/*
   *  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/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 <linux/file.h>

  #include <asm/uaccess.h>

  #include "internal.h"

  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 const struct super_operations default_op;

  
  	if (s) {

  		if (security_sb_alloc(s)) {
  			kfree(s);
  			s = NULL;
  			goto out;
  		}

  		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_LIST_HEAD(&s->s_dentry_lru);

  		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);

  		/*
  		 * sget() can have s_umount recursion.
  		 *
  		 * When it cannot find a suitable sb, it allocates a new
  		 * one (this one), and tries again to find a suitable old
  		 * one.
  		 *
  		 * In case that succeeds, it will acquire the s_umount
  		 * lock of the old one. Since these are clearly distrinct
  		 * locks, and this object isn't exposed yet, there's no
  		 * risk of deadlocks.
  		 *
  		 * Annotate this by putting this lock in a different
  		 * subclass.
  		 */
  		down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);

  		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->s_subtype);

  	kfree(s->s_options);

  	kfree(s);
  }
  
  /* Superblock refcounting  */
  
  /*
   * Drop a superblock's refcount.  Returns non-zero if the superblock was
   * destroyed.  The caller must hold sb_lock.
   */

  static 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.
   */

  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);

  		vfs_dq_off(s, 0);

  		down_write(&s->s_umount);
  		fs->kill_sb(s);
  		put_filesystem(fs);
  		put_super(s);
  	}
  }
  
  EXPORT_SYMBOL(deactivate_super);
  
  /**

   *	deactivate_locked_super	-	drop an active reference to superblock
   *	@s: superblock to deactivate
   *
   *	Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
   *	it does not unlock it until it's all over.  As the result, it's safe to
   *	use to dispose of new superblock on ->get_sb() failure exits - nobody
   *	will see the sucker until it's all over.  Equivalent using up_write +
   *	deactivate_super is safe for that purpose only if superblock is either
   *	safe to use or has NULL ->s_root when we unlock.
   */
  void deactivate_locked_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);
  		vfs_dq_off(s, 0);
  		fs->kill_sb(s);
  		put_filesystem(fs);
  		put_super(s);
  	} else {
  		up_write(&s->s_umount);
  	}
  }
  
  EXPORT_SYMBOL(deactivate_locked_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) __releases(sb_lock)

  {
  	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;
  }

  /*

   * Superblock locking.  We really ought to get rid of these two.
   */
  void lock_super(struct super_block * sb)
  {
  	get_fs_excl();
  	mutex_lock(&sb->s_lock);
  }
  
  void unlock_super(struct super_block * sb)
  {
  	put_fs_excl();
  	mutex_unlock(&sb->s_lock);
  }
  
  EXPORT_SYMBOL(lock_super);
  EXPORT_SYMBOL(unlock_super);

  /**
   *	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.

   *
   *	Upon calling this function, the filesystem may no longer alter or
   *	rearrange the set of dentries belonging to this super_block, nor may it
   *	change the attachments of dentries to inodes.

   */
  void generic_shutdown_super(struct super_block *sb)
  {

  	const struct super_operations *sop = sb->s_op;

  	if (sb->s_root) {
  		shrink_dcache_for_umount(sb);

  		sync_filesystem(sb);

  		get_fs_excl();

  		sb->s_flags &= ~MS_ACTIVE;

  		/* bad name - it should be evict_inodes() */
  		invalidate_inodes(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);

  		}

  		put_fs_excl();

  	}
  	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 super_block *old;

  	int err;
  
  retry:
  	spin_lock(&sb_lock);

  	if (test) {
  		list_for_each_entry(old, &type->fs_supers, s_instances) {
  			if (!test(old, data))
  				continue;
  			if (!grab_super(old))
  				goto retry;

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

  				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);

  		up_write(&s->s_umount);

  		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);

  /**
   * sync_supers - helper for periodic superblock writeback
   *
   * Call the write_super method if present on all dirty superblocks in
   * the system.  This is for the periodic writeback used by most older
   * filesystems.  For data integrity superblock writeback use
   * sync_filesystems() instead.
   *

   * 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_op->write_super && sb->s_dirt) {

  			sb->s_count++;
  			spin_unlock(&sb_lock);

  			down_read(&sb->s_umount);

  			if (sb->s_root && sb->s_dirt)
  				sb->s_op->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);
  }

  /**
   *	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);

  
  /**
   * get_active_super - get an active reference to 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.  Returns the superblock with an active
   * reference and s_umount held exclusively or %NULL if none was found.
   */
  struct super_block *get_active_super(struct block_device *bdev)
  {
  	struct super_block *sb;
  
  	if (!bdev)
  		return NULL;
  
  	spin_lock(&sb_lock);
  	list_for_each_entry(sb, &super_blocks, s_list) {
  		if (sb->s_bdev != bdev)
  			continue;
  
  		sb->s_count++;
  		spin_unlock(&sb_lock);
  		down_write(&sb->s_umount);
  		if (sb->s_root) {
  			spin_lock(&sb_lock);
  			if (sb->s_count > S_BIAS) {
  				atomic_inc(&sb->s_active);
  				sb->s_count--;
  				spin_unlock(&sb_lock);
  				return sb;
  			}
  			spin_unlock(&sb_lock);
  		}
  		up_write(&sb->s_umount);
  		put_super(sb);
  		yield();
  		spin_lock(&sb_lock);
  	}
  	spin_unlock(&sb_lock);
  	return NULL;
  }

   
  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;
  }

  SYSCALL_DEFINE2(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;
  }
  
  /**

   *	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;

  	int remount_rw;

  
  	if (sb->s_frozen != SB_UNFROZEN)
  		return -EBUSY;

  #ifdef CONFIG_BLOCK

  	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
  		return -EACCES;

  #endif

  	if (flags & MS_RDONLY)
  		acct_auto_close(sb);
  	shrink_dcache_sb(sb);

  	sync_filesystem(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;

  		retval = vfs_dq_off(sb, 1);

  		if (retval < 0 && retval != -ENOSYS)

  			return -EBUSY;

  	}

  	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);

  
  	if (sb->s_op->remount_fs) {

  		retval = sb->s_op->remount_fs(sb, &flags, data);

  		if (retval)

  			return retval;
  	}
  	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);

  	if (remount_rw)

  		vfs_dq_quota_on_remount(sb);

  	return 0;
  }

  static void do_emergency_remount(struct work_struct *work)

  {
  	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_write(&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??
  			 */

  			do_remount_sb(sb, MS_RDONLY, NULL, 1);

  		}

  		up_write(&sb->s_umount);
  		put_super(sb);

  		spin_lock(&sb_lock);
  	}
  	spin_unlock(&sb_lock);

  	kfree(work);

  	printk("Emergency Remount complete
  ");
  }
  
  void emergency_remount(void)
  {

  	struct work_struct *work;
  
  	work = kmalloc(sizeof(*work), GFP_ATOMIC);
  	if (work) {
  		INIT_WORK(work, do_emergency_remount);
  		schedule_work(work);
  	}

  }
  
  /*
   * Unnamed block devices are dummy devices used by virtual
   * filesystems which don't use real block-devices.  -- jrs
   */

  static DEFINE_IDA(unnamed_dev_ida);

  static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */

  static int unnamed_dev_start = 0; /* don't bother trying below it */

  
  int set_anon_super(struct super_block *s, void *data)
  {
  	int dev;
  	int error;
  
   retry:

  	if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)

  		return -ENOMEM;
  	spin_lock(&unnamed_dev_lock);

  	error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);

  	if (!error)
  		unnamed_dev_start = dev + 1;

  	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);

  		ida_remove(&unnamed_dev_ida, dev);

  		if (unnamed_dev_start > dev)
  			unnamed_dev_start = 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);

  	ida_remove(&unnamed_dev_ida, slot);

  	if (slot < unnamed_dev_start)
  		unnamed_dev_start = slot;

  	spin_unlock(&unnamed_dev_lock);
  }
  
  EXPORT_SYMBOL(kill_anon_super);

  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 ns_test_super(struct super_block *sb, void *data)
  {
  	return sb->s_fs_info == data;
  }
  
  static int ns_set_super(struct super_block *sb, void *data)
  {
  	sb->s_fs_info = data;
  	return set_anon_super(sb, NULL);
  }
  
  int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
  	int (*fill_super)(struct super_block *, void *, int),
  	struct vfsmount *mnt)
  {
  	struct super_block *sb;
  
  	sb = sget(fs_type, ns_test_super, ns_set_super, data);
  	if (IS_ERR(sb))
  		return PTR_ERR(sb);
  
  	if (!sb->s_root) {
  		int err;
  		sb->s_flags = flags;
  		err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
  		if (err) {

  			deactivate_locked_super(sb);

  			return err;
  		}
  
  		sb->s_flags |= MS_ACTIVE;
  	}
  
  	simple_set_mnt(mnt, sb);
  	return 0;
  }
  
  EXPORT_SYMBOL(get_sb_ns);

  #ifdef CONFIG_BLOCK

  static int set_bdev_super(struct super_block *s, void *data)
  {
  	s->s_bdev = data;
  	s->s_dev = s->s_bdev->bd_dev;

  
  	/*
  	 * We set the bdi here to the queue backing, file systems can
  	 * overwrite this in ->fill_super()
  	 */
  	s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;

  	return 0;
  }
  
  static int test_bdev_super(struct super_block *s, void *data)
  {
  	return (void *)s->s_bdev == data;
  }

  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;

  	fmode_t mode = FMODE_READ;

  	int error = 0;

  	if (!(flags & MS_RDONLY))
  		mode |= FMODE_WRITE;
  
  	bdev = open_bdev_exclusive(dev_name, mode, 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_fsfreeze_mutex);
  	if (bdev->bd_fsfreeze_count > 0) {
  		mutex_unlock(&bdev->bd_fsfreeze_mutex);
  		error = -EBUSY;
  		goto error_bdev;
  	}

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

  	mutex_unlock(&bdev->bd_fsfreeze_mutex);

  	if (IS_ERR(s))

  		goto error_s;

  
  	if (s->s_root) {
  		if ((flags ^ s->s_flags) & MS_RDONLY) {

  			deactivate_locked_super(s);

  			error = -EBUSY;
  			goto error_bdev;

  		}

  		close_bdev_exclusive(bdev, mode);

  	} else {
  		char b[BDEVNAME_SIZE];
  
  		s->s_flags = flags;

  		s->s_mode = mode;

  		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) {

  			deactivate_locked_super(s);

  			goto error;

  		}

  
  		s->s_flags |= MS_ACTIVE;

  		bdev->bd_super = s;

  	}

  	simple_set_mnt(mnt, s);
  	return 0;

  error_s:
  	error = PTR_ERR(s);
  error_bdev:

  	close_bdev_exclusive(bdev, mode);

  error:
  	return error;

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

  	fmode_t mode = sb->s_mode;

  	bdev->bd_super = NULL;

  	generic_shutdown_super(sb);
  	sync_blockdev(bdev);

  	close_bdev_exclusive(bdev, mode);

  }
  
  EXPORT_SYMBOL(kill_block_super);

  #endif

  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) {

  		deactivate_locked_super(s);

  		return error;

  	}
  	s->s_flags |= MS_ACTIVE;

  	simple_set_mnt(mnt, s);
  	return 0;

  }
  
  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) {

  			deactivate_locked_super(s);

  			return error;

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

  	simple_set_mnt(mnt, s);
  	return 0;

  }
  
  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 && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {

  		secdata = alloc_secdata();

  		if (!secdata)

  			goto out_mnt;

  		error = security_sb_copy_data(data, secdata);

  		if (error)

  			goto out_free_secdata;

  	}

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

  		goto out_free_secdata;

  	BUG_ON(!mnt->mnt_sb);

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

   	if (error)
   		goto out_sb;

  	/*
  	 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
  	 * but s_maxbytes was an unsigned long long for many releases. Throw
  	 * this warning for a little while to try and catch filesystems that
  	 * violate this rule. This warning should be either removed or
  	 * converted to a BUG() in 2.6.34.
  	 */
  	WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
  		"negative value (%lld)
  ", type->name, mnt->mnt_sb->s_maxbytes);

  	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);

  	deactivate_locked_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);

  static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
  {
  	int err;
  	const char *subtype = strchr(fstype, '.');
  	if (subtype) {
  		subtype++;
  		err = -EINVAL;
  		if (!subtype[0])
  			goto err;
  	} else
  		subtype = "";
  
  	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
  	err = -ENOMEM;
  	if (!mnt->mnt_sb->s_subtype)
  		goto err;
  	return mnt;
  
   err:
  	mntput(mnt);
  	return ERR_PTR(err);
  }

  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);

  	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
  	    !mnt->mnt_sb->s_subtype)
  		mnt = fs_set_subtype(mnt, fstype);

  	put_filesystem(type);
  	return mnt;
  }

  EXPORT_SYMBOL_GPL(do_kern_mount);

  struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)

  {

  	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);

  }

  EXPORT_SYMBOL_GPL(kern_mount_data);