original development tree for Linux kernel GTP module; now long in mainline.
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/* -*- 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, 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 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,
};