1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* -*- mode: c; c-basic-offset: 8; -*-
3 * vim: noexpandtab sw=8 ts=8 sts=0:
5 * symlink.c - operations for configfs symlinks.
8 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
10 * configfs Copyright (C) 2005 Oracle. All rights reserved.
14 #include <linux/module.h>
15 #include <linux/namei.h>
16 #include <linux/slab.h>
18 #include <linux/configfs.h>
19 #include "configfs_internal.h"
21 /* Protects attachments of new symlinks */
22 DEFINE_MUTEX(configfs_symlink_mutex);
24 static int item_depth(struct config_item * item)
26 struct config_item * p = item;
28 do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
32 static int item_path_length(struct config_item * item)
34 struct config_item * p = item;
37 length += strlen(config_item_name(p)) + 1;
39 } while (p && !configfs_is_root(p));
43 static void fill_item_path(struct config_item * item, char * buffer, int length)
45 struct config_item * p;
48 for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
49 int cur = strlen(config_item_name(p));
51 /* back up enough to print this bus id with '/' */
53 memcpy(buffer + length, config_item_name(p), cur);
54 *(buffer + --length) = '/';
58 static int create_link(struct config_item *parent_item,
59 struct config_item *item,
60 struct dentry *dentry)
62 struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
63 struct configfs_symlink *sl;
67 if (!configfs_dirent_is_ready(target_sd))
70 sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
72 spin_lock(&configfs_dirent_lock);
73 if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
74 spin_unlock(&configfs_dirent_lock);
78 sl->sl_target = config_item_get(item);
79 list_add(&sl->sl_list, &target_sd->s_links);
80 spin_unlock(&configfs_dirent_lock);
81 ret = configfs_create_link(sl, parent_item->ci_dentry,
84 spin_lock(&configfs_dirent_lock);
85 list_del_init(&sl->sl_list);
86 spin_unlock(&configfs_dirent_lock);
87 config_item_put(item);
97 static int get_target(const char *symname, struct path *path,
98 struct config_item **target, struct super_block *sb)
102 ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
104 if (path->dentry->d_sb == sb) {
105 *target = configfs_get_config_item(path->dentry);
120 int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
124 struct configfs_dirent *sd;
125 struct config_item *parent_item;
126 struct config_item *target_item = NULL;
127 const struct config_item_type *type;
129 sd = dentry->d_parent->d_fsdata;
131 * Fake invisibility if dir belongs to a group/default groups hierarchy
135 if (!configfs_dirent_is_ready(sd))
138 parent_item = configfs_get_config_item(dentry->d_parent);
139 type = parent_item->ci_type;
142 if (!type || !type->ct_item_ops ||
143 !type->ct_item_ops->allow_link)
146 ret = get_target(symname, &path, &target_item, dentry->d_sb);
150 ret = type->ct_item_ops->allow_link(parent_item, target_item);
152 mutex_lock(&configfs_symlink_mutex);
153 ret = create_link(parent_item, target_item, dentry);
154 mutex_unlock(&configfs_symlink_mutex);
155 if (ret && type->ct_item_ops->drop_link)
156 type->ct_item_ops->drop_link(parent_item,
160 config_item_put(target_item);
164 config_item_put(parent_item);
170 int configfs_unlink(struct inode *dir, struct dentry *dentry)
172 struct configfs_dirent *sd = dentry->d_fsdata;
173 struct configfs_symlink *sl;
174 struct config_item *parent_item;
175 const struct config_item_type *type;
178 ret = -EPERM; /* What lack-of-symlink returns */
179 if (!(sd->s_type & CONFIGFS_ITEM_LINK))
184 parent_item = configfs_get_config_item(dentry->d_parent);
185 type = parent_item->ci_type;
187 spin_lock(&configfs_dirent_lock);
188 list_del_init(&sd->s_sibling);
189 spin_unlock(&configfs_dirent_lock);
190 configfs_drop_dentry(sd, dentry->d_parent);
195 * drop_link() must be called before
196 * list_del_init(&sl->sl_list), so that the order of
197 * drop_link(this, target) and drop_item(target) is preserved.
199 if (type && type->ct_item_ops &&
200 type->ct_item_ops->drop_link)
201 type->ct_item_ops->drop_link(parent_item,
204 spin_lock(&configfs_dirent_lock);
205 list_del_init(&sl->sl_list);
206 spin_unlock(&configfs_dirent_lock);
208 /* Put reference from create_link() */
209 config_item_put(sl->sl_target);
212 config_item_put(parent_item);
220 static int configfs_get_target_path(struct config_item * item, struct config_item * target,
226 depth = item_depth(item);
227 size = item_path_length(target) + depth * 3 - 1;
229 return -ENAMETOOLONG;
231 pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
233 for (s = path; depth--; s += 3)
236 fill_item_path(target, path, size);
237 pr_debug("%s: path = '%s'\n", __func__, path);
242 static int configfs_getlink(struct dentry *dentry, char * path)
244 struct config_item *item, *target_item;
247 item = configfs_get_config_item(dentry->d_parent);
251 target_item = configfs_get_config_item(dentry);
253 config_item_put(item);
257 down_read(&configfs_rename_sem);
258 error = configfs_get_target_path(item, target_item, path);
259 up_read(&configfs_rename_sem);
261 config_item_put(item);
262 config_item_put(target_item);
267 static const char *configfs_get_link(struct dentry *dentry,
269 struct delayed_call *done)
275 return ERR_PTR(-ECHILD);
277 body = kzalloc(PAGE_SIZE, GFP_KERNEL);
279 return ERR_PTR(-ENOMEM);
281 error = configfs_getlink(dentry, body);
283 set_delayed_call(done, kfree_link, body);
288 return ERR_PTR(error);
291 const struct inode_operations configfs_symlink_inode_operations = {
292 .get_link = configfs_get_link,
293 .setattr = configfs_setattr,