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