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