to inform the size of the openreq descendant for
  a specific protocol

The protocol specific fields in struct open_request were moved to a
class hierarchy, with the things that are common to all connection
oriented PF_INET protocols in struct inet_request_sock, the TCP ones
in tcp_request_sock, that is an inet_request_sock, that is an
open_request.

I.e. this uses the same approach used for the struct sock class
hierarchy, with sk_prot indicating if the protocol wants to use the
open_request infrastructure by filling in sk_prot->rsk_prot with an
or_calltable.

Results? Performance is improved and TCP v4 now uses only 64 bytes per
open request minisock, down from 96 without this patch :-)

Next changeset will rename some of the structs, fields and functions
mentioned above, struct or_calltable is way unclear, better name it
struct request_sock_ops, s/struct open_request/struct request_sock/g,
etc.

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

1 files changed, 35 insertions, 0 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index 96e00b08698..a6ec3ada7f9 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -118,6 +118,7 @@
 #include <linux/netdevice.h>
 #include <net/protocol.h>
 #include <linux/skbuff.h>
+#include <net/request_sock.h>
 #include <net/sock.h>
 #include <net/xfrm.h>
 #include <linux/ipsec.h>
@@ -1363,6 +1364,7 @@ static LIST_HEAD(proto_list);
 
 int proto_register(struct proto *prot, int alloc_slab)
 {
+        char *request_sock_slab_name;
         int rc = -ENOBUFS;
 
         if (alloc_slab) {
@@ -1374,6 +1376,25 @@ int proto_register(struct proto *prot, int alloc_slab)
                                prot->name);
                         goto out;
                 }
+
+                if (prot->rsk_prot != NULL) {
+                        static const char mask[] = "request_sock_%s";
+
+                        request_sock_slab_name = kmalloc(strlen(prot->name) + sizeof(mask) - 1, GFP_KERNEL);
+                        if (request_sock_slab_name == NULL)
+                                goto out_free_sock_slab;
+
+                        sprintf(request_sock_slab_name, mask, prot->name);
+                        prot->rsk_prot->slab = kmem_cache_create(request_sock_slab_name,
+                                                                 prot->rsk_prot->obj_size, 0,
+                                                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
+
+                        if (prot->rsk_prot->slab == NULL) {
+                                printk(KERN_CRIT "%s: Can't create request sock SLAB cache!\n",
+                                       prot->name);
+                                goto out_free_request_sock_slab_name;
+                        }
+                }
         }
 
         write_lock(&proto_list_lock);
@@ -1382,6 +1403,12 @@ int proto_register(struct proto *prot, int alloc_slab)
         rc = 0;
 out:
         return rc;
+out_free_request_sock_slab_name:
+        kfree(request_sock_slab_name);
+out_free_sock_slab:
+        kmem_cache_destroy(prot->slab);
+        prot->slab = NULL;
+        goto out;
 }
 
 EXPORT_SYMBOL(proto_register);
@@ -1395,6 +1422,14 @@ void proto_unregister(struct proto *prot)
                 prot->slab = NULL;
         }
 
+        if (prot->rsk_prot != NULL && prot->rsk_prot->slab != NULL) {
+                const char *name = kmem_cache_name(prot->rsk_prot->slab);
+
+                kmem_cache_destroy(prot->rsk_prot->slab);
+                kfree(name);
+                prot->rsk_prot->slab = NULL;
+        }
+
         list_del(&prot->node);
         write_unlock(&proto_list_lock);
 }