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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * symlink.c - operations for sysfs symlinks. | |
3 | */ | |
4 | ||
5 | #include <linux/fs.h> | |
ceeee1fb | 6 | #include <linux/mount.h> |
1da177e4 LT |
7 | #include <linux/module.h> |
8 | #include <linux/kobject.h> | |
9 | #include <linux/namei.h> | |
94bebf4d | 10 | #include <asm/semaphore.h> |
1da177e4 LT |
11 | |
12 | #include "sysfs.h" | |
13 | ||
2b29ac25 | 14 | static int object_depth(struct sysfs_dirent *sd) |
1da177e4 | 15 | { |
1da177e4 | 16 | int depth = 0; |
2b29ac25 TH |
17 | |
18 | for (; sd->s_parent; sd = sd->s_parent) | |
19 | depth++; | |
20 | ||
1da177e4 LT |
21 | return depth; |
22 | } | |
23 | ||
2b29ac25 | 24 | static int object_path_length(struct sysfs_dirent * sd) |
1da177e4 | 25 | { |
1da177e4 | 26 | int length = 1; |
2b29ac25 TH |
27 | |
28 | for (; sd->s_parent; sd = sd->s_parent) | |
29 | length += strlen(sd->s_name) + 1; | |
30 | ||
1da177e4 LT |
31 | return length; |
32 | } | |
33 | ||
2b29ac25 | 34 | static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length) |
1da177e4 | 35 | { |
1da177e4 | 36 | --length; |
2b29ac25 TH |
37 | for (; sd->s_parent; sd = sd->s_parent) { |
38 | int cur = strlen(sd->s_name); | |
1da177e4 LT |
39 | |
40 | /* back up enough to print this bus id with '/' */ | |
41 | length -= cur; | |
2b29ac25 | 42 | strncpy(buffer + length, sd->s_name, cur); |
1da177e4 LT |
43 | *(buffer + --length) = '/'; |
44 | } | |
45 | } | |
46 | ||
2b29ac25 TH |
47 | static int sysfs_add_link(struct sysfs_dirent * parent_sd, const char * name, |
48 | struct sysfs_dirent * target_sd) | |
1da177e4 | 49 | { |
a26cd722 | 50 | struct sysfs_dirent * sd; |
1da177e4 | 51 | |
3e519038 | 52 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); |
a26cd722 | 53 | if (!sd) |
3e519038 | 54 | return -ENOMEM; |
dfeb9fb0 | 55 | |
2b29ac25 | 56 | sd->s_elem.symlink.target_sd = target_sd; |
3e519038 | 57 | sysfs_attach_dirent(sd, parent_sd, NULL); |
dfeb9fb0 | 58 | return 0; |
1da177e4 LT |
59 | } |
60 | ||
61 | /** | |
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. | |
66 | */ | |
e3a15db2 | 67 | int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name) |
1da177e4 | 68 | { |
ceeee1fb | 69 | struct dentry *dentry = NULL; |
2b29ac25 TH |
70 | struct sysfs_dirent *parent_sd = NULL; |
71 | struct sysfs_dirent *target_sd = NULL; | |
c516865c | 72 | int error = -EEXIST; |
1da177e4 | 73 | |
ceeee1fb GKH |
74 | BUG_ON(!name); |
75 | ||
76 | if (!kobj) { | |
77 | if (sysfs_mount && sysfs_mount->mnt_sb) | |
78 | dentry = sysfs_mount->mnt_sb->s_root; | |
79 | } else | |
80 | dentry = kobj->dentry; | |
81 | ||
82 | if (!dentry) | |
83 | return -EFAULT; | |
2b29ac25 TH |
84 | parent_sd = dentry->d_fsdata; |
85 | ||
86 | /* target->dentry can go away beneath us but is protected with | |
87 | * kobj_sysfs_assoc_lock. Fetch target_sd from it. | |
88 | */ | |
89 | spin_lock(&kobj_sysfs_assoc_lock); | |
90 | if (target->dentry) | |
91 | target_sd = sysfs_get(target->dentry->d_fsdata); | |
92 | spin_unlock(&kobj_sysfs_assoc_lock); | |
93 | ||
94 | if (!target_sd) | |
95 | return -ENOENT; | |
1da177e4 | 96 | |
1b1dcc1b | 97 | mutex_lock(&dentry->d_inode->i_mutex); |
f0b0af47 | 98 | if (!sysfs_find_dirent(dentry->d_fsdata, name)) |
2b29ac25 | 99 | error = sysfs_add_link(parent_sd, name, target_sd); |
1b1dcc1b | 100 | mutex_unlock(&dentry->d_inode->i_mutex); |
2b29ac25 TH |
101 | |
102 | if (error) | |
103 | sysfs_put(target_sd); | |
104 | ||
1da177e4 LT |
105 | return error; |
106 | } | |
107 | ||
108 | ||
109 | /** | |
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. | |
113 | */ | |
114 | ||
e3a15db2 | 115 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
1da177e4 LT |
116 | { |
117 | sysfs_hash_and_remove(kobj->dentry,name); | |
118 | } | |
119 | ||
2b29ac25 TH |
120 | static int sysfs_get_target_path(struct sysfs_dirent * parent_sd, |
121 | struct sysfs_dirent * target_sd, char *path) | |
1da177e4 LT |
122 | { |
123 | char * s; | |
124 | int depth, size; | |
125 | ||
2b29ac25 TH |
126 | depth = object_depth(parent_sd); |
127 | size = object_path_length(target_sd) + depth * 3 - 1; | |
1da177e4 LT |
128 | if (size > PATH_MAX) |
129 | return -ENAMETOOLONG; | |
130 | ||
131 | pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); | |
132 | ||
133 | for (s = path; depth--; s += 3) | |
134 | strcpy(s,"../"); | |
135 | ||
2b29ac25 | 136 | fill_object_path(target_sd, path, size); |
1da177e4 LT |
137 | pr_debug("%s: path = '%s'\n", __FUNCTION__, path); |
138 | ||
139 | return 0; | |
140 | } | |
141 | ||
142 | static int sysfs_getlink(struct dentry *dentry, char * path) | |
143 | { | |
2b29ac25 TH |
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; | |
147 | int error; | |
1da177e4 LT |
148 | |
149 | down_read(&sysfs_rename_sem); | |
2b29ac25 | 150 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
1da177e4 | 151 | up_read(&sysfs_rename_sem); |
1da177e4 | 152 | |
2b29ac25 | 153 | return error; |
1da177e4 LT |
154 | } |
155 | ||
cc314eef | 156 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
1da177e4 LT |
157 | { |
158 | int error = -ENOMEM; | |
159 | unsigned long page = get_zeroed_page(GFP_KERNEL); | |
160 | if (page) | |
161 | error = sysfs_getlink(dentry, (char *) page); | |
162 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); | |
cc314eef | 163 | return NULL; |
1da177e4 LT |
164 | } |
165 | ||
cc314eef | 166 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
1da177e4 LT |
167 | { |
168 | char *page = nd_get_link(nd); | |
169 | if (!IS_ERR(page)) | |
170 | free_page((unsigned long)page); | |
171 | } | |
172 | ||
c5ef1c42 | 173 | const struct inode_operations sysfs_symlink_inode_operations = { |
1da177e4 LT |
174 | .readlink = generic_readlink, |
175 | .follow_link = sysfs_follow_link, | |
176 | .put_link = sysfs_put_link, | |
177 | }; | |
178 | ||
179 | ||
180 | EXPORT_SYMBOL_GPL(sysfs_create_link); | |
181 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |