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(objp: 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(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 | 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, fill_super: 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, mount: &configfs_mount, |
125 | count: &configfs_mnt_count); |
126 | return err ? ERR_PTR(error: err) : configfs_mount->mnt_root; |
127 | } |
128 | |
129 | void configfs_release_fs(void) |
130 | { |
131 | simple_release_fs(mount: &configfs_mount, count: &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(name: "configfs_dir_cache" , |
140 | size: sizeof(struct configfs_dirent), |
141 | align: 0, flags: 0, NULL); |
142 | if (!configfs_dir_cachep) |
143 | goto out; |
144 | |
145 | err = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "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(parent_kobj: kernel_kobj, name: "config" ); |
157 | out2: |
158 | kmem_cache_destroy(s: 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(parent_kobj: kernel_kobj, name: "config" ); |
168 | kmem_cache_destroy(s: 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 | |