blob: cc9f2546ea4a041273654b6076d1fbc774d447e4 [file] [log] [blame]
Joel Becker7063fbf2005-12-15 14:29:43 -08001/* -*- mode: c; c-basic-offset: 8; -*-
2 * vim: noexpandtab sw=8 ts=8 sts=0:
3 *
4 * symlink.c - operations for configfs symlinks.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public
17 * License along with this program; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 021110-1307, USA.
20 *
21 * Based on sysfs:
22 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
23 *
24 * configfs Copyright (C) 2005 Oracle. All rights reserved.
25 */
26
27#include <linux/fs.h>
28#include <linux/module.h>
29#include <linux/namei.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090030#include <linux/slab.h>
Joel Becker7063fbf2005-12-15 14:29:43 -080031
32#include <linux/configfs.h>
33#include "configfs_internal.h"
34
Louis Rilling9a73d782008-06-20 14:09:22 +020035/* Protects attachments of new symlinks */
36DEFINE_MUTEX(configfs_symlink_mutex);
37
Joel Becker7063fbf2005-12-15 14:29:43 -080038static int item_depth(struct config_item * item)
39{
40 struct config_item * p = item;
41 int depth = 0;
42 do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
43 return depth;
44}
45
46static int item_path_length(struct config_item * item)
47{
48 struct config_item * p = item;
49 int length = 1;
50 do {
51 length += strlen(config_item_name(p)) + 1;
52 p = p->ci_parent;
53 } while (p && !configfs_is_root(p));
54 return length;
55}
56
57static void fill_item_path(struct config_item * item, char * buffer, int length)
58{
59 struct config_item * p;
60
61 --length;
62 for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
63 int cur = strlen(config_item_name(p));
64
65 /* back up enough to print this bus id with '/' */
66 length -= cur;
67 strncpy(buffer + length,config_item_name(p),cur);
68 *(buffer + --length) = '/';
69 }
70}
71
72static int create_link(struct config_item *parent_item,
Joel Beckere7515d02006-03-10 11:42:30 -080073 struct config_item *item,
Joel Becker7063fbf2005-12-15 14:29:43 -080074 struct dentry *dentry)
75{
76 struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
77 struct configfs_symlink *sl;
78 int ret;
79
Louis Rilling2a109f22008-07-04 16:56:05 +020080 ret = -ENOENT;
81 if (!configfs_dirent_is_ready(target_sd))
82 goto out;
Joel Becker7063fbf2005-12-15 14:29:43 -080083 ret = -ENOMEM;
84 sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
85 if (sl) {
86 sl->sl_target = config_item_get(item);
Louis Rilling5301a772008-06-16 19:00:59 +020087 spin_lock(&configfs_dirent_lock);
Louis Rilling4768e9b2008-06-23 14:16:17 +020088 if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
89 spin_unlock(&configfs_dirent_lock);
90 config_item_put(item);
91 kfree(sl);
92 return -ENOENT;
93 }
Joel Becker7063fbf2005-12-15 14:29:43 -080094 list_add(&sl->sl_list, &target_sd->s_links);
Louis Rilling5301a772008-06-16 19:00:59 +020095 spin_unlock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -080096 ret = configfs_create_link(sl, parent_item->ci_dentry,
97 dentry);
98 if (ret) {
Louis Rilling5301a772008-06-16 19:00:59 +020099 spin_lock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800100 list_del_init(&sl->sl_list);
Louis Rilling5301a772008-06-16 19:00:59 +0200101 spin_unlock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800102 config_item_put(item);
103 kfree(sl);
104 }
105 }
106
Louis Rilling2a109f22008-07-04 16:56:05 +0200107out:
Joel Becker7063fbf2005-12-15 14:29:43 -0800108 return ret;
109}
110
111
Al Viro421748e2008-08-02 01:04:36 -0400112static int get_target(const char *symname, struct path *path,
Al Virob7c177f2012-03-17 16:24:54 -0400113 struct config_item **target, struct super_block *sb)
Joel Becker7063fbf2005-12-15 14:29:43 -0800114{
115 int ret;
116
Al Viro421748e2008-08-02 01:04:36 -0400117 ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
Joel Becker7063fbf2005-12-15 14:29:43 -0800118 if (!ret) {
Al Virob7c177f2012-03-17 16:24:54 -0400119 if (path->dentry->d_sb == sb) {
Al Viro421748e2008-08-02 01:04:36 -0400120 *target = configfs_get_config_item(path->dentry);
Joel Becker7063fbf2005-12-15 14:29:43 -0800121 if (!*target) {
122 ret = -ENOENT;
Al Viro421748e2008-08-02 01:04:36 -0400123 path_put(path);
Joel Becker7063fbf2005-12-15 14:29:43 -0800124 }
Al Viro9b6e3102010-01-13 22:10:57 -0500125 } else {
Joel Becker7063fbf2005-12-15 14:29:43 -0800126 ret = -EPERM;
Al Viro9b6e3102010-01-13 22:10:57 -0500127 path_put(path);
128 }
Joel Becker7063fbf2005-12-15 14:29:43 -0800129 }
130
131 return ret;
132}
133
134
135int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
136{
137 int ret;
Al Viro421748e2008-08-02 01:04:36 -0400138 struct path path;
Louis Rilling2a109f22008-07-04 16:56:05 +0200139 struct configfs_dirent *sd;
Joel Becker7063fbf2005-12-15 14:29:43 -0800140 struct config_item *parent_item;
Subrata Modak3c48f232009-04-19 01:10:03 +0530141 struct config_item *target_item = NULL;
Joel Becker7063fbf2005-12-15 14:29:43 -0800142 struct config_item_type *type;
143
Louis Rilling2a109f22008-07-04 16:56:05 +0200144 sd = dentry->d_parent->d_fsdata;
145 /*
146 * Fake invisibility if dir belongs to a group/default groups hierarchy
147 * being attached
148 */
149 ret = -ENOENT;
150 if (!configfs_dirent_is_ready(sd))
151 goto out;
152
Joel Becker7063fbf2005-12-15 14:29:43 -0800153 parent_item = configfs_get_config_item(dentry->d_parent);
154 type = parent_item->ci_type;
155
Louis Rilling2a109f22008-07-04 16:56:05 +0200156 ret = -EPERM;
Joel Becker7063fbf2005-12-15 14:29:43 -0800157 if (!type || !type->ct_item_ops ||
158 !type->ct_item_ops->allow_link)
159 goto out_put;
160
Al Virob7c177f2012-03-17 16:24:54 -0400161 ret = get_target(symname, &path, &target_item, dentry->d_sb);
Joel Becker7063fbf2005-12-15 14:29:43 -0800162 if (ret)
163 goto out_put;
164
165 ret = type->ct_item_ops->allow_link(parent_item, target_item);
Louis Rillinge7520652008-06-12 17:26:47 +0200166 if (!ret) {
Louis Rilling9a73d782008-06-20 14:09:22 +0200167 mutex_lock(&configfs_symlink_mutex);
Joel Becker7063fbf2005-12-15 14:29:43 -0800168 ret = create_link(parent_item, target_item, dentry);
Louis Rilling9a73d782008-06-20 14:09:22 +0200169 mutex_unlock(&configfs_symlink_mutex);
Louis Rillinge7520652008-06-12 17:26:47 +0200170 if (ret && type->ct_item_ops->drop_link)
171 type->ct_item_ops->drop_link(parent_item,
172 target_item);
173 }
Joel Becker7063fbf2005-12-15 14:29:43 -0800174
175 config_item_put(target_item);
Al Viro421748e2008-08-02 01:04:36 -0400176 path_put(&path);
Joel Becker7063fbf2005-12-15 14:29:43 -0800177
178out_put:
179 config_item_put(parent_item);
180
181out:
182 return ret;
183}
184
185int configfs_unlink(struct inode *dir, struct dentry *dentry)
186{
187 struct configfs_dirent *sd = dentry->d_fsdata;
188 struct configfs_symlink *sl;
189 struct config_item *parent_item;
190 struct config_item_type *type;
191 int ret;
192
193 ret = -EPERM; /* What lack-of-symlink returns */
194 if (!(sd->s_type & CONFIGFS_ITEM_LINK))
195 goto out;
196
Joel Becker7063fbf2005-12-15 14:29:43 -0800197 sl = sd->s_element;
198
199 parent_item = configfs_get_config_item(dentry->d_parent);
200 type = parent_item->ci_type;
201
Louis Rilling6f610762008-06-16 19:00:58 +0200202 spin_lock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800203 list_del_init(&sd->s_sibling);
Louis Rilling6f610762008-06-16 19:00:58 +0200204 spin_unlock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800205 configfs_drop_dentry(sd, dentry->d_parent);
206 dput(dentry);
207 configfs_put(sd);
208
209 /*
210 * drop_link() must be called before
211 * list_del_init(&sl->sl_list), so that the order of
212 * drop_link(this, target) and drop_item(target) is preserved.
213 */
214 if (type && type->ct_item_ops &&
215 type->ct_item_ops->drop_link)
216 type->ct_item_ops->drop_link(parent_item,
217 sl->sl_target);
218
Louis Rilling5301a772008-06-16 19:00:59 +0200219 spin_lock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800220 list_del_init(&sl->sl_list);
Louis Rilling5301a772008-06-16 19:00:59 +0200221 spin_unlock(&configfs_dirent_lock);
Joel Becker7063fbf2005-12-15 14:29:43 -0800222
223 /* Put reference from create_link() */
224 config_item_put(sl->sl_target);
225 kfree(sl);
226
227 config_item_put(parent_item);
228
229 ret = 0;
230
231out:
232 return ret;
233}
234
235static int configfs_get_target_path(struct config_item * item, struct config_item * target,
236 char *path)
237{
238 char * s;
239 int depth, size;
240
241 depth = item_depth(item);
242 size = item_path_length(target) + depth * 3 - 1;
243 if (size > PATH_MAX)
244 return -ENAMETOOLONG;
245
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700246 pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
Joel Becker7063fbf2005-12-15 14:29:43 -0800247
248 for (s = path; depth--; s += 3)
249 strcpy(s,"../");
250
251 fill_item_path(target, path, size);
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700252 pr_debug("%s: path = '%s'\n", __func__, path);
Joel Becker7063fbf2005-12-15 14:29:43 -0800253
254 return 0;
255}
256
257static int configfs_getlink(struct dentry *dentry, char * path)
258{
259 struct config_item *item, *target_item;
260 int error = 0;
261
262 item = configfs_get_config_item(dentry->d_parent);
263 if (!item)
264 return -EINVAL;
265
266 target_item = configfs_get_config_item(dentry);
267 if (!target_item) {
268 config_item_put(item);
269 return -EINVAL;
270 }
271
272 down_read(&configfs_rename_sem);
273 error = configfs_get_target_path(item, target_item, path);
274 up_read(&configfs_rename_sem);
275
276 config_item_put(item);
277 config_item_put(target_item);
278 return error;
279
280}
281
282static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
283{
284 int error = -ENOMEM;
285 unsigned long page = get_zeroed_page(GFP_KERNEL);
286
287 if (page) {
288 error = configfs_getlink(dentry, (char *)page);
289 if (!error) {
290 nd_set_link(nd, (char *)page);
291 return (void *)page;
292 }
293 }
294
295 nd_set_link(nd, ERR_PTR(error));
296 return NULL;
297}
298
299static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
300 void *cookie)
301{
302 if (cookie) {
303 unsigned long page = (unsigned long)cookie;
304 free_page(page);
305 }
306}
307
Arjan van de Ven754661f2007-02-12 00:55:38 -0800308const struct inode_operations configfs_symlink_inode_operations = {
Joel Becker7063fbf2005-12-15 14:29:43 -0800309 .follow_link = configfs_follow_link,
310 .readlink = generic_readlink,
311 .put_link = configfs_put_link,
Joel Becker3d0f89b2006-01-25 13:31:07 -0800312 .setattr = configfs_setattr,
Joel Becker7063fbf2005-12-15 14:29:43 -0800313};
314