2 * fs/kernfs/symlink.c - kernfs symlink implementation
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 * This file is released under the GPLv2.
12 #include <linux/gfp.h>
13 #include <linux/namei.h>
15 #include "kernfs-internal.h"
18 * kernfs_create_link - create a symlink
19 * @parent: directory to create the symlink in
20 * @name: name of the symlink
21 * @target: target node for the symlink to point to
23 * Returns the created node on success, ERR_PTR() value on error.
25 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
27 struct kernfs_node *target)
29 struct kernfs_node *kn;
30 struct kernfs_addrm_cxt acxt;
33 kn = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
36 return ERR_PTR(-ENOMEM);
38 if (kernfs_ns_enabled(parent))
40 kn->symlink.target_kn = target;
41 kernfs_get(target); /* ref owned by symlink */
43 sysfs_addrm_start(&acxt);
44 error = sysfs_add_one(&acxt, kn, parent);
45 sysfs_addrm_finish(&acxt);
51 return ERR_PTR(error);
54 static int sysfs_get_target_path(struct kernfs_node *parent,
55 struct kernfs_node *target, char *path)
57 struct kernfs_node *base, *kn;
61 /* go up to the root, stop at the base */
63 while (base->parent) {
65 while (kn->parent && base != kn)
76 /* determine end of target string for reverse fillup */
78 while (kn->parent && kn != base) {
79 len += strlen(kn->name) + 1;
87 if ((s - path) + len > PATH_MAX)
90 /* reverse fillup of target string from target to base */
92 while (kn->parent && kn != base) {
93 int slen = strlen(kn->name);
96 strncpy(s + len, kn->name, slen);
106 static int sysfs_getlink(struct dentry *dentry, char *path)
108 struct kernfs_node *kn = dentry->d_fsdata;
109 struct kernfs_node *parent = kn->parent;
110 struct kernfs_node *target = kn->symlink.target_kn;
113 mutex_lock(&sysfs_mutex);
114 error = sysfs_get_target_path(parent, target, path);
115 mutex_unlock(&sysfs_mutex);
120 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
123 unsigned long page = get_zeroed_page(GFP_KERNEL);
125 error = sysfs_getlink(dentry, (char *) page);
127 free_page((unsigned long)page);
129 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
133 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd,
136 char *page = nd_get_link(nd);
138 free_page((unsigned long)page);
141 const struct inode_operations sysfs_symlink_inode_operations = {
142 .setxattr = sysfs_setxattr,
143 .removexattr = sysfs_removexattr,
144 .getxattr = sysfs_getxattr,
145 .listxattr = sysfs_listxattr,
146 .readlink = generic_readlink,
147 .follow_link = sysfs_follow_link,
148 .put_link = sysfs_put_link,
149 .setattr = sysfs_setattr,
150 .getattr = sysfs_getattr,
151 .permission = sysfs_permission,