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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 | #include <linux/slab.h> |
31 | |
32 | #include <linux/configfs.h> |
33 | #include "configfs_internal.h" |
34 | |
35 | /* Protects attachments of new symlinks */ |
36 | DEFINE_MUTEX(configfs_symlink_mutex); |
37 | |
38 | static 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 | |
46 | static 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 | |
57 | static 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 | |
72 | static int create_link(struct config_item *parent_item, |
73 | struct config_item *item, |
74 | struct dentry *dentry) |
75 | { |
76 | struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata; |
77 | struct configfs_symlink *sl; |
78 | int ret; |
79 | |
80 | ret = -ENOENT; |
81 | if (!configfs_dirent_is_ready(target_sd)) |
82 | goto out; |
83 | ret = -ENOMEM; |
84 | sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); |
85 | if (sl) { |
86 | sl->sl_target = config_item_get(item); |
87 | spin_lock(&configfs_dirent_lock); |
88 | 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 | } |
94 | list_add(&sl->sl_list, &target_sd->s_links); |
95 | spin_unlock(&configfs_dirent_lock); |
96 | ret = configfs_create_link(sl, parent_item->ci_dentry, |
97 | dentry); |
98 | if (ret) { |
99 | spin_lock(&configfs_dirent_lock); |
100 | list_del_init(&sl->sl_list); |
101 | spin_unlock(&configfs_dirent_lock); |
102 | config_item_put(item); |
103 | kfree(sl); |
104 | } |
105 | } |
106 | |
107 | out: |
108 | return ret; |
109 | } |
110 | |
111 | |
112 | static int get_target(const char *symname, struct path *path, |
113 | struct config_item **target) |
114 | { |
115 | int ret; |
116 | |
117 | ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path); |
118 | if (!ret) { |
119 | if (path->dentry->d_sb == configfs_sb) { |
120 | *target = configfs_get_config_item(path->dentry); |
121 | if (!*target) { |
122 | ret = -ENOENT; |
123 | path_put(path); |
124 | } |
125 | } else { |
126 | ret = -EPERM; |
127 | path_put(path); |
128 | } |
129 | } |
130 | |
131 | return ret; |
132 | } |
133 | |
134 | |
135 | int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) |
136 | { |
137 | int ret; |
138 | struct path path; |
139 | struct configfs_dirent *sd; |
140 | struct config_item *parent_item; |
141 | struct config_item *target_item = NULL; |
142 | struct config_item_type *type; |
143 | |
144 | ret = -EPERM; /* What lack-of-symlink returns */ |
145 | if (dentry->d_parent == configfs_sb->s_root) |
146 | goto out; |
147 | |
148 | sd = dentry->d_parent->d_fsdata; |
149 | /* |
150 | * Fake invisibility if dir belongs to a group/default groups hierarchy |
151 | * being attached |
152 | */ |
153 | ret = -ENOENT; |
154 | if (!configfs_dirent_is_ready(sd)) |
155 | goto out; |
156 | |
157 | parent_item = configfs_get_config_item(dentry->d_parent); |
158 | type = parent_item->ci_type; |
159 | |
160 | ret = -EPERM; |
161 | if (!type || !type->ct_item_ops || |
162 | !type->ct_item_ops->allow_link) |
163 | goto out_put; |
164 | |
165 | ret = get_target(symname, &path, &target_item); |
166 | if (ret) |
167 | goto out_put; |
168 | |
169 | ret = type->ct_item_ops->allow_link(parent_item, target_item); |
170 | if (!ret) { |
171 | mutex_lock(&configfs_symlink_mutex); |
172 | ret = create_link(parent_item, target_item, dentry); |
173 | mutex_unlock(&configfs_symlink_mutex); |
174 | if (ret && type->ct_item_ops->drop_link) |
175 | type->ct_item_ops->drop_link(parent_item, |
176 | target_item); |
177 | } |
178 | |
179 | config_item_put(target_item); |
180 | path_put(&path); |
181 | |
182 | out_put: |
183 | config_item_put(parent_item); |
184 | |
185 | out: |
186 | return ret; |
187 | } |
188 | |
189 | int configfs_unlink(struct inode *dir, struct dentry *dentry) |
190 | { |
191 | struct configfs_dirent *sd = dentry->d_fsdata; |
192 | struct configfs_symlink *sl; |
193 | struct config_item *parent_item; |
194 | struct config_item_type *type; |
195 | int ret; |
196 | |
197 | ret = -EPERM; /* What lack-of-symlink returns */ |
198 | if (!(sd->s_type & CONFIGFS_ITEM_LINK)) |
199 | goto out; |
200 | |
201 | BUG_ON(dentry->d_parent == configfs_sb->s_root); |
202 | |
203 | sl = sd->s_element; |
204 | |
205 | parent_item = configfs_get_config_item(dentry->d_parent); |
206 | type = parent_item->ci_type; |
207 | |
208 | spin_lock(&configfs_dirent_lock); |
209 | list_del_init(&sd->s_sibling); |
210 | spin_unlock(&configfs_dirent_lock); |
211 | configfs_drop_dentry(sd, dentry->d_parent); |
212 | dput(dentry); |
213 | configfs_put(sd); |
214 | |
215 | /* |
216 | * drop_link() must be called before |
217 | * list_del_init(&sl->sl_list), so that the order of |
218 | * drop_link(this, target) and drop_item(target) is preserved. |
219 | */ |
220 | if (type && type->ct_item_ops && |
221 | type->ct_item_ops->drop_link) |
222 | type->ct_item_ops->drop_link(parent_item, |
223 | sl->sl_target); |
224 | |
225 | spin_lock(&configfs_dirent_lock); |
226 | list_del_init(&sl->sl_list); |
227 | spin_unlock(&configfs_dirent_lock); |
228 | |
229 | /* Put reference from create_link() */ |
230 | config_item_put(sl->sl_target); |
231 | kfree(sl); |
232 | |
233 | config_item_put(parent_item); |
234 | |
235 | ret = 0; |
236 | |
237 | out: |
238 | return ret; |
239 | } |
240 | |
241 | static int configfs_get_target_path(struct config_item * item, struct config_item * target, |
242 | char *path) |
243 | { |
244 | char * s; |
245 | int depth, size; |
246 | |
247 | depth = item_depth(item); |
248 | size = item_path_length(target) + depth * 3 - 1; |
249 | if (size > PATH_MAX) |
250 | return -ENAMETOOLONG; |
251 | |
252 | pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size); |
253 | |
254 | for (s = path; depth--; s += 3) |
255 | strcpy(s,"../"); |
256 | |
257 | fill_item_path(target, path, size); |
258 | pr_debug("%s: path = '%s'\n", __func__, path); |
259 | |
260 | return 0; |
261 | } |
262 | |
263 | static int configfs_getlink(struct dentry *dentry, char * path) |
264 | { |
265 | struct config_item *item, *target_item; |
266 | int error = 0; |
267 | |
268 | item = configfs_get_config_item(dentry->d_parent); |
269 | if (!item) |
270 | return -EINVAL; |
271 | |
272 | target_item = configfs_get_config_item(dentry); |
273 | if (!target_item) { |
274 | config_item_put(item); |
275 | return -EINVAL; |
276 | } |
277 | |
278 | down_read(&configfs_rename_sem); |
279 | error = configfs_get_target_path(item, target_item, path); |
280 | up_read(&configfs_rename_sem); |
281 | |
282 | config_item_put(item); |
283 | config_item_put(target_item); |
284 | return error; |
285 | |
286 | } |
287 | |
288 | static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
289 | { |
290 | int error = -ENOMEM; |
291 | unsigned long page = get_zeroed_page(GFP_KERNEL); |
292 | |
293 | if (page) { |
294 | error = configfs_getlink(dentry, (char *)page); |
295 | if (!error) { |
296 | nd_set_link(nd, (char *)page); |
297 | return (void *)page; |
298 | } |
299 | } |
300 | |
301 | nd_set_link(nd, ERR_PTR(error)); |
302 | return NULL; |
303 | } |
304 | |
305 | static void configfs_put_link(struct dentry *dentry, struct nameidata *nd, |
306 | void *cookie) |
307 | { |
308 | if (cookie) { |
309 | unsigned long page = (unsigned long)cookie; |
310 | free_page(page); |
311 | } |
312 | } |
313 | |
314 | const struct inode_operations configfs_symlink_inode_operations = { |
315 | .follow_link = configfs_follow_link, |
316 | .readlink = generic_readlink, |
317 | .put_link = configfs_put_link, |
318 | .setattr = configfs_setattr, |
319 | }; |
320 | |
321 |
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