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7063fbf2 JB |
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 | ||
9a73d78c LR |
34 | /* Protects attachments of new symlinks */ |
35 | DEFINE_MUTEX(configfs_symlink_mutex); | |
36 | ||
7063fbf2 JB |
37 | static 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 | ||
45 | static 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 | ||
56 | static 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 | ||
71 | static int create_link(struct config_item *parent_item, | |
e7515d06 | 72 | struct config_item *item, |
7063fbf2 JB |
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 | ||
2a109f2a LR |
79 | ret = -ENOENT; |
80 | if (!configfs_dirent_is_ready(target_sd)) | |
81 | goto out; | |
7063fbf2 JB |
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); |
4768e9b1 LR |
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); |
7063fbf2 JB |
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); |
7063fbf2 JB |
101 | config_item_put(item); |
102 | kfree(sl); | |
103 | } | |
104 | } | |
105 | ||
2a109f2a | 106 | out: |
7063fbf2 JB |
107 | return ret; |
108 | } | |
109 | ||
110 | ||
421748ec | 111 | static int get_target(const char *symname, struct path *path, |
7063fbf2 JB |
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) { |
421748ec AV |
118 | if (path->dentry->d_sb == configfs_sb) { |
119 | *target = configfs_get_config_item(path->dentry); | |
7063fbf2 JB |
120 | if (!*target) { |
121 | ret = -ENOENT; | |
421748ec | 122 | path_put(path); |
7063fbf2 JB |
123 | } |
124 | } else | |
125 | ret = -EPERM; | |
126 | } | |
127 | ||
128 | return ret; | |
129 | } | |
130 | ||
131 | ||
132 | int 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; |
7063fbf2 JB |
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 | ||
2a109f2a LR |
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 | ||
7063fbf2 JB |
154 | parent_item = configfs_get_config_item(dentry->d_parent); |
155 | type = parent_item->ci_type; | |
156 | ||
2a109f2a | 157 | ret = -EPERM; |
7063fbf2 JB |
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); |
7063fbf2 JB |
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); |
e7520651 LR |
171 | if (ret && type->ct_item_ops->drop_link) |
172 | type->ct_item_ops->drop_link(parent_item, | |
173 | target_item); | |
174 | } | |
7063fbf2 JB |
175 | |
176 | config_item_put(target_item); | |
421748ec | 177 | path_put(&path); |
7063fbf2 JB |
178 | |
179 | out_put: | |
180 | config_item_put(parent_item); | |
181 | ||
182 | out: | |
183 | return ret; | |
184 | } | |
185 | ||
186 | int 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); |
7063fbf2 JB |
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); |
7063fbf2 JB |
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); |
7063fbf2 JB |
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 | ||
234 | out: | |
235 | return ret; | |
236 | } | |
237 | ||
238 | static 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); |
7063fbf2 JB |
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); |
7063fbf2 JB |
256 | |
257 | return 0; | |
258 | } | |
259 | ||
260 | static 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 | ||
285 | static 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 | ||
302 | static 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 | 311 | const struct inode_operations configfs_symlink_inode_operations = { |
7063fbf2 JB |
312 | .follow_link = configfs_follow_link, |
313 | .readlink = generic_readlink, | |
314 | .put_link = configfs_put_link, | |
3d0f89bb | 315 | .setattr = configfs_setattr, |
7063fbf2 JB |
316 | }; |
317 |