2 * symlink.c - operations for sysfs symlinks.
6 #include <linux/mount.h>
7 #include <linux/module.h>
8 #include <linux/kobject.h>
9 #include <linux/namei.h>
10 #include <linux/mutex.h>
14 static int object_depth(struct sysfs_dirent *sd)
18 for (; sd->s_parent; sd = sd->s_parent)
24 static int object_path_length(struct sysfs_dirent * sd)
28 for (; sd->s_parent; sd = sd->s_parent)
29 length += strlen(sd->s_name) + 1;
34 static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
37 for (; sd->s_parent; sd = sd->s_parent) {
38 int cur = strlen(sd->s_name);
40 /* back up enough to print this bus id with '/' */
42 strncpy(buffer + length, sd->s_name, cur);
43 *(buffer + --length) = '/';
48 * sysfs_create_link - create symlink between two objects.
49 * @kobj: object whose directory we're creating the link in.
50 * @target: object we're pointing to.
51 * @name: name of the symlink.
53 int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
55 struct sysfs_dirent *parent_sd = NULL;
56 struct sysfs_dirent *target_sd = NULL;
57 struct sysfs_dirent *sd = NULL;
58 struct sysfs_addrm_cxt acxt;
64 if (sysfs_mount && sysfs_mount->mnt_sb)
65 parent_sd = sysfs_mount->mnt_sb->s_root->d_fsdata;
73 /* target->sd can go away beneath us but is protected with
74 * sysfs_assoc_lock. Fetch target_sd from it.
76 spin_lock(&sysfs_assoc_lock);
78 target_sd = sysfs_get(target->sd);
79 spin_unlock(&sysfs_assoc_lock);
86 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
90 sd->s_elem.symlink.target_sd = target_sd;
91 target_sd = NULL; /* reference is now owned by the symlink */
93 sysfs_addrm_start(&acxt, parent_sd);
94 error = sysfs_add_one(&acxt, sd);
95 sysfs_addrm_finish(&acxt);
103 sysfs_put(target_sd);
110 * sysfs_remove_link - remove symlink in object's directory.
111 * @kobj: object we're acting for.
112 * @name: name of the symlink to remove.
115 void sysfs_remove_link(struct kobject * kobj, const char * name)
117 sysfs_hash_and_remove(kobj->sd, name);
120 static int sysfs_get_target_path(struct sysfs_dirent * parent_sd,
121 struct sysfs_dirent * target_sd, char *path)
126 depth = object_depth(parent_sd);
127 size = object_path_length(target_sd) + depth * 3 - 1;
129 return -ENAMETOOLONG;
131 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
133 for (s = path; depth--; s += 3)
136 fill_object_path(target_sd, path, size);
137 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
142 static int sysfs_getlink(struct dentry *dentry, char * path)
144 struct sysfs_dirent *sd = dentry->d_fsdata;
145 struct sysfs_dirent *parent_sd = sd->s_parent;
146 struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd;
149 mutex_lock(&sysfs_mutex);
150 error = sysfs_get_target_path(parent_sd, target_sd, path);
151 mutex_unlock(&sysfs_mutex);
156 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
159 unsigned long page = get_zeroed_page(GFP_KERNEL);
161 error = sysfs_getlink(dentry, (char *) page);
162 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
166 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
168 char *page = nd_get_link(nd);
170 free_page((unsigned long)page);
173 const struct inode_operations sysfs_symlink_inode_operations = {
174 .readlink = generic_readlink,
175 .follow_link = sysfs_follow_link,
176 .put_link = sysfs_put_link,
180 EXPORT_SYMBOL_GPL(sysfs_create_link);
181 EXPORT_SYMBOL_GPL(sysfs_remove_link);