kernel/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         int ret;
  26
  27         _enter("{%s}", netfs->name);
  28
  29         INIT_LIST_HEAD(&netfs->link);
  30
  31         /* allocate a cookie for the primary index */
  32         netfs->primary_index =
  33                 kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
  34
  35         if (!netfs->primary_index) {
  36                 _leave(" = -ENOMEM");
  37                 return -ENOMEM;
  38         }
  39
  40         /* initialise the primary index cookie */
  41         atomic_set(&netfs->primary_index->usage, 1);
  42         atomic_set(&netfs->primary_index->n_children, 0);
  43         atomic_set(&netfs->primary_index->n_active, 1);
  44
  45         netfs->primary_index->def               = &fscache_fsdef_netfs_def;
  46         netfs->primary_index->parent            = &fscache_fsdef_index;
  47         netfs->primary_index->netfs_data        = netfs;
  48         netfs->primary_index->flags             = 1 << FSCACHE_COOKIE_ENABLED;
  49
  50         atomic_inc(&netfs->primary_index->parent->usage);
  51         atomic_inc(&netfs->primary_index->parent->n_children);
  52
  53         spin_lock_init(&netfs->primary_index->lock);
  54         INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);
  55
  56         /* check the netfs type is not already present */
  57         down_write(&fscache_addremove_sem);
  58
  59         ret = -EEXIST;
  60         list_for_each_entry(ptr, &fscache_netfs_list, link) {
  61                 if (strcmp(ptr->name, netfs->name) == 0)
  62                         goto already_registered;
  63         }
  64
  65         list_add(&netfs->link, &fscache_netfs_list);
  66         ret = 0;
  67
  68         pr_notice("Netfs '%s' registered for caching\n", netfs->name);
  69
  70 already_registered:
  71         up_write(&fscache_addremove_sem);
  72
  73         if (ret < 0) {
  74                 netfs->primary_index->parent = NULL;
  75                 __fscache_cookie_put(netfs->primary_index);
  76                 netfs->primary_index = NULL;
  77         }
  78
  79         _leave(" = %d", ret);
  80         return ret;
  81 }
  82 EXPORT_SYMBOL(__fscache_register_netfs);
  83
  84 /*
  85  * unregister a network filesystem from the cache
  86  * - all cookies must have been released first
  87  */
  88 void __fscache_unregister_netfs(struct fscache_netfs *netfs)
  89 {
  90         _enter("{%s.%u}", netfs->name, netfs->version);
  91
  92         down_write(&fscache_addremove_sem);
  93
  94         list_del(&netfs->link);
  95         fscache_relinquish_cookie(netfs->primary_index, 0);
  96
  97         up_write(&fscache_addremove_sem);
  98
  99         pr_notice("Netfs '%s' unregistered from caching\n",
 100                   netfs->name);
 101
 102         _leave("");
 103 }
 104 EXPORT_SYMBOL(__fscache_unregister_netfs);