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/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 /* Random magic number */
24 #define CONFIGFS_MAGIC 0x62656570
25
26 static struct vfsmount *configfs_mount = NULL;
27 struct kmem_cache *configfs_dir_cachep;
28 static int configfs_mnt_count = 0;
29
30 static const struct super_operations configfs_ops = {
31 .statfs = simple_statfs,
32 .drop_inode = generic_delete_inode,
33 };
34
35 static struct config_group configfs_root_group = {
36 .cg_item = {
37 .ci_namebuf = "root",
38 .ci_name = configfs_root_group.cg_item.ci_namebuf,
39 },
40 };
41
42 int configfs_is_root(struct config_item *item)
43 {
44 return item == &configfs_root_group.cg_item;
45 }
46
47 static struct configfs_dirent configfs_root = {
48 .s_sibling = LIST_HEAD_INIT(configfs_root.s_sibling),
49 .s_children = LIST_HEAD_INIT(configfs_root.s_children),
50 .s_element = &configfs_root_group.cg_item,
51 .s_type = CONFIGFS_ROOT,
52 .s_iattr = NULL,
53 };
54
55 static int configfs_fill_super(struct super_block *sb, void *data, int silent)
56 {
57 struct inode *inode;
58 struct dentry *root;
59
60 sb->s_blocksize = PAGE_SIZE;
61 sb->s_blocksize_bits = PAGE_SHIFT;
62 sb->s_magic = CONFIGFS_MAGIC;
63 sb->s_op = &configfs_ops;
64 sb->s_time_gran = 1;
65
66 inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
67 &configfs_root, sb);
68 if (inode) {
69 inode->i_op = &configfs_root_inode_operations;
70 inode->i_fop = &configfs_dir_operations;
71 /* directory inodes start off with i_nlink == 2 (for "." entry) */
72 inc_nlink(inode);
73 } else {
74 pr_debug("could not get root inode\n");
75 return -ENOMEM;
76 }
77
78 root = d_make_root(inode);
79 if (!root) {
80 pr_debug("%s: could not get root dentry!\n",__func__);
81 return -ENOMEM;
82 }
83 config_group_init(&configfs_root_group);
84 configfs_root_group.cg_item.ci_dentry = root;
85 root->d_fsdata = &configfs_root;
86 sb->s_root = root;
87 sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
88 return 0;
89 }
90
91 static struct dentry *configfs_do_mount(struct file_system_type *fs_type,
92 int flags, const char *dev_name, void *data)
93 {
94 return mount_single(fs_type, flags, data, configfs_fill_super);
95 }
96
97 static struct file_system_type configfs_fs_type = {
98 .owner = THIS_MODULE,
99 .name = "configfs",
100 .mount = configfs_do_mount,
101 .kill_sb = kill_litter_super,
102 };
103 MODULE_ALIAS_FS("configfs");
104
105 struct dentry *configfs_pin_fs(void)
106 {
107 int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
108 &configfs_mnt_count);
109 return err ? ERR_PTR(err) : configfs_mount->mnt_root;
110 }
111
112 void configfs_release_fs(void)
113 {
114 simple_release_fs(&configfs_mount, &configfs_mnt_count);
115 }
116
117
118 static int __init configfs_init(void)
119 {
120 int err = -ENOMEM;
121
122 configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
123 sizeof(struct configfs_dirent),
124 0, 0, NULL);
125 if (!configfs_dir_cachep)
126 goto out;
127
128 err = sysfs_create_mount_point(kernel_kobj, "config");
129 if (err)
130 goto out2;
131
132 err = register_filesystem(&configfs_fs_type);
133 if (err)
134 goto out3;
135
136 return 0;
137 out3:
138 pr_err("Unable to register filesystem!\n");
139 sysfs_remove_mount_point(kernel_kobj, "config");
140 out2:
141 kmem_cache_destroy(configfs_dir_cachep);
142 configfs_dir_cachep = NULL;
143 out:
144 return err;
145 }
146
147 static void __exit configfs_exit(void)
148 {
149 unregister_filesystem(&configfs_fs_type);
150 sysfs_remove_mount_point(kernel_kobj, "config");
151 kmem_cache_destroy(configfs_dir_cachep);
152 configfs_dir_cachep = NULL;
153 }
154
155 MODULE_AUTHOR("Oracle");
156 MODULE_LICENSE("GPL");
157 MODULE_VERSION("0.0.2");
158 MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
159
160 core_initcall(configfs_init);
161 module_exit(configfs_exit);
162
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