/*
   * Copyright (C) 2003 Sistina Software.
   * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
   *
   * Module Author: Heinz Mauelshagen
   *
   * This file is released under the GPL.
   *
   * Path selector registration.
   */

  #include <linux/device-mapper.h>

  #include <linux/module.h>

  #include "dm-path-selector.h"
  
  #include <linux/slab.h>
  
  struct ps_internal {
  	struct path_selector_type pst;

  	struct list_head list;

  };
  
  #define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
  
  static LIST_HEAD(_path_selectors);
  static DECLARE_RWSEM(_ps_lock);

  static struct ps_internal *__find_path_selector_type(const char *name)

  {
  	struct ps_internal *psi;
  
  	list_for_each_entry(psi, &_path_selectors, list) {
  		if (!strcmp(name, psi->pst.name))
  			return psi;
  	}
  
  	return NULL;
  }
  
  static struct ps_internal *get_path_selector(const char *name)
  {
  	struct ps_internal *psi;
  
  	down_read(&_ps_lock);
  	psi = __find_path_selector_type(name);

  	if (psi && !try_module_get(psi->pst.module))
  		psi = NULL;

  	up_read(&_ps_lock);
  
  	return psi;
  }
  
  struct path_selector_type *dm_get_path_selector(const char *name)
  {
  	struct ps_internal *psi;
  
  	if (!name)
  		return NULL;
  
  	psi = get_path_selector(name);
  	if (!psi) {
  		request_module("dm-%s", name);
  		psi = get_path_selector(name);
  	}
  
  	return psi ? &psi->pst : NULL;
  }
  
  void dm_put_path_selector(struct path_selector_type *pst)
  {
  	struct ps_internal *psi;
  
  	if (!pst)
  		return;
  
  	down_read(&_ps_lock);
  	psi = __find_path_selector_type(pst->name);
  	if (!psi)
  		goto out;

  	module_put(psi->pst.module);

  out:
  	up_read(&_ps_lock);
  }
  
  static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
  {

  	struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);

  	if (psi)

  		psi->pst = *pst;

  
  	return psi;
  }
  
  int dm_register_path_selector(struct path_selector_type *pst)
  {
  	int r = 0;
  	struct ps_internal *psi = _alloc_path_selector(pst);
  
  	if (!psi)
  		return -ENOMEM;
  
  	down_write(&_ps_lock);
  
  	if (__find_path_selector_type(pst->name)) {
  		kfree(psi);
  		r = -EEXIST;
  	} else
  		list_add(&psi->list, &_path_selectors);
  
  	up_write(&_ps_lock);
  
  	return r;
  }
  
  int dm_unregister_path_selector(struct path_selector_type *pst)
  {
  	struct ps_internal *psi;
  
  	down_write(&_ps_lock);
  
  	psi = __find_path_selector_type(pst->name);
  	if (!psi) {
  		up_write(&_ps_lock);
  		return -EINVAL;
  	}

  	list_del(&psi->list);
  
  	up_write(&_ps_lock);
  
  	kfree(psi);
  
  	return 0;
  }
  
  EXPORT_SYMBOL_GPL(dm_register_path_selector);
  EXPORT_SYMBOL_GPL(dm_unregister_path_selector);