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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); | |
80 | /* FIXME: needs a lock, I'd bet */ | |
81 | list_add(&sl->sl_list, &target_sd->s_links); | |
82 | ret = configfs_create_link(sl, parent_item->ci_dentry, | |
83 | dentry); | |
84 | if (ret) { | |
85 | list_del_init(&sl->sl_list); | |
86 | config_item_put(item); | |
87 | kfree(sl); | |
88 | } | |
89 | } | |
90 | ||
91 | return ret; | |
92 | } | |
93 | ||
94 | ||
95 | static int get_target(const char *symname, struct nameidata *nd, | |
96 | struct config_item **target) | |
97 | { | |
98 | int ret; | |
99 | ||
100 | ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd); | |
101 | if (!ret) { | |
4ac91378 JB |
102 | if (nd->path.dentry->d_sb == configfs_sb) { |
103 | *target = configfs_get_config_item(nd->path.dentry); | |
7063fbf2 JB |
104 | if (!*target) { |
105 | ret = -ENOENT; | |
1d957f9b | 106 | path_put(&nd->path); |
7063fbf2 JB |
107 | } |
108 | } else | |
109 | ret = -EPERM; | |
110 | } | |
111 | ||
112 | return ret; | |
113 | } | |
114 | ||
115 | ||
116 | int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname) | |
117 | { | |
118 | int ret; | |
119 | struct nameidata nd; | |
120 | struct config_item *parent_item; | |
121 | struct config_item *target_item; | |
122 | struct config_item_type *type; | |
123 | ||
124 | ret = -EPERM; /* What lack-of-symlink returns */ | |
125 | if (dentry->d_parent == configfs_sb->s_root) | |
126 | goto out; | |
127 | ||
128 | parent_item = configfs_get_config_item(dentry->d_parent); | |
129 | type = parent_item->ci_type; | |
130 | ||
131 | if (!type || !type->ct_item_ops || | |
132 | !type->ct_item_ops->allow_link) | |
133 | goto out_put; | |
134 | ||
135 | ret = get_target(symname, &nd, &target_item); | |
136 | if (ret) | |
137 | goto out_put; | |
138 | ||
139 | ret = type->ct_item_ops->allow_link(parent_item, target_item); | |
140 | if (!ret) | |
141 | ret = create_link(parent_item, target_item, dentry); | |
142 | ||
143 | config_item_put(target_item); | |
1d957f9b | 144 | path_put(&nd.path); |
7063fbf2 JB |
145 | |
146 | out_put: | |
147 | config_item_put(parent_item); | |
148 | ||
149 | out: | |
150 | return ret; | |
151 | } | |
152 | ||
153 | int configfs_unlink(struct inode *dir, struct dentry *dentry) | |
154 | { | |
155 | struct configfs_dirent *sd = dentry->d_fsdata; | |
156 | struct configfs_symlink *sl; | |
157 | struct config_item *parent_item; | |
158 | struct config_item_type *type; | |
159 | int ret; | |
160 | ||
161 | ret = -EPERM; /* What lack-of-symlink returns */ | |
162 | if (!(sd->s_type & CONFIGFS_ITEM_LINK)) | |
163 | goto out; | |
164 | ||
1a1974fd | 165 | BUG_ON(dentry->d_parent == configfs_sb->s_root); |
7063fbf2 JB |
166 | |
167 | sl = sd->s_element; | |
168 | ||
169 | parent_item = configfs_get_config_item(dentry->d_parent); | |
170 | type = parent_item->ci_type; | |
171 | ||
172 | list_del_init(&sd->s_sibling); | |
173 | configfs_drop_dentry(sd, dentry->d_parent); | |
174 | dput(dentry); | |
175 | configfs_put(sd); | |
176 | ||
177 | /* | |
178 | * drop_link() must be called before | |
179 | * list_del_init(&sl->sl_list), so that the order of | |
180 | * drop_link(this, target) and drop_item(target) is preserved. | |
181 | */ | |
182 | if (type && type->ct_item_ops && | |
183 | type->ct_item_ops->drop_link) | |
184 | type->ct_item_ops->drop_link(parent_item, | |
185 | sl->sl_target); | |
186 | ||
187 | /* FIXME: Needs lock */ | |
188 | list_del_init(&sl->sl_list); | |
189 | ||
190 | /* Put reference from create_link() */ | |
191 | config_item_put(sl->sl_target); | |
192 | kfree(sl); | |
193 | ||
194 | config_item_put(parent_item); | |
195 | ||
196 | ret = 0; | |
197 | ||
198 | out: | |
199 | return ret; | |
200 | } | |
201 | ||
202 | static int configfs_get_target_path(struct config_item * item, struct config_item * target, | |
203 | char *path) | |
204 | { | |
205 | char * s; | |
206 | int depth, size; | |
207 | ||
208 | depth = item_depth(item); | |
209 | size = item_path_length(target) + depth * 3 - 1; | |
210 | if (size > PATH_MAX) | |
211 | return -ENAMETOOLONG; | |
212 | ||
213 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
214 | ||
215 | for (s = path; depth--; s += 3) | |
216 | strcpy(s,"../"); | |
217 | ||
218 | fill_item_path(target, path, size); | |
219 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); | |
220 | ||
221 | return 0; | |
222 | } | |
223 | ||
224 | static int configfs_getlink(struct dentry *dentry, char * path) | |
225 | { | |
226 | struct config_item *item, *target_item; | |
227 | int error = 0; | |
228 | ||
229 | item = configfs_get_config_item(dentry->d_parent); | |
230 | if (!item) | |
231 | return -EINVAL; | |
232 | ||
233 | target_item = configfs_get_config_item(dentry); | |
234 | if (!target_item) { | |
235 | config_item_put(item); | |
236 | return -EINVAL; | |
237 | } | |
238 | ||
239 | down_read(&configfs_rename_sem); | |
240 | error = configfs_get_target_path(item, target_item, path); | |
241 | up_read(&configfs_rename_sem); | |
242 | ||
243 | config_item_put(item); | |
244 | config_item_put(target_item); | |
245 | return error; | |
246 | ||
247 | } | |
248 | ||
249 | static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd) | |
250 | { | |
251 | int error = -ENOMEM; | |
252 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
253 | ||
254 | if (page) { | |
255 | error = configfs_getlink(dentry, (char *)page); | |
256 | if (!error) { | |
257 | nd_set_link(nd, (char *)page); | |
258 | return (void *)page; | |
259 | } | |
260 | } | |
261 | ||
262 | nd_set_link(nd, ERR_PTR(error)); | |
263 | return NULL; | |
264 | } | |
265 | ||
266 | static void configfs_put_link(struct dentry *dentry, struct nameidata *nd, | |
267 | void *cookie) | |
268 | { | |
269 | if (cookie) { | |
270 | unsigned long page = (unsigned long)cookie; | |
271 | free_page(page); | |
272 | } | |
273 | } | |
274 | ||
754661f1 | 275 | const struct inode_operations configfs_symlink_inode_operations = { |
7063fbf2 JB |
276 | .follow_link = configfs_follow_link, |
277 | .readlink = generic_readlink, | |
278 | .put_link = configfs_put_link, | |
3d0f89bb | 279 | .setattr = configfs_setattr, |
7063fbf2 JB |
280 | }; |
281 |