fs/configfs/mount.c

   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);