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
) = '/';
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
);
95 if (!sysfs_find_dirent(parent_sd
, name
)) {
96 sysfs_add_one(&acxt
, sd
);
97 sysfs_link_sibling(sd
);
100 if (!sysfs_addrm_finish(&acxt
)) {
108 sysfs_put(target_sd
);
115 * sysfs_remove_link - remove symlink in object's directory.
116 * @kobj: object we're acting for.
117 * @name: name of the symlink to remove.
120 void sysfs_remove_link(struct kobject
* kobj
, const char * name
)
122 sysfs_hash_and_remove(kobj
->sd
, name
);
125 static int sysfs_get_target_path(struct sysfs_dirent
* parent_sd
,
126 struct sysfs_dirent
* target_sd
, char *path
)
131 depth
= object_depth(parent_sd
);
132 size
= object_path_length(target_sd
) + depth
* 3 - 1;
134 return -ENAMETOOLONG
;
136 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__
, depth
, size
);
138 for (s
= path
; depth
--; s
+= 3)
141 fill_object_path(target_sd
, path
, size
);
142 pr_debug("%s: path = '%s'\n", __FUNCTION__
, path
);
147 static int sysfs_getlink(struct dentry
*dentry
, char * path
)
149 struct sysfs_dirent
*sd
= dentry
->d_fsdata
;
150 struct sysfs_dirent
*parent_sd
= sd
->s_parent
;
151 struct sysfs_dirent
*target_sd
= sd
->s_elem
.symlink
.target_sd
;
154 mutex_lock(&sysfs_mutex
);
155 error
= sysfs_get_target_path(parent_sd
, target_sd
, path
);
156 mutex_unlock(&sysfs_mutex
);
161 static void *sysfs_follow_link(struct dentry
*dentry
, struct nameidata
*nd
)
164 unsigned long page
= get_zeroed_page(GFP_KERNEL
);
166 error
= sysfs_getlink(dentry
, (char *) page
);
167 nd_set_link(nd
, error
? ERR_PTR(error
) : (char *)page
);
171 static void sysfs_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
173 char *page
= nd_get_link(nd
);
175 free_page((unsigned long)page
);
178 const struct inode_operations sysfs_symlink_inode_operations
= {
179 .readlink
= generic_readlink
,
180 .follow_link
= sysfs_follow_link
,
181 .put_link
= sysfs_put_link
,
185 EXPORT_SYMBOL_GPL(sysfs_create_link
);
186 EXPORT_SYMBOL_GPL(sysfs_remove_link
);