linux/fs/configfs/mount.c
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   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
  25static struct vfsmount *configfs_mount = NULL;
  26struct kmem_cache *configfs_dir_cachep;
  27static int configfs_mnt_count = 0;
  28
  29
  30static void configfs_free_inode(struct inode *inode)
  31{
  32        if (S_ISLNK(inode->i_mode))
  33                kfree(inode->i_link);
  34        free_inode_nonrcu(inode);
  35}
  36
  37static const struct super_operations configfs_ops = {
  38        .statfs         = simple_statfs,
  39        .drop_inode     = generic_delete_inode,
  40        .free_inode     = configfs_free_inode,
  41};
  42
  43static 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
  50int configfs_is_root(struct config_item *item)
  51{
  52        return item == &configfs_root_group.cg_item;
  53}
  54
  55static 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
  63static 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(&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
  99static int configfs_get_tree(struct fs_context *fc)
 100{
 101        return get_tree_single(fc, configfs_fill_super);
 102}
 103
 104static const struct fs_context_operations configfs_context_ops = {
 105        .get_tree       = configfs_get_tree,
 106};
 107
 108static int configfs_init_fs_context(struct fs_context *fc)
 109{
 110        fc->ops = &configfs_context_ops;
 111        return 0;
 112}
 113
 114static 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};
 120MODULE_ALIAS_FS("configfs");
 121
 122struct dentry *configfs_pin_fs(void)
 123{
 124        int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
 125                             &configfs_mnt_count);
 126        return err ? ERR_PTR(err) : configfs_mount->mnt_root;
 127}
 128
 129void configfs_release_fs(void)
 130{
 131        simple_release_fs(&configfs_mount, &configfs_mnt_count);
 132}
 133
 134
 135static int __init configfs_init(void)
 136{
 137        int err = -ENOMEM;
 138
 139        configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
 140                                                sizeof(struct configfs_dirent),
 141                                                0, 0, NULL);
 142        if (!configfs_dir_cachep)
 143                goto out;
 144
 145        err = sysfs_create_mount_point(kernel_kobj, "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;
 154out3:
 155        pr_err("Unable to register filesystem!\n");
 156        sysfs_remove_mount_point(kernel_kobj, "config");
 157out2:
 158        kmem_cache_destroy(configfs_dir_cachep);
 159        configfs_dir_cachep = NULL;
 160out:
 161        return err;
 162}
 163
 164static void __exit configfs_exit(void)
 165{
 166        unregister_filesystem(&configfs_fs_type);
 167        sysfs_remove_mount_point(kernel_kobj, "config");
 168        kmem_cache_destroy(configfs_dir_cachep);
 169        configfs_dir_cachep = NULL;
 170}
 171
 172MODULE_AUTHOR("Oracle");
 173MODULE_LICENSE("GPL");
 174MODULE_VERSION("0.0.2");
 175MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
 176
 177core_initcall(configfs_init);
 178module_exit(configfs_exit);
 179
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