/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * symlink.c - operations for configfs symlinks.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  #include <linux/fs.h>
  #include <linux/module.h>
  #include <linux/namei.h>

  #include <linux/slab.h>

  
  #include <linux/configfs.h>
  #include "configfs_internal.h"

  /* Protects attachments of new symlinks */
  DEFINE_MUTEX(configfs_symlink_mutex);

  static int item_depth(struct config_item * item)
  {
  	struct config_item * p = item;
  	int depth = 0;
  	do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
  	return depth;
  }
  
  static int item_path_length(struct config_item * item)
  {
  	struct config_item * p = item;
  	int length = 1;
  	do {
  		length += strlen(config_item_name(p)) + 1;
  		p = p->ci_parent;
  	} while (p && !configfs_is_root(p));
  	return length;
  }
  
  static void fill_item_path(struct config_item * item, char * buffer, int length)
  {
  	struct config_item * p;
  
  	--length;
  	for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
  		int cur = strlen(config_item_name(p));
  
  		/* back up enough to print this bus id with '/' */
  		length -= cur;
  		strncpy(buffer + length,config_item_name(p),cur);
  		*(buffer + --length) = '/';
  	}
  }
  
  static int create_link(struct config_item *parent_item,

  		       struct config_item *item,

  		       struct dentry *dentry)
  {
  	struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
  	struct configfs_symlink *sl;
  	int ret;

  	ret = -ENOENT;
  	if (!configfs_dirent_is_ready(target_sd))
  		goto out;

  	ret = -ENOMEM;
  	sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
  	if (sl) {
  		sl->sl_target = config_item_get(item);

  		spin_lock(&configfs_dirent_lock);

  		if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
  			spin_unlock(&configfs_dirent_lock);
  			config_item_put(item);
  			kfree(sl);
  			return -ENOENT;
  		}

  		list_add(&sl->sl_list, &target_sd->s_links);

  		spin_unlock(&configfs_dirent_lock);

  		ret = configfs_create_link(sl, parent_item->ci_dentry,
  					   dentry);
  		if (ret) {

  			spin_lock(&configfs_dirent_lock);

  			list_del_init(&sl->sl_list);

  			spin_unlock(&configfs_dirent_lock);

  			config_item_put(item);
  			kfree(sl);
  		}
  	}

  out:

  	return ret;
  }

  static int get_target(const char *symname, struct path *path,

  		      struct config_item **target)
  {
  	int ret;

  	ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);

  	if (!ret) {

  		if (path->dentry->d_sb == configfs_sb) {
  			*target = configfs_get_config_item(path->dentry);

  			if (!*target) {
  				ret = -ENOENT;

  				path_put(path);

  			}

  		} else {

  			ret = -EPERM;

  			path_put(path);
  		}

  	}
  
  	return ret;
  }
  
  
  int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
  {
  	int ret;

  	struct path path;

  	struct configfs_dirent *sd;

  	struct config_item *parent_item;

  	struct config_item *target_item = NULL;

  	struct config_item_type *type;
  
  	ret = -EPERM;  /* What lack-of-symlink returns */
  	if (dentry->d_parent == configfs_sb->s_root)
  		goto out;

  	sd = dentry->d_parent->d_fsdata;
  	/*
  	 * Fake invisibility if dir belongs to a group/default groups hierarchy
  	 * being attached
  	 */
  	ret = -ENOENT;
  	if (!configfs_dirent_is_ready(sd))
  		goto out;

  	parent_item = configfs_get_config_item(dentry->d_parent);
  	type = parent_item->ci_type;

  	ret = -EPERM;

  	if (!type || !type->ct_item_ops ||
  	    !type->ct_item_ops->allow_link)
  		goto out_put;

  	ret = get_target(symname, &path, &target_item);

  	if (ret)
  		goto out_put;
  
  	ret = type->ct_item_ops->allow_link(parent_item, target_item);

  	if (!ret) {

  		mutex_lock(&configfs_symlink_mutex);

  		ret = create_link(parent_item, target_item, dentry);

  		mutex_unlock(&configfs_symlink_mutex);

  		if (ret && type->ct_item_ops->drop_link)
  			type->ct_item_ops->drop_link(parent_item,
  						     target_item);
  	}

  
  	config_item_put(target_item);

  	path_put(&path);

  
  out_put:
  	config_item_put(parent_item);
  
  out:
  	return ret;
  }
  
  int configfs_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct configfs_dirent *sd = dentry->d_fsdata;
  	struct configfs_symlink *sl;
  	struct config_item *parent_item;
  	struct config_item_type *type;
  	int ret;
  
  	ret = -EPERM;  /* What lack-of-symlink returns */
  	if (!(sd->s_type & CONFIGFS_ITEM_LINK))
  		goto out;

  	BUG_ON(dentry->d_parent == configfs_sb->s_root);

  
  	sl = sd->s_element;
  
  	parent_item = configfs_get_config_item(dentry->d_parent);
  	type = parent_item->ci_type;

  	spin_lock(&configfs_dirent_lock);

  	list_del_init(&sd->s_sibling);

  	spin_unlock(&configfs_dirent_lock);

  	configfs_drop_dentry(sd, dentry->d_parent);
  	dput(dentry);
  	configfs_put(sd);
  
  	/*
  	 * drop_link() must be called before
  	 * list_del_init(&sl->sl_list), so that the order of
  	 * drop_link(this, target) and drop_item(target) is preserved.
  	 */
  	if (type && type->ct_item_ops &&
  	    type->ct_item_ops->drop_link)
  		type->ct_item_ops->drop_link(parent_item,
  					       sl->sl_target);

  	spin_lock(&configfs_dirent_lock);

  	list_del_init(&sl->sl_list);

  	spin_unlock(&configfs_dirent_lock);

  
  	/* Put reference from create_link() */
  	config_item_put(sl->sl_target);
  	kfree(sl);
  
  	config_item_put(parent_item);
  
  	ret = 0;
  
  out:
  	return ret;
  }
  
  static int configfs_get_target_path(struct config_item * item, struct config_item * target,
  				   char *path)
  {
  	char * s;
  	int depth, size;
  
  	depth = item_depth(item);
  	size = item_path_length(target) + depth * 3 - 1;
  	if (size > PATH_MAX)
  		return -ENAMETOOLONG;

  	pr_debug("%s: depth = %d, size = %d
  ", __func__, depth, size);

  
  	for (s = path; depth--; s += 3)
  		strcpy(s,"../");
  
  	fill_item_path(target, path, size);

  	pr_debug("%s: path = '%s'
  ", __func__, path);

  
  	return 0;
  }
  
  static int configfs_getlink(struct dentry *dentry, char * path)
  {
  	struct config_item *item, *target_item;
  	int error = 0;
  
  	item = configfs_get_config_item(dentry->d_parent);
  	if (!item)
  		return -EINVAL;
  
  	target_item = configfs_get_config_item(dentry);
  	if (!target_item) {
  		config_item_put(item);
  		return -EINVAL;
  	}
  
  	down_read(&configfs_rename_sem);
  	error = configfs_get_target_path(item, target_item, path);
  	up_read(&configfs_rename_sem);
  
  	config_item_put(item);
  	config_item_put(target_item);
  	return error;
  
  }
  
  static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  {
  	int error = -ENOMEM;
  	unsigned long page = get_zeroed_page(GFP_KERNEL);
  
  	if (page) {
  		error = configfs_getlink(dentry, (char *)page);
  		if (!error) {
  			nd_set_link(nd, (char *)page);
  			return (void *)page;
  		}
  	}
  
  	nd_set_link(nd, ERR_PTR(error));
  	return NULL;
  }
  
  static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
  			      void *cookie)
  {
  	if (cookie) {
  		unsigned long page = (unsigned long)cookie;
  		free_page(page);
  	}
  }

  const struct inode_operations configfs_symlink_inode_operations = {

  	.follow_link = configfs_follow_link,
  	.readlink = generic_readlink,
  	.put_link = configfs_put_link,

  	.setattr = configfs_setattr,

  };