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 struct kmem_cache *sysfs_dir_cachep;
29 static const struct super_operations sysfs_ops = {
30 .statfs = simple_statfs,
31 .drop_inode = generic_delete_inode,
32 .evict_inode = sysfs_evict_inode,
35 static struct sysfs_dirent sysfs_root = {
37 .s_count = ATOMIC_INIT(1),
39 .s_mode = S_IFDIR | S_IRUGO | S_IXUGO,
43 struct sysfs_dirent *sysfs_root_sd = &sysfs_root;
45 static int sysfs_fill_super(struct super_block *sb)
50 sb->s_blocksize = PAGE_CACHE_SIZE;
51 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
52 sb->s_magic = SYSFS_MAGIC;
53 sb->s_op = &sysfs_ops;
56 /* get root inode, initialize and unlock it */
57 mutex_lock(&sysfs_mutex);
58 inode = sysfs_get_inode(sb, sysfs_root_sd);
59 mutex_unlock(&sysfs_mutex);
61 pr_debug("sysfs: could not get root inode\n");
65 /* instantiate and link root dentry */
66 root = d_make_root(inode);
68 pr_debug("%s: could not get root dentry!\n", __func__);
71 root->d_fsdata = sysfs_root_sd;
73 sb->s_d_op = &sysfs_dentry_ops;
77 static int sysfs_test_super(struct super_block *sb, void *data)
79 struct sysfs_super_info *sb_info = sysfs_info(sb);
80 struct sysfs_super_info *info = data;
82 return sb_info->ns == info->ns;
85 static int sysfs_set_super(struct super_block *sb, void *data)
88 error = set_anon_super(sb, data);
94 static void free_sysfs_super_info(struct sysfs_super_info *info)
96 kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)info->ns);
100 static struct dentry *sysfs_mount(struct file_system_type *fs_type,
101 int flags, const char *dev_name, void *data)
103 struct sysfs_super_info *info;
104 struct super_block *sb;
107 if (!(flags & MS_KERNMOUNT)) {
108 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
109 return ERR_PTR(-EPERM);
111 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
112 return ERR_PTR(-EPERM);
115 info = kzalloc(sizeof(*info), GFP_KERNEL);
117 return ERR_PTR(-ENOMEM);
119 info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
121 sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
122 if (IS_ERR(sb) || sb->s_fs_info != info)
123 free_sysfs_super_info(info);
127 error = sysfs_fill_super(sb);
129 deactivate_locked_super(sb);
130 return ERR_PTR(error);
132 sb->s_flags |= MS_ACTIVE;
135 return dget(sb->s_root);
138 static void sysfs_kill_sb(struct super_block *sb)
140 struct sysfs_super_info *info = sysfs_info(sb);
141 /* Remove the superblock from fs_supers/s_instances
142 * so we can't find it, before freeing sysfs_super_info.
145 free_sysfs_super_info(info);
148 static struct file_system_type sysfs_fs_type = {
150 .mount = sysfs_mount,
151 .kill_sb = sysfs_kill_sb,
152 .fs_flags = FS_USERNS_MOUNT,
155 int __init sysfs_init(void)
159 sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
160 sizeof(struct sysfs_dirent),
162 if (!sysfs_dir_cachep)
165 err = sysfs_inode_init();
169 err = register_filesystem(&sysfs_fs_type);
176 kmem_cache_destroy(sysfs_dir_cachep);
177 sysfs_dir_cachep = NULL;