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kernel/linux-imx6_3.14.28/fs/fscache/netfs.c 2.71 KB
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  /* FS-Cache netfs (client) registration
   *
   * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #define FSCACHE_DEBUG_LEVEL COOKIE
  #include <linux/module.h>
  #include <linux/slab.h>
  #include "internal.h"
  
  static LIST_HEAD(fscache_netfs_list);
  
  /*
   * register a network filesystem for caching
   */
  int __fscache_register_netfs(struct fscache_netfs *netfs)
  {
  	struct fscache_netfs *ptr;
  	int ret;
  
  	_enter("{%s}", netfs->name);
  
  	INIT_LIST_HEAD(&netfs->link);
  
  	/* allocate a cookie for the primary index */
  	netfs->primary_index =
  		kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
  
  	if (!netfs->primary_index) {
  		_leave(" = -ENOMEM");
  		return -ENOMEM;
  	}
  
  	/* initialise the primary index cookie */
  	atomic_set(&netfs->primary_index->usage, 1);
  	atomic_set(&netfs->primary_index->n_children, 0);
  	atomic_set(&netfs->primary_index->n_active, 1);
  
  	netfs->primary_index->def		= &fscache_fsdef_netfs_def;
  	netfs->primary_index->parent		= &fscache_fsdef_index;
  	netfs->primary_index->netfs_data	= netfs;
  	netfs->primary_index->flags		= 1 << FSCACHE_COOKIE_ENABLED;
  
  	atomic_inc(&netfs->primary_index->parent->usage);
  	atomic_inc(&netfs->primary_index->parent->n_children);
  
  	spin_lock_init(&netfs->primary_index->lock);
  	INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);
  
  	/* check the netfs type is not already present */
  	down_write(&fscache_addremove_sem);
  
  	ret = -EEXIST;
  	list_for_each_entry(ptr, &fscache_netfs_list, link) {
  		if (strcmp(ptr->name, netfs->name) == 0)
  			goto already_registered;
  	}
  
  	list_add(&netfs->link, &fscache_netfs_list);
  	ret = 0;
  
  	printk(KERN_NOTICE "FS-Cache: Netfs '%s' registered for caching
  ",
  	       netfs->name);
  
  already_registered:
  	up_write(&fscache_addremove_sem);
  
  	if (ret < 0) {
  		netfs->primary_index->parent = NULL;
  		__fscache_cookie_put(netfs->primary_index);
  		netfs->primary_index = NULL;
  	}
  
  	_leave(" = %d", ret);
  	return ret;
  }
  EXPORT_SYMBOL(__fscache_register_netfs);
  
  /*
   * unregister a network filesystem from the cache
   * - all cookies must have been released first
   */
  void __fscache_unregister_netfs(struct fscache_netfs *netfs)
  {
  	_enter("{%s.%u}", netfs->name, netfs->version);
  
  	down_write(&fscache_addremove_sem);
  
  	list_del(&netfs->link);
  	fscache_relinquish_cookie(netfs->primary_index, 0);
  
  	up_write(&fscache_addremove_sem);
  
  	printk(KERN_NOTICE "FS-Cache: Netfs '%s' unregistered from caching
  ",
  	       netfs->name);
  
  	_leave("");
  }
  EXPORT_SYMBOL(__fscache_unregister_netfs);