fs/fscache/netfs.c

   1 /* FS-Cache netfs (client) registration
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #define FSCACHE_DEBUG_LEVEL COOKIE
  13 #include <linux/module.h>
  14 #include <linux/slab.h>
  15 #include "internal.h"
  16
  17 static LIST_HEAD(fscache_netfs_list);
  18
  19 /*
  20  * register a network filesystem for caching
  21  */
  22 int __fscache_register_netfs(struct fscache_netfs *netfs)
  23 {
  24         struct fscache_netfs *ptr;
  25         struct fscache_cookie *cookie;
  26         int ret;
  27
  28         _enter("{%s}", netfs->name);
  29
  30         INIT_LIST_HEAD(&netfs->link);
  31
  32         /* allocate a cookie for the primary index */
  33         cookie = kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
  34
  35         if (!cookie) {
  36                 _leave(" = -ENOMEM");
  37                 return -ENOMEM;
  38         }
  39
  40         /* initialise the primary index cookie */
  41         atomic_set(&cookie->usage, 1);
  42         atomic_set(&cookie->n_children, 0);
  43         atomic_set(&cookie->n_active, 1);
  44
  45         cookie->def             = &fscache_fsdef_netfs_def;
  46         cookie->parent          = &fscache_fsdef_index;
  47         cookie->netfs_data      = netfs;
  48         cookie->flags           = 1 << FSCACHE_COOKIE_ENABLED;
  49
  50         spin_lock_init(&cookie->lock);
  51         INIT_HLIST_HEAD(&cookie->backing_objects);
  52
  53         /* check the netfs type is not already present */
  54         down_write(&fscache_addremove_sem);
  55
  56         ret = -EEXIST;
  57         list_for_each_entry(ptr, &fscache_netfs_list, link) {
  58                 if (strcmp(ptr->name, netfs->name) == 0)
  59                         goto already_registered;
  60         }
  61
  62         atomic_inc(&cookie->parent->usage);
  63         atomic_inc(&cookie->parent->n_children);
  64
  65         netfs->primary_index = cookie;
  66         list_add(&netfs->link, &fscache_netfs_list);
  67         ret = 0;
  68
  69         pr_notice("Netfs '%s' registered for caching\n", netfs->name);
  70
  71 already_registered:
  72         up_write(&fscache_addremove_sem);
  73
  74         if (ret < 0)
  75                 kmem_cache_free(fscache_cookie_jar, cookie);
  76
  77         _leave(" = %d", ret);
  78         return ret;
  79 }
  80 EXPORT_SYMBOL(__fscache_register_netfs);
  81
  82 /*
  83  * unregister a network filesystem from the cache
  84  * - all cookies must have been released first
  85  */
  86 void __fscache_unregister_netfs(struct fscache_netfs *netfs)
  87 {
  88         _enter("{%s.%u}", netfs->name, netfs->version);
  89
  90         down_write(&fscache_addremove_sem);
  91
  92         list_del(&netfs->link);
  93         fscache_relinquish_cookie(netfs->primary_index, 0);
  94
  95         up_write(&fscache_addremove_sem);
  96
  97         pr_notice("Netfs '%s' unregistered from caching\n",
  98                   netfs->name);
  99
 100         _leave("");
 101 }
 102 EXPORT_SYMBOL(__fscache_unregister_netfs);