/*
   *  linux/fs/namespace.c
   *
   * (C) Copyright Al Viro 2000, 2001
   *	Released under GPL v2.
   *
   * Based on code from fs/super.c, copyright Linus Torvalds and others.
   * Heavily rewritten.
   */

  #include <linux/syscalls.h>
  #include <linux/slab.h>
  #include <linux/sched.h>
  #include <linux/smp_lock.h>
  #include <linux/init.h>

  #include <linux/kernel.h>

  #include <linux/acct.h>

  #include <linux/capability.h>

  #include <linux/cpumask.h>

  #include <linux/module.h>

  #include <linux/sysfs.h>

  #include <linux/seq_file.h>

  #include <linux/mnt_namespace.h>

  #include <linux/namei.h>
  #include <linux/security.h>
  #include <linux/mount.h>

  #include <linux/ramfs.h>

  #include <linux/log2.h>

  #include <linux/idr.h>

  #include <linux/fs_struct.h>

  #include <asm/uaccess.h>
  #include <asm/unistd.h>

  #include "pnode.h"

  #include "internal.h"

  #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
  #define HASH_SIZE (1UL << HASH_SHIFT)

  /* spinlock for vfsmount related operations, inplace of dcache_lock */

  __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
  
  static int event;

  static DEFINE_IDA(mnt_id_ida);

  static DEFINE_IDA(mnt_group_ida);

  static struct list_head *mount_hashtable __read_mostly;

  static struct kmem_cache *mnt_cache __read_mostly;

  static struct rw_semaphore namespace_sem;

  /* /sys/fs */

  struct kobject *fs_kobj;
  EXPORT_SYMBOL_GPL(fs_kobj);

  static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
  {

  	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
  	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);

  	tmp = tmp + (tmp >> HASH_SHIFT);
  	return tmp & (HASH_SIZE - 1);

  }

  #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)

  /* allocation is serialized by namespace_sem */
  static int mnt_alloc_id(struct vfsmount *mnt)
  {
  	int res;
  
  retry:
  	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
  	spin_lock(&vfsmount_lock);
  	res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
  	spin_unlock(&vfsmount_lock);
  	if (res == -EAGAIN)
  		goto retry;
  
  	return res;
  }
  
  static void mnt_free_id(struct vfsmount *mnt)
  {
  	spin_lock(&vfsmount_lock);
  	ida_remove(&mnt_id_ida, mnt->mnt_id);
  	spin_unlock(&vfsmount_lock);
  }

  /*
   * Allocate a new peer group ID
   *
   * mnt_group_ida is protected by namespace_sem
   */
  static int mnt_alloc_group_id(struct vfsmount *mnt)
  {
  	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
  		return -ENOMEM;
  
  	return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
  }
  
  /*
   * Release a peer group ID
   */
  void mnt_release_group_id(struct vfsmount *mnt)
  {
  	ida_remove(&mnt_group_ida, mnt->mnt_group_id);
  	mnt->mnt_group_id = 0;
  }

  struct vfsmount *alloc_vfsmnt(const char *name)
  {

  	struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);

  	if (mnt) {

  		int err;
  
  		err = mnt_alloc_id(mnt);

  		if (err)
  			goto out_free_cache;
  
  		if (name) {
  			mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
  			if (!mnt->mnt_devname)
  				goto out_free_id;

  		}

  		atomic_set(&mnt->mnt_count, 1);

  		INIT_LIST_HEAD(&mnt->mnt_hash);
  		INIT_LIST_HEAD(&mnt->mnt_child);
  		INIT_LIST_HEAD(&mnt->mnt_mounts);
  		INIT_LIST_HEAD(&mnt->mnt_list);

  		INIT_LIST_HEAD(&mnt->mnt_expire);

  		INIT_LIST_HEAD(&mnt->mnt_share);

  		INIT_LIST_HEAD(&mnt->mnt_slave_list);
  		INIT_LIST_HEAD(&mnt->mnt_slave);

  		atomic_set(&mnt->__mnt_writers, 0);

  	}
  	return mnt;

  
  out_free_id:
  	mnt_free_id(mnt);
  out_free_cache:
  	kmem_cache_free(mnt_cache, mnt);
  	return NULL;

  }

  /*
   * Most r/o checks on a fs are for operations that take
   * discrete amounts of time, like a write() or unlink().
   * We must keep track of when those operations start
   * (for permission checks) and when they end, so that
   * we can determine when writes are able to occur to
   * a filesystem.
   */

  /*
   * __mnt_is_readonly: check whether a mount is read-only
   * @mnt: the mount to check for its write status
   *
   * This shouldn't be used directly ouside of the VFS.
   * It does not guarantee that the filesystem will stay
   * r/w, just that it is right *now*.  This can not and
   * should not be used in place of IS_RDONLY(inode).
   * mnt_want/drop_write() will _keep_ the filesystem
   * r/w.
   */
  int __mnt_is_readonly(struct vfsmount *mnt)
  {

  	if (mnt->mnt_flags & MNT_READONLY)
  		return 1;
  	if (mnt->mnt_sb->s_flags & MS_RDONLY)
  		return 1;
  	return 0;

  }
  EXPORT_SYMBOL_GPL(__mnt_is_readonly);
  
  struct mnt_writer {
  	/*
  	 * If holding multiple instances of this lock, they
  	 * must be ordered by cpu number.
  	 */
  	spinlock_t lock;
  	struct lock_class_key lock_class; /* compiles out with !lockdep */
  	unsigned long count;
  	struct vfsmount *mnt;
  } ____cacheline_aligned_in_smp;
  static DEFINE_PER_CPU(struct mnt_writer, mnt_writers);
  
  static int __init init_mnt_writers(void)
  {
  	int cpu;
  	for_each_possible_cpu(cpu) {
  		struct mnt_writer *writer = &per_cpu(mnt_writers, cpu);
  		spin_lock_init(&writer->lock);
  		lockdep_set_class(&writer->lock, &writer->lock_class);
  		writer->count = 0;
  	}
  	return 0;
  }
  fs_initcall(init_mnt_writers);
  
  static void unlock_mnt_writers(void)
  {
  	int cpu;
  	struct mnt_writer *cpu_writer;
  
  	for_each_possible_cpu(cpu) {
  		cpu_writer = &per_cpu(mnt_writers, cpu);
  		spin_unlock(&cpu_writer->lock);
  	}
  }
  
  static inline void __clear_mnt_count(struct mnt_writer *cpu_writer)
  {
  	if (!cpu_writer->mnt)
  		return;
  	/*
  	 * This is in case anyone ever leaves an invalid,
  	 * old ->mnt and a count of 0.
  	 */
  	if (!cpu_writer->count)
  		return;
  	atomic_add(cpu_writer->count, &cpu_writer->mnt->__mnt_writers);
  	cpu_writer->count = 0;
  }
   /*
   * must hold cpu_writer->lock
   */
  static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer,
  					  struct vfsmount *mnt)
  {
  	if (cpu_writer->mnt == mnt)
  		return;
  	__clear_mnt_count(cpu_writer);
  	cpu_writer->mnt = mnt;
  }
  
  /*
   * Most r/o checks on a fs are for operations that take
   * discrete amounts of time, like a write() or unlink().
   * We must keep track of when those operations start
   * (for permission checks) and when they end, so that
   * we can determine when writes are able to occur to
   * a filesystem.
   */

  /**
   * mnt_want_write - get write access to a mount
   * @mnt: the mount on which to take a write
   *
   * This tells the low-level filesystem that a write is
   * about to be performed to it, and makes sure that
   * writes are allowed before returning success.  When
   * the write operation is finished, mnt_drop_write()
   * must be called.  This is effectively a refcount.
   */
  int mnt_want_write(struct vfsmount *mnt)
  {

  	int ret = 0;
  	struct mnt_writer *cpu_writer;
  
  	cpu_writer = &get_cpu_var(mnt_writers);
  	spin_lock(&cpu_writer->lock);
  	if (__mnt_is_readonly(mnt)) {
  		ret = -EROFS;
  		goto out;
  	}
  	use_cpu_writer_for_mount(cpu_writer, mnt);
  	cpu_writer->count++;
  out:
  	spin_unlock(&cpu_writer->lock);
  	put_cpu_var(mnt_writers);
  	return ret;

  }
  EXPORT_SYMBOL_GPL(mnt_want_write);

  static void lock_mnt_writers(void)
  {
  	int cpu;
  	struct mnt_writer *cpu_writer;
  
  	for_each_possible_cpu(cpu) {
  		cpu_writer = &per_cpu(mnt_writers, cpu);
  		spin_lock(&cpu_writer->lock);
  		__clear_mnt_count(cpu_writer);
  		cpu_writer->mnt = NULL;
  	}
  }
  
  /*
   * These per-cpu write counts are not guaranteed to have
   * matched increments and decrements on any given cpu.
   * A file open()ed for write on one cpu and close()d on
   * another cpu will imbalance this count.  Make sure it
   * does not get too far out of whack.
   */
  static void handle_write_count_underflow(struct vfsmount *mnt)
  {
  	if (atomic_read(&mnt->__mnt_writers) >=
  	    MNT_WRITER_UNDERFLOW_LIMIT)
  		return;
  	/*
  	 * It isn't necessary to hold all of the locks
  	 * at the same time, but doing it this way makes
  	 * us share a lot more code.
  	 */
  	lock_mnt_writers();
  	/*
  	 * vfsmount_lock is for mnt_flags.
  	 */
  	spin_lock(&vfsmount_lock);
  	/*
  	 * If coalescing the per-cpu writer counts did not
  	 * get us back to a positive writer count, we have
  	 * a bug.
  	 */
  	if ((atomic_read(&mnt->__mnt_writers) < 0) &&
  	    !(mnt->mnt_flags & MNT_IMBALANCED_WRITE_COUNT)) {

  		WARN(1, KERN_DEBUG "leak detected on mount(%p) writers "

  				"count: %d
  ",
  			mnt, atomic_read(&mnt->__mnt_writers));

  		/* use the flag to keep the dmesg spam down */
  		mnt->mnt_flags |= MNT_IMBALANCED_WRITE_COUNT;
  	}
  	spin_unlock(&vfsmount_lock);
  	unlock_mnt_writers();
  }

  /**
   * mnt_drop_write - give up write access to a mount
   * @mnt: the mount on which to give up write access
   *
   * Tells the low-level filesystem that we are done
   * performing writes to it.  Must be matched with
   * mnt_want_write() call above.
   */
  void mnt_drop_write(struct vfsmount *mnt)
  {

  	int must_check_underflow = 0;
  	struct mnt_writer *cpu_writer;
  
  	cpu_writer = &get_cpu_var(mnt_writers);
  	spin_lock(&cpu_writer->lock);
  
  	use_cpu_writer_for_mount(cpu_writer, mnt);
  	if (cpu_writer->count > 0) {
  		cpu_writer->count--;
  	} else {
  		must_check_underflow = 1;
  		atomic_dec(&mnt->__mnt_writers);
  	}
  
  	spin_unlock(&cpu_writer->lock);
  	/*
  	 * Logically, we could call this each time,
  	 * but the __mnt_writers cacheline tends to
  	 * be cold, and makes this expensive.
  	 */
  	if (must_check_underflow)
  		handle_write_count_underflow(mnt);
  	/*
  	 * This could be done right after the spinlock
  	 * is taken because the spinlock keeps us on
  	 * the cpu, and disables preemption.  However,
  	 * putting it here bounds the amount that
  	 * __mnt_writers can underflow.  Without it,
  	 * we could theoretically wrap __mnt_writers.
  	 */
  	put_cpu_var(mnt_writers);

  }
  EXPORT_SYMBOL_GPL(mnt_drop_write);

  static int mnt_make_readonly(struct vfsmount *mnt)

  {

  	int ret = 0;
  
  	lock_mnt_writers();
  	/*
  	 * With all the locks held, this value is stable
  	 */
  	if (atomic_read(&mnt->__mnt_writers) > 0) {
  		ret = -EBUSY;
  		goto out;
  	}
  	/*

  	 * nobody can do a successful mnt_want_write() with all
  	 * of the counts in MNT_DENIED_WRITE and the locks held.

  	 */

  	spin_lock(&vfsmount_lock);
  	if (!ret)
  		mnt->mnt_flags |= MNT_READONLY;
  	spin_unlock(&vfsmount_lock);

  out:
  	unlock_mnt_writers();
  	return ret;

  }

  static void __mnt_unmake_readonly(struct vfsmount *mnt)
  {
  	spin_lock(&vfsmount_lock);
  	mnt->mnt_flags &= ~MNT_READONLY;
  	spin_unlock(&vfsmount_lock);
  }

  void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)

  {
  	mnt->mnt_sb = sb;
  	mnt->mnt_root = dget(sb->s_root);

  }
  
  EXPORT_SYMBOL(simple_set_mnt);

  void free_vfsmnt(struct vfsmount *mnt)
  {
  	kfree(mnt->mnt_devname);

  	mnt_free_id(mnt);

  	kmem_cache_free(mnt_cache, mnt);
  }
  
  /*

   * find the first or last mount at @dentry on vfsmount @mnt depending on
   * @dir. If @dir is set return the first mount else return the last mount.

   */

  struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
  			      int dir)

  {

  	struct list_head *head = mount_hashtable + hash(mnt, dentry);
  	struct list_head *tmp = head;

  	struct vfsmount *p, *found = NULL;

  	for (;;) {

  		tmp = dir ? tmp->next : tmp->prev;

  		p = NULL;
  		if (tmp == head)
  			break;
  		p = list_entry(tmp, struct vfsmount, mnt_hash);
  		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {

  			found = p;

  			break;
  		}
  	}

  	return found;
  }

  /*
   * lookup_mnt increments the ref count before returning
   * the vfsmount struct.
   */
  struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
  {
  	struct vfsmount *child_mnt;
  	spin_lock(&vfsmount_lock);
  	if ((child_mnt = __lookup_mnt(mnt, dentry, 1)))
  		mntget(child_mnt);
  	spin_unlock(&vfsmount_lock);
  	return child_mnt;
  }

  static inline int check_mnt(struct vfsmount *mnt)
  {

  	return mnt->mnt_ns == current->nsproxy->mnt_ns;

  }

  static void touch_mnt_namespace(struct mnt_namespace *ns)

  {
  	if (ns) {
  		ns->event = ++event;
  		wake_up_interruptible(&ns->poll);
  	}
  }

  static void __touch_mnt_namespace(struct mnt_namespace *ns)

  {
  	if (ns && ns->event != event) {
  		ns->event = event;
  		wake_up_interruptible(&ns->poll);
  	}
  }

  static void detach_mnt(struct vfsmount *mnt, struct path *old_path)

  {

  	old_path->dentry = mnt->mnt_mountpoint;
  	old_path->mnt = mnt->mnt_parent;

  	mnt->mnt_parent = mnt;
  	mnt->mnt_mountpoint = mnt->mnt_root;
  	list_del_init(&mnt->mnt_child);
  	list_del_init(&mnt->mnt_hash);

  	old_path->dentry->d_mounted--;

  }

  void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
  			struct vfsmount *child_mnt)
  {
  	child_mnt->mnt_parent = mntget(mnt);
  	child_mnt->mnt_mountpoint = dget(dentry);
  	dentry->d_mounted++;
  }

  static void attach_mnt(struct vfsmount *mnt, struct path *path)

  {

  	mnt_set_mountpoint(path->mnt, path->dentry, mnt);

  	list_add_tail(&mnt->mnt_hash, mount_hashtable +

  			hash(path->mnt, path->dentry));
  	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);

  }
  
  /*
   * the caller must hold vfsmount_lock
   */
  static void commit_tree(struct vfsmount *mnt)
  {
  	struct vfsmount *parent = mnt->mnt_parent;
  	struct vfsmount *m;
  	LIST_HEAD(head);

  	struct mnt_namespace *n = parent->mnt_ns;

  
  	BUG_ON(parent == mnt);
  
  	list_add_tail(&head, &mnt->mnt_list);
  	list_for_each_entry(m, &head, mnt_list)

  		m->mnt_ns = n;

  	list_splice(&head, n->list.prev);
  
  	list_add_tail(&mnt->mnt_hash, mount_hashtable +
  				hash(parent, mnt->mnt_mountpoint));
  	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);

  	touch_mnt_namespace(n);

  }
  
  static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
  {
  	struct list_head *next = p->mnt_mounts.next;
  	if (next == &p->mnt_mounts) {
  		while (1) {
  			if (p == root)
  				return NULL;
  			next = p->mnt_child.next;
  			if (next != &p->mnt_parent->mnt_mounts)
  				break;
  			p = p->mnt_parent;
  		}
  	}
  	return list_entry(next, struct vfsmount, mnt_child);
  }

  static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
  {
  	struct list_head *prev = p->mnt_mounts.prev;
  	while (prev != &p->mnt_mounts) {
  		p = list_entry(prev, struct vfsmount, mnt_child);
  		prev = p->mnt_mounts.prev;
  	}
  	return p;
  }

  static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
  					int flag)

  {
  	struct super_block *sb = old->mnt_sb;
  	struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
  
  	if (mnt) {

  		if (flag & (CL_SLAVE | CL_PRIVATE))
  			mnt->mnt_group_id = 0; /* not a peer of original */
  		else
  			mnt->mnt_group_id = old->mnt_group_id;
  
  		if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
  			int err = mnt_alloc_group_id(mnt);
  			if (err)
  				goto out_free;
  		}

  		mnt->mnt_flags = old->mnt_flags;
  		atomic_inc(&sb->s_active);
  		mnt->mnt_sb = sb;
  		mnt->mnt_root = dget(root);
  		mnt->mnt_mountpoint = mnt->mnt_root;
  		mnt->mnt_parent = mnt;

  		if (flag & CL_SLAVE) {
  			list_add(&mnt->mnt_slave, &old->mnt_slave_list);
  			mnt->mnt_master = old;
  			CLEAR_MNT_SHARED(mnt);

  		} else if (!(flag & CL_PRIVATE)) {

  			if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
  				list_add(&mnt->mnt_share, &old->mnt_share);
  			if (IS_MNT_SLAVE(old))
  				list_add(&mnt->mnt_slave, &old->mnt_slave);
  			mnt->mnt_master = old->mnt_master;
  		}

  		if (flag & CL_MAKE_SHARED)
  			set_mnt_shared(mnt);

  
  		/* stick the duplicate mount on the same expiry list
  		 * as the original if that was on one */

  		if (flag & CL_EXPIRE) {

  			if (!list_empty(&old->mnt_expire))
  				list_add(&mnt->mnt_expire, &old->mnt_expire);

  		}

  	}
  	return mnt;

  
   out_free:
  	free_vfsmnt(mnt);
  	return NULL;

  }

  static inline void __mntput(struct vfsmount *mnt)

  {

  	int cpu;

  	struct super_block *sb = mnt->mnt_sb;

  	/*
  	 * We don't have to hold all of the locks at the
  	 * same time here because we know that we're the
  	 * last reference to mnt and that no new writers
  	 * can come in.
  	 */
  	for_each_possible_cpu(cpu) {
  		struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu);

  		spin_lock(&cpu_writer->lock);

  		if (cpu_writer->mnt != mnt) {
  			spin_unlock(&cpu_writer->lock);
  			continue;
  		}

  		atomic_add(cpu_writer->count, &mnt->__mnt_writers);
  		cpu_writer->count = 0;
  		/*
  		 * Might as well do this so that no one
  		 * ever sees the pointer and expects
  		 * it to be valid.
  		 */
  		cpu_writer->mnt = NULL;
  		spin_unlock(&cpu_writer->lock);
  	}
  	/*
  	 * This probably indicates that somebody messed
  	 * up a mnt_want/drop_write() pair.  If this
  	 * happens, the filesystem was probably unable
  	 * to make r/w->r/o transitions.
  	 */
  	WARN_ON(atomic_read(&mnt->__mnt_writers));

  	dput(mnt->mnt_root);
  	free_vfsmnt(mnt);
  	deactivate_super(sb);
  }

  void mntput_no_expire(struct vfsmount *mnt)
  {
  repeat:
  	if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
  		if (likely(!mnt->mnt_pinned)) {
  			spin_unlock(&vfsmount_lock);
  			__mntput(mnt);
  			return;
  		}
  		atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
  		mnt->mnt_pinned = 0;
  		spin_unlock(&vfsmount_lock);
  		acct_auto_close_mnt(mnt);
  		security_sb_umount_close(mnt);
  		goto repeat;
  	}
  }
  
  EXPORT_SYMBOL(mntput_no_expire);
  
  void mnt_pin(struct vfsmount *mnt)
  {
  	spin_lock(&vfsmount_lock);
  	mnt->mnt_pinned++;
  	spin_unlock(&vfsmount_lock);
  }
  
  EXPORT_SYMBOL(mnt_pin);
  
  void mnt_unpin(struct vfsmount *mnt)
  {
  	spin_lock(&vfsmount_lock);
  	if (mnt->mnt_pinned) {
  		atomic_inc(&mnt->mnt_count);
  		mnt->mnt_pinned--;
  	}
  	spin_unlock(&vfsmount_lock);
  }
  
  EXPORT_SYMBOL(mnt_unpin);

  static inline void mangle(struct seq_file *m, const char *s)
  {
  	seq_escape(m, s, " \t
  \\");
  }
  
  /*
   * Simple .show_options callback for filesystems which don't want to
   * implement more complex mount option showing.
   *
   * See also save_mount_options().
   */
  int generic_show_options(struct seq_file *m, struct vfsmount *mnt)
  {

  	const char *options;
  
  	rcu_read_lock();
  	options = rcu_dereference(mnt->mnt_sb->s_options);

  
  	if (options != NULL && options[0]) {
  		seq_putc(m, ',');
  		mangle(m, options);
  	}

  	rcu_read_unlock();

  
  	return 0;
  }
  EXPORT_SYMBOL(generic_show_options);
  
  /*
   * If filesystem uses generic_show_options(), this function should be
   * called from the fill_super() callback.
   *
   * The .remount_fs callback usually needs to be handled in a special
   * way, to make sure, that previous options are not overwritten if the
   * remount fails.
   *
   * Also note, that if the filesystem's .remount_fs function doesn't
   * reset all options to their default value, but changes only newly
   * given options, then the displayed options will not reflect reality
   * any more.
   */
  void save_mount_options(struct super_block *sb, char *options)
  {

  	BUG_ON(sb->s_options);
  	rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));

  }
  EXPORT_SYMBOL(save_mount_options);

  void replace_mount_options(struct super_block *sb, char *options)
  {
  	char *old = sb->s_options;
  	rcu_assign_pointer(sb->s_options, options);
  	if (old) {
  		synchronize_rcu();
  		kfree(old);
  	}
  }
  EXPORT_SYMBOL(replace_mount_options);

  #ifdef CONFIG_PROC_FS

  /* iterator */
  static void *m_start(struct seq_file *m, loff_t *pos)
  {

  	struct proc_mounts *p = m->private;

  	down_read(&namespace_sem);

  	return seq_list_start(&p->ns->list, *pos);

  }
  
  static void *m_next(struct seq_file *m, void *v, loff_t *pos)
  {

  	struct proc_mounts *p = m->private;

  	return seq_list_next(v, &p->ns->list, pos);

  }
  
  static void m_stop(struct seq_file *m, void *v)
  {

  	up_read(&namespace_sem);

  }

  struct proc_fs_info {
  	int flag;
  	const char *str;
  };

  static int show_sb_opts(struct seq_file *m, struct super_block *sb)

  {

  	static const struct proc_fs_info fs_info[] = {

  		{ MS_SYNCHRONOUS, ",sync" },
  		{ MS_DIRSYNC, ",dirsync" },
  		{ MS_MANDLOCK, ",mand" },

  		{ 0, NULL }
  	};

  	const struct proc_fs_info *fs_infop;
  
  	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
  		if (sb->s_flags & fs_infop->flag)
  			seq_puts(m, fs_infop->str);
  	}

  
  	return security_sb_show_options(m, sb);

  }
  
  static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
  {
  	static const struct proc_fs_info mnt_info[] = {

  		{ MNT_NOSUID, ",nosuid" },
  		{ MNT_NODEV, ",nodev" },
  		{ MNT_NOEXEC, ",noexec" },

  		{ MNT_NOATIME, ",noatime" },
  		{ MNT_NODIRATIME, ",nodiratime" },

  		{ MNT_RELATIME, ",relatime" },

  		{ MNT_STRICTATIME, ",strictatime" },

  		{ 0, NULL }
  	};

  	const struct proc_fs_info *fs_infop;
  
  	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
  		if (mnt->mnt_flags & fs_infop->flag)
  			seq_puts(m, fs_infop->str);
  	}
  }
  
  static void show_type(struct seq_file *m, struct super_block *sb)
  {
  	mangle(m, sb->s_type->name);
  	if (sb->s_subtype && sb->s_subtype[0]) {
  		seq_putc(m, '.');
  		mangle(m, sb->s_subtype);
  	}
  }
  
  static int show_vfsmnt(struct seq_file *m, void *v)
  {
  	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
  	int err = 0;

  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

  
  	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
  	seq_putc(m, ' ');

  	seq_path(m, &mnt_path, " \t
  \\");

  	seq_putc(m, ' ');

  	show_type(m, mnt->mnt_sb);

  	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");

  	err = show_sb_opts(m, mnt->mnt_sb);
  	if (err)
  		goto out;

  	show_mnt_opts(m, mnt);

  	if (mnt->mnt_sb->s_op->show_options)
  		err = mnt->mnt_sb->s_op->show_options(m, mnt);
  	seq_puts(m, " 0 0
  ");

  out:

  	return err;
  }

  const struct seq_operations mounts_op = {

  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_vfsmnt
  };

  static int show_mountinfo(struct seq_file *m, void *v)
  {
  	struct proc_mounts *p = m->private;
  	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
  	struct super_block *sb = mnt->mnt_sb;
  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
  	struct path root = p->root;
  	int err = 0;
  
  	seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
  		   MAJOR(sb->s_dev), MINOR(sb->s_dev));
  	seq_dentry(m, mnt->mnt_root, " \t
  \\");
  	seq_putc(m, ' ');
  	seq_path_root(m, &mnt_path, &root, " \t
  \\");
  	if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
  		/*
  		 * Mountpoint is outside root, discard that one.  Ugly,
  		 * but less so than trying to do that in iterator in a
  		 * race-free way (due to renames).
  		 */
  		return SEQ_SKIP;
  	}
  	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
  	show_mnt_opts(m, mnt);
  
  	/* Tagged fields ("foo:X" or "bar") */
  	if (IS_MNT_SHARED(mnt))
  		seq_printf(m, " shared:%i", mnt->mnt_group_id);

  	if (IS_MNT_SLAVE(mnt)) {
  		int master = mnt->mnt_master->mnt_group_id;
  		int dom = get_dominating_id(mnt, &p->root);
  		seq_printf(m, " master:%i", master);
  		if (dom && dom != master)
  			seq_printf(m, " propagate_from:%i", dom);
  	}

  	if (IS_MNT_UNBINDABLE(mnt))
  		seq_puts(m, " unbindable");
  
  	/* Filesystem specific data */
  	seq_puts(m, " - ");
  	show_type(m, sb);
  	seq_putc(m, ' ');
  	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
  	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");

  	err = show_sb_opts(m, sb);
  	if (err)
  		goto out;

  	if (sb->s_op->show_options)
  		err = sb->s_op->show_options(m, mnt);
  	seq_putc(m, '
  ');

  out:

  	return err;
  }
  
  const struct seq_operations mountinfo_op = {
  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_mountinfo,
  };

  static int show_vfsstat(struct seq_file *m, void *v)
  {

  	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);

  	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

  	int err = 0;
  
  	/* device */
  	if (mnt->mnt_devname) {
  		seq_puts(m, "device ");
  		mangle(m, mnt->mnt_devname);
  	} else
  		seq_puts(m, "no device");
  
  	/* mount point */
  	seq_puts(m, " mounted on ");

  	seq_path(m, &mnt_path, " \t
  \\");

  	seq_putc(m, ' ');
  
  	/* file system type */
  	seq_puts(m, "with fstype ");

  	show_type(m, mnt->mnt_sb);

  
  	/* optional statistics */
  	if (mnt->mnt_sb->s_op->show_stats) {
  		seq_putc(m, ' ');
  		err = mnt->mnt_sb->s_op->show_stats(m, mnt);
  	}
  
  	seq_putc(m, '
  ');
  	return err;
  }

  const struct seq_operations mountstats_op = {

  	.start	= m_start,
  	.next	= m_next,
  	.stop	= m_stop,
  	.show	= show_vfsstat,
  };

  #endif  /* CONFIG_PROC_FS */

  /**
   * may_umount_tree - check if a mount tree is busy
   * @mnt: root of mount tree
   *
   * This is called to check if a tree of mounts has any
   * open files, pwds, chroots or sub mounts that are
   * busy.
   */
  int may_umount_tree(struct vfsmount *mnt)
  {

  	int actual_refs = 0;
  	int minimum_refs = 0;
  	struct vfsmount *p;

  
  	spin_lock(&vfsmount_lock);

  	for (p = mnt; p; p = next_mnt(p, mnt)) {

  		actual_refs += atomic_read(&p->mnt_count);
  		minimum_refs += 2;

  	}
  	spin_unlock(&vfsmount_lock);
  
  	if (actual_refs > minimum_refs)

  		return 0;

  	return 1;

  }
  
  EXPORT_SYMBOL(may_umount_tree);
  
  /**
   * may_umount - check if a mount point is busy
   * @mnt: root of mount
   *
   * This is called to check if a mount point has any
   * open files, pwds, chroots or sub mounts. If the
   * mount has sub mounts this will return busy
   * regardless of whether the sub mounts are busy.
   *
   * Doesn't take quota and stuff into account. IOW, in some cases it will
   * give false negatives. The main reason why it's here is that we need
   * a non-destructive way to look for easily umountable filesystems.
   */
  int may_umount(struct vfsmount *mnt)
  {

  	int ret = 1;

  	spin_lock(&vfsmount_lock);
  	if (propagate_mount_busy(mnt, 2))

  		ret = 0;

  	spin_unlock(&vfsmount_lock);
  	return ret;

  }
  
  EXPORT_SYMBOL(may_umount);

  void release_mounts(struct list_head *head)

  {
  	struct vfsmount *mnt;

  	while (!list_empty(head)) {

  		mnt = list_first_entry(head, struct vfsmount, mnt_hash);

  		list_del_init(&mnt->mnt_hash);
  		if (mnt->mnt_parent != mnt) {
  			struct dentry *dentry;
  			struct vfsmount *m;
  			spin_lock(&vfsmount_lock);
  			dentry = mnt->mnt_mountpoint;
  			m = mnt->mnt_parent;
  			mnt->mnt_mountpoint = mnt->mnt_root;
  			mnt->mnt_parent = mnt;

  			m->mnt_ghosts--;

  			spin_unlock(&vfsmount_lock);
  			dput(dentry);
  			mntput(m);
  		}
  		mntput(mnt);
  	}
  }

  void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)

  {
  	struct vfsmount *p;

  	for (p = mnt; p; p = next_mnt(p, mnt))
  		list_move(&p->mnt_hash, kill);

  	if (propagate)
  		propagate_umount(kill);

  	list_for_each_entry(p, kill, mnt_hash) {
  		list_del_init(&p->mnt_expire);
  		list_del_init(&p->mnt_list);

  		__touch_mnt_namespace(p->mnt_ns);
  		p->mnt_ns = NULL;

  		list_del_init(&p->mnt_child);

  		if (p->mnt_parent != p) {
  			p->mnt_parent->mnt_ghosts++;

  			p->mnt_mountpoint->d_mounted--;

  		}

  		change_mnt_propagation(p, MS_PRIVATE);

  	}
  }

  static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);

  static int do_umount(struct vfsmount *mnt, int flags)
  {

  	struct super_block *sb = mnt->mnt_sb;

  	int retval;

  	LIST_HEAD(umount_list);

  
  	retval = security_sb_umount(mnt, flags);
  	if (retval)
  		return retval;
  
  	/*
  	 * Allow userspace to request a mountpoint be expired rather than
  	 * unmounting unconditionally. Unmount only happens if:
  	 *  (1) the mark is already set (the mark is cleared by mntput())
  	 *  (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
  	 */
  	if (flags & MNT_EXPIRE) {

  		if (mnt == current->fs->root.mnt ||

  		    flags & (MNT_FORCE | MNT_DETACH))
  			return -EINVAL;
  
  		if (atomic_read(&mnt->mnt_count) != 2)
  			return -EBUSY;
  
  		if (!xchg(&mnt->mnt_expiry_mark, 1))
  			return -EAGAIN;
  	}
  
  	/*
  	 * If we may have to abort operations to get out of this
  	 * mount, and they will themselves hold resources we must
  	 * allow the fs to do things. In the Unix tradition of
  	 * 'Gee thats tricky lets do it in userspace' the umount_begin
  	 * might fail to complete on the first run through as other tasks
  	 * must return, and the like. Thats for the mount program to worry
  	 * about for the moment.
  	 */

  	if (flags & MNT_FORCE && sb->s_op->umount_begin) {

  		sb->s_op->umount_begin(sb);

  	}

  
  	/*
  	 * No sense to grab the lock for this test, but test itself looks
  	 * somewhat bogus. Suggestions for better replacement?
  	 * Ho-hum... In principle, we might treat that as umount + switch
  	 * to rootfs. GC would eventually take care of the old vfsmount.
  	 * Actually it makes sense, especially if rootfs would contain a
  	 * /reboot - static binary that would close all descriptors and
  	 * call reboot(9). Then init(8) could umount root and exec /reboot.
  	 */

  	if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {

  		/*
  		 * Special case for "unmounting" root ...
  		 * we just try to remount it readonly.
  		 */
  		down_write(&sb->s_umount);
  		if (!(sb->s_flags & MS_RDONLY)) {
  			lock_kernel();

  			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
  			unlock_kernel();
  		}
  		up_write(&sb->s_umount);
  		return retval;
  	}

  	down_write(&namespace_sem);

  	spin_lock(&vfsmount_lock);

  	event++;

  	if (!(flags & MNT_DETACH))
  		shrink_submounts(mnt, &umount_list);

  	retval = -EBUSY;

  	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {

  		if (!list_empty(&mnt->mnt_list))

  			umount_tree(mnt, 1, &umount_list);

  		retval = 0;
  	}
  	spin_unlock(&vfsmount_lock);
  	if (retval)
  		security_sb_umount_busy(mnt);

  	up_write(&namespace_sem);

  	release_mounts(&umount_list);

  	return retval;
  }
  
  /*
   * Now umount can handle mount points as well as block devices.
   * This is important for filesystems which use unnamed block devices.
   *
   * We now support a flag for forced unmount like the other 'big iron'
   * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
   */

  SYSCALL_DEFINE2(umount, char __user *, name, int, flags)

  {

  	struct path path;

  	int retval;

  	retval = user_path(name, &path);

  	if (retval)
  		goto out;
  	retval = -EINVAL;

  	if (path.dentry != path.mnt->mnt_root)

  		goto dput_and_out;

  	if (!check_mnt(path.mnt))

  		goto dput_and_out;
  
  	retval = -EPERM;
  	if (!capable(CAP_SYS_ADMIN))
  		goto dput_and_out;

  	retval = do_umount(path.mnt, flags);

  dput_and_out:

  	/* we mustn't call path_put() as that would clear mnt_expiry_mark */

  	dput(path.dentry);
  	mntput_no_expire(path.mnt);

  out:
  	return retval;
  }
  
  #ifdef __ARCH_WANT_SYS_OLDUMOUNT
  
  /*

   *	The 2.0 compatible umount. No flags.

   */

  SYSCALL_DEFINE1(oldumount, char __user *, name)

  {

  	return sys_umount(name, 0);

  }
  
  #endif

  static int mount_is_safe(struct path *path)

  {
  	if (capable(CAP_SYS_ADMIN))
  		return 0;
  	return -EPERM;
  #ifdef notyet

  	if (S_ISLNK(path->dentry->d_inode->i_mode))

  		return -EPERM;

  	if (path->dentry->d_inode->i_mode & S_ISVTX) {

  		if (current_uid() != path->dentry->d_inode->i_uid)

  			return -EPERM;
  	}

  	if (inode_permission(path->dentry->d_inode, MAY_WRITE))

  		return -EPERM;
  	return 0;
  #endif
  }

  struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,

  					int flag)

  {
  	struct vfsmount *res, *p, *q, *r, *s;

  	struct path path;

  	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
  		return NULL;

  	res = q = clone_mnt(mnt, dentry, flag);

  	if (!q)
  		goto Enomem;
  	q->mnt_mountpoint = mnt->mnt_mountpoint;
  
  	p = mnt;

  	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {

  		if (!is_subdir(r->mnt_mountpoint, dentry))

  			continue;
  
  		for (s = r; s; s = next_mnt(s, r)) {

  			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
  				s = skip_mnt_tree(s);
  				continue;
  			}

  			while (p != s->mnt_parent) {
  				p = p->mnt_parent;
  				q = q->mnt_parent;
  			}
  			p = s;

  			path.mnt = q;
  			path.dentry = p->mnt_mountpoint;

  			q = clone_mnt(p, p->mnt_root, flag);

  			if (!q)
  				goto Enomem;
  			spin_lock(&vfsmount_lock);
  			list_add_tail(&q->mnt_list, &res->mnt_list);

  			attach_mnt(q, &path);

  			spin_unlock(&vfsmount_lock);
  		}
  	}
  	return res;

  Enomem:

  	if (res) {

  		LIST_HEAD(umount_list);

  		spin_lock(&vfsmount_lock);

  		umount_tree(res, 0, &umount_list);

  		spin_unlock(&vfsmount_lock);

  		release_mounts(&umount_list);

  	}
  	return NULL;
  }

  struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry)
  {
  	struct vfsmount *tree;

  	down_write(&namespace_sem);

  	tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE);

  	up_write(&namespace_sem);

  	return tree;
  }
  
  void drop_collected_mounts(struct vfsmount *mnt)
  {
  	LIST_HEAD(umount_list);

  	down_write(&namespace_sem);

  	spin_lock(&vfsmount_lock);
  	umount_tree(mnt, 0, &umount_list);
  	spin_unlock(&vfsmount_lock);

  	up_write(&namespace_sem);

  	release_mounts(&umount_list);
  }

  static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
  {
  	struct vfsmount *p;
  
  	for (p = mnt; p != end; p = next_mnt(p, mnt)) {
  		if (p->mnt_group_id && !IS_MNT_SHARED(p))
  			mnt_release_group_id(p);
  	}
  }
  
  static int invent_group_ids(struct vfsmount *mnt, bool recurse)
  {
  	struct vfsmount *p;
  
  	for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
  		if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
  			int err = mnt_alloc_group_id(p);
  			if (err) {
  				cleanup_group_ids(mnt, p);
  				return err;
  			}
  		}
  	}
  
  	return 0;
  }

  /*
   *  @source_mnt : mount tree to be attached

   *  @nd         : place the mount tree @source_mnt is attached
   *  @parent_nd  : if non-null, detach the source_mnt from its parent and
   *  		   store the parent mount and mountpoint dentry.
   *  		   (done when source_mnt is moved)

   *
   *  NOTE: in the table below explains the semantics when a source mount
   *  of a given type is attached to a destination mount of a given type.

   * ---------------------------------------------------------------------------
   * |         BIND MOUNT OPERATION                                            |
   * |**************************************************************************
   * | source-->| shared        |       private  |       slave    | unbindable |
   * | dest     |               |                |                |            |
   * |   |      |               |                |                |            |
   * |   v      |               |                |                |            |
   * |**************************************************************************
   * |  shared  | shared (++)   |     shared (+) |     shared(+++)|  invalid   |
   * |          |               |                |                |            |
   * |non-shared| shared (+)    |      private   |      slave (*) |  invalid   |
   * ***************************************************************************

   * A bind operation clones the source mount and mounts the clone on the
   * destination mount.
   *
   * (++)  the cloned mount is propagated to all the mounts in the propagation
   * 	 tree of the destination mount and the cloned mount is added to
   * 	 the peer group of the source mount.
   * (+)   the cloned mount is created under the destination mount and is marked
   *       as shared. The cloned mount is added to the peer group of the source
   *       mount.

   * (+++) the mount is propagated to all the mounts in the propagation tree
   *       of the destination mount and the cloned mount is made slave
   *       of the same master as that of the source mount. The cloned mount
   *       is marked as 'shared and slave'.
   * (*)   the cloned mount is made a slave of the same master as that of the
   * 	 source mount.
   *

   * ---------------------------------------------------------------------------
   * |         		MOVE MOUNT OPERATION                                 |
   * |**************************************************************************
   * | source-->| shared        |       private  |       slave    | unbindable |
   * | dest     |               |                |                |            |
   * |   |      |               |                |                |            |
   * |   v      |               |                |                |            |
   * |**************************************************************************
   * |  shared  | shared (+)    |     shared (+) |    shared(+++) |  invalid   |
   * |          |               |                |                |            |
   * |non-shared| shared (+*)   |      private   |    slave (*)   | unbindable |
   * ***************************************************************************

   *
   * (+)  the mount is moved to the destination. And is then propagated to
   * 	all the mounts in the propagation tree of the destination mount.

   * (+*)  the mount is moved to the destination.

   * (+++)  the mount is moved to the destination and is then propagated to
   * 	all the mounts belonging to the destination mount's propagation tree.
   * 	the mount is marked as 'shared and slave'.
   * (*)	the mount continues to be a slave at the new location.

   *
   * if the source mount is a tree, the operations explained above is
   * applied to each mount in the tree.
   * Must be called without spinlocks held, since this function can sleep
   * in allocations.
   */
  static int attach_recursive_mnt(struct vfsmount *source_mnt,

  			struct path *path, struct path *parent_path)

  {
  	LIST_HEAD(tree_list);

  	struct vfsmount *dest_mnt = path->mnt;
  	struct dentry *dest_dentry = path->dentry;

  	struct vfsmount *child, *p;

  	int err;

  	if (IS_MNT_SHARED(dest_mnt)) {
  		err = invent_group_ids(source_mnt, true);
  		if (err)
  			goto out;
  	}
  	err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
  	if (err)
  		goto out_cleanup_ids;

  
  	if (IS_MNT_SHARED(dest_mnt)) {
  		for (p = source_mnt; p; p = next_mnt(p, source_mnt))
  			set_mnt_shared(p);
  	}
  
  	spin_lock(&vfsmount_lock);

  	if (parent_path) {
  		detach_mnt(source_mnt, parent_path);
  		attach_mnt(source_mnt, path);

  		touch_mnt_namespace(parent_path->mnt->mnt_ns);

  	} else {
  		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
  		commit_tree(source_mnt);
  	}

  
  	list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
  		list_del_init(&child->mnt_hash);
  		commit_tree(child);
  	}
  	spin_unlock(&vfsmount_lock);
  	return 0;

  
   out_cleanup_ids:
  	if (IS_MNT_SHARED(dest_mnt))
  		cleanup_group_ids(source_mnt, NULL);
   out:
  	return err;

  }

  static int graft_tree(struct vfsmount *mnt, struct path *path)

  {
  	int err;
  	if (mnt->mnt_sb->s_flags & MS_NOUSER)
  		return -EINVAL;

  	if (S_ISDIR(path->dentry->d_inode->i_mode) !=

  	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
  		return -ENOTDIR;
  
  	err = -ENOENT;

  	mutex_lock(&path->dentry->d_inode->i_mutex);
  	if (IS_DEADDIR(path->dentry->d_inode))

  		goto out_unlock;

  	err = security_sb_check_sb(mnt, path);

  	if (err)
  		goto out_unlock;
  
  	err = -ENOENT;

  	if (IS_ROOT(path->dentry) || !d_unhashed(path->dentry))
  		err = attach_recursive_mnt(mnt, path, NULL);

  out_unlock:

  	mutex_unlock(&path->dentry->d_inode->i_mutex);

  	if (!err)

  		security_sb_post_addmount(mnt, path);

  	return err;
  }
  
  /*

   * recursively change the type of the mountpoint.
   */

  static int do_change_type(struct path *path, int flag)

  {

  	struct vfsmount *m, *mnt = path->mnt;

  	int recurse = flag & MS_REC;
  	int type = flag & ~MS_REC;

  	int err = 0;

  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;

  	if (path->dentry != path->mnt->mnt_root)

  		return -EINVAL;
  
  	down_write(&namespace_sem);

  	if (type == MS_SHARED) {
  		err = invent_group_ids(mnt, recurse);
  		if (err)
  			goto out_unlock;
  	}

  	spin_lock(&vfsmount_lock);
  	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
  		change_mnt_propagation(m, type);
  	spin_unlock(&vfsmount_lock);

  
   out_unlock:

  	up_write(&namespace_sem);

  	return err;

  }
  
  /*

   * do loopback mount.
   */

  static int do_loopback(struct path *path, char *old_name,

  				int recurse)

  {

  	struct path old_path;

  	struct vfsmount *mnt = NULL;

  	int err = mount_is_safe(path);

  	if (err)
  		return err;
  	if (!old_name || !*old_name)
  		return -EINVAL;

  	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);

  	if (err)
  		return err;

  	down_write(&namespace_sem);

  	err = -EINVAL;

  	if (IS_MNT_UNBINDABLE(old_path.mnt))

  		goto out;

  	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))

  		goto out;

  	err = -ENOMEM;
  	if (recurse)

  		mnt = copy_tree(old_path.mnt, old_path.dentry, 0);

  	else

  		mnt = clone_mnt(old_path.mnt, old_path.dentry, 0);

  
  	if (!mnt)
  		goto out;

  	err = graft_tree(mnt, path);

  	if (err) {

  		LIST_HEAD(umount_list);

  		spin_lock(&vfsmount_lock);

  		umount_tree(mnt, 0, &umount_list);

  		spin_unlock(&vfsmount_lock);

  		release_mounts(&umount_list);

  	}

  out:

  	up_write(&namespace_sem);

  	path_put(&old_path);

  	return err;
  }

  static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
  {
  	int error = 0;
  	int readonly_request = 0;
  
  	if (ms_flags & MS_RDONLY)
  		readonly_request = 1;
  	if (readonly_request == __mnt_is_readonly(mnt))
  		return 0;
  
  	if (readonly_request)
  		error = mnt_make_readonly(mnt);
  	else
  		__mnt_unmake_readonly(mnt);
  	return error;
  }

  /*
   * change filesystem flags. dir should be a physical root of filesystem.
   * If you've mounted a non-root directory somewhere and want to do remount
   * on it - tough luck.
   */

  static int do_remount(struct path *path, int flags, int mnt_flags,

  		      void *data)
  {
  	int err;

  	struct super_block *sb = path->mnt->mnt_sb;

  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;

  	if (!check_mnt(path->mnt))

  		return -EINVAL;

  	if (path->dentry != path->mnt->mnt_root)

  		return -EINVAL;
  
  	down_write(&sb->s_umount);

  	if (flags & MS_BIND)

  		err = change_mount_flags(path->mnt, flags);

  	else
  		err = do_remount_sb(sb, flags, data, 0);

  	if (!err)

  		path->mnt->mnt_flags = mnt_flags;

  	up_write(&sb->s_umount);

  	if (!err) {

  		security_sb_post_remount(path->mnt, flags, data);

  
  		spin_lock(&vfsmount_lock);
  		touch_mnt_namespace(path->mnt->mnt_ns);
  		spin_unlock(&vfsmount_lock);
  	}

  	return err;
  }

  static inline int tree_contains_unbindable(struct vfsmount *mnt)
  {
  	struct vfsmount *p;
  	for (p = mnt; p; p = next_mnt(p, mnt)) {
  		if (IS_MNT_UNBINDABLE(p))
  			return 1;
  	}
  	return 0;
  }

  static int do_move_mount(struct path *path, char *old_name)

  {

  	struct path old_path, parent_path;

  	struct vfsmount *p;
  	int err = 0;
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  	if (!old_name || !*old_name)
  		return -EINVAL;

  	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);

  	if (err)
  		return err;

  	down_write(&namespace_sem);

  	while (d_mountpoint(path->dentry) &&
  	       follow_down(&path->mnt, &path->dentry))

  		;
  	err = -EINVAL;

  	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))

  		goto out;
  
  	err = -ENOENT;

  	mutex_lock(&path->dentry->d_inode->i_mutex);
  	if (IS_DEADDIR(path->dentry->d_inode))

  		goto out1;

  	if (!IS_ROOT(path->dentry) && d_unhashed(path->dentry))

  		goto out1;

  
  	err = -EINVAL;

  	if (old_path.dentry != old_path.mnt->mnt_root)

  		goto out1;

  	if (old_path.mnt == old_path.mnt->mnt_parent)

  		goto out1;

  	if (S_ISDIR(path->dentry->d_inode->i_mode) !=
  	      S_ISDIR(old_path.dentry->d_inode->i_mode))

  		goto out1;
  	/*
  	 * Don't move a mount residing in a shared parent.
  	 */

  	if (old_path.mnt->mnt_parent &&
  	    IS_MNT_SHARED(old_path.mnt->mnt_parent))

  		goto out1;

  	/*
  	 * Don't move a mount tree containing unbindable mounts to a destination
  	 * mount which is shared.
  	 */

  	if (IS_MNT_SHARED(path->mnt) &&
  	    tree_contains_unbindable(old_path.mnt))

  		goto out1;

  	err = -ELOOP;

  	for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent)
  		if (p == old_path.mnt)

  			goto out1;

  	err = attach_recursive_mnt(old_path.mnt, path, &parent_path);

  	if (err)

  		goto out1;

  
  	/* if the mount is moved, it should no longer be expire
  	 * automatically */

  	list_del_init(&old_path.mnt->mnt_expire);

  out1:

  	mutex_unlock(&path->dentry->d_inode->i_mutex);

  out:

  	up_write(&namespace_sem);

  	if (!err)

  		path_put(&parent_path);

  	path_put(&old_path);

  	return err;
  }
  
  /*
   * create a new mount for userspace and request it to be added into the
   * namespace's tree
   */

  static int do_new_mount(struct path *path, char *type, int flags,

  			int mnt_flags, char *name, void *data)
  {
  	struct vfsmount *mnt;
  
  	if (!type || !memchr(type, 0, PAGE_SIZE))
  		return -EINVAL;
  
  	/* we need capabilities... */
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	mnt = do_kern_mount(type, flags, name, data);
  	if (IS_ERR(mnt))
  		return PTR_ERR(mnt);

  	return do_add_mount(mnt, path, mnt_flags, NULL);

  }
  
  /*
   * add a mount into a namespace's mount tree
   * - provide the option of adding the new mount to an expiration list
   */

  int do_add_mount(struct vfsmount *newmnt, struct path *path,

  		 int mnt_flags, struct list_head *fslist)
  {
  	int err;

  	down_write(&namespace_sem);

  	/* Something was mounted here while we slept */

  	while (d_mountpoint(path->dentry) &&
  	       follow_down(&path->mnt, &path->dentry))

  		;
  	err = -EINVAL;

  	if (!check_mnt(path->mnt))

  		goto unlock;
  
  	/* Refuse the same filesystem on the same mount point */
  	err = -EBUSY;

  	if (path->mnt->mnt_sb == newmnt->mnt_sb &&
  	    path->mnt->mnt_root == path->dentry)

  		goto unlock;
  
  	err = -EINVAL;
  	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
  		goto unlock;
  
  	newmnt->mnt_flags = mnt_flags;

  	if ((err = graft_tree(newmnt, path)))

  		goto unlock;

  	if (fslist) /* add to the specified expiration list */

  		list_add_tail(&newmnt->mnt_expire, fslist);

  	up_write(&namespace_sem);

  	return 0;

  
  unlock:

  	up_write(&namespace_sem);

  	mntput(newmnt);
  	return err;
  }
  
  EXPORT_SYMBOL_GPL(do_add_mount);

  /*

   * process a list of expirable mountpoints with the intent of discarding any
   * mountpoints that aren't in use and haven't been touched since last we came
   * here
   */
  void mark_mounts_for_expiry(struct list_head *mounts)
  {

  	struct vfsmount *mnt, *next;
  	LIST_HEAD(graveyard);

  	LIST_HEAD(umounts);

  
  	if (list_empty(mounts))
  		return;

  	down_write(&namespace_sem);

  	spin_lock(&vfsmount_lock);
  
  	/* extract from the expiration list every vfsmount that matches the
  	 * following criteria:
  	 * - only referenced by its parent vfsmount
  	 * - still marked for expiry (marked on the last call here; marks are
  	 *   cleared by mntput())
  	 */

  	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {

  		if (!xchg(&mnt->mnt_expiry_mark, 1) ||

  			propagate_mount_busy(mnt, 1))

  			continue;

  		list_move(&mnt->mnt_expire, &graveyard);

  	}

  	while (!list_empty(&graveyard)) {
  		mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
  		touch_mnt_namespace(mnt->mnt_ns);
  		umount_tree(mnt, 1, &umounts);
  	}

  	spin_unlock(&vfsmount_lock);

  	up_write(&namespace_sem);
  
  	release_mounts(&umounts);

  }
  
  EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
  
  /*
   * Ripoff of 'select_parent()'
   *
   * search the list of submounts for a given mountpoint, and move any
   * shrinkable submounts to the 'graveyard' list.
   */
  static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
  {
  	struct vfsmount *this_parent = parent;
  	struct list_head *next;
  	int found = 0;
  
  repeat:
  	next = this_parent->mnt_mounts.next;
  resume:
  	while (next != &this_parent->mnt_mounts) {
  		struct list_head *tmp = next;
  		struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
  
  		next = tmp->next;
  		if (!(mnt->mnt_flags & MNT_SHRINKABLE))

  			continue;

  		/*
  		 * Descend a level if the d_mounts list is non-empty.
  		 */
  		if (!list_empty(&mnt->mnt_mounts)) {
  			this_parent = mnt;
  			goto repeat;
  		}

  		if (!propagate_mount_busy(mnt, 1)) {

  			list_move_tail(&mnt->mnt_expire, graveyard);
  			found++;
  		}

  	}

  	/*
  	 * All done at this level ... ascend and resume the search
  	 */
  	if (this_parent != parent) {
  		next = this_parent->mnt_child.next;
  		this_parent = this_parent->mnt_parent;
  		goto resume;
  	}
  	return found;
  }
  
  /*
   * process a list of expirable mountpoints with the intent of discarding any
   * submounts of a specific parent mountpoint
   */

  static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)

  {
  	LIST_HEAD(graveyard);

  	struct vfsmount *m;

  	/* extract submounts of 'mountpoint' from the expiration list */

  	while (select_submounts(mnt, &graveyard)) {

  		while (!list_empty(&graveyard)) {

  			m = list_first_entry(&graveyard, struct vfsmount,

  						mnt_expire);

  			touch_mnt_namespace(m->mnt_ns);
  			umount_tree(m, 1, umounts);

  		}
  	}

  }

  /*
   * Some copy_from_user() implementations do not return the exact number of
   * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
   * Note that this function differs from copy_from_user() in that it will oops
   * on bad values of `to', rather than returning a short copy.
   */

  static long exact_copy_from_user(void *to, const void __user * from,
  				 unsigned long n)

  {
  	char *t = to;
  	const char __user *f = from;
  	char c;
  
  	if (!access_ok(VERIFY_READ, from, n))
  		return n;
  
  	while (n) {
  		if (__get_user(c, f)) {
  			memset(t, 0, n);
  			break;
  		}
  		*t++ = c;
  		f++;
  		n--;
  	}
  	return n;
  }

  int copy_mount_options(const void __user * data, unsigned long *where)

  {
  	int i;
  	unsigned long page;
  	unsigned long size;

  	*where = 0;
  	if (!data)
  		return 0;
  
  	if (!(page = __get_free_page(GFP_KERNEL)))
  		return -ENOMEM;
  
  	/* We only care that *some* data at the address the user
  	 * gave us is valid.  Just in case, we'll zero
  	 * the remainder of the page.
  	 */
  	/* copy_from_user cannot cross TASK_SIZE ! */
  	size = TASK_SIZE - (unsigned long)data;
  	if (size > PAGE_SIZE)
  		size = PAGE_SIZE;
  
  	i = size - exact_copy_from_user((void *)page, data, size);
  	if (!i) {

  		free_page(page);

  		return -EFAULT;
  	}
  	if (i != PAGE_SIZE)
  		memset((char *)page + i, 0, PAGE_SIZE - i);
  	*where = page;
  	return 0;
  }
  
  /*
   * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
   * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
   *
   * data is a (void *) that can point to any structure up to
   * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
   * information (or be NULL).
   *
   * Pre-0.97 versions of mount() didn't have a flags word.
   * When the flags word was introduced its top half was required
   * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
   * Therefore, if this magic number is present, it carries no information
   * and must be discarded.
   */

  long do_mount(char *dev_name, char *dir_name, char *type_page,

  		  unsigned long flags, void *data_page)
  {

  	struct path path;

  	int retval = 0;
  	int mnt_flags = 0;
  
  	/* Discard magic */
  	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
  		flags &= ~MS_MGC_MSK;
  
  	/* Basic sanity checks */
  
  	if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
  		return -EINVAL;
  	if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
  		return -EINVAL;
  
  	if (data_page)
  		((char *)data_page)[PAGE_SIZE - 1] = 0;

  	/* Default to relatime unless overriden */
  	if (!(flags & MS_NOATIME))
  		mnt_flags |= MNT_RELATIME;

  	/* Separate the per-mountpoint flags */
  	if (flags & MS_NOSUID)
  		mnt_flags |= MNT_NOSUID;
  	if (flags & MS_NODEV)
  		mnt_flags |= MNT_NODEV;
  	if (flags & MS_NOEXEC)
  		mnt_flags |= MNT_NOEXEC;

  	if (flags & MS_NOATIME)
  		mnt_flags |= MNT_NOATIME;
  	if (flags & MS_NODIRATIME)
  		mnt_flags |= MNT_NODIRATIME;

  	if (flags & MS_STRICTATIME)
  		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);

  	if (flags & MS_RDONLY)
  		mnt_flags |= MNT_READONLY;

  
  	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |

  		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
  		   MS_STRICTATIME);

  
  	/* ... and get the mountpoint */

  	retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);

  	if (retval)
  		return retval;

  	retval = security_sb_mount(dev_name, &path,

  				   type_page, flags, data_page);

  	if (retval)
  		goto dput_out;
  
  	if (flags & MS_REMOUNT)

  		retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,

  				    data_page);
  	else if (flags & MS_BIND)

  		retval = do_loopback(&path, dev_name, flags & MS_REC);

  	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))

  		retval = do_change_type(&path, flags);

  	else if (flags & MS_MOVE)

  		retval = do_move_mount(&path, dev_name);

  	else

  		retval = do_new_mount(&path, type_page, flags, mnt_flags,

  				      dev_name, data_page);
  dput_out:

  	path_put(&path);

  	return retval;
  }

  /*
   * Allocate a new namespace structure and populate it with contents
   * copied from the namespace of the passed in task structure.
   */

  static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,

  		struct fs_struct *fs)

  {

  	struct mnt_namespace *new_ns;

  	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;

  	struct vfsmount *p, *q;

  	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);

  	if (!new_ns)

  		return ERR_PTR(-ENOMEM);

  
  	atomic_set(&new_ns->count, 1);

  	INIT_LIST_HEAD(&new_ns->list);

  	init_waitqueue_head(&new_ns->poll);
  	new_ns->event = 0;

  	down_write(&namespace_sem);

  	/* First pass: copy the tree topology */

  	new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,

  					CL_COPY_ALL | CL_EXPIRE);

  	if (!new_ns->root) {

  		up_write(&namespace_sem);

  		kfree(new_ns);

  		return ERR_PTR(-ENOMEM);

  	}
  	spin_lock(&vfsmount_lock);
  	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
  	spin_unlock(&vfsmount_lock);
  
  	/*
  	 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
  	 * as belonging to new namespace.  We have already acquired a private
  	 * fs_struct, so tsk->fs->lock is not needed.
  	 */

  	p = mnt_ns->root;

  	q = new_ns->root;
  	while (p) {

  		q->mnt_ns = new_ns;

  		if (fs) {

  			if (p == fs->root.mnt) {

  				rootmnt = p;

  				fs->root.mnt = mntget(q);

  			}

  			if (p == fs->pwd.mnt) {

  				pwdmnt = p;

  				fs->pwd.mnt = mntget(q);

  			}

  		}

  		p = next_mnt(p, mnt_ns->root);

  		q = next_mnt(q, new_ns->root);
  	}

  	up_write(&namespace_sem);

  	if (rootmnt)
  		mntput(rootmnt);
  	if (pwdmnt)
  		mntput(pwdmnt);

  	return new_ns;
  }

  struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,

  		struct fs_struct *new_fs)

  {

  	struct mnt_namespace *new_ns;

  	BUG_ON(!ns);

  	get_mnt_ns(ns);

  
  	if (!(flags & CLONE_NEWNS))

  		return ns;

  	new_ns = dup_mnt_ns(ns, new_fs);

  	put_mnt_ns(ns);