/*
   *  linux/fs/super.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  super.c contains code to handle: - mount structures
   *                                   - super-block tables
   *                                   - filesystem drivers list
   *                                   - mount system call
   *                                   - umount system call
   *                                   - ustat system call
   *
   * GK 2/5/95  -  Changed to support mounting the root fs via NFS
   *
   *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
   *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
   *  Added options to /proc/mounts:
   *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
   *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
   *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
   */

  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/smp_lock.h>
  #include <linux/acct.h>
  #include <linux/blkdev.h>
  #include <linux/quotaops.h>
  #include <linux/namei.h>
  #include <linux/buffer_head.h>		/* for fsync_super() */
  #include <linux/mount.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/vfs.h>
  #include <linux/writeback.h>		/* for the emergency remount stuff */
  #include <linux/idr.h>
  #include <linux/kobject.h>

  #include <linux/mutex.h>

  #include <asm/uaccess.h>
  
  
  void get_filesystem(struct file_system_type *fs);
  void put_filesystem(struct file_system_type *fs);
  struct file_system_type *get_fs_type(const char *name);
  
  LIST_HEAD(super_blocks);
  DEFINE_SPINLOCK(sb_lock);
  
  /**
   *	alloc_super	-	create new superblock

   *	@type:	filesystem type superblock should belong to

   *
   *	Allocates and initializes a new &struct super_block.  alloc_super()
   *	returns a pointer new superblock or %NULL if allocation had failed.
   */

  static struct super_block *alloc_super(struct file_system_type *type)

  {

  	struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);

  	static struct super_operations default_op;
  
  	if (s) {

  		if (security_sb_alloc(s)) {
  			kfree(s);
  			s = NULL;
  			goto out;
  		}
  		INIT_LIST_HEAD(&s->s_dirty);
  		INIT_LIST_HEAD(&s->s_io);
  		INIT_LIST_HEAD(&s->s_files);
  		INIT_LIST_HEAD(&s->s_instances);
  		INIT_HLIST_HEAD(&s->s_anon);
  		INIT_LIST_HEAD(&s->s_inodes);
  		init_rwsem(&s->s_umount);

  		mutex_init(&s->s_lock);

  		lockdep_set_class(&s->s_umount, &type->s_umount_key);

  		/*
  		 * The locking rules for s_lock are up to the
  		 * filesystem. For example ext3fs has different
  		 * lock ordering than usbfs:
  		 */
  		lockdep_set_class(&s->s_lock, &type->s_lock_key);

  		down_write(&s->s_umount);
  		s->s_count = S_BIAS;
  		atomic_set(&s->s_active, 1);

  		mutex_init(&s->s_vfs_rename_mutex);

  		mutex_init(&s->s_dquot.dqio_mutex);
  		mutex_init(&s->s_dquot.dqonoff_mutex);

  		init_rwsem(&s->s_dquot.dqptr_sem);
  		init_waitqueue_head(&s->s_wait_unfrozen);
  		s->s_maxbytes = MAX_NON_LFS;
  		s->dq_op = sb_dquot_ops;
  		s->s_qcop = sb_quotactl_ops;
  		s->s_op = &default_op;
  		s->s_time_gran = 1000000000;
  	}
  out:
  	return s;
  }
  
  /**
   *	destroy_super	-	frees a superblock
   *	@s: superblock to free
   *
   *	Frees a superblock.
   */
  static inline void destroy_super(struct super_block *s)
  {
  	security_sb_free(s);
  	kfree(s);
  }
  
  /* Superblock refcounting  */
  
  /*
   * Drop a superblock's refcount.  Returns non-zero if the superblock was
   * destroyed.  The caller must hold sb_lock.
   */
  int __put_super(struct super_block *sb)
  {
  	int ret = 0;
  
  	if (!--sb->s_count) {
  		destroy_super(sb);
  		ret = 1;
  	}
  	return ret;
  }
  
  /*
   * Drop a superblock's refcount.
   * Returns non-zero if the superblock is about to be destroyed and
   * at least is already removed from super_blocks list, so if we are
   * making a loop through super blocks then we need to restart.
   * The caller must hold sb_lock.
   */
  int __put_super_and_need_restart(struct super_block *sb)
  {
  	/* check for race with generic_shutdown_super() */
  	if (list_empty(&sb->s_list)) {
  		/* super block is removed, need to restart... */
  		__put_super(sb);
  		return 1;
  	}
  	/* can't be the last, since s_list is still in use */
  	sb->s_count--;
  	BUG_ON(sb->s_count == 0);
  	return 0;
  }
  
  /**
   *	put_super	-	drop a temporary reference to superblock
   *	@sb: superblock in question
   *
   *	Drops a temporary reference, frees superblock if there's no
   *	references left.
   */
  static void put_super(struct super_block *sb)
  {
  	spin_lock(&sb_lock);
  	__put_super(sb);
  	spin_unlock(&sb_lock);
  }
  
  
  /**
   *	deactivate_super	-	drop an active reference to superblock
   *	@s: superblock to deactivate
   *
   *	Drops an active reference to superblock, acquiring a temprory one if
   *	there is no active references left.  In that case we lock superblock,
   *	tell fs driver to shut it down and drop the temporary reference we
   *	had just acquired.
   */
  void deactivate_super(struct super_block *s)
  {
  	struct file_system_type *fs = s->s_type;
  	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
  		s->s_count -= S_BIAS-1;
  		spin_unlock(&sb_lock);

  		DQUOT_OFF(s);

  		down_write(&s->s_umount);
  		fs->kill_sb(s);
  		put_filesystem(fs);
  		put_super(s);
  	}
  }
  
  EXPORT_SYMBOL(deactivate_super);
  
  /**
   *	grab_super - acquire an active reference
   *	@s: reference we are trying to make active
   *
   *	Tries to acquire an active reference.  grab_super() is used when we
   * 	had just found a superblock in super_blocks or fs_type->fs_supers
   *	and want to turn it into a full-blown active reference.  grab_super()
   *	is called with sb_lock held and drops it.  Returns 1 in case of
   *	success, 0 if we had failed (superblock contents was already dead or
   *	dying when grab_super() had been called).
   */
  static int grab_super(struct super_block *s)
  {
  	s->s_count++;
  	spin_unlock(&sb_lock);
  	down_write(&s->s_umount);
  	if (s->s_root) {
  		spin_lock(&sb_lock);
  		if (s->s_count > S_BIAS) {
  			atomic_inc(&s->s_active);
  			s->s_count--;
  			spin_unlock(&sb_lock);
  			return 1;
  		}
  		spin_unlock(&sb_lock);
  	}
  	up_write(&s->s_umount);
  	put_super(s);
  	yield();
  	return 0;
  }
  
  /**
   *	generic_shutdown_super	-	common helper for ->kill_sb()
   *	@sb: superblock to kill
   *
   *	generic_shutdown_super() does all fs-independent work on superblock
   *	shutdown.  Typical ->kill_sb() should pick all fs-specific objects
   *	that need destruction out of superblock, call generic_shutdown_super()
   *	and release aforementioned objects.  Note: dentries and inodes _are_
   *	taken care of and do not need specific handling.
   */
  void generic_shutdown_super(struct super_block *sb)
  {
  	struct dentry *root = sb->s_root;
  	struct super_operations *sop = sb->s_op;
  
  	if (root) {
  		sb->s_root = NULL;
  		shrink_dcache_parent(root);

  		shrink_dcache_sb(sb);

  		dput(root);
  		fsync_super(sb);
  		lock_super(sb);
  		sb->s_flags &= ~MS_ACTIVE;
  		/* bad name - it should be evict_inodes() */
  		invalidate_inodes(sb);
  		lock_kernel();
  
  		if (sop->write_super && sb->s_dirt)
  			sop->write_super(sb);
  		if (sop->put_super)
  			sop->put_super(sb);
  
  		/* Forget any remaining inodes */
  		if (invalidate_inodes(sb)) {

  			printk("VFS: Busy inodes after unmount of %s. "
  			   "Self-destruct in 5 seconds.  Have a nice day...
  ",
  			   sb->s_id);

  		}
  
  		unlock_kernel();
  		unlock_super(sb);
  	}
  	spin_lock(&sb_lock);
  	/* should be initialized for __put_super_and_need_restart() */
  	list_del_init(&sb->s_list);
  	list_del(&sb->s_instances);
  	spin_unlock(&sb_lock);
  	up_write(&sb->s_umount);
  }
  
  EXPORT_SYMBOL(generic_shutdown_super);
  
  /**
   *	sget	-	find or create a superblock
   *	@type:	filesystem type superblock should belong to
   *	@test:	comparison callback
   *	@set:	setup callback
   *	@data:	argument to each of them
   */
  struct super_block *sget(struct file_system_type *type,
  			int (*test)(struct super_block *,void *),
  			int (*set)(struct super_block *,void *),
  			void *data)
  {
  	struct super_block *s = NULL;
  	struct list_head *p;
  	int err;
  
  retry:
  	spin_lock(&sb_lock);
  	if (test) list_for_each(p, &type->fs_supers) {
  		struct super_block *old;
  		old = list_entry(p, struct super_block, s_instances);
  		if (!test(old, data))
  			continue;
  		if (!grab_super(old))
  			goto retry;
  		if (s)
  			destroy_super(s);
  		return old;
  	}
  	if (!s) {
  		spin_unlock(&sb_lock);

  		s = alloc_super(type);

  		if (!s)
  			return ERR_PTR(-ENOMEM);
  		goto retry;
  	}
  		
  	err = set(s, data);
  	if (err) {
  		spin_unlock(&sb_lock);
  		destroy_super(s);
  		return ERR_PTR(err);
  	}
  	s->s_type = type;
  	strlcpy(s->s_id, type->name, sizeof(s->s_id));
  	list_add_tail(&s->s_list, &super_blocks);
  	list_add(&s->s_instances, &type->fs_supers);
  	spin_unlock(&sb_lock);
  	get_filesystem(type);
  	return s;
  }
  
  EXPORT_SYMBOL(sget);
  
  void drop_super(struct super_block *sb)
  {
  	up_read(&sb->s_umount);
  	put_super(sb);
  }
  
  EXPORT_SYMBOL(drop_super);
  
  static inline void write_super(struct super_block *sb)
  {
  	lock_super(sb);
  	if (sb->s_root && sb->s_dirt)
  		if (sb->s_op->write_super)
  			sb->s_op->write_super(sb);
  	unlock_super(sb);
  }
  
  /*
   * Note: check the dirty flag before waiting, so we don't
   * hold up the sync while mounting a device. (The newly
   * mounted device won't need syncing.)
   */
  void sync_supers(void)
  {

  	struct super_block *sb;

  	spin_lock(&sb_lock);

  restart:
  	list_for_each_entry(sb, &super_blocks, s_list) {

  		if (sb->s_dirt) {
  			sb->s_count++;
  			spin_unlock(&sb_lock);
  			down_read(&sb->s_umount);
  			write_super(sb);

  			up_read(&sb->s_umount);
  			spin_lock(&sb_lock);
  			if (__put_super_and_need_restart(sb))
  				goto restart;
  		}
  	}

  	spin_unlock(&sb_lock);
  }
  
  /*
   * Call the ->sync_fs super_op against all filesytems which are r/w and
   * which implement it.
   *
   * This operation is careful to avoid the livelock which could easily happen
   * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
   * is used only here.  We set it against all filesystems and then clear it as
   * we sync them.  So redirtied filesystems are skipped.
   *
   * But if process A is currently running sync_filesytems and then process B
   * calls sync_filesystems as well, process B will set all the s_need_sync_fs
   * flags again, which will cause process A to resync everything.  Fix that with
   * a local mutex.
   *
   * (Fabian) Avoid sync_fs with clean fs & wait mode 0
   */
  void sync_filesystems(int wait)
  {
  	struct super_block *sb;

  	static DEFINE_MUTEX(mutex);

  	mutex_lock(&mutex);		/* Could be down_interruptible */

  	spin_lock(&sb_lock);

  	list_for_each_entry(sb, &super_blocks, s_list) {

  		if (!sb->s_op->sync_fs)
  			continue;
  		if (sb->s_flags & MS_RDONLY)
  			continue;
  		sb->s_need_sync_fs = 1;
  	}

  
  restart:

  	list_for_each_entry(sb, &super_blocks, s_list) {

  		if (!sb->s_need_sync_fs)
  			continue;
  		sb->s_need_sync_fs = 0;
  		if (sb->s_flags & MS_RDONLY)
  			continue;	/* hm.  Was remounted r/o meanwhile */
  		sb->s_count++;
  		spin_unlock(&sb_lock);
  		down_read(&sb->s_umount);
  		if (sb->s_root && (wait || sb->s_dirt))
  			sb->s_op->sync_fs(sb, wait);

  		up_read(&sb->s_umount);
  		/* restart only when sb is no longer on the list */
  		spin_lock(&sb_lock);
  		if (__put_super_and_need_restart(sb))
  			goto restart;

  	}
  	spin_unlock(&sb_lock);

  	mutex_unlock(&mutex);

  }
  
  /**
   *	get_super - get the superblock of a device
   *	@bdev: device to get the superblock for
   *	
   *	Scans the superblock list and finds the superblock of the file system
   *	mounted on the device given. %NULL is returned if no match is found.
   */
  
  struct super_block * get_super(struct block_device *bdev)
  {

  	struct super_block *sb;

  	if (!bdev)
  		return NULL;

  	spin_lock(&sb_lock);

  rescan:
  	list_for_each_entry(sb, &super_blocks, s_list) {
  		if (sb->s_bdev == bdev) {
  			sb->s_count++;

  			spin_unlock(&sb_lock);

  			down_read(&sb->s_umount);
  			if (sb->s_root)
  				return sb;
  			up_read(&sb->s_umount);
  			/* restart only when sb is no longer on the list */
  			spin_lock(&sb_lock);
  			if (__put_super_and_need_restart(sb))
  				goto rescan;

  		}
  	}
  	spin_unlock(&sb_lock);
  	return NULL;
  }
  
  EXPORT_SYMBOL(get_super);
   
  struct super_block * user_get_super(dev_t dev)
  {

  	struct super_block *sb;

  	spin_lock(&sb_lock);

  rescan:
  	list_for_each_entry(sb, &super_blocks, s_list) {
  		if (sb->s_dev ==  dev) {
  			sb->s_count++;

  			spin_unlock(&sb_lock);

  			down_read(&sb->s_umount);
  			if (sb->s_root)
  				return sb;
  			up_read(&sb->s_umount);
  			/* restart only when sb is no longer on the list */
  			spin_lock(&sb_lock);
  			if (__put_super_and_need_restart(sb))
  				goto rescan;

  		}
  	}
  	spin_unlock(&sb_lock);
  	return NULL;
  }

  asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
  {
          struct super_block *s;
          struct ustat tmp;
          struct kstatfs sbuf;
  	int err = -EINVAL;
  
          s = user_get_super(new_decode_dev(dev));
          if (s == NULL)
                  goto out;

  	err = vfs_statfs(s->s_root, &sbuf);

  	drop_super(s);
  	if (err)
  		goto out;
  
          memset(&tmp,0,sizeof(struct ustat));
          tmp.f_tfree = sbuf.f_bfree;
          tmp.f_tinode = sbuf.f_ffree;
  
          err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
  out:
  	return err;
  }
  
  /**
   *	mark_files_ro
   *	@sb: superblock in question
   *
   *	All files are marked read/only.  We don't care about pending
   *	delete files so this should be used in 'force' mode only
   */
  
  static void mark_files_ro(struct super_block *sb)
  {
  	struct file *f;
  
  	file_list_lock();

  	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {

  		if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
  			f->f_mode &= ~FMODE_WRITE;
  	}
  	file_list_unlock();
  }
  
  /**
   *	do_remount_sb - asks filesystem to change mount options.
   *	@sb:	superblock in question
   *	@flags:	numeric part of options
   *	@data:	the rest of options
   *      @force: whether or not to force the change
   *
   *	Alters the mount options of a mounted file system.
   */
  int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
  {
  	int retval;
  	
  	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
  		return -EACCES;
  	if (flags & MS_RDONLY)
  		acct_auto_close(sb);
  	shrink_dcache_sb(sb);
  	fsync_super(sb);
  
  	/* If we are remounting RDONLY and current sb is read/write,
  	   make sure there are no rw files opened */
  	if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
  		if (force)
  			mark_files_ro(sb);
  		else if (!fs_may_remount_ro(sb))
  			return -EBUSY;
  	}
  
  	if (sb->s_op->remount_fs) {
  		lock_super(sb);
  		retval = sb->s_op->remount_fs(sb, &flags, data);
  		unlock_super(sb);
  		if (retval)
  			return retval;
  	}
  	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
  	return 0;
  }
  
  static void do_emergency_remount(unsigned long foo)
  {
  	struct super_block *sb;
  
  	spin_lock(&sb_lock);
  	list_for_each_entry(sb, &super_blocks, s_list) {
  		sb->s_count++;
  		spin_unlock(&sb_lock);
  		down_read(&sb->s_umount);
  		if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
  			/*
  			 * ->remount_fs needs lock_kernel().
  			 *
  			 * What lock protects sb->s_flags??
  			 */
  			lock_kernel();
  			do_remount_sb(sb, MS_RDONLY, NULL, 1);
  			unlock_kernel();
  		}
  		drop_super(sb);
  		spin_lock(&sb_lock);
  	}
  	spin_unlock(&sb_lock);
  	printk("Emergency Remount complete
  ");
  }
  
  void emergency_remount(void)
  {
  	pdflush_operation(do_emergency_remount, 0);
  }
  
  /*
   * Unnamed block devices are dummy devices used by virtual
   * filesystems which don't use real block-devices.  -- jrs
   */
  
  static struct idr unnamed_dev_idr;
  static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
  
  int set_anon_super(struct super_block *s, void *data)
  {
  	int dev;
  	int error;
  
   retry:
  	if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
  		return -ENOMEM;
  	spin_lock(&unnamed_dev_lock);
  	error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
  	spin_unlock(&unnamed_dev_lock);
  	if (error == -EAGAIN)
  		/* We raced and lost with another CPU. */
  		goto retry;
  	else if (error)
  		return -EAGAIN;
  
  	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
  		spin_lock(&unnamed_dev_lock);
  		idr_remove(&unnamed_dev_idr, dev);
  		spin_unlock(&unnamed_dev_lock);
  		return -EMFILE;
  	}
  	s->s_dev = MKDEV(0, dev & MINORMASK);
  	return 0;
  }
  
  EXPORT_SYMBOL(set_anon_super);
  
  void kill_anon_super(struct super_block *sb)
  {
  	int slot = MINOR(sb->s_dev);
  
  	generic_shutdown_super(sb);
  	spin_lock(&unnamed_dev_lock);
  	idr_remove(&unnamed_dev_idr, slot);
  	spin_unlock(&unnamed_dev_lock);
  }
  
  EXPORT_SYMBOL(kill_anon_super);
  
  void __init unnamed_dev_init(void)
  {
  	idr_init(&unnamed_dev_idr);
  }
  
  void kill_litter_super(struct super_block *sb)
  {
  	if (sb->s_root)
  		d_genocide(sb->s_root);
  	kill_anon_super(sb);
  }
  
  EXPORT_SYMBOL(kill_litter_super);
  
  static int set_bdev_super(struct super_block *s, void *data)
  {
  	s->s_bdev = data;
  	s->s_dev = s->s_bdev->bd_dev;
  	return 0;
  }
  
  static int test_bdev_super(struct super_block *s, void *data)
  {
  	return (void *)s->s_bdev == data;
  }

  static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
  {
  	if (bdev->bd_disk) {
  		if (bdev->bd_part)
  			kobject_uevent(&bdev->bd_part->kobj, action);
  		else
  			kobject_uevent(&bdev->bd_disk->kobj, action);
  	}
  }

  int get_sb_bdev(struct file_system_type *fs_type,

  	int flags, const char *dev_name, void *data,

  	int (*fill_super)(struct super_block *, void *, int),
  	struct vfsmount *mnt)

  {
  	struct block_device *bdev;
  	struct super_block *s;
  	int error = 0;
  
  	bdev = open_bdev_excl(dev_name, flags, fs_type);
  	if (IS_ERR(bdev))

  		return PTR_ERR(bdev);

  
  	/*
  	 * once the super is inserted into the list by sget, s_umount
  	 * will protect the lockfs code from trying to start a snapshot
  	 * while we are mounting
  	 */

  	mutex_lock(&bdev->bd_mount_mutex);

  	s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);

  	mutex_unlock(&bdev->bd_mount_mutex);

  	if (IS_ERR(s))

  		goto error_s;

  
  	if (s->s_root) {
  		if ((flags ^ s->s_flags) & MS_RDONLY) {
  			up_write(&s->s_umount);
  			deactivate_super(s);

  			error = -EBUSY;
  			goto error_bdev;

  		}

  
  		close_bdev_excl(bdev);

  	} else {
  		char b[BDEVNAME_SIZE];
  
  		s->s_flags = flags;
  		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));

  		sb_set_blocksize(s, block_size(bdev));

  		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);

  		if (error) {
  			up_write(&s->s_umount);
  			deactivate_super(s);

  			goto error;

  		}

  
  		s->s_flags |= MS_ACTIVE;
  		bdev_uevent(bdev, KOBJ_MOUNT);

  	}

  	return simple_set_mnt(mnt, s);

  error_s:
  	error = PTR_ERR(s);
  error_bdev:

  	close_bdev_excl(bdev);

  error:
  	return error;

  }
  
  EXPORT_SYMBOL(get_sb_bdev);
  
  void kill_block_super(struct super_block *sb)
  {
  	struct block_device *bdev = sb->s_bdev;

  	bdev_uevent(bdev, KOBJ_UMOUNT);

  	generic_shutdown_super(sb);
  	sync_blockdev(bdev);
  	close_bdev_excl(bdev);
  }
  
  EXPORT_SYMBOL(kill_block_super);

  int get_sb_nodev(struct file_system_type *fs_type,

  	int flags, void *data,

  	int (*fill_super)(struct super_block *, void *, int),
  	struct vfsmount *mnt)

  {
  	int error;
  	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
  
  	if (IS_ERR(s))

  		return PTR_ERR(s);

  
  	s->s_flags = flags;

  	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);

  	if (error) {
  		up_write(&s->s_umount);
  		deactivate_super(s);

  		return error;

  	}
  	s->s_flags |= MS_ACTIVE;

  	return simple_set_mnt(mnt, s);

  }
  
  EXPORT_SYMBOL(get_sb_nodev);
  
  static int compare_single(struct super_block *s, void *p)
  {
  	return 1;
  }

  int get_sb_single(struct file_system_type *fs_type,

  	int flags, void *data,

  	int (*fill_super)(struct super_block *, void *, int),
  	struct vfsmount *mnt)

  {
  	struct super_block *s;
  	int error;
  
  	s = sget(fs_type, compare_single, set_anon_super, NULL);
  	if (IS_ERR(s))

  		return PTR_ERR(s);

  	if (!s->s_root) {
  		s->s_flags = flags;

  		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);

  		if (error) {
  			up_write(&s->s_umount);
  			deactivate_super(s);

  			return error;

  		}
  		s->s_flags |= MS_ACTIVE;
  	}
  	do_remount_sb(s, flags, data, 0);

  	return simple_set_mnt(mnt, s);

  }
  
  EXPORT_SYMBOL(get_sb_single);
  
  struct vfsmount *

  vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)

  {

  	struct vfsmount *mnt;

  	char *secdata = NULL;

  	int error;

  
  	if (!type)
  		return ERR_PTR(-ENODEV);

  	error = -ENOMEM;

  	mnt = alloc_vfsmnt(name);
  	if (!mnt)
  		goto out;
  
  	if (data) {
  		secdata = alloc_secdata();

  		if (!secdata)

  			goto out_mnt;

  
  		error = security_sb_copy_data(type, data, secdata);

  		if (error)

  			goto out_free_secdata;

  	}

  	error = type->get_sb(type, flags, name, data, mnt);
  	if (error < 0)

  		goto out_free_secdata;

  
   	error = security_sb_kern_mount(mnt->mnt_sb, secdata);

   	if (error)
   		goto out_sb;

  
  	mnt->mnt_mountpoint = mnt->mnt_root;

  	mnt->mnt_parent = mnt;

  	up_write(&mnt->mnt_sb->s_umount);

  	free_secdata(secdata);

  	return mnt;
  out_sb:

  	dput(mnt->mnt_root);
  	up_write(&mnt->mnt_sb->s_umount);
  	deactivate_super(mnt->mnt_sb);

  out_free_secdata:
  	free_secdata(secdata);
  out_mnt:
  	free_vfsmnt(mnt);
  out:

  	return ERR_PTR(error);

  }

  EXPORT_SYMBOL_GPL(vfs_kern_mount);
  
  struct vfsmount *
  do_kern_mount(const char *fstype, int flags, const char *name, void *data)
  {
  	struct file_system_type *type = get_fs_type(fstype);
  	struct vfsmount *mnt;
  	if (!type)
  		return ERR_PTR(-ENODEV);
  	mnt = vfs_kern_mount(type, flags, name, data);
  	put_filesystem(type);
  	return mnt;
  }

  struct vfsmount *kern_mount(struct file_system_type *type)
  {

  	return vfs_kern_mount(type, 0, type->name, NULL);

  }
  
  EXPORT_SYMBOL(kern_mount);