LXR linux/fs/sysfs/mount.c

   1/*
   2 * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
   3 *
   4 * Copyright (c) 2001-3 Patrick Mochel
   5 * Copyright (c) 2007 SUSE Linux Products GmbH
   6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7 *
   8 * This file is released under the GPLv2.
   9 *
  10 * Please see Documentation/filesystems/sysfs.txt for more information.
  11 */
  12
  13#define DEBUG
  14
  15#include <linux/fs.h>
  16#include <linux/magic.h>
  17#include <linux/mount.h>
  18#include <linux/init.h>
  19#include <linux/user_namespace.h>
  20
  21#include "sysfs.h"
  22
  23static struct kernfs_root *sysfs_root;
  24struct kernfs_node *sysfs_root_kn;
  25
  26static struct dentry *sysfs_mount(struct file_system_type *fs_type,
  27        int flags, const char *dev_name, void *data)
  28{
  29        struct dentry *root;
  30        void *ns;
  31        bool new_sb;
  32
  33        if (!(flags & MS_KERNMOUNT)) {
  34                if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
  35                        return ERR_PTR(-EPERM);
  36        }
  37
  38        ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
  39        root = kernfs_mount_ns(fs_type, flags, sysfs_root,
  40                                SYSFS_MAGIC, &new_sb, ns);
  41        if (IS_ERR(root) || !new_sb)
  42                kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  43        else if (new_sb)
  44                root->d_sb->s_iflags |= SB_I_USERNS_VISIBLE;
  45
  46        return root;
  47}
  48
  49static void sysfs_kill_sb(struct super_block *sb)
  50{
  51        void *ns = (void *)kernfs_super_ns(sb);
  52
  53        kernfs_kill_sb(sb);
  54        kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
  55}
  56
  57static struct file_system_type sysfs_fs_type = {
  58        .name           = "sysfs",
  59        .mount          = sysfs_mount,
  60        .kill_sb        = sysfs_kill_sb,
  61        .fs_flags       = FS_USERNS_MOUNT,
  62};
  63
  64int __init sysfs_init(void)
  65{
  66        int err;
  67
  68        sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
  69                                        NULL);
  70        if (IS_ERR(sysfs_root))
  71                return PTR_ERR(sysfs_root);
  72
  73        sysfs_root_kn = sysfs_root->kn;
  74
  75        err = register_filesystem(&sysfs_fs_type);
  76        if (err) {
  77                kernfs_destroy_root(sysfs_root);
  78                return err;
  79        }
  80
  81        return 0;
  82}
  83