ipn/ipn_msgbuf.c

   1 /*
   2  * Inter process networking (virtual distributed ethernet) module
   3  * management of ipn_msgbuf (one slab for each MTU)
   4  *  (part of the View-OS project: wiki.virtualsquare.org)
   5  *
   6  * N.B. all these functions need global locking! (ipn_glob_lock)
   7  *
   8  * Copyright (C) 2007   Renzo Davoli (renzo@cs.unibo.it)
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License as published by
  12  *  the Free Software Foundation; either version 2 of the License, or
  13  *  (at your option) any later version.
  14  *
  15  *  Due to this file being licensed under the GPL there is controversy over
  16  *  whether this permits you to write a module that #includes this file
  17  *  without placing your module under the GPL.  Please consult a lawyer for
  18  *  advice before doing this.
  19  *
  20  * WARNING: THIS CODE IS ALREADY EXPERIMENTAL
  21  *
  22  */
  23
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26
  27 #include "af_ipn.h"
  28 #include "ipn_netdev.h"
  29
  30 struct ipn_msgbuf {
  31         struct list_head list;
  32         int mtu;
  33         int refcnt;
  34         char cachename[12];
  35         struct kmem_cache *cache;
  36 };
  37
  38 static LIST_HEAD(ipn_msgbufh);
  39 static struct kmem_cache *ipn_msgbuf_cache;
  40
  41 /* get a kmem_cache pointer for a given mtu.
  42  * it is a cache for struct msgpool_item elements (the latter field of
  43  * the struct, i.e. the payload, has variable length depending on the mtu)
  44  * if it exists already a cache with the given mtu, ipn_msgbuf_get creates
  45  * one more reference for that cache, otherwise a new one is created.
  46  */
  47 struct kmem_cache *ipn_msgbuf_get(int mtu)
  48 {
  49         struct ipn_msgbuf *ipn_msgbuf;
  50         list_for_each_entry(ipn_msgbuf, &ipn_msgbufh, list) {
  51                 if (mtu == ipn_msgbuf->mtu) {
  52                         ipn_msgbuf->refcnt++;
  53                         return ipn_msgbuf->cache;
  54                 }
  55         }
  56         ipn_msgbuf=kmem_cache_alloc(ipn_msgbuf_cache,GFP_KERNEL);
  57         if (ipn_msgbuf == NULL)
  58                 return NULL;
  59         else {
  60                 ipn_msgbuf->mtu=mtu;
  61                 ipn_msgbuf->refcnt=1;
  62                 snprintf(ipn_msgbuf->cachename,12,"ipn%d",mtu);
  63                 ipn_msgbuf->cache=kmem_cache_create(ipn_msgbuf->cachename,sizeof(struct msgpool_item)+mtu,0,0,NULL);
  64                 list_add_tail(&ipn_msgbuf->list,&ipn_msgbufh);
  65                 return ipn_msgbuf->cache;
  66         }
  67 }
  68
  69 /* release a reference of a msgbuf cache (a network with a given mtu
  70  * is terminating).
  71  * the last reference for a given mtu releases the slub*/
  72 void ipn_msgbuf_put(struct kmem_cache *cache)
  73 {
  74         struct ipn_msgbuf *ipn_msgbuf;
  75         list_for_each_entry(ipn_msgbuf, &ipn_msgbufh, list) {
  76                 if (ipn_msgbuf->cache == cache) {
  77                         ipn_msgbuf->refcnt--;
  78                         if (ipn_msgbuf->refcnt == 0) {
  79                                 kmem_cache_destroy(ipn_msgbuf->cache);
  80                                 list_del(&ipn_msgbuf->list);
  81                                 kmem_cache_free(ipn_msgbuf_cache,ipn_msgbuf);
  82                                 return;
  83                         }
  84                 }
  85         }
  86 }
  87
  88 int ipn_msgbuf_init(void)
  89 {
  90         ipn_msgbuf_cache=kmem_cache_create("ipn_msgbuf",sizeof(struct ipn_msgbuf),0,0,NULL);
  91         if (!ipn_msgbuf_cache)
  92                 return -ENOMEM;
  93         else
  94                 return 0;
  95 }
  96
  97 void ipn_msgbuf_fini(void)
  98 {
  99         if (ipn_msgbuf_cache) {
 100                 while (!list_empty(&ipn_msgbufh)) {
 101                         struct ipn_msgbuf *ipn_msgbuf=list_first_entry(&ipn_msgbufh, struct ipn_msgbuf, list);
 102                         list_del(&ipn_msgbuf->list);
 103                         kmem_cache_destroy(ipn_msgbuf->cache);
 104                         kmem_cache_free(ipn_msgbuf_cache,ipn_msgbuf);
 105                 }
 106                 kmem_cache_destroy(ipn_msgbuf_cache);
 107         }
 108 }