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 <asm/semaphore.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
) = '/';
47 static int sysfs_add_link(struct sysfs_dirent
* parent_sd
, const char * name
,
48 struct sysfs_dirent
* target_sd
)
50 struct sysfs_dirent
* sd
;
52 sd
= sysfs_new_dirent(name
, S_IFLNK
|S_IRWXUGO
, SYSFS_KOBJ_LINK
);
56 sd
->s_elem
.symlink
.target_sd
= target_sd
;
57 sysfs_attach_dirent(sd
, parent_sd
, NULL
);
62 * sysfs_create_link - create symlink between two objects.
63 * @kobj: object whose directory we're creating the link in.
64 * @target: object we're pointing to.
65 * @name: name of the symlink.
67 int sysfs_create_link(struct kobject
* kobj
, struct kobject
* target
, const char * name
)
69 struct dentry
*dentry
= NULL
;
70 struct sysfs_dirent
*parent_sd
= NULL
;
71 struct sysfs_dirent
*target_sd
= NULL
;
77 if (sysfs_mount
&& sysfs_mount
->mnt_sb
)
78 dentry
= sysfs_mount
->mnt_sb
->s_root
;
80 dentry
= kobj
->dentry
;
84 parent_sd
= dentry
->d_fsdata
;
86 /* target->dentry can go away beneath us but is protected with
87 * kobj_sysfs_assoc_lock. Fetch target_sd from it.
89 spin_lock(&kobj_sysfs_assoc_lock
);
91 target_sd
= sysfs_get(target
->dentry
->d_fsdata
);
92 spin_unlock(&kobj_sysfs_assoc_lock
);
97 mutex_lock(&dentry
->d_inode
->i_mutex
);
98 if (!sysfs_find_dirent(dentry
->d_fsdata
, name
))
99 error
= sysfs_add_link(parent_sd
, name
, target_sd
);
100 mutex_unlock(&dentry
->d_inode
->i_mutex
);
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
->dentry
,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 down_read(&sysfs_rename_sem
);
150 error
= sysfs_get_target_path(parent_sd
, target_sd
, path
);
151 up_read(&sysfs_rename_sem
);
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
);