ClabureDB: Classified Bug-Reports Database

   /*
    *  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 <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\n",
                         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);
 }
 
 int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
 {
         mnt->mnt_sb = sb;
         mnt->mnt_root = dget(sb->s_root);
         return 0;
 }
 
 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);
                 if (cpu_writer->mnt != mnt)
                         continue;
                 spin_lock(&cpu_writer->lock);
                 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\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 = mnt->mnt_sb->s_options;
 
         if (options != NULL && options[0]) {
                 seq_putc(m, ',');
                 mangle(m, options);
         }
 
         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)
 {
         kfree(sb->s_options);
         sb->s_options = kstrdup(options, GFP_KERNEL);
 }
 EXPORT_SYMBOL(save_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" },
                 { 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\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));
         seq_dentry(m, mnt->mnt_root, " \t\n\\");
         seq_putc(m, ' ');
         seq_path_root(m, &mnt_path, &root, " \t\n\\");
         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, '\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_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, ' ');
                 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;
 
         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) {
                lock_kernel();
                sb->s_op->umount_begin(sb);
                unlock_kernel();
        }

        /*
         * 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
 */

asmlinkage long sys_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.
 */
asmlinkage long sys_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(current->nsproxy->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;

        /* 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_RELATIME)
                mnt_flags |= MNT_RELATIME;
        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);

        /* ... 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);
        return new_ns;
}

asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
                          char __user * type, unsigned long flags,
                          void __user * data)
{
        int retval;
        unsigned long data_page;
        unsigned long type_page;
        unsigned long dev_page;
        char *dir_page;

        retval = copy_mount_options(type, &type_page);
        if (retval < 0)
                return retval;

        dir_page = getname(dir_name);
        retval = PTR_ERR(dir_page);
        if (IS_ERR(dir_page))
                goto out1;

        retval = copy_mount_options(dev_name, &dev_page);
        if (retval < 0)
                goto out2;

        retval = copy_mount_options(data, &data_page);
        if (retval < 0)
                goto out3;

        lock_kernel();
        retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
                          flags, (void *)data_page);
        unlock_kernel();
        free_page(data_page);

out3:
        free_page(dev_page);
out2:
        putname(dir_page);
out1:
        free_page(type_page);
        return retval;
}

/*
 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
 * It can block. Requires the big lock held.
 */
void set_fs_root(struct fs_struct *fs, struct path *path)
{
        struct path old_root;

        write_lock(&fs->lock);
        old_root = fs->root;
        fs->root = *path;
        path_get(path);
        write_unlock(&fs->lock);
        if (old_root.dentry)
                path_put(&old_root);
}

/*
 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
 * It can block. Requires the big lock held.
 */
void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
        struct path old_pwd;

        write_lock(&fs->lock);
        old_pwd = fs->pwd;
        fs->pwd = *path;
        path_get(path);
        write_unlock(&fs->lock);

        if (old_pwd.dentry)
                path_put(&old_pwd);
}

static void chroot_fs_refs(struct path *old_root, struct path *new_root)
{
        struct task_struct *g, *p;
        struct fs_struct *fs;

        read_lock(&tasklist_lock);
        do_each_thread(g, p) {
                task_lock(p);
                fs = p->fs;
                if (fs) {
                        atomic_inc(&fs->count);
                        task_unlock(p);
                        if (fs->root.dentry == old_root->dentry
                            && fs->root.mnt == old_root->mnt)
                                set_fs_root(fs, new_root);
                        if (fs->pwd.dentry == old_root->dentry
                            && fs->pwd.mnt == old_root->mnt)
                                set_fs_pwd(fs, new_root);
                        put_fs_struct(fs);
                } else
                        task_unlock(p);
        } while_each_thread(g, p);
        read_unlock(&tasklist_lock);
}

/*
 * 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.
 */
asmlinkage long sys_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 = -EINVAL;
        if (!check_mnt(new.mnt))
                goto out1;

        error = user_path_dir(put_old, &old);
        if (error)
                goto out1;

        error = security_sb_pivotroot(&old, &new);
        if (error) {
                path_put(&old);
                goto out1;
        }

        read_lock(&current->fs->lock);
        root = current->fs->root;
        path_get(&current->fs->root);
        read_unlock(&current->fs->lock);
        down_write(&namespace_sem);
        mutex_lock(&old.dentry->d_inode->i_mutex);
        error = -EINVAL;
        if (IS_MNT_SHARED(old.mnt) ||
                IS_MNT_SHARED(new.mnt->mnt_parent) ||
                IS_MNT_SHARED(root.mnt->mnt_parent))
                goto out2;
        if (!check_mnt(root.mnt))
                goto out2;
        error = -ENOENT;
        if (IS_DEADDIR(new.dentry->d_inode))
                goto out2;
        if (d_unhashed(new.dentry) && !IS_ROOT(new.dentry))
                goto out2;
        if (d_unhashed(old.dentry) && !IS_ROOT(old.dentry))
                goto out2;
        error = -EBUSY;
        if (new.mnt == root.mnt ||
            old.mnt == root.mnt)
                goto out2; /* loop, on the same file system  */
        error = -EINVAL;
        if (root.mnt->mnt_root != root.dentry)
                goto out2; /* not a mountpoint */
        if (root.mnt->mnt_parent == root.mnt)
                goto out2; /* not attached */
        if (new.mnt->mnt_root != new.dentry)
                goto out2; /* not a mountpoint */
        if (new.mnt->mnt_parent == new.mnt)
                goto out2; /* not attached */
        /* make sure we can reach put_old from new_root */
        tmp = old.mnt;
        spin_lock(&vfsmount_lock);
        if (tmp != new.mnt) {
                for (;;) {
                        if (tmp->mnt_parent == tmp)
                                goto out3; /* 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 out3;
        } else if (!is_subdir(old.dentry, new.dentry))
                goto out3;
        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);
        spin_unlock(&vfsmount_lock);
        chroot_fs_refs(&root, &new);
        security_sb_post_pivotroot(&root, &new);
        error = 0;
        path_put(&root_parent);
        path_put(&parent_path);
out2:
        mutex_unlock(&old.dentry->d_inode->i_mutex);
        up_write(&namespace_sem);
        path_put(&root);
        path_put(&old);
out1:
        path_put(&new);
out0:
        return error;
out3:
        spin_unlock(&vfsmount_lock);
        goto out2;
}

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 = kmalloc(sizeof(*ns), GFP_KERNEL);
        if (!ns)
                panic("Can't allocate initial namespace");
        atomic_set(&ns->count, 1);
        INIT_LIST_HEAD(&ns->list);
        init_waitqueue_head(&ns->poll);
        ns->event = 0;
        list_add(&mnt->mnt_list, &ns->list);
        ns->root = mnt;
        mnt->mnt_ns = ns;

        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("Mount-cache hash table entries: %lu\n", HASH_SIZE);

        for (u = 0; u < HASH_SIZE; u++)
                INIT_LIST_HEAD(&mount_hashtable[u]);

        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)
{
        struct vfsmount *root = ns->root;
        LIST_HEAD(umount_list);
        ns->root = NULL;
        spin_unlock(&vfsmount_lock);
        down_write(&namespace_sem);
        spin_lock(&vfsmount_lock);
        umount_tree(root, 0, &umount_list);
        spin_unlock(&vfsmount_lock);
        up_write(&namespace_sem);
        release_mounts(&umount_list);
        kfree(ns);
}