1 /* -*- mode: c; c-basic-offset: 8; -*- 2 * vim: noexpandtab sw=8 ts=8 sts=0: 3 * 4 * mount.c - operations for initializing and mounting configfs. 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public 8 * License as published by the Free Software Foundation; either 9 * version 2 of the License, or (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public 17 * License along with this program; if not, write to the 18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, 19 * Boston, MA 021110-1307, USA. 20 * 21 * Based on sysfs: 22 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel 23 * 24 * configfs Copyright (C) 2005 Oracle. All rights reserved. 25 */ 26 27 #include <linux/fs.h> 28 #include <linux/module.h> 29 #include <linux/mount.h> 30 #include <linux/fs_context.h> 31 #include <linux/pagemap.h> 32 #include <linux/init.h> 33 #include <linux/slab.h> 34 35 #include <linux/configfs.h> 36 #include "configfs_internal.h" 37 38 /* Random magic number */ 39 #define CONFIGFS_MAGIC 0x62656570 40 41 static struct vfsmount *configfs_mount = NULL; 42 struct kmem_cache *configfs_dir_cachep; 43 static int configfs_mnt_count = 0; 44 45 static const struct super_operations configfs_ops = { 46 .statfs = simple_statfs, 47 .drop_inode = generic_delete_inode, 48 }; 49 50 static struct config_group configfs_root_group = { 51 .cg_item = { 52 .ci_namebuf = "root", 53 .ci_name = configfs_root_group.cg_item.ci_namebuf, 54 }, 55 }; 56 57 int configfs_is_root(struct config_item *item) 58 { 59 return item == &configfs_root_group.cg_item; 60 } 61 62 static struct configfs_dirent configfs_root = { 63 .s_sibling = LIST_HEAD_INIT(configfs_root.s_sibling), 64 .s_children = LIST_HEAD_INIT(configfs_root.s_children), 65 .s_element = &configfs_root_group.cg_item, 66 .s_type = CONFIGFS_ROOT, 67 .s_iattr = NULL, 68 }; 69 70 static int configfs_fill_super(struct super_block *sb, struct fs_context *fc) 71 { 72 struct inode *inode; 73 struct dentry *root; 74 75 sb->s_blocksize = PAGE_SIZE; 76 sb->s_blocksize_bits = PAGE_SHIFT; 77 sb->s_magic = CONFIGFS_MAGIC; 78 sb->s_op = &configfs_ops; 79 sb->s_time_gran = 1; 80 81 inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO, 82 &configfs_root, sb); 83 if (inode) { 84 inode->i_op = &configfs_root_inode_operations; 85 inode->i_fop = &configfs_dir_operations; 86 /* directory inodes start off with i_nlink == 2 (for "." entry) */ 87 inc_nlink(inode); 88 } else { 89 pr_debug("could not get root inode\n"); 90 return -ENOMEM; 91 } 92 93 root = d_make_root(inode); 94 if (!root) { 95 pr_debug("%s: could not get root dentry!\n",__func__); 96 return -ENOMEM; 97 } 98 config_group_init(&configfs_root_group); 99 configfs_root_group.cg_item.ci_dentry = root; 100 root->d_fsdata = &configfs_root; 101 sb->s_root = root; 102 sb->s_d_op = &configfs_dentry_ops; /* the rest get that */ 103 return 0; 104 } 105 106 static int configfs_get_tree(struct fs_context *fc) 107 { 108 return get_tree_single(fc, configfs_fill_super); 109 } 110 111 static const struct fs_context_operations configfs_context_ops = { 112 .get_tree = configfs_get_tree, 113 }; 114 115 static int configfs_init_fs_context(struct fs_context *fc) 116 { 117 fc->ops = &configfs_context_ops; 118 return 0; 119 } 120 121 static struct file_system_type configfs_fs_type = { 122 .owner = THIS_MODULE, 123 .name = "configfs", 124 .init_fs_context = configfs_init_fs_context, 125 .kill_sb = kill_litter_super, 126 }; 127 MODULE_ALIAS_FS("configfs"); 128 129 struct dentry *configfs_pin_fs(void) 130 { 131 int err = simple_pin_fs(&configfs_fs_type, &configfs_mount, 132 &configfs_mnt_count); 133 return err ? ERR_PTR(err) : configfs_mount->mnt_root; 134 } 135 136 void configfs_release_fs(void) 137 { 138 simple_release_fs(&configfs_mount, &configfs_mnt_count); 139 } 140 141 142 static int __init configfs_init(void) 143 { 144 int err = -ENOMEM; 145 146 configfs_dir_cachep = kmem_cache_create("configfs_dir_cache", 147 sizeof(struct configfs_dirent), 148 0, 0, NULL); 149 if (!configfs_dir_cachep) 150 goto out; 151 152 err = sysfs_create_mount_point(kernel_kobj, "config"); 153 if (err) 154 goto out2; 155 156 err = register_filesystem(&configfs_fs_type); 157 if (err) 158 goto out3; 159 160 return 0; 161 out3: 162 pr_err("Unable to register filesystem!\n"); 163 sysfs_remove_mount_point(kernel_kobj, "config"); 164 out2: 165 kmem_cache_destroy(configfs_dir_cachep); 166 configfs_dir_cachep = NULL; 167 out: 168 return err; 169 } 170 171 static void __exit configfs_exit(void) 172 { 173 unregister_filesystem(&configfs_fs_type); 174 sysfs_remove_mount_point(kernel_kobj, "config"); 175 kmem_cache_destroy(configfs_dir_cachep); 176 configfs_dir_cachep = NULL; 177 } 178 179 MODULE_AUTHOR("Oracle"); 180 MODULE_LICENSE("GPL"); 181 MODULE_VERSION("0.0.2"); 182 MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration."); 183 184 core_initcall(configfs_init); 185 module_exit(configfs_exit); 186