2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 * This file is released under the GPLv2.
10 * Please see Documentation/filesystems/sysfs.txt for more information.
16 #include <linux/mount.h>
17 #include <linux/pagemap.h>
18 #include <linux/init.h>
19 #include <linux/module.h>
20 #include <linux/magic.h>
21 #include <linux/slab.h>
22 #include <linux/user_namespace.h>
27 static struct vfsmount *sysfs_mnt;
28 struct kmem_cache *sysfs_dir_cachep;
30 static const struct super_operations sysfs_ops = {
31 .statfs = simple_statfs,
32 .drop_inode = generic_delete_inode,
33 .evict_inode = sysfs_evict_inode,
36 struct sysfs_dirent sysfs_root = {
38 .s_count = ATOMIC_INIT(1),
40 .s_mode = S_IFDIR | S_IRUGO | S_IXUGO,
44 static int sysfs_fill_super(struct super_block *sb)
49 sb->s_blocksize = PAGE_CACHE_SIZE;
50 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
51 sb->s_magic = SYSFS_MAGIC;
52 sb->s_op = &sysfs_ops;
55 /* get root inode, initialize and unlock it */
56 mutex_lock(&sysfs_mutex);
57 inode = sysfs_get_inode(sb, &sysfs_root);
58 mutex_unlock(&sysfs_mutex);
60 pr_debug("sysfs: could not get root inode\n");
64 /* instantiate and link root dentry */
65 root = d_make_root(inode);
67 pr_debug("%s: could not get root dentry!\n", __func__);
70 root->d_fsdata = &sysfs_root;
72 sb->s_d_op = &sysfs_dentry_ops;
76 static int sysfs_test_super(struct super_block *sb, void *data)
78 struct sysfs_super_info *sb_info = sysfs_info(sb);
79 struct sysfs_super_info *info = data;
81 return sb_info->ns == info->ns;
84 static int sysfs_set_super(struct super_block *sb, void *data)
87 error = set_anon_super(sb, data);
93 static void free_sysfs_super_info(struct sysfs_super_info *info)
95 kobj_ns_drop(KOBJ_NS_TYPE_NET, info->ns);
99 static struct dentry *sysfs_mount(struct file_system_type *fs_type,
100 int flags, const char *dev_name, void *data)
102 struct sysfs_super_info *info;
103 struct super_block *sb;
106 if (!(flags & MS_KERNMOUNT)) {
107 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
108 return ERR_PTR(-EPERM);
110 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
111 return ERR_PTR(-EPERM);
114 info = kzalloc(sizeof(*info), GFP_KERNEL);
116 return ERR_PTR(-ENOMEM);
118 info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
120 sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
121 if (IS_ERR(sb) || sb->s_fs_info != info)
122 free_sysfs_super_info(info);
126 error = sysfs_fill_super(sb);
128 deactivate_locked_super(sb);
129 return ERR_PTR(error);
131 sb->s_flags |= MS_ACTIVE;
134 return dget(sb->s_root);
137 static void sysfs_kill_sb(struct super_block *sb)
139 struct sysfs_super_info *info = sysfs_info(sb);
140 /* Remove the superblock from fs_supers/s_instances
141 * so we can't find it, before freeing sysfs_super_info.
144 free_sysfs_super_info(info);
147 static struct file_system_type sysfs_fs_type = {
149 .mount = sysfs_mount,
150 .kill_sb = sysfs_kill_sb,
151 .fs_flags = FS_USERNS_MOUNT,
154 int __init sysfs_init(void)
158 sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
159 sizeof(struct sysfs_dirent),
161 if (!sysfs_dir_cachep)
164 err = sysfs_inode_init();
168 err = register_filesystem(&sysfs_fs_type);
170 sysfs_mnt = kern_mount(&sysfs_fs_type);
171 if (IS_ERR(sysfs_mnt)) {
172 printk(KERN_ERR "sysfs: could not mount!\n");
173 err = PTR_ERR(sysfs_mnt);
175 unregister_filesystem(&sysfs_fs_type);
183 kmem_cache_destroy(sysfs_dir_cachep);
184 sysfs_dir_cachep = NULL;