1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * mount.c - operations for initializing and mounting configfs.
4 *
5 * Based on sysfs:
6 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
7 *
8 * configfs Copyright (C) 2005 Oracle. All rights reserved.
9 */
10
11#include <linux/fs.h>
12#include <linux/module.h>
13#include <linux/mount.h>
14#include <linux/fs_context.h>
15#include <linux/pagemap.h>
16#include <linux/init.h>
17#include <linux/slab.h>
18
19#include <linux/configfs.h>
20#include "configfs_internal.h"
21
22/* Random magic number */
23#define CONFIGFS_MAGIC 0x62656570
24
25static struct vfsmount *configfs_mount = NULL;
26struct kmem_cache *configfs_dir_cachep;
27static int configfs_mnt_count = 0;
28
29
30static void configfs_free_inode(struct inode *inode)
31{
32 if (S_ISLNK(inode->i_mode))
33 kfree(objp: inode->i_link);
34 free_inode_nonrcu(inode);
35}
36
37static const struct super_operations configfs_ops = {
38 .statfs = simple_statfs,
39 .drop_inode = inode_just_drop,
40 .free_inode = configfs_free_inode,
41};
42
43static struct config_group configfs_root_group = {
44 .cg_item = {
45 .ci_namebuf = "root",
46 .ci_name = configfs_root_group.cg_item.ci_namebuf,
47 },
48};
49
50int configfs_is_root(struct config_item *item)
51{
52 return item == &configfs_root_group.cg_item;
53}
54
55static struct configfs_dirent configfs_root = {
56 .s_sibling = LIST_HEAD_INIT(configfs_root.s_sibling),
57 .s_children = LIST_HEAD_INIT(configfs_root.s_children),
58 .s_element = &configfs_root_group.cg_item,
59 .s_type = CONFIGFS_ROOT,
60 .s_iattr = NULL,
61};
62
63static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
64{
65 struct inode *inode;
66 struct dentry *root;
67
68 sb->s_blocksize = PAGE_SIZE;
69 sb->s_blocksize_bits = PAGE_SHIFT;
70 sb->s_magic = CONFIGFS_MAGIC;
71 sb->s_op = &configfs_ops;
72 sb->s_time_gran = 1;
73
74 inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
75 &configfs_root, sb);
76 if (inode) {
77 inode->i_op = &configfs_root_inode_operations;
78 inode->i_fop = &configfs_dir_operations;
79 /* directory inodes start off with i_nlink == 2 (for "." entry) */
80 inc_nlink(inode);
81 } else {
82 pr_debug("could not get root inode\n");
83 return -ENOMEM;
84 }
85
86 root = d_make_root(inode);
87 if (!root) {
88 pr_debug("%s: could not get root dentry!\n",__func__);
89 return -ENOMEM;
90 }
91 config_group_init(group: &configfs_root_group);
92 configfs_root_group.cg_item.ci_dentry = root;
93 root->d_fsdata = &configfs_root;
94 sb->s_root = root;
95 set_default_d_op(sb, &configfs_dentry_ops); /* the rest get that */
96 sb->s_d_flags |= DCACHE_DONTCACHE;
97 return 0;
98}
99
100static int configfs_get_tree(struct fs_context *fc)
101{
102 return get_tree_single(fc, fill_super: configfs_fill_super);
103}
104
105static const struct fs_context_operations configfs_context_ops = {
106 .get_tree = configfs_get_tree,
107};
108
109static int configfs_init_fs_context(struct fs_context *fc)
110{
111 fc->ops = &configfs_context_ops;
112 return 0;
113}
114
115static struct file_system_type configfs_fs_type = {
116 .owner = THIS_MODULE,
117 .name = "configfs",
118 .init_fs_context = configfs_init_fs_context,
119 .kill_sb = kill_anon_super,
120};
121MODULE_ALIAS_FS("configfs");
122
123struct dentry *configfs_pin_fs(void)
124{
125 int err = simple_pin_fs(&configfs_fs_type, mount: &configfs_mount,
126 count: &configfs_mnt_count);
127 return err ? ERR_PTR(error: err) : configfs_mount->mnt_root;
128}
129
130void configfs_release_fs(void)
131{
132 simple_release_fs(mount: &configfs_mount, count: &configfs_mnt_count);
133}
134
135
136static int __init configfs_init(void)
137{
138 int err = -ENOMEM;
139
140 configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
141 sizeof(struct configfs_dirent),
142 0, 0, NULL);
143 if (!configfs_dir_cachep)
144 goto out;
145
146 err = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "config");
147 if (err)
148 goto out2;
149
150 err = register_filesystem(&configfs_fs_type);
151 if (err)
152 goto out3;
153
154 return 0;
155out3:
156 pr_err("Unable to register filesystem!\n");
157 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "config");
158out2:
159 kmem_cache_destroy(s: configfs_dir_cachep);
160 configfs_dir_cachep = NULL;
161out:
162 return err;
163}
164
165static void __exit configfs_exit(void)
166{
167 unregister_filesystem(&configfs_fs_type);
168 sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "config");
169 kmem_cache_destroy(s: configfs_dir_cachep);
170 configfs_dir_cachep = NULL;
171}
172
173MODULE_AUTHOR("Oracle");
174MODULE_LICENSE("GPL");
175MODULE_VERSION("0.0.2");
176MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
177
178core_initcall(configfs_init);
179module_exit(configfs_exit);
180

source code of linux/fs/configfs/mount.c