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
25 static struct vfsmount *configfs_mount = NULL;
26 struct kmem_cache *configfs_dir_cachep;
27 static int configfs_mnt_count = 0;
28
29
30 static void configfs_free_inode(struct inode *inode)
31 {
32 if (S_ISLNK(inode->i_mode))
33 kfree(inode->i_link);
34 free_inode_nonrcu(inode);
35 }
36
37 static const struct super_operations configfs_ops = {
38 .statfs = simple_statfs,
39 .drop_inode = generic_delete_inode,
40 .free_inode = configfs_free_inode,
41 };
42
43 static 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
50 int configfs_is_root(struct config_item *item)
51 {
52 return item == &configfs_root_group.cg_item;
53 }
54
55 static 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
63 static 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(&configfs_root_group);
92 configfs_root_group.cg_item.ci_dentry = root;
93 root->d_fsdata = &configfs_root;
94 sb->s_root = root;
95 sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
96 return 0;
97 }
98
99 static int configfs_get_tree(struct fs_context *fc)
100 {
101 return get_tree_single(fc, configfs_fill_super);
102 }
103
104 static const struct fs_context_operations configfs_context_ops = {
105 .get_tree = configfs_get_tree,
106 };
107
108 static int configfs_init_fs_context(struct fs_context *fc)
109 {
110 fc->ops = &configfs_context_ops;
111 return 0;
112 }
113
114 static struct file_system_type configfs_fs_type = {
115 .owner = THIS_MODULE,
116 .name = "configfs",
117 .init_fs_context = configfs_init_fs_context,
118 .kill_sb = kill_litter_super,
119 };
120 MODULE_ALIAS_FS("configfs");
121
122 struct dentry *configfs_pin_fs(void)
123 {
124 int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
125 &configfs_mnt_count);
126 return err ? ERR_PTR(err) : configfs_mount->mnt_root;
127 }
128
129 void configfs_release_fs(void)
130 {
131 simple_release_fs(&configfs_mount, &configfs_mnt_count);
132 }
133
134
135 static int __init configfs_init(void)
136 {
137 int err = -ENOMEM;
138
139 configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
140 sizeof(struct configfs_dirent),
141 0, 0, NULL);
142 if (!configfs_dir_cachep)
143 goto out;
144
145 err = sysfs_create_mount_point(kernel_kobj, "config");
146 if (err)
147 goto out2;
148
149 err = register_filesystem(&configfs_fs_type);
150 if (err)
151 goto out3;
152
153 return 0;
154 out3:
155 pr_err("Unable to register filesystem!\n");
156 sysfs_remove_mount_point(kernel_kobj, "config");
157 out2:
158 kmem_cache_destroy(configfs_dir_cachep);
159 configfs_dir_cachep = NULL;
160 out:
161 return err;
162 }
163
164 static void __exit configfs_exit(void)
165 {
166 unregister_filesystem(&configfs_fs_type);
167 sysfs_remove_mount_point(kernel_kobj, "config");
168 kmem_cache_destroy(configfs_dir_cachep);
169 configfs_dir_cachep = NULL;
170 }
171
172 MODULE_AUTHOR("Oracle");
173 MODULE_LICENSE("GPL");
174 MODULE_VERSION("0.0.2");
175 MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
176
177 core_initcall(configfs_init);
178 module_exit(configfs_exit);
179
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.