fs/configfs/mount.c

   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(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(&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, 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, &configfs_mount,
 125                              &configfs_mnt_count);
 126         return err ? ERR_PTR(err) : configfs_mount->mnt_root;
 127 }
 128
 129 void configfs_release_fs(void)
 130 {
 131         simple_release_fs(&configfs_mount, &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("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;
 154 out3:
 155         pr_err("Unable to register filesystem!\n");
 156         sysfs_remove_mount_point(kernel_kobj, "config");
 157 out2:
 158         kmem_cache_destroy(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(kernel_kobj, "config");
 168         kmem_cache_destroy(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);