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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 | ||
34 | static int item_depth(struct config_item * item) | |
35 | { | |
36 | struct config_item * p = item; | |
37 | int depth = 0; | |
38 | do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p)); | |
39 | return depth; | |
40 | } | |
41 | ||
42 | static int item_path_length(struct config_item * item) | |
43 | { | |
44 | struct config_item * p = item; | |
45 | int length = 1; | |
46 | do { | |
47 | length += strlen(config_item_name(p)) + 1; | |
48 | p = p->ci_parent; | |
49 | } while (p && !configfs_is_root(p)); | |
50 | return length; | |
51 | } | |
52 | ||
53 | static void fill_item_path(struct config_item * item, char * buffer, int length) | |
54 | { | |
55 | struct config_item * p; | |
56 | ||
57 | --length; | |
58 | for (p = item; p && !configfs_is_root(p); p = p->ci_parent) { | |
59 | int cur = strlen(config_item_name(p)); | |
60 | ||
61 | /* back up enough to print this bus id with '/' */ | |
62 | length -= cur; | |
63 | strncpy(buffer + length,config_item_name(p),cur); | |
64 | *(buffer + --length) = '/'; | |
65 | } | |
66 | } | |
67 | ||
68 | static int create_link(struct config_item *parent_item, | |
e7515d06 | 69 | struct config_item *item, |
7063fbf2 JB |
70 | struct dentry *dentry) |
71 | { | |
72 | struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata; | |
73 | struct configfs_symlink *sl; | |
74 | int ret; | |
75 | ||
76 | ret = -ENOMEM; | |
77 | sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); | |
78 | if (sl) { | |
79 | sl->sl_target = config_item_get(item); | |
5301a77d | 80 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 81 | list_add(&sl->sl_list, &target_sd->s_links); |
5301a77d | 82 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
83 | ret = configfs_create_link(sl, parent_item->ci_dentry, |
84 | dentry); | |
85 | if (ret) { | |
5301a77d | 86 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 87 | list_del_init(&sl->sl_list); |
5301a77d | 88 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
89 | config_item_put(item); |
90 | kfree(sl); | |
91 | } | |
92 | } | |
93 | ||
94 | return ret; | |
95 | } | |
96 | ||
97 | ||
98 | static int get_target(const char *symname, struct nameidata *nd, | |
99 | struct config_item **target) | |
100 | { | |
101 | int ret; | |
102 | ||
103 | ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd); | |
104 | if (!ret) { | |
4ac91378 JB |
105 | if (nd->path.dentry->d_sb == configfs_sb) { |
106 | *target = configfs_get_config_item(nd->path.dentry); | |
7063fbf2 JB |
107 | if (!*target) { |
108 | ret = -ENOENT; | |
1d957f9b | 109 | path_put(&nd->path); |
7063fbf2 JB |
110 | } |
111 | } else | |
112 | ret = -EPERM; | |
113 | } | |
114 | ||
115 | return ret; | |
116 | } | |
117 | ||
118 | ||
119 | int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) | |
120 | { | |
121 | int ret; | |
122 | struct nameidata nd; | |
123 | struct config_item *parent_item; | |
124 | struct config_item *target_item; | |
125 | struct config_item_type *type; | |
126 | ||
127 | ret = -EPERM; /* What lack-of-symlink returns */ | |
128 | if (dentry->d_parent == configfs_sb->s_root) | |
129 | goto out; | |
130 | ||
131 | parent_item = configfs_get_config_item(dentry->d_parent); | |
132 | type = parent_item->ci_type; | |
133 | ||
134 | if (!type || !type->ct_item_ops || | |
135 | !type->ct_item_ops->allow_link) | |
136 | goto out_put; | |
137 | ||
138 | ret = get_target(symname, &nd, &target_item); | |
139 | if (ret) | |
140 | goto out_put; | |
141 | ||
142 | ret = type->ct_item_ops->allow_link(parent_item, target_item); | |
e7520651 | 143 | if (!ret) { |
7063fbf2 | 144 | ret = create_link(parent_item, target_item, dentry); |
e7520651 LR |
145 | if (ret && type->ct_item_ops->drop_link) |
146 | type->ct_item_ops->drop_link(parent_item, | |
147 | target_item); | |
148 | } | |
7063fbf2 JB |
149 | |
150 | config_item_put(target_item); | |
1d957f9b | 151 | path_put(&nd.path); |
7063fbf2 JB |
152 | |
153 | out_put: | |
154 | config_item_put(parent_item); | |
155 | ||
156 | out: | |
157 | return ret; | |
158 | } | |
159 | ||
160 | int configfs_unlink(struct inode *dir, struct dentry *dentry) | |
161 | { | |
162 | struct configfs_dirent *sd = dentry->d_fsdata; | |
163 | struct configfs_symlink *sl; | |
164 | struct config_item *parent_item; | |
165 | struct config_item_type *type; | |
166 | int ret; | |
167 | ||
168 | ret = -EPERM; /* What lack-of-symlink returns */ | |
169 | if (!(sd->s_type & CONFIGFS_ITEM_LINK)) | |
170 | goto out; | |
171 | ||
1a1974fd | 172 | BUG_ON(dentry->d_parent == configfs_sb->s_root); |
7063fbf2 JB |
173 | |
174 | sl = sd->s_element; | |
175 | ||
176 | parent_item = configfs_get_config_item(dentry->d_parent); | |
177 | type = parent_item->ci_type; | |
178 | ||
6f610764 | 179 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 180 | list_del_init(&sd->s_sibling); |
6f610764 | 181 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
182 | configfs_drop_dentry(sd, dentry->d_parent); |
183 | dput(dentry); | |
184 | configfs_put(sd); | |
185 | ||
186 | /* | |
187 | * drop_link() must be called before | |
188 | * list_del_init(&sl->sl_list), so that the order of | |
189 | * drop_link(this, target) and drop_item(target) is preserved. | |
190 | */ | |
191 | if (type && type->ct_item_ops && | |
192 | type->ct_item_ops->drop_link) | |
193 | type->ct_item_ops->drop_link(parent_item, | |
194 | sl->sl_target); | |
195 | ||
5301a77d | 196 | spin_lock(&configfs_dirent_lock); |
7063fbf2 | 197 | list_del_init(&sl->sl_list); |
5301a77d | 198 | spin_unlock(&configfs_dirent_lock); |
7063fbf2 JB |
199 | |
200 | /* Put reference from create_link() */ | |
201 | config_item_put(sl->sl_target); | |
202 | kfree(sl); | |
203 | ||
204 | config_item_put(parent_item); | |
205 | ||
206 | ret = 0; | |
207 | ||
208 | out: | |
209 | return ret; | |
210 | } | |
211 | ||
212 | static int configfs_get_target_path(struct config_item * item, struct config_item * target, | |
213 | char *path) | |
214 | { | |
215 | char * s; | |
216 | int depth, size; | |
217 | ||
218 | depth = item_depth(item); | |
219 | size = item_path_length(target) + depth * 3 - 1; | |
220 | if (size > PATH_MAX) | |
221 | return -ENAMETOOLONG; | |
222 | ||
8e24eea7 | 223 | pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size); |
7063fbf2 JB |
224 | |
225 | for (s = path; depth--; s += 3) | |
226 | strcpy(s,"../"); | |
227 | ||
228 | fill_item_path(target, path, size); | |
8e24eea7 | 229 | pr_debug("%s: path = '%s'\n", __func__, path); |
7063fbf2 JB |
230 | |
231 | return 0; | |
232 | } | |
233 | ||
234 | static int configfs_getlink(struct dentry *dentry, char * path) | |
235 | { | |
236 | struct config_item *item, *target_item; | |
237 | int error = 0; | |
238 | ||
239 | item = configfs_get_config_item(dentry->d_parent); | |
240 | if (!item) | |
241 | return -EINVAL; | |
242 | ||
243 | target_item = configfs_get_config_item(dentry); | |
244 | if (!target_item) { | |
245 | config_item_put(item); | |
246 | return -EINVAL; | |
247 | } | |
248 | ||
249 | down_read(&configfs_rename_sem); | |
250 | error = configfs_get_target_path(item, target_item, path); | |
251 | up_read(&configfs_rename_sem); | |
252 | ||
253 | config_item_put(item); | |
254 | config_item_put(target_item); | |
255 | return error; | |
256 | ||
257 | } | |
258 | ||
259 | static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd) | |
260 | { | |
261 | int error = -ENOMEM; | |
262 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
263 | ||
264 | if (page) { | |
265 | error = configfs_getlink(dentry, (char *)page); | |
266 | if (!error) { | |
267 | nd_set_link(nd, (char *)page); | |
268 | return (void *)page; | |
269 | } | |
270 | } | |
271 | ||
272 | nd_set_link(nd, ERR_PTR(error)); | |
273 | return NULL; | |
274 | } | |
275 | ||
276 | static void configfs_put_link(struct dentry *dentry, struct nameidata *nd, | |
277 | void *cookie) | |
278 | { | |
279 | if (cookie) { | |
280 | unsigned long page = (unsigned long)cookie; | |
281 | free_page(page); | |
282 | } | |
283 | } | |
284 | ||
754661f1 | 285 | const struct inode_operations configfs_symlink_inode_operations = { |
7063fbf2 JB |
286 | .follow_link = configfs_follow_link, |
287 | .readlink = generic_readlink, | |
288 | .put_link = configfs_put_link, | |
3d0f89bb | 289 | .setattr = configfs_setattr, |
7063fbf2 JB |
290 | }; |
291 |