fs: no games with DCACHE_UNHASHED
[linux-2.6-block.git] / fs / configfs / symlink.c
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1/* -*- 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>
30
31#include <linux/configfs.h>
32#include "configfs_internal.h"
33
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34/* Protects attachments of new symlinks */
35DEFINE_MUTEX(configfs_symlink_mutex);
36
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37static int item_depth(struct config_item * item)
38{
39 struct config_item * p = item;
40 int depth = 0;
41 do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
42 return depth;
43}
44
45static int item_path_length(struct config_item * item)
46{
47 struct config_item * p = item;
48 int length = 1;
49 do {
50 length += strlen(config_item_name(p)) + 1;
51 p = p->ci_parent;
52 } while (p && !configfs_is_root(p));
53 return length;
54}
55
56static void fill_item_path(struct config_item * item, char * buffer, int length)
57{
58 struct config_item * p;
59
60 --length;
61 for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
62 int cur = strlen(config_item_name(p));
63
64 /* back up enough to print this bus id with '/' */
65 length -= cur;
66 strncpy(buffer + length,config_item_name(p),cur);
67 *(buffer + --length) = '/';
68 }
69}
70
71static int create_link(struct config_item *parent_item,
e7515d06 72 struct config_item *item,
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73 struct dentry *dentry)
74{
75 struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
76 struct configfs_symlink *sl;
77 int ret;
78
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79 ret = -ENOENT;
80 if (!configfs_dirent_is_ready(target_sd))
81 goto out;
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82 ret = -ENOMEM;
83 sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
84 if (sl) {
85 sl->sl_target = config_item_get(item);
5301a77d 86 spin_lock(&configfs_dirent_lock);
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87 if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
88 spin_unlock(&configfs_dirent_lock);
89 config_item_put(item);
90 kfree(sl);
91 return -ENOENT;
92 }
7063fbf2 93 list_add(&sl->sl_list, &target_sd->s_links);
5301a77d 94 spin_unlock(&configfs_dirent_lock);
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95 ret = configfs_create_link(sl, parent_item->ci_dentry,
96 dentry);
97 if (ret) {
5301a77d 98 spin_lock(&configfs_dirent_lock);
7063fbf2 99 list_del_init(&sl->sl_list);
5301a77d 100 spin_unlock(&configfs_dirent_lock);
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101 config_item_put(item);
102 kfree(sl);
103 }
104 }
105
2a109f2a 106out:
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107 return ret;
108}
109
110
421748ec 111static int get_target(const char *symname, struct path *path,
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112 struct config_item **target)
113{
114 int ret;
115
421748ec 116 ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
7063fbf2 117 if (!ret) {
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118 if (path->dentry->d_sb == configfs_sb) {
119 *target = configfs_get_config_item(path->dentry);
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120 if (!*target) {
121 ret = -ENOENT;
421748ec 122 path_put(path);
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123 }
124 } else
125 ret = -EPERM;
126 }
127
128 return ret;
129}
130
131
132int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
133{
134 int ret;
421748ec 135 struct path path;
2a109f2a 136 struct configfs_dirent *sd;
7063fbf2 137 struct config_item *parent_item;
3c48f23a 138 struct config_item *target_item = NULL;
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139 struct config_item_type *type;
140
141 ret = -EPERM; /* What lack-of-symlink returns */
142 if (dentry->d_parent == configfs_sb->s_root)
143 goto out;
144
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145 sd = dentry->d_parent->d_fsdata;
146 /*
147 * Fake invisibility if dir belongs to a group/default groups hierarchy
148 * being attached
149 */
150 ret = -ENOENT;
151 if (!configfs_dirent_is_ready(sd))
152 goto out;
153
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154 parent_item = configfs_get_config_item(dentry->d_parent);
155 type = parent_item->ci_type;
156
2a109f2a 157 ret = -EPERM;
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158 if (!type || !type->ct_item_ops ||
159 !type->ct_item_ops->allow_link)
160 goto out_put;
161
421748ec 162 ret = get_target(symname, &path, &target_item);
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163 if (ret)
164 goto out_put;
165
166 ret = type->ct_item_ops->allow_link(parent_item, target_item);
e7520651 167 if (!ret) {
9a73d78c 168 mutex_lock(&configfs_symlink_mutex);
7063fbf2 169 ret = create_link(parent_item, target_item, dentry);
9a73d78c 170 mutex_unlock(&configfs_symlink_mutex);
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171 if (ret && type->ct_item_ops->drop_link)
172 type->ct_item_ops->drop_link(parent_item,
173 target_item);
174 }
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175
176 config_item_put(target_item);
421748ec 177 path_put(&path);
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178
179out_put:
180 config_item_put(parent_item);
181
182out:
183 return ret;
184}
185
186int configfs_unlink(struct inode *dir, struct dentry *dentry)
187{
188 struct configfs_dirent *sd = dentry->d_fsdata;
189 struct configfs_symlink *sl;
190 struct config_item *parent_item;
191 struct config_item_type *type;
192 int ret;
193
194 ret = -EPERM; /* What lack-of-symlink returns */
195 if (!(sd->s_type & CONFIGFS_ITEM_LINK))
196 goto out;
197
1a1974fd 198 BUG_ON(dentry->d_parent == configfs_sb->s_root);
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199
200 sl = sd->s_element;
201
202 parent_item = configfs_get_config_item(dentry->d_parent);
203 type = parent_item->ci_type;
204
6f610764 205 spin_lock(&configfs_dirent_lock);
7063fbf2 206 list_del_init(&sd->s_sibling);
6f610764 207 spin_unlock(&configfs_dirent_lock);
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208 configfs_drop_dentry(sd, dentry->d_parent);
209 dput(dentry);
210 configfs_put(sd);
211
212 /*
213 * drop_link() must be called before
214 * list_del_init(&sl->sl_list), so that the order of
215 * drop_link(this, target) and drop_item(target) is preserved.
216 */
217 if (type && type->ct_item_ops &&
218 type->ct_item_ops->drop_link)
219 type->ct_item_ops->drop_link(parent_item,
220 sl->sl_target);
221
5301a77d 222 spin_lock(&configfs_dirent_lock);
7063fbf2 223 list_del_init(&sl->sl_list);
5301a77d 224 spin_unlock(&configfs_dirent_lock);
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225
226 /* Put reference from create_link() */
227 config_item_put(sl->sl_target);
228 kfree(sl);
229
230 config_item_put(parent_item);
231
232 ret = 0;
233
234out:
235 return ret;
236}
237
238static int configfs_get_target_path(struct config_item * item, struct config_item * target,
239 char *path)
240{
241 char * s;
242 int depth, size;
243
244 depth = item_depth(item);
245 size = item_path_length(target) + depth * 3 - 1;
246 if (size > PATH_MAX)
247 return -ENAMETOOLONG;
248
8e24eea7 249 pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
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250
251 for (s = path; depth--; s += 3)
252 strcpy(s,"../");
253
254 fill_item_path(target, path, size);
8e24eea7 255 pr_debug("%s: path = '%s'\n", __func__, path);
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256
257 return 0;
258}
259
260static int configfs_getlink(struct dentry *dentry, char * path)
261{
262 struct config_item *item, *target_item;
263 int error = 0;
264
265 item = configfs_get_config_item(dentry->d_parent);
266 if (!item)
267 return -EINVAL;
268
269 target_item = configfs_get_config_item(dentry);
270 if (!target_item) {
271 config_item_put(item);
272 return -EINVAL;
273 }
274
275 down_read(&configfs_rename_sem);
276 error = configfs_get_target_path(item, target_item, path);
277 up_read(&configfs_rename_sem);
278
279 config_item_put(item);
280 config_item_put(target_item);
281 return error;
282
283}
284
285static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
286{
287 int error = -ENOMEM;
288 unsigned long page = get_zeroed_page(GFP_KERNEL);
289
290 if (page) {
291 error = configfs_getlink(dentry, (char *)page);
292 if (!error) {
293 nd_set_link(nd, (char *)page);
294 return (void *)page;
295 }
296 }
297
298 nd_set_link(nd, ERR_PTR(error));
299 return NULL;
300}
301
302static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
303 void *cookie)
304{
305 if (cookie) {
306 unsigned long page = (unsigned long)cookie;
307 free_page(page);
308 }
309}
310
754661f1 311const struct inode_operations configfs_symlink_inode_operations = {
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312 .follow_link = configfs_follow_link,
313 .readlink = generic_readlink,
314 .put_link = configfs_put_link,
3d0f89bb 315 .setattr = configfs_setattr,
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316};
317