fs/configfs/symlink.c - kernel/common.git - Git at Google

 /* -*- 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) {
 		spin_lock(&configfs_dirent_lock);
 		if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
 			spin_unlock(&configfs_dirent_lock);
 			kfree(sl);
 			return -ENOENT;
 		}
 		sl->sl_target = config_item_get(item);
 		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, struct super_block *sb)
 {
 	int ret;

 	ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
 	if (!ret) {
 		if (path->dentry->d_sb == 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;

 	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, dentry->d_sb);
 	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;

 	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\n", __func__, depth, size);

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

 	fill_item_path(target, path, size);
 	pr_debug("%s: path = '%s'\n", __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 const char *configfs_get_link(struct dentry *dentry,
 				     struct inode *inode,
 				     struct delayed_call *done)
 {
 	char *body;
 	int error;

 	if (!dentry)
 		return ERR_PTR(-ECHILD);

 	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
 	if (!body)
 		return ERR_PTR(-ENOMEM);

 	error = configfs_getlink(dentry, body);
 	if (!error) {
 		set_delayed_call(done, kfree_link, body);
 		return body;
 	}

 	kfree(body);
 	return ERR_PTR(error);
 }

 const struct inode_operations configfs_symlink_inode_operations = {
 	.get_link = configfs_get_link,
 	.readlink = generic_readlink,
 	.setattr = configfs_setattr,
 };
	/* -- 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) {
	spin_lock(&configfs_dirent_lock);
	if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
	spin_unlock(&configfs_dirent_lock);
	kfree(sl);
	return -ENOENT;
	}
	sl->sl_target = config_item_get(item);
	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, struct super_block sb)
	{
	int ret;

	ret = kern_path(symname, LOOKUP_FOLLOW\|LOOKUP_DIRECTORY, path);
	if (!ret) {
	if (path->dentry->d_sb == 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;

	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, dentry->d_sb);
	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;

	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\n", __func__, depth, size);

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

	fill_item_path(target, path, size);
	pr_debug("%s: path = '%s'\n", __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 const char configfs_get_link(struct dentry dentry,
	struct inode *inode,
	struct delayed_call *done)
	{
	char *body;
	int error;

	if (!dentry)
	return ERR_PTR(-ECHILD);

	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (!body)
	return ERR_PTR(-ENOMEM);

	error = configfs_getlink(dentry, body);
	if (!error) {
	set_delayed_call(done, kfree_link, body);
	return body;
	}

	kfree(body);
	return ERR_PTR(error);
	}

	const struct inode_operations configfs_symlink_inode_operations = {
	.get_link = configfs_get_link,
	.readlink = generic_readlink,
	.setattr = configfs_setattr,
	};