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 kernfs_root *sysfs_root;
36 struct sysfs_dirent *sysfs_root_sd;
38 static int sysfs_fill_super(struct super_block *sb)
40 struct sysfs_super_info *info = sysfs_info(sb);
44 sb->s_blocksize = PAGE_CACHE_SIZE;
45 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
46 sb->s_magic = SYSFS_MAGIC;
47 sb->s_op = &sysfs_ops;
50 /* get root inode, initialize and unlock it */
51 mutex_lock(&sysfs_mutex);
52 inode = sysfs_get_inode(sb, info->root->sd);
53 mutex_unlock(&sysfs_mutex);
55 pr_debug("sysfs: could not get root inode\n");
59 /* instantiate and link root dentry */
60 root = d_make_root(inode);
62 pr_debug("%s: could not get root dentry!\n", __func__);
65 kernfs_get(info->root->sd);
66 root->d_fsdata = info->root->sd;
68 sb->s_d_op = &sysfs_dentry_ops;
72 static int sysfs_test_super(struct super_block *sb, void *data)
74 struct sysfs_super_info *sb_info = sysfs_info(sb);
75 struct sysfs_super_info *info = data;
77 return sb_info->root == info->root && sb_info->ns == info->ns;
80 static int sysfs_set_super(struct super_block *sb, void *data)
83 error = set_anon_super(sb, data);
90 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
91 * @sb: super_block of interest
93 * Return the namespace tag associated with kernfs super_block @sb.
95 const void *kernfs_super_ns(struct super_block *sb)
97 struct sysfs_super_info *info = sysfs_info(sb);
102 static struct dentry *sysfs_mount(struct file_system_type *fs_type,
103 int flags, const char *dev_name, void *data)
108 if (!(flags & MS_KERNMOUNT)) {
109 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
110 return ERR_PTR(-EPERM);
112 if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
113 return ERR_PTR(-EPERM);
116 ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
117 root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns);
119 kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
124 * kernfs_mount_ns - kernfs mount helper
125 * @fs_type: file_system_type of the fs being mounted
126 * @flags: mount flags specified for the mount
127 * @root: kernfs_root of the hierarchy being mounted
128 * @ns: optional namespace tag of the mount
130 * This is to be called from each kernfs user's file_system_type->mount()
131 * implementation, which should pass through the specified @fs_type and
132 * @flags, and specify the hierarchy and namespace tag to mount via @root
133 * and @ns, respectively.
135 * The return value can be passed to the vfs layer verbatim.
137 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
138 struct kernfs_root *root, const void *ns)
140 struct super_block *sb;
141 struct sysfs_super_info *info;
144 info = kzalloc(sizeof(*info), GFP_KERNEL);
146 return ERR_PTR(-ENOMEM);
151 sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
152 if (IS_ERR(sb) || sb->s_fs_info != info)
157 error = sysfs_fill_super(sb);
159 deactivate_locked_super(sb);
160 return ERR_PTR(error);
162 sb->s_flags |= MS_ACTIVE;
165 return dget(sb->s_root);
168 static void sysfs_kill_sb(struct super_block *sb)
171 kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb));
175 * kernfs_kill_sb - kill_sb for kernfs
176 * @sb: super_block being killed
178 * This can be used directly for file_system_type->kill_sb(). If a kernfs
179 * user needs extra cleanup, it can implement its own kill_sb() and call
180 * this function at the end.
182 void kernfs_kill_sb(struct super_block *sb)
184 struct sysfs_super_info *info = sysfs_info(sb);
185 struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
188 * Remove the superblock from fs_supers/s_instances
189 * so we can't find it, before freeing sysfs_super_info.
196 static struct file_system_type sysfs_fs_type = {
198 .mount = sysfs_mount,
199 .kill_sb = sysfs_kill_sb,
200 .fs_flags = FS_USERNS_MOUNT,
203 void __init kernfs_init(void)
205 sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
206 sizeof(struct sysfs_dirent),
207 0, SLAB_PANIC, NULL);
211 int __init sysfs_init(void)
215 sysfs_root = kernfs_create_root(NULL);
216 if (IS_ERR(sysfs_root))
217 return PTR_ERR(sysfs_root);
219 sysfs_root_sd = sysfs_root->sd;
221 err = register_filesystem(&sysfs_fs_type);
223 kernfs_destroy_root(sysfs_root);