LXR linux/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
  17static LIST_HEAD(fscache_netfs_list);
  18
  19/*
  20 * register a network filesystem for caching
  21 */
  22int __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
  71already_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}
  80EXPORT_SYMBOL(__fscache_register_netfs);
  81
  82/*
  83 * unregister a network filesystem from the cache
  84 * - all cookies must have been released first
  85 */
  86void __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}
 102EXPORT_SYMBOL(__fscache_unregister_netfs);
 103