ia64/linux-2.6.18-xen.hg

view fs/configfs/symlink.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
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 */
27 #include <linux/fs.h>
28 #include <linux/module.h>
29 #include <linux/namei.h>
31 #include <linux/configfs.h>
32 #include "configfs_internal.h"
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 }
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 }
53 static void fill_item_path(struct config_item * item, char * buffer, int length)
54 {
55 struct config_item * p;
57 --length;
58 for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
59 int cur = strlen(config_item_name(p));
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 }
68 static int create_link(struct config_item *parent_item,
69 struct config_item *item,
70 struct dentry *dentry)
71 {
72 struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
73 struct configfs_symlink *sl;
74 int ret;
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 }
91 return ret;
92 }
95 static int get_target(const char *symname, struct nameidata *nd,
96 struct config_item **target)
97 {
98 int ret;
100 ret = path_lookup(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, nd);
101 if (!ret) {
102 if (nd->dentry->d_sb == configfs_sb) {
103 *target = configfs_get_config_item(nd->dentry);
104 if (!*target) {
105 ret = -ENOENT;
106 path_release(nd);
107 }
108 } else
109 ret = -EPERM;
110 }
112 return ret;
113 }
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;
124 ret = -EPERM; /* What lack-of-symlink returns */
125 if (dentry->d_parent == configfs_sb->s_root)
126 goto out;
128 parent_item = configfs_get_config_item(dentry->d_parent);
129 type = parent_item->ci_type;
131 if (!type || !type->ct_item_ops ||
132 !type->ct_item_ops->allow_link)
133 goto out_put;
135 ret = get_target(symname, &nd, &target_item);
136 if (ret)
137 goto out_put;
139 ret = type->ct_item_ops->allow_link(parent_item, target_item);
140 if (!ret)
141 ret = create_link(parent_item, target_item, dentry);
143 config_item_put(target_item);
144 path_release(&nd);
146 out_put:
147 config_item_put(parent_item);
149 out:
150 return ret;
151 }
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;
161 ret = -EPERM; /* What lack-of-symlink returns */
162 if (!(sd->s_type & CONFIGFS_ITEM_LINK))
163 goto out;
165 BUG_ON(dentry->d_parent == configfs_sb->s_root);
167 sl = sd->s_element;
169 parent_item = configfs_get_config_item(dentry->d_parent);
170 type = parent_item->ci_type;
172 list_del_init(&sd->s_sibling);
173 configfs_drop_dentry(sd, dentry->d_parent);
174 dput(dentry);
175 configfs_put(sd);
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);
187 /* FIXME: Needs lock */
188 list_del_init(&sl->sl_list);
190 /* Put reference from create_link() */
191 config_item_put(sl->sl_target);
192 kfree(sl);
194 config_item_put(parent_item);
196 ret = 0;
198 out:
199 return ret;
200 }
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;
208 depth = item_depth(item);
209 size = item_path_length(target) + depth * 3 - 1;
210 if (size > PATH_MAX)
211 return -ENAMETOOLONG;
213 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
215 for (s = path; depth--; s += 3)
216 strcpy(s,"../");
218 fill_item_path(target, path, size);
219 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
221 return 0;
222 }
224 static int configfs_getlink(struct dentry *dentry, char * path)
225 {
226 struct config_item *item, *target_item;
227 int error = 0;
229 item = configfs_get_config_item(dentry->d_parent);
230 if (!item)
231 return -EINVAL;
233 target_item = configfs_get_config_item(dentry);
234 if (!target_item) {
235 config_item_put(item);
236 return -EINVAL;
237 }
239 down_read(&configfs_rename_sem);
240 error = configfs_get_target_path(item, target_item, path);
241 up_read(&configfs_rename_sem);
243 config_item_put(item);
244 config_item_put(target_item);
245 return error;
247 }
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);
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 }
262 nd_set_link(nd, ERR_PTR(error));
263 return NULL;
264 }
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 }
275 struct inode_operations configfs_symlink_inode_operations = {
276 .follow_link = configfs_follow_link,
277 .readlink = generic_readlink,
278 .put_link = configfs_put_link,
279 .setattr = configfs_setattr,
280 };