initial_commit

1 files changed, 2730 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
new file mode 100644
index 00000000..b3d8f51c
--- /dev/null
+++ b/fs/namespace.c
@@ -0,0 +1,2730 @@
+/*
+ *  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/spinlock.h>
+#include <linux/percpu.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/nsproxy.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 <linux/fsnotify.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)
+
+static int event;
+static DEFINE_IDA(mnt_id_ida);
+static DEFINE_IDA(mnt_group_ida);
+static DEFINE_SPINLOCK(mnt_id_lock);
+static int mnt_id_start = 0;
+static int mnt_group_start = 1;
+
+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);
+
+/*
+ * vfsmount lock may be taken for read to prevent changes to the
+ * vfsmount hash, ie. during mountpoint lookups or walking back
+ * up the tree.
+ *
+ * It should be taken for write in all cases where the vfsmount
+ * tree or hash is modified or when a vfsmount structure is modified.
+ */
+DEFINE_BRLOCK(vfsmount_lock);
+
+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, but we need the spinlock to
+ * serialize with freeing.
+ */
+static int mnt_alloc_id(struct vfsmount *mnt)
+{
+	int res;
+
+retry:
+	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
+	spin_lock(&mnt_id_lock);
+	res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
+	if (!res)
+		mnt_id_start = mnt->mnt_id + 1;
+	spin_unlock(&mnt_id_lock);
+	if (res == -EAGAIN)
+		goto retry;
+
+	return res;
+}
+
+static void mnt_free_id(struct vfsmount *mnt)
+{
+	int id = mnt->mnt_id;
+	spin_lock(&mnt_id_lock);
+	ida_remove(&mnt_id_ida, id);
+	if (mnt_id_start > id)
+		mnt_id_start = id;
+	spin_unlock(&mnt_id_lock);
+}
+
+/*
+ * Allocate a new peer group ID
+ *
+ * mnt_group_ida is protected by namespace_sem
+ */
+static int mnt_alloc_group_id(struct vfsmount *mnt)
+{
+	int res;
+
+	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
+		return -ENOMEM;
+
+	res = ida_get_new_above(&mnt_group_ida,
+				mnt_group_start,
+				&mnt->mnt_group_id);
+	if (!res)
+		mnt_group_start = mnt->mnt_group_id + 1;
+
+	return res;
+}
+
+/*
+ * Release a peer group ID
+ */
+void mnt_release_group_id(struct vfsmount *mnt)
+{
+	int id = mnt->mnt_group_id;
+	ida_remove(&mnt_group_ida, id);
+	if (mnt_group_start > id)
+		mnt_group_start = id;
+	mnt->mnt_group_id = 0;
+}
+
+/*
+ * vfsmount lock must be held for read
+ */
+static inline void mnt_add_count(struct vfsmount *mnt, int n)
+{
+#ifdef CONFIG_SMP
+	this_cpu_add(mnt->mnt_pcp->mnt_count, n);
+#else
+	preempt_disable();
+	mnt->mnt_count += n;
+	preempt_enable();
+#endif
+}
+
+static inline void mnt_set_count(struct vfsmount *mnt, int n)
+{
+#ifdef CONFIG_SMP
+	this_cpu_write(mnt->mnt_pcp->mnt_count, n);
+#else
+	mnt->mnt_count = n;
+#endif
+}
+
+/*
+ * vfsmount lock must be held for read
+ */
+static inline void mnt_inc_count(struct vfsmount *mnt)
+{
+	mnt_add_count(mnt, 1);
+}
+
+/*
+ * vfsmount lock must be held for read
+ */
+static inline void mnt_dec_count(struct vfsmount *mnt)
+{
+	mnt_add_count(mnt, -1);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+unsigned int mnt_get_count(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	unsigned int count = 0;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
+	}
+
+	return count;
+#else
+	return mnt->mnt_count;
+#endif
+}
+
+static 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;
+		}
+
+#ifdef CONFIG_SMP
+		mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
+		if (!mnt->mnt_pcp)
+			goto out_free_devname;
+
+		this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
+#else
+		mnt->mnt_count = 1;
+		mnt->mnt_writers = 0;
+#endif
+
+		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);
+#ifdef CONFIG_FSNOTIFY
+		INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
+#endif
+	}
+	return mnt;
+
+#ifdef CONFIG_SMP
+out_free_devname:
+	kfree(mnt->mnt_devname);
+#endif
+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);
+
+static inline void mnt_inc_writers(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	this_cpu_inc(mnt->mnt_pcp->mnt_writers);
+#else
+	mnt->mnt_writers++;
+#endif
+}
+
+static inline void mnt_dec_writers(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	this_cpu_dec(mnt->mnt_pcp->mnt_writers);
+#else
+	mnt->mnt_writers--;
+#endif
+}
+
+static unsigned int mnt_get_writers(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	unsigned int count = 0;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
+	}
+
+	return count;
+#else
+	return mnt->mnt_writers;
+#endif
+}
+
+/*
+ * 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;
+
+	preempt_disable();
+	mnt_inc_writers(mnt);
+	/*
+	 * The store to mnt_inc_writers must be visible before we pass
+	 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
+	 * incremented count after it has set MNT_WRITE_HOLD.
+	 */
+	smp_mb();
+	while (mnt->mnt_flags & MNT_WRITE_HOLD)
+		cpu_relax();
+	/*
+	 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
+	 * be set to match its requirements. So we must not load that until
+	 * MNT_WRITE_HOLD is cleared.
+	 */
+	smp_rmb();
+	if (__mnt_is_readonly(mnt)) {
+		mnt_dec_writers(mnt);
+		ret = -EROFS;
+		goto out;
+	}
+out:
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(mnt_want_write);
+
+/**
+ * mnt_clone_write - get write access to a mount
+ * @mnt: the mount on which to take a write
+ *
+ * This is effectively like mnt_want_write, except
+ * it must only be used to take an extra write reference
+ * on a mountpoint that we already know has a write reference
+ * on it. This allows some optimisation.
+ *
+ * After finished, mnt_drop_write must be called as usual to
+ * drop the reference.
+ */
+int mnt_clone_write(struct vfsmount *mnt)
+{
+	/* superblock may be r/o */
+	if (__mnt_is_readonly(mnt))
+		return -EROFS;
+	preempt_disable();
+	mnt_inc_writers(mnt);
+	preempt_enable();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mnt_clone_write);
+
+/**
+ * mnt_want_write_file - get write access to a file's mount
+ * @file: the file who's mount on which to take a write
+ *
+ * This is like mnt_want_write, but it takes a file and can
+ * do some optimisations if the file is open for write already
+ */
+int mnt_want_write_file(struct file *file)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
+		return mnt_want_write(file->f_path.mnt);
+	else
+		return mnt_clone_write(file->f_path.mnt);
+}
+EXPORT_SYMBOL_GPL(mnt_want_write_file);
+
+/**
+ * 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)
+{
+	preempt_disable();
+	mnt_dec_writers(mnt);
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(mnt_drop_write);
+
+static int mnt_make_readonly(struct vfsmount *mnt)
+{
+	int ret = 0;
+
+	br_write_lock(vfsmount_lock);
+	mnt->mnt_flags |= MNT_WRITE_HOLD;
+	/*
+	 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
+	 * should be visible before we do.
+	 */
+	smp_mb();
+
+	/*
+	 * With writers on hold, if this value is zero, then there are
+	 * definitely no active writers (although held writers may subsequently
+	 * increment the count, they'll have to wait, and decrement it after
+	 * seeing MNT_READONLY).
+	 *
+	 * It is OK to have counter incremented on one CPU and decremented on
+	 * another: the sum will add up correctly. The danger would be when we
+	 * sum up each counter, if we read a counter before it is incremented,
+	 * but then read another CPU's count which it has been subsequently
+	 * decremented from -- we would see more decrements than we should.
+	 * MNT_WRITE_HOLD protects against this scenario, because
+	 * mnt_want_write first increments count, then smp_mb, then spins on
+	 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
+	 * we're counting up here.
+	 */
+	if (mnt_get_writers(mnt) > 0)
+		ret = -EBUSY;
+	else
+		mnt->mnt_flags |= MNT_READONLY;
+	/*
+	 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
+	 * that become unheld will see MNT_READONLY.
+	 */
+	smp_wmb();
+	mnt->mnt_flags &= ~MNT_WRITE_HOLD;
+	br_write_unlock(vfsmount_lock);
+	return ret;
+}
+
+static void __mnt_unmake_readonly(struct vfsmount *mnt)
+{
+	br_write_lock(vfsmount_lock);
+	mnt->mnt_flags &= ~MNT_READONLY;
+	br_write_unlock(vfsmount_lock);
+}
+
+static void free_vfsmnt(struct vfsmount *mnt)
+{
+	kfree(mnt->mnt_devname);
+	mnt_free_id(mnt);
+#ifdef CONFIG_SMP
+	free_percpu(mnt->mnt_pcp);
+#endif
+	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.
+ * vfsmount_lock must be held for read or write.
+ */
+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 path *path)
+{
+	struct vfsmount *child_mnt;
+
+	br_read_lock(vfsmount_lock);
+	if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1)))
+		mntget(child_mnt);
+	br_read_unlock(vfsmount_lock);
+	return child_mnt;
+}
+
+static inline int check_mnt(struct vfsmount *mnt)
+{
+	return mnt->mnt_ns == current->nsproxy->mnt_ns;
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void touch_mnt_namespace(struct mnt_namespace *ns)
+{
+	if (ns) {
+		ns->event = ++event;
+		wake_up_interruptible(&ns->poll);
+	}
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+static void __touch_mnt_namespace(struct mnt_namespace *ns)
+{
+	if (ns && ns->event != event) {
+		ns->event = event;
+		wake_up_interruptible(&ns->poll);
+	}
+}
+
+/*
+ * Clear dentry's mounted state if it has no remaining mounts.
+ * vfsmount_lock must be held for write.
+ */
+static void dentry_reset_mounted(struct vfsmount *mnt, struct dentry *dentry)
+{
+	unsigned u;
+
+	for (u = 0; u < HASH_SIZE; u++) {
+		struct vfsmount *p;
+
+		list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
+			if (p->mnt_mountpoint == dentry)
+				return;
+		}
+	}
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags &= ~DCACHE_MOUNTED;
+	spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+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);
+	dentry_reset_mounted(old_path->mnt, old_path->dentry);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+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);
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags |= DCACHE_MOUNTED;
+	spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+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);
+}
+
+static inline void __mnt_make_longterm(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	atomic_inc(&mnt->mnt_longterm);
+#endif
+}
+
+/* needs vfsmount lock for write */
+static inline void __mnt_make_shortterm(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	atomic_dec(&mnt->mnt_longterm);
+#endif
+}
+
+/*
+ * vfsmount lock must be held for write
+ */
+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;
+		__mnt_make_longterm(m);
+	}
+
+	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;
+}
+
+struct vfsmount *
+vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
+{
+	struct vfsmount *mnt;
+	struct dentry *root;
+
+	if (!type)
+		return ERR_PTR(-ENODEV);
+
+	mnt = alloc_vfsmnt(name);
+	if (!mnt)
+		return ERR_PTR(-ENOMEM);
+
+	if (flags & MS_KERNMOUNT)
+		mnt->mnt_flags = MNT_INTERNAL;
+
+	root = mount_fs(type, flags, name, data);
+	if (IS_ERR(root)) {
+		free_vfsmnt(mnt);
+		return ERR_CAST(root);
+	}
+
+	mnt->mnt_root = root;
+	mnt->mnt_sb = root->d_sb;
+	mnt->mnt_mountpoint = mnt->mnt_root;
+	mnt->mnt_parent = mnt;
+	return mnt;
+}
+EXPORT_SYMBOL_GPL(vfs_kern_mount);
+
+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 & ~MNT_WRITE_HOLD;
+		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_MAKE_SHARED) || 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 mntfree(struct vfsmount *mnt)
+{
+	struct super_block *sb = mnt->mnt_sb;
+
+	/*
+	 * 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.
+	 */
+	/*
+	 * The locking used to deal with mnt_count decrement provides barriers,
+	 * so mnt_get_writers() below is safe.
+	 */
+	WARN_ON(mnt_get_writers(mnt));
+	fsnotify_vfsmount_delete(mnt);
+	dput(mnt->mnt_root);
+	free_vfsmnt(mnt);
+	deactivate_super(sb);
+}
+
+static void mntput_no_expire(struct vfsmount *mnt)
+{
+put_again:
+#ifdef CONFIG_SMP
+	br_read_lock(vfsmount_lock);
+	if (likely(atomic_read(&mnt->mnt_longterm))) {
+		mnt_dec_count(mnt);
+		br_read_unlock(vfsmount_lock);
+		return;
+	}
+	br_read_unlock(vfsmount_lock);
+
+	br_write_lock(vfsmount_lock);
+	mnt_dec_count(mnt);
+	if (mnt_get_count(mnt)) {
+		br_write_unlock(vfsmount_lock);
+		return;
+	}
+#else
+	mnt_dec_count(mnt);
+	if (likely(mnt_get_count(mnt)))
+		return;
+	br_write_lock(vfsmount_lock);
+#endif
+	if (unlikely(mnt->mnt_pinned)) {
+		mnt_add_count(mnt, mnt->mnt_pinned + 1);
+		mnt->mnt_pinned = 0;
+		br_write_unlock(vfsmount_lock);
+		acct_auto_close_mnt(mnt);
+		goto put_again;
+	}
+	br_write_unlock(vfsmount_lock);
+	mntfree(mnt);
+}
+
+void mntput(struct vfsmount *mnt)
+{
+	if (mnt) {
+		/* avoid cacheline pingpong, hope gcc doesn't get "smart" */
+		if (unlikely(mnt->mnt_expiry_mark))
+			mnt->mnt_expiry_mark = 0;
+		mntput_no_expire(mnt);
+	}
+}
+EXPORT_SYMBOL(mntput);
+
+struct vfsmount *mntget(struct vfsmount *mnt)
+{
+	if (mnt)
+		mnt_inc_count(mnt);
+	return mnt;
+}
+EXPORT_SYMBOL(mntget);
+
+void mnt_pin(struct vfsmount *mnt)
+{
+	br_write_lock(vfsmount_lock);
+	mnt->mnt_pinned++;
+	br_write_unlock(vfsmount_lock);
+}
+EXPORT_SYMBOL(mnt_pin);
+
+void mnt_unpin(struct vfsmount *mnt)
+{
+	br_write_lock(vfsmount_lock);
+	if (mnt->mnt_pinned) {
+		mnt_inc_count(mnt);
+		mnt->mnt_pinned--;
+	}
+	br_write_unlock(vfsmount_lock);
+}
+EXPORT_SYMBOL(mnt_unpin);
+
+static inline void mangle(struct seq_file *m, const char *s)
+{
+	seq_escape(m, s, " \t\n\\");
+}
+
+/*
+ * 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);
+}
+
+int mnt_had_events(struct proc_mounts *p)
+{
+	struct mnt_namespace *ns = p->ns;
+	int res = 0;
+
+	br_read_lock(vfsmount_lock);
+	if (p->event != ns->event) {
+		p->event = ns->event;
+		res = 1;
+	}
+	br_read_unlock(vfsmount_lock);
+
+	return res;
+}
+
+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" },
+		{ 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 };
+
+	if (mnt->mnt_sb->s_op->show_devname) {
+		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+		if (err)
+			goto out;
+	} else {
+		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+	}
+	seq_putc(m, ' ');
+	seq_path(m, &mnt_path, " \t\n\\");
+	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\n");
+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));
+	if (sb->s_op->show_path)
+		err = sb->s_op->show_path(m, mnt);
+	else
+		seq_dentry(m, mnt->mnt_root, " \t\n\\");
+	if (err)
+		goto out;
+	seq_putc(m, ' ');
+
+	/* mountpoints outside of chroot jail will give SEQ_SKIP on this */
+	err = seq_path_root(m, &mnt_path, &root, " \t\n\\");
+	if (err)
+		goto out;
+
+	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, ' ');
+	if (sb->s_op->show_devname)
+		err = sb->s_op->show_devname(m, mnt);
+	else
+		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+	if (err)
+		goto out;
+	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, '\n');
+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_sb->s_op->show_devname) {
+		seq_puts(m, "device ");
+		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
+	} else {
+		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\n\\");
+	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, ' ');
+		if (!err)
+			err = mnt->mnt_sb->s_op->show_stats(m, mnt);
+	}
+
+	seq_putc(m, '\n');
+	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;
+
+	/* write lock needed for mnt_get_count */
+	br_write_lock(vfsmount_lock);
+	for (p = mnt; p; p = next_mnt(p, mnt)) {
+		actual_refs += mnt_get_count(p);
+		minimum_refs += 2;
+	}
+	br_write_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;
+	down_read(&namespace_sem);
+	br_write_lock(vfsmount_lock);
+	if (propagate_mount_busy(mnt, 2))
+		ret = 0;
+	br_write_unlock(vfsmount_lock);
+	up_read(&namespace_sem);
+	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;
+
+			br_write_lock(vfsmount_lock);
+			dentry = mnt->mnt_mountpoint;
+			m = mnt->mnt_parent;
+			mnt->mnt_mountpoint = mnt->mnt_root;
+			mnt->mnt_parent = mnt;
+			m->mnt_ghosts--;
+			br_write_unlock(vfsmount_lock);
+			dput(dentry);
+			mntput(m);
+		}
+		mntput(mnt);
+	}
+}
+
+/*
+ * vfsmount lock must be held for write
+ * namespace_sem must be held for write
+ */
+void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
+{
+	LIST_HEAD(tmp_list);
+	struct vfsmount *p;
+
+	for (p = mnt; p; p = next_mnt(p, mnt))
+		list_move(&p->mnt_hash, &tmp_list);
+
+	if (propagate)
+		propagate_umount(&tmp_list);
+
+	list_for_each_entry(p, &tmp_list, mnt_hash) {
+		list_del_init(&p->mnt_expire);
+		list_del_init(&p->mnt_list);
+		__touch_mnt_namespace(p->mnt_ns);
+		if (p->mnt_ns)
+			__mnt_make_shortterm(p);
+		p->mnt_ns = NULL;
+		list_del_init(&p->mnt_child);
+		if (p->mnt_parent != p) {
+			p->mnt_parent->mnt_ghosts++;
+			dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint);
+		}
+		change_mnt_propagation(p, MS_PRIVATE);
+	}
+	list_splice(&tmp_list, kill);
+}
+
+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;
+
+		/*
+		 * probably don't strictly need the lock here if we examined
+		 * all race cases, but it's a slowpath.
+		 */
+		br_write_lock(vfsmount_lock);
+		if (mnt_get_count(mnt) != 2) {
+			br_write_unlock(vfsmount_lock);
+			return -EBUSY;
+		}
+		br_write_unlock(vfsmount_lock);
+
+		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))
+			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
+		up_write(&sb->s_umount);
+		return retval;
+	}
+
+	down_write(&namespace_sem);
+	br_write_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;
+	}
+	br_write_unlock(vfsmount_lock);
+	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;
+	int lookup_flags = 0;
+
+	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
+		return -EINVAL;
+
+	if (!(flags & UMOUNT_NOFOLLOW))
+		lookup_flags |= LOOKUP_FOLLOW;
+
+	retval = user_path_at(AT_FDCWD, name, lookup_flags, &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;
+			br_write_lock(vfsmount_lock);
+			list_add_tail(&q->mnt_list, &res->mnt_list);
+			attach_mnt(q, &path);
+			br_write_unlock(vfsmount_lock);
+		}
+	}
+	return res;
+Enomem:
+	if (res) {
+		LIST_HEAD(umount_list);
+		br_write_lock(vfsmount_lock);
+		umount_tree(res, 0, &umount_list);
+		br_write_unlock(vfsmount_lock);
+		release_mounts(&umount_list);
+	}
+	return NULL;
+}
+
+struct vfsmount *collect_mounts(struct path *path)
+{
+	struct vfsmount *tree;
+	down_write(&namespace_sem);
+	tree = copy_tree(path->mnt, path->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);
+	br_write_lock(vfsmount_lock);
+	umount_tree(mnt, 0, &umount_list);
+	br_write_unlock(vfsmount_lock);
+	up_write(&namespace_sem);
+	release_mounts(&umount_list);
+}
+
+int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
+		   struct vfsmount *root)
+{
+	struct vfsmount *mnt;
+	int res = f(root, arg);
+	if (res)
+		return res;
+	list_for_each_entry(mnt, &root->mnt_list, mnt_list) {
+		res = f(mnt, arg);
+		if (res)
+			return res;
+	}
+	return 0;
+}
+
+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;
+
+	br_write_lock(vfsmount_lock);
+
+	if (IS_MNT_SHARED(dest_mnt)) {
+		for (p = source_mnt; p; p = next_mnt(p, source_mnt))
+			set_mnt_shared(p);
+	}
+	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);
+	}
+	br_write_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 lock_mount(struct path *path)
+{
+	struct vfsmount *mnt;
+retry:
+	mutex_lock(&path->dentry->d_inode->i_mutex);
+	if (unlikely(cant_mount(path->dentry))) {
+		mutex_unlock(&path->dentry->d_inode->i_mutex);
+		return -ENOENT;
+	}
+	down_write(&namespace_sem);
+	mnt = lookup_mnt(path);
+	if (likely(!mnt))
+		return 0;
+	up_write(&namespace_sem);
+	mutex_unlock(&path->dentry->d_inode->i_mutex);
+	path_put(path);
+	path->mnt = mnt;
+	path->dentry = dget(mnt->mnt_root);
+	goto retry;
+}
+
+static void unlock_mount(struct path *path)
+{
+	up_write(&namespace_sem);
+	mutex_unlock(&path->dentry->d_inode->i_mutex);
+}
+
+static int graft_tree(struct vfsmount *mnt, struct path *path)
+{
+	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;
+
+	if (d_unlinked(path->dentry))
+		return -ENOENT;
+
+	return attach_recursive_mnt(mnt, path, NULL);
+}
+
+/*
+ * Sanity check the flags to change_mnt_propagation.
+ */
+
+static int flags_to_propagation_type(int flags)
+{
+	int type = flags & ~(MS_REC | MS_SILENT);
+
+	/* Fail if any non-propagation flags are set */
+	if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+		return 0;
+	/* Only one propagation flag should be set */
+	if (!is_power_of_2(type))
+		return 0;
+	return type;
+}
+
+/*
+ * 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;
+	int err = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (path->dentry != path->mnt->mnt_root)
+		return -EINVAL;
+
+	type = flags_to_propagation_type(flag);
+	if (!type)
+		return -EINVAL;
+
+	down_write(&namespace_sem);
+	if (type == MS_SHARED) {
+		err = invent_group_ids(mnt, recurse);
+		if (err)
+			goto out_unlock;
+	}
+
+	br_write_lock(vfsmount_lock);
+	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
+		change_mnt_propagation(m, type);
+	br_write_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)
+{
+	LIST_HEAD(umount_list);
+	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|LOOKUP_AUTOMOUNT, &old_path);
+	if (err)
+		return err;
+
+	err = lock_mount(path);
+	if (err)
+		goto out;
+
+	err = -EINVAL;
+	if (IS_MNT_UNBINDABLE(old_path.mnt))
+		goto out2;
+
+	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
+		goto out2;
+
+	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 out2;
+
+	err = graft_tree(mnt, path);
+	if (err) {
+		br_write_lock(vfsmount_lock);
+		umount_tree(mnt, 0, &umount_list);
+		br_write_unlock(vfsmount_lock);
+	}
+out2:
+	unlock_mount(path);
+	release_mounts(&umount_list);
+out:
+	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;
+
+	err = security_sb_remount(sb, data);
+	if (err)
+		return err;
+
+	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) {
+		br_write_lock(vfsmount_lock);
+		mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK;
+		path->mnt->mnt_flags = mnt_flags;
+		br_write_unlock(vfsmount_lock);
+	}
+	up_write(&sb->s_umount);
+	if (!err) {
+		br_write_lock(vfsmount_lock);
+		touch_mnt_namespace(path->mnt->mnt_ns);
+		br_write_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;
+
+	err = lock_mount(path);
+	if (err < 0)
+		goto out;
+
+	err = -EINVAL;
+	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
+		goto out1;
+
+	if (d_unlinked(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:
+	unlock_mount(path);
+out:
+	if (!err)
+		path_put(&parent_path);
+	path_put(&old_path);
+	return err;
+}
+
+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);
+
+/*
+ * add a mount into a namespace's mount tree
+ */
+static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
+{
+	int err;
+
+	mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
+
+	err = lock_mount(path);
+	if (err)
+		return err;
+
+	err = -EINVAL;
+	if (!(mnt_flags & MNT_SHRINKABLE) && !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;
+	err = graft_tree(newmnt, path);
+
+unlock:
+	unlock_mount(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;
+	int err;
+
+	if (!type)
+		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);
+
+	err = do_add_mount(mnt, path, mnt_flags);
+	if (err)
+		mntput(mnt);
+	return err;
+}
+
+int finish_automount(struct vfsmount *m, struct path *path)
+{
+	int err;
+	/* The new mount record should have at least 2 refs to prevent it being
+	 * expired before we get a chance to add it
+	 */
+	BUG_ON(mnt_get_count(m) < 2);
+
+	if (m->mnt_sb == path->mnt->mnt_sb &&
+	    m->mnt_root == path->dentry) {
+		err = -ELOOP;
+		goto fail;
+	}
+
+	err = do_add_mount(m, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
+	if (!err)
+		return 0;
+fail:
+	/* remove m from any expiration list it may be on */
+	if (!list_empty(&m->mnt_expire)) {
+		down_write(&namespace_sem);
+		br_write_lock(vfsmount_lock);
+		list_del_init(&m->mnt_expire);
+		br_write_unlock(vfsmount_lock);
+		up_write(&namespace_sem);
+	}
+	mntput(m);
+	mntput(m);
+	return err;
+}
+
+/**
+ * mnt_set_expiry - Put a mount on an expiration list
+ * @mnt: The mount to list.
+ * @expiry_list: The list to add the mount to.
+ */
+void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
+{
+	down_write(&namespace_sem);
+	br_write_lock(vfsmount_lock);
+
+	list_add_tail(&mnt->mnt_expire, expiry_list);
+
+	br_write_unlock(vfsmount_lock);
+	up_write(&namespace_sem);
+}
+EXPORT_SYMBOL(mnt_set_expiry);
+
+/*
+ * 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);
+	br_write_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);
+	}
+	br_write_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
+ *
+ * vfsmount_lock must be held for write
+ */
+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;
+}
+
+int copy_mount_string(const void __user *data, char **where)
+{
+	char *tmp;
+
+	if (!data) {
+		*where = NULL;
+		return 0;
+	}
+
+	tmp = strndup_user(data, PAGE_SIZE);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+
+	*where = tmp;
+	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 (data_page)
+		((char *)data_page)[PAGE_SIZE - 1] = 0;
+
+	/* ... 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;
+
+	/* 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_BORN |
+		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
+		   MS_STRICTATIME);
+
+	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;
+}
+
+static struct mnt_namespace *alloc_mnt_ns(void)
+{
+	struct mnt_namespace *new_ns;
+
+	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+	if (!new_ns)
+		return ERR_PTR(-ENOMEM);
+	atomic_set(&new_ns->count, 1);
+	new_ns->root = NULL;
+	INIT_LIST_HEAD(&new_ns->list);
+	init_waitqueue_head(&new_ns->poll);
+	new_ns->event = 0;
+	return new_ns;
+}
+
+void mnt_make_longterm(struct vfsmount *mnt)
+{
+	__mnt_make_longterm(mnt);
+}
+
+void mnt_make_shortterm(struct vfsmount *mnt)
+{
+#ifdef CONFIG_SMP
+	if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
+		return;
+	br_write_lock(vfsmount_lock);
+	atomic_dec(&mnt->mnt_longterm);
+	br_write_unlock(vfsmount_lock);
+#endif
+}
+
+/*
+ * 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 = alloc_mnt_ns();
+	if (IS_ERR(new_ns))
+		return new_ns;
+
+	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);
+	}
+	br_write_lock(vfsmount_lock);
+	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
+	br_write_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;
+		__mnt_make_longterm(q);
+		if (fs) {
+			if (p == fs->root.mnt) {
+				fs->root.mnt = mntget(q);
+				__mnt_make_longterm(q);
+				mnt_make_shortterm(p);
+				rootmnt = p;
+			}
+			if (p == fs->pwd.mnt) {
+				fs->pwd.mnt = mntget(q);
+				__mnt_make_longterm(q);
+				mnt_make_shortterm(p);
+				pwdmnt = p;
+			}
+		}
+		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);
+	return new_ns;
+}
+
+/**
+ * create_mnt_ns - creates a private namespace and adds a root filesystem
+ * @mnt: pointer to the new root filesystem mountpoint
+ */
+struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
+{
+	struct mnt_namespace *new_ns;
+
+	new_ns = alloc_mnt_ns();
+	if (!IS_ERR(new_ns)) {
+		mnt->mnt_ns = new_ns;
+		__mnt_make_longterm(mnt);
+		new_ns->root = mnt;
+		list_add(&new_ns->list, &new_ns->root->mnt_list);
+	}
+	return new_ns;
+}
+EXPORT_SYMBOL(create_mnt_ns);
+
+SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
+		char __user *, type, unsigned long, flags, void __user *, data)
+{
+	int ret;
+	char *kernel_type;
+	char *kernel_dir;
+	char *kernel_dev;
+	unsigned long data_page;
+
+	ret = copy_mount_string(type, &kernel_type);
+	if (ret < 0)
+		goto out_type;
+
+	kernel_dir = getname(dir_name);
+	if (IS_ERR(kernel_dir)) {
+		ret = PTR_ERR(kernel_dir);
+		goto out_dir;
+	}
+
+	ret = copy_mount_string(dev_name, &kernel_dev);
+	if (ret < 0)
+		goto out_dev;
+
+	ret = copy_mount_options(data, &data_page);
+	if (ret < 0)
+		goto out_data;
+
+	ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags,
+		(void *) data_page);
+
+	free_page(data_page);
+out_data:
+	kfree(kernel_dev);
+out_dev:
+	putname(kernel_dir);
+out_dir:
+	kfree(kernel_type);
+out_type:
+	return ret;
+}
+
+/*
+ * pivot_root Semantics:
+ * Moves the root file system of the current process to the directory put_old,
+ * makes new_root as the new root file system of the current process, and sets
+ * root/cwd of all processes which had them on the current root to new_root.
+ *
+ * Restrictions:
+ * The new_root and put_old must be directories, and  must not be on the
+ * same file  system as the current process root. The put_old  must  be
+ * underneath new_root,  i.e. adding a non-zero number of /.. to the string
+ * pointed to by put_old must yield the same directory as new_root. No other
+ * file system may be mounted on put_old. After all, new_root is a mountpoint.
+ *
+ * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
+ * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
+ * in this situation.
+ *
+ * Notes:
+ *  - we don't move root/cwd if they are not at the root (reason: if something
+ *    cared enough to change them, it's probably wrong to force them elsewhere)
+ *  - it's okay to pick a root that isn't the root of a file system, e.g.
+ *    /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
+ *    though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
+ *    first.
+ */
+SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
+		const char __user *, put_old)
+{
+	struct vfsmount *tmp;
+	struct path new, old, parent_path, root_parent, root;
+	int error;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	error = user_path_dir(new_root, &new);
+	if (error)
+		goto out0;
+
+	error = user_path_dir(put_old, &old);
+	if (error)
+		goto out1;
+
+	error = security_sb_pivotroot(&old, &new);
+	if (error)
+		goto out2;
+
+	get_fs_root(current->fs, &root);
+	error = lock_mount(&old);
+	if (error)
+		goto out3;
+
+	error = -EINVAL;
+	if (IS_MNT_SHARED(old.mnt) ||
+		IS_MNT_SHARED(new.mnt->mnt_parent) ||
+		IS_MNT_SHARED(root.mnt->mnt_parent))
+		goto out4;
+	if (!check_mnt(root.mnt) || !check_mnt(new.mnt))
+		goto out4;
+	error = -ENOENT;
+	if (d_unlinked(new.dentry))
+		goto out4;
+	if (d_unlinked(old.dentry))
+		goto out4;
+	error = -EBUSY;
+	if (new.mnt == root.mnt ||
+	    old.mnt == root.mnt)
+		goto out4; /* loop, on the same file system  */
+	error = -EINVAL;
+	if (root.mnt->mnt_root != root.dentry)
+		goto out4; /* not a mountpoint */
+	if (root.mnt->mnt_parent == root.mnt)
+		goto out4; /* not attached */
+	if (new.mnt->mnt_root != new.dentry)
+		goto out4; /* not a mountpoint */
+	if (new.mnt->mnt_parent == new.mnt)
+		goto out4; /* not attached */
+	/* make sure we can reach put_old from new_root */
+	tmp = old.mnt;
+	if (tmp != new.mnt) {
+		for (;;) {
+			if (tmp->mnt_parent == tmp)
+				goto out4; /* already mounted on put_old */
+			if (tmp->mnt_parent == new.mnt)
+				break;
+			tmp = tmp->mnt_parent;
+		}
+		if (!is_subdir(tmp->mnt_mountpoint, new.dentry))
+			goto out4;
+	} else if (!is_subdir(old.dentry, new.dentry))
+		goto out4;
+	br_write_lock(vfsmount_lock);
+	detach_mnt(new.mnt, &parent_path);
+	detach_mnt(root.mnt, &root_parent);
+	/* mount old root on put_old */
+	attach_mnt(root.mnt, &old);
+	/* mount new_root on / */
+	attach_mnt(new.mnt, &root_parent);
+	touch_mnt_namespace(current->nsproxy->mnt_ns);
+	br_write_unlock(vfsmount_lock);
+	chroot_fs_refs(&root, &new);
+	error = 0;
+out4:
+	unlock_mount(&old);
+	if (!error) {
+		path_put(&root_parent);
+		path_put(&parent_path);
+	}
+out3:
+	path_put(&root);
+out2:
+	path_put(&old);
+out1:
+	path_put(&new);
+out0:
+	return error;
+}
+
+static void __init init_mount_tree(void)
+{
+	struct vfsmount *mnt;
+	struct mnt_namespace *ns;
+	struct path root;
+
+	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
+	if (IS_ERR(mnt))
+		panic("Can't create rootfs");
+
+	ns = create_mnt_ns(mnt);
+	if (IS_ERR(ns))
+		panic("Can't allocate initial namespace");
+
+	init_task.nsproxy->mnt_ns = ns;
+	get_mnt_ns(ns);
+
+	root.mnt = ns->root;
+	root.dentry = ns->root->mnt_root;
+
+	set_fs_pwd(current->fs, &root);
+	set_fs_root(current->fs, &root);
+}
+
+void __init mnt_init(void)
+{
+	unsigned u;
+	int err;
+
+	init_rwsem(&namespace_sem);
+
+	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+
+	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
+
+	if (!mount_hashtable)
+		panic("Failed to allocate mount hash table\n");
+
+	printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
+
+	for (u = 0; u < HASH_SIZE; u++)
+		INIT_LIST_HEAD(&mount_hashtable[u]);
+
+	br_lock_init(vfsmount_lock);
+
+	err = sysfs_init();
+	if (err)
+		printk(KERN_WARNING "%s: sysfs_init error: %d\n",
+			__func__, err);
+	fs_kobj = kobject_create_and_add("fs", NULL);
+	if (!fs_kobj)
+		printk(KERN_WARNING "%s: kobj create error\n", __func__);
+	init_rootfs();
+	init_mount_tree();
+}
+
+void put_mnt_ns(struct mnt_namespace *ns)
+{
+	LIST_HEAD(umount_list);
+
+	if (!atomic_dec_and_test(&ns->count))
+		return;
+	down_write(&namespace_sem);
+	br_write_lock(vfsmount_lock);
+	umount_tree(ns->root, 0, &umount_list);
+	br_write_unlock(vfsmount_lock);
+	up_write(&namespace_sem);
+	release_mounts(&umount_list);
+	kfree(ns);
+}
+EXPORT_SYMBOL(put_mnt_ns);
+
+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);
+
+bool our_mnt(struct vfsmount *mnt)
+{
+	return check_mnt(mnt);
+}