1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* -*- mode: c; c-basic-offset: 8; -*-
3 * vim: noexpandtab sw=8 ts=8 sts=0:
4 *
5 * mount.c - operations for initializing and mounting configfs.
6 *
7 * Based on sysfs:
8 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
9 *
10 * configfs Copyright (C) 2005 Oracle. All rights reserved.
11 */
12
13 #include <linux/fs.h>
14 #include <linux/module.h>
15 #include <linux/mount.h>
16 #include <linux/fs_context.h>
17 #include <linux/pagemap.h>
18 #include <linux/init.h>
19 #include <linux/slab.h>
20
21 #include <linux/configfs.h>
22 #include "configfs_internal.h"
23
24 /* Random magic number */
25 #define CONFIGFS_MAGIC 0x62656570
26
27 static struct vfsmount *configfs_mount = NULL;
28 struct kmem_cache *configfs_dir_cachep;
29 static int configfs_mnt_count = 0;
30
31
32 static void configfs_free_inode(struct inode *inode)
33 {
34 if (S_ISLNK(inode->i_mode))
35 kfree(inode->i_link);
36 free_inode_nonrcu(inode);
37 }
38
39 static const struct super_operations configfs_ops = {
40 .statfs = simple_statfs,
41 .drop_inode = generic_delete_inode,
42 .free_inode = configfs_free_inode,
43 };
44
45 static struct config_group configfs_root_group = {
46 .cg_item = {
47 .ci_namebuf = "root",
48 .ci_name = configfs_root_group.cg_item.ci_namebuf,
49 },
50 };
51
52 int configfs_is_root(struct config_item *item)
53 {
54 return item == &configfs_root_group.cg_item;
55 }
56
57 static struct configfs_dirent configfs_root = {
58 .s_sibling = LIST_HEAD_INIT(configfs_root.s_sibling),
59 .s_children = LIST_HEAD_INIT(configfs_root.s_children),
60 .s_element = &configfs_root_group.cg_item,
61 .s_type = CONFIGFS_ROOT,
62 .s_iattr = NULL,
63 };
64
65 static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
66 {
67 struct inode *inode;
68 struct dentry *root;
69
70 sb->s_blocksize = PAGE_SIZE;
71 sb->s_blocksize_bits = PAGE_SHIFT;
72 sb->s_magic = CONFIGFS_MAGIC;
73 sb->s_op = &configfs_ops;
74 sb->s_time_gran = 1;
75
76 inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
77 &configfs_root, sb);
78 if (inode) {
79 inode->i_op = &configfs_root_inode_operations;
80 inode->i_fop = &configfs_dir_operations;
81 /* directory inodes start off with i_nlink == 2 (for "." entry) */
82 inc_nlink(inode);
83 } else {
84 pr_debug("could not get root inode\n");
85 return -ENOMEM;
86 }
87
88 root = d_make_root(inode);
89 if (!root) {
90 pr_debug("%s: could not get root dentry!\n",__func__);
91 return -ENOMEM;
92 }
93 config_group_init(&configfs_root_group);
94 configfs_root_group.cg_item.ci_dentry = root;
95 root->d_fsdata = &configfs_root;
96 sb->s_root = root;
97 sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
98 return 0;
99 }
100
101 static int configfs_get_tree(struct fs_context *fc)
102 {
103 return get_tree_single(fc, configfs_fill_super);
104 }
105
106 static const struct fs_context_operations configfs_context_ops = {
107 .get_tree = configfs_get_tree,
108 };
109
110 static int configfs_init_fs_context(struct fs_context *fc)
111 {
112 fc->ops = &configfs_context_ops;
113 return 0;
114 }
115
116 static struct file_system_type configfs_fs_type = {
117 .owner = THIS_MODULE,
118 .name = "configfs",
119 .init_fs_context = configfs_init_fs_context,
120 .kill_sb = kill_litter_super,
121 };
122 MODULE_ALIAS_FS("configfs");
123
124 struct dentry *configfs_pin_fs(void)
125 {
126 int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
127 &configfs_mnt_count);
128 return err ? ERR_PTR(err) : configfs_mount->mnt_root;
129 }
130
131 void configfs_release_fs(void)
132 {
133 simple_release_fs(&configfs_mount, &configfs_mnt_count);
134 }
135
136
137 static int __init configfs_init(void)
138 {
139 int err = -ENOMEM;
140
141 configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
142 sizeof(struct configfs_dirent),
143 0, 0, NULL);
144 if (!configfs_dir_cachep)
145 goto out;
146
147 err = sysfs_create_mount_point(kernel_kobj, "config");
148 if (err)
149 goto out2;
150
151 err = register_filesystem(&configfs_fs_type);
152 if (err)
153 goto out3;
154
155 return 0;
156 out3:
157 pr_err("Unable to register filesystem!\n");
158 sysfs_remove_mount_point(kernel_kobj, "config");
159 out2:
160 kmem_cache_destroy(configfs_dir_cachep);
161 configfs_dir_cachep = NULL;
162 out:
163 return err;
164 }
165
166 static void __exit configfs_exit(void)
167 {
168 unregister_filesystem(&configfs_fs_type);
169 sysfs_remove_mount_point(kernel_kobj, "config");
170 kmem_cache_destroy(configfs_dir_cachep);
171 configfs_dir_cachep = NULL;
172 }
173
174 MODULE_AUTHOR("Oracle");
175 MODULE_LICENSE("GPL");
176 MODULE_VERSION("0.0.2");
177 MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
178
179 core_initcall(configfs_init);
180 module_exit(configfs_exit);
181
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