/*
   *  linux/fs/namei.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  /*
   * Some corrections by tytso.
   */
  
  /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
   * lookup logic.
   */
  /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
   */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/fs.h>
  #include <linux/namei.h>
  #include <linux/quotaops.h>
  #include <linux/pagemap.h>

  #include <linux/fsnotify.h>

  #include <linux/personality.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/mount.h>
  #include <linux/audit.h>

  #include <linux/capability.h>

  #include <linux/file.h>

  #include <linux/fcntl.h>

  #include <asm/namei.h>
  #include <asm/uaccess.h>
  
  #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
  
  /* [Feb-1997 T. Schoebel-Theuer]
   * Fundamental changes in the pathname lookup mechanisms (namei)
   * were necessary because of omirr.  The reason is that omirr needs
   * to know the _real_ pathname, not the user-supplied one, in case
   * of symlinks (and also when transname replacements occur).
   *
   * The new code replaces the old recursive symlink resolution with
   * an iterative one (in case of non-nested symlink chains).  It does
   * this with calls to <fs>_follow_link().
   * As a side effect, dir_namei(), _namei() and follow_link() are now 
   * replaced with a single function lookup_dentry() that can handle all 
   * the special cases of the former code.
   *
   * With the new dcache, the pathname is stored at each inode, at least as
   * long as the refcount of the inode is positive.  As a side effect, the
   * size of the dcache depends on the inode cache and thus is dynamic.
   *
   * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
   * resolution to correspond with current state of the code.
   *
   * Note that the symlink resolution is not *completely* iterative.
   * There is still a significant amount of tail- and mid- recursion in
   * the algorithm.  Also, note that <fs>_readlink() is not used in
   * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
   * may return different results than <fs>_follow_link().  Many virtual
   * filesystems (including /proc) exhibit this behavior.
   */
  
  /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
   * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
   * and the name already exists in form of a symlink, try to create the new
   * name indicated by the symlink. The old code always complained that the
   * name already exists, due to not following the symlink even if its target
   * is nonexistent.  The new semantics affects also mknod() and link() when
   * the name is a symlink pointing to a non-existant name.
   *
   * I don't know which semantics is the right one, since I have no access
   * to standards. But I found by trial that HP-UX 9.0 has the full "new"
   * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
   * "old" one. Personally, I think the new semantics is much more logical.
   * Note that "ln old new" where "new" is a symlink pointing to a non-existing
   * file does succeed in both HP-UX and SunOs, but not in Solaris
   * and in the old Linux semantics.
   */
  
  /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
   * semantics.  See the comments in "open_namei" and "do_link" below.
   *
   * [10-Sep-98 Alan Modra] Another symlink change.
   */
  
  /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
   *	inside the path - always follow.
   *	in the last component in creation/removal/renaming - never follow.
   *	if LOOKUP_FOLLOW passed - follow.
   *	if the pathname has trailing slashes - follow.
   *	otherwise - don't follow.
   * (applied in that order).
   *
   * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
   * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
   * During the 2.4 we need to fix the userland stuff depending on it -
   * hopefully we will be able to get rid of that wart in 2.5. So far only
   * XEmacs seems to be relying on it...
   */
  /*
   * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)

   * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives

   * any extra contention...
   */

  static int link_path_walk(const char *name, struct nameidata *nd);

  /* In order to reduce some races, while at the same time doing additional
   * checking and hopefully speeding things up, we copy filenames to the
   * kernel data space before using them..
   *
   * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
   * PATH_MAX includes the nul terminator --RR.
   */

  static int do_getname(const char __user *filename, char *page)

  {
  	int retval;
  	unsigned long len = PATH_MAX;
  
  	if (!segment_eq(get_fs(), KERNEL_DS)) {
  		if ((unsigned long) filename >= TASK_SIZE)
  			return -EFAULT;
  		if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
  			len = TASK_SIZE - (unsigned long) filename;
  	}
  
  	retval = strncpy_from_user(page, filename, len);
  	if (retval > 0) {
  		if (retval < len)
  			return 0;
  		return -ENAMETOOLONG;
  	} else if (!retval)
  		retval = -ENOENT;
  	return retval;
  }
  
  char * getname(const char __user * filename)
  {
  	char *tmp, *result;
  
  	result = ERR_PTR(-ENOMEM);
  	tmp = __getname();
  	if (tmp)  {
  		int retval = do_getname(filename, tmp);
  
  		result = tmp;
  		if (retval < 0) {
  			__putname(tmp);
  			result = ERR_PTR(retval);
  		}
  	}
  	audit_getname(result);
  	return result;
  }
  
  #ifdef CONFIG_AUDITSYSCALL
  void putname(const char *name)
  {

  	if (unlikely(!audit_dummy_context()))

  		audit_putname(name);
  	else
  		__putname(name);
  }
  EXPORT_SYMBOL(putname);
  #endif
  
  
  /**
   * generic_permission  -  check for access rights on a Posix-like filesystem
   * @inode:	inode to check access rights for
   * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
   * @check_acl:	optional callback to check for Posix ACLs
   *
   * Used to check for read/write/execute permissions on a file.
   * We use "fsuid" for this, letting us set arbitrary permissions
   * for filesystem access without changing the "normal" uids which
   * are used for other things..
   */
  int generic_permission(struct inode *inode, int mask,
  		int (*check_acl)(struct inode *inode, int mask))
  {
  	umode_t			mode = inode->i_mode;
  
  	if (current->fsuid == inode->i_uid)
  		mode >>= 6;
  	else {
  		if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
  			int error = check_acl(inode, mask);
  			if (error == -EACCES)
  				goto check_capabilities;
  			else if (error != -EAGAIN)
  				return error;
  		}
  
  		if (in_group_p(inode->i_gid))
  			mode >>= 3;
  	}
  
  	/*
  	 * If the DACs are ok we don't need any capability check.
  	 */
  	if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
  		return 0;
  
   check_capabilities:
  	/*
  	 * Read/write DACs are always overridable.
  	 * Executable DACs are overridable if at least one exec bit is set.
  	 */
  	if (!(mask & MAY_EXEC) ||
  	    (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
  		if (capable(CAP_DAC_OVERRIDE))
  			return 0;
  
  	/*
  	 * Searching includes executable on directories, else just read.
  	 */
  	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
  		if (capable(CAP_DAC_READ_SEARCH))
  			return 0;
  
  	return -EACCES;
  }
  
  int permission(struct inode *inode, int mask, struct nameidata *nd)
  {
  	int retval, submask;

  	struct vfsmount *mnt = NULL;
  
  	if (nd)
  		mnt = nd->mnt;

  
  	if (mask & MAY_WRITE) {

  		umode_t mode = inode->i_mode;

  
  		/*
  		 * Nobody gets write access to a read-only fs.
  		 */
  		if (IS_RDONLY(inode) &&
  		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
  			return -EROFS;
  
  		/*
  		 * Nobody gets write access to an immutable file.
  		 */
  		if (IS_IMMUTABLE(inode))
  			return -EACCES;
  	}

  	if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
  		/*
  		 * MAY_EXEC on regular files is denied if the fs is mounted
  		 * with the "noexec" flag.
  		 */

  		if (mnt && (mnt->mnt_flags & MNT_NOEXEC))

  			return -EACCES;
  	}

  	/* Ordinary permission routines do not understand MAY_APPEND. */
  	submask = mask & ~MAY_APPEND;

  	if (inode->i_op && inode->i_op->permission) {

  		retval = inode->i_op->permission(inode, submask, nd);

  		if (!retval) {
  			/*
  			 * Exec permission on a regular file is denied if none
  			 * of the execute bits are set.
  			 *
  			 * This check should be done by the ->permission()
  			 * method.
  			 */
  			if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode) &&
  			    !(inode->i_mode & S_IXUGO))
  				return -EACCES;
  		}
  	} else {

  		retval = generic_permission(inode, submask, NULL);

  	}

  	if (retval)
  		return retval;
  
  	return security_inode_permission(inode, mask, nd);
  }

  /**
   * vfs_permission  -  check for access rights to a given path
   * @nd:		lookup result that describes the path
   * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
   *
   * Used to check for read/write/execute permissions on a path.
   * We use "fsuid" for this, letting us set arbitrary permissions
   * for filesystem access without changing the "normal" uids which
   * are used for other things.
   */
  int vfs_permission(struct nameidata *nd, int mask)
  {
  	return permission(nd->dentry->d_inode, mask, nd);
  }

  /**
   * file_permission  -  check for additional access rights to a given file
   * @file:	file to check access rights for
   * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
   *
   * Used to check for read/write/execute permissions on an already opened
   * file.
   *
   * Note:
   *	Do not use this function in new code.  All access checks should
   *	be done using vfs_permission().
   */
  int file_permission(struct file *file, int mask)
  {

  	return permission(file->f_path.dentry->d_inode, mask, NULL);

  }

  /*
   * get_write_access() gets write permission for a file.
   * put_write_access() releases this write permission.
   * This is used for regular files.
   * We cannot support write (and maybe mmap read-write shared) accesses and
   * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
   * can have the following values:
   * 0: no writers, no VM_DENYWRITE mappings
   * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
   * > 0: (i_writecount) users are writing to the file.
   *
   * Normally we operate on that counter with atomic_{inc,dec} and it's safe
   * except for the cases where we don't hold i_writecount yet. Then we need to
   * use {get,deny}_write_access() - these functions check the sign and refuse
   * to do the change if sign is wrong. Exclusion between them is provided by
   * the inode->i_lock spinlock.
   */
  
  int get_write_access(struct inode * inode)
  {
  	spin_lock(&inode->i_lock);
  	if (atomic_read(&inode->i_writecount) < 0) {
  		spin_unlock(&inode->i_lock);
  		return -ETXTBSY;
  	}
  	atomic_inc(&inode->i_writecount);
  	spin_unlock(&inode->i_lock);
  
  	return 0;
  }
  
  int deny_write_access(struct file * file)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  
  	spin_lock(&inode->i_lock);
  	if (atomic_read(&inode->i_writecount) > 0) {
  		spin_unlock(&inode->i_lock);
  		return -ETXTBSY;
  	}
  	atomic_dec(&inode->i_writecount);
  	spin_unlock(&inode->i_lock);
  
  	return 0;
  }
  
  void path_release(struct nameidata *nd)
  {
  	dput(nd->dentry);
  	mntput(nd->mnt);
  }
  
  /*
   * umount() mustn't call path_release()/mntput() as that would clear
   * mnt_expiry_mark
   */
  void path_release_on_umount(struct nameidata *nd)
  {
  	dput(nd->dentry);

  	mntput_no_expire(nd->mnt);

  }

  /**
   * release_open_intent - free up open intent resources
   * @nd: pointer to nameidata
   */
  void release_open_intent(struct nameidata *nd)
  {

  	if (nd->intent.open.file->f_path.dentry == NULL)

  		put_filp(nd->intent.open.file);
  	else
  		fput(nd->intent.open.file);
  }

  static inline struct dentry *
  do_revalidate(struct dentry *dentry, struct nameidata *nd)
  {
  	int status = dentry->d_op->d_revalidate(dentry, nd);
  	if (unlikely(status <= 0)) {
  		/*
  		 * The dentry failed validation.
  		 * If d_revalidate returned 0 attempt to invalidate
  		 * the dentry otherwise d_revalidate is asking us
  		 * to return a fail status.
  		 */
  		if (!status) {
  			if (!d_invalidate(dentry)) {
  				dput(dentry);
  				dentry = NULL;
  			}
  		} else {
  			dput(dentry);
  			dentry = ERR_PTR(status);
  		}
  	}
  	return dentry;
  }

  /*
   * Internal lookup() using the new generic dcache.
   * SMP-safe
   */
  static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
  {
  	struct dentry * dentry = __d_lookup(parent, name);
  
  	/* lockess __d_lookup may fail due to concurrent d_move() 
  	 * in some unrelated directory, so try with d_lookup
  	 */
  	if (!dentry)
  		dentry = d_lookup(parent, name);

  	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
  		dentry = do_revalidate(dentry, nd);

  	return dentry;
  }
  
  /*
   * Short-cut version of permission(), for calling by
   * path_walk(), when dcache lock is held.  Combines parts
   * of permission() and generic_permission(), and tests ONLY for
   * MAY_EXEC permission.
   *
   * If appropriate, check DAC only.  If not appropriate, or
   * short-cut DAC fails, then call permission() to do more
   * complete permission check.
   */

  static int exec_permission_lite(struct inode *inode,

  				       struct nameidata *nd)
  {
  	umode_t	mode = inode->i_mode;
  
  	if (inode->i_op && inode->i_op->permission)
  		return -EAGAIN;
  
  	if (current->fsuid == inode->i_uid)
  		mode >>= 6;
  	else if (in_group_p(inode->i_gid))
  		mode >>= 3;
  
  	if (mode & MAY_EXEC)
  		goto ok;
  
  	if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
  		goto ok;
  
  	if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
  		goto ok;
  
  	if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
  		goto ok;
  
  	return -EACCES;
  ok:
  	return security_inode_permission(inode, MAY_EXEC, nd);
  }
  
  /*
   * This is called when everything else fails, and we actually have
   * to go to the low-level filesystem to find out what we should do..
   *
   * We get the directory semaphore, and after getting that we also
   * make sure that nobody added the entry to the dcache in the meantime..
   * SMP-safe
   */
  static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
  {
  	struct dentry * result;
  	struct inode *dir = parent->d_inode;

  	mutex_lock(&dir->i_mutex);

  	/*
  	 * First re-do the cached lookup just in case it was created
  	 * while we waited for the directory semaphore..
  	 *
  	 * FIXME! This could use version numbering or similar to
  	 * avoid unnecessary cache lookups.
  	 *
  	 * The "dcache_lock" is purely to protect the RCU list walker
  	 * from concurrent renames at this point (we mustn't get false
  	 * negatives from the RCU list walk here, unlike the optimistic
  	 * fast walk).
  	 *
  	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
  	 */
  	result = d_lookup(parent, name);
  	if (!result) {
  		struct dentry * dentry = d_alloc(parent, name);
  		result = ERR_PTR(-ENOMEM);
  		if (dentry) {
  			result = dir->i_op->lookup(dir, dentry, nd);
  			if (result)
  				dput(dentry);
  			else
  				result = dentry;
  		}

  		mutex_unlock(&dir->i_mutex);

  		return result;
  	}
  
  	/*
  	 * Uhhuh! Nasty case: the cache was re-populated while
  	 * we waited on the semaphore. Need to revalidate.
  	 */

  	mutex_unlock(&dir->i_mutex);

  	if (result->d_op && result->d_op->d_revalidate) {

  		result = do_revalidate(result, nd);
  		if (!result)

  			result = ERR_PTR(-ENOENT);

  	}
  	return result;
  }
  
  static int __emul_lookup_dentry(const char *, struct nameidata *);
  
  /* SMP-safe */

  static __always_inline int

  walk_init_root(const char *name, struct nameidata *nd)
  {

  	struct fs_struct *fs = current->fs;
  
  	read_lock(&fs->lock);
  	if (fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
  		nd->mnt = mntget(fs->altrootmnt);
  		nd->dentry = dget(fs->altroot);
  		read_unlock(&fs->lock);

  		if (__emul_lookup_dentry(name,nd))
  			return 0;

  		read_lock(&fs->lock);

  	}

  	nd->mnt = mntget(fs->rootmnt);
  	nd->dentry = dget(fs->root);
  	read_unlock(&fs->lock);

  	return 1;
  }

  static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)

  {
  	int res = 0;
  	char *name;
  	if (IS_ERR(link))
  		goto fail;
  
  	if (*link == '/') {
  		path_release(nd);
  		if (!walk_init_root(link, nd))
  			/* weird __emul_prefix() stuff did it */
  			goto out;
  	}
  	res = link_path_walk(link, nd);
  out:
  	if (nd->depth || res || nd->last_type!=LAST_NORM)
  		return res;
  	/*
  	 * If it is an iterative symlinks resolution in open_namei() we
  	 * have to copy the last component. And all that crap because of
  	 * bloody create() on broken symlinks. Furrfu...
  	 */
  	name = __getname();
  	if (unlikely(!name)) {
  		path_release(nd);
  		return -ENOMEM;
  	}
  	strcpy(name, nd->last.name);
  	nd->last.name = name;
  	return 0;
  fail:
  	path_release(nd);
  	return PTR_ERR(link);
  }

  static inline void dput_path(struct path *path, struct nameidata *nd)
  {
  	dput(path->dentry);
  	if (path->mnt != nd->mnt)
  		mntput(path->mnt);
  }
  
  static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
  {
  	dput(nd->dentry);
  	if (nd->mnt != path->mnt)
  		mntput(nd->mnt);
  	nd->mnt = path->mnt;
  	nd->dentry = path->dentry;
  }

  static __always_inline int __do_follow_link(struct path *path, struct nameidata *nd)

  {
  	int error;

  	void *cookie;

  	struct dentry *dentry = path->dentry;

  	touch_atime(path->mnt, dentry);

  	nd_set_link(nd, NULL);

  	if (path->mnt != nd->mnt) {
  		path_to_nameidata(path, nd);
  		dget(dentry);
  	}
  	mntget(path->mnt);

  	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
  	error = PTR_ERR(cookie);
  	if (!IS_ERR(cookie)) {

  		char *s = nd_get_link(nd);

  		error = 0;

  		if (s)
  			error = __vfs_follow_link(nd, s);
  		if (dentry->d_inode->i_op->put_link)

  			dentry->d_inode->i_op->put_link(dentry, nd, cookie);

  	}

  	dput(dentry);
  	mntput(path->mnt);

  
  	return error;
  }
  
  /*
   * This limits recursive symlink follows to 8, while
   * limiting consecutive symlinks to 40.
   *
   * Without that kind of total limit, nasty chains of consecutive
   * symlinks can cause almost arbitrarily long lookups. 
   */

  static inline int do_follow_link(struct path *path, struct nameidata *nd)

  {
  	int err = -ELOOP;
  	if (current->link_count >= MAX_NESTED_LINKS)
  		goto loop;
  	if (current->total_link_count >= 40)
  		goto loop;
  	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
  	cond_resched();

  	err = security_inode_follow_link(path->dentry, nd);

  	if (err)
  		goto loop;
  	current->link_count++;
  	current->total_link_count++;
  	nd->depth++;

  	err = __do_follow_link(path, nd);

  	current->link_count--;
  	nd->depth--;

  	return err;
  loop:

  	dput_path(path, nd);

  	path_release(nd);

  	return err;
  }
  
  int follow_up(struct vfsmount **mnt, struct dentry **dentry)
  {
  	struct vfsmount *parent;
  	struct dentry *mountpoint;
  	spin_lock(&vfsmount_lock);
  	parent=(*mnt)->mnt_parent;
  	if (parent == *mnt) {
  		spin_unlock(&vfsmount_lock);
  		return 0;
  	}
  	mntget(parent);
  	mountpoint=dget((*mnt)->mnt_mountpoint);
  	spin_unlock(&vfsmount_lock);
  	dput(*dentry);
  	*dentry = mountpoint;
  	mntput(*mnt);
  	*mnt = parent;
  	return 1;
  }
  
  /* no need for dcache_lock, as serialization is taken care in
   * namespace.c
   */

  static int __follow_mount(struct path *path)
  {
  	int res = 0;
  	while (d_mountpoint(path->dentry)) {
  		struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry);
  		if (!mounted)
  			break;
  		dput(path->dentry);
  		if (res)
  			mntput(path->mnt);
  		path->mnt = mounted;
  		path->dentry = dget(mounted->mnt_root);
  		res = 1;
  	}
  	return res;
  }

  static void follow_mount(struct vfsmount **mnt, struct dentry **dentry)

  {

  	while (d_mountpoint(*dentry)) {
  		struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
  		if (!mounted)
  			break;

  		dput(*dentry);

  		mntput(*mnt);
  		*mnt = mounted;

  		*dentry = dget(mounted->mnt_root);

  	}

  }
  
  /* no need for dcache_lock, as serialization is taken care in
   * namespace.c
   */

  int follow_down(struct vfsmount **mnt, struct dentry **dentry)

  {
  	struct vfsmount *mounted;
  
  	mounted = lookup_mnt(*mnt, *dentry);
  	if (mounted) {

  		dput(*dentry);

  		mntput(*mnt);
  		*mnt = mounted;

  		*dentry = dget(mounted->mnt_root);
  		return 1;
  	}
  	return 0;
  }

  static __always_inline void follow_dotdot(struct nameidata *nd)

  {

  	struct fs_struct *fs = current->fs;

  	while(1) {
  		struct vfsmount *parent;

  		struct dentry *old = nd->dentry;

                  read_lock(&fs->lock);
  		if (nd->dentry == fs->root &&
  		    nd->mnt == fs->rootmnt) {
                          read_unlock(&fs->lock);

  			break;
  		}

                  read_unlock(&fs->lock);

  		spin_lock(&dcache_lock);

  		if (nd->dentry != nd->mnt->mnt_root) {
  			nd->dentry = dget(nd->dentry->d_parent);

  			spin_unlock(&dcache_lock);
  			dput(old);
  			break;
  		}
  		spin_unlock(&dcache_lock);
  		spin_lock(&vfsmount_lock);

  		parent = nd->mnt->mnt_parent;
  		if (parent == nd->mnt) {

  			spin_unlock(&vfsmount_lock);
  			break;
  		}
  		mntget(parent);

  		nd->dentry = dget(nd->mnt->mnt_mountpoint);

  		spin_unlock(&vfsmount_lock);
  		dput(old);

  		mntput(nd->mnt);
  		nd->mnt = parent;

  	}

  	follow_mount(&nd->mnt, &nd->dentry);

  }

  /*
   *  It's more convoluted than I'd like it to be, but... it's still fairly
   *  small and for now I'd prefer to have fast path as straight as possible.
   *  It _is_ time-critical.
   */
  static int do_lookup(struct nameidata *nd, struct qstr *name,
  		     struct path *path)
  {
  	struct vfsmount *mnt = nd->mnt;
  	struct dentry *dentry = __d_lookup(nd->dentry, name);
  
  	if (!dentry)
  		goto need_lookup;
  	if (dentry->d_op && dentry->d_op->d_revalidate)
  		goto need_revalidate;
  done:
  	path->mnt = mnt;
  	path->dentry = dentry;

  	__follow_mount(path);

  	return 0;
  
  need_lookup:
  	dentry = real_lookup(nd->dentry, name, nd);
  	if (IS_ERR(dentry))
  		goto fail;
  	goto done;
  
  need_revalidate:

  	dentry = do_revalidate(dentry, nd);
  	if (!dentry)
  		goto need_lookup;
  	if (IS_ERR(dentry))
  		goto fail;
  	goto done;

  
  fail:
  	return PTR_ERR(dentry);
  }
  
  /*
   * Name resolution.

   * This is the basic name resolution function, turning a pathname into
   * the final dentry. We expect 'base' to be positive and a directory.

   *

   * Returns 0 and nd will have valid dentry and mnt on success.
   * Returns error and drops reference to input namei data on failure.

   */

  static int __link_path_walk(const char *name, struct nameidata *nd)

  {
  	struct path next;
  	struct inode *inode;
  	int err;
  	unsigned int lookup_flags = nd->flags;
  	
  	while (*name=='/')
  		name++;
  	if (!*name)
  		goto return_reval;
  
  	inode = nd->dentry->d_inode;
  	if (nd->depth)

  		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);

  
  	/* At this point we know we have a real path component. */
  	for(;;) {
  		unsigned long hash;
  		struct qstr this;
  		unsigned int c;

  		nd->flags |= LOOKUP_CONTINUE;

  		err = exec_permission_lite(inode, nd);

  		if (err == -EAGAIN)
  			err = vfs_permission(nd, MAY_EXEC);

   		if (err)
  			break;
  
  		this.name = name;
  		c = *(const unsigned char *)name;
  
  		hash = init_name_hash();
  		do {
  			name++;
  			hash = partial_name_hash(c, hash);
  			c = *(const unsigned char *)name;
  		} while (c && (c != '/'));
  		this.len = name - (const char *) this.name;
  		this.hash = end_name_hash(hash);
  
  		/* remove trailing slashes? */
  		if (!c)
  			goto last_component;
  		while (*++name == '/');
  		if (!*name)
  			goto last_with_slashes;
  
  		/*
  		 * "." and ".." are special - ".." especially so because it has
  		 * to be able to know about the current root directory and
  		 * parent relationships.
  		 */
  		if (this.name[0] == '.') switch (this.len) {
  			default:
  				break;
  			case 2:	
  				if (this.name[1] != '.')
  					break;

  				follow_dotdot(nd);

  				inode = nd->dentry->d_inode;
  				/* fallthrough */
  			case 1:
  				continue;
  		}
  		/*
  		 * See if the low-level filesystem might want
  		 * to use its own hash..
  		 */
  		if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
  			err = nd->dentry->d_op->d_hash(nd->dentry, &this);
  			if (err < 0)
  				break;
  		}

  		/* This does the actual lookups.. */
  		err = do_lookup(nd, &this, &next);
  		if (err)
  			break;

  
  		err = -ENOENT;
  		inode = next.dentry->d_inode;
  		if (!inode)
  			goto out_dput;
  		err = -ENOTDIR; 
  		if (!inode->i_op)
  			goto out_dput;
  
  		if (inode->i_op->follow_link) {

  			err = do_follow_link(&next, nd);

  			if (err)
  				goto return_err;
  			err = -ENOENT;
  			inode = nd->dentry->d_inode;
  			if (!inode)
  				break;
  			err = -ENOTDIR; 
  			if (!inode->i_op)
  				break;

  		} else
  			path_to_nameidata(&next, nd);

  		err = -ENOTDIR; 
  		if (!inode->i_op->lookup)
  			break;
  		continue;
  		/* here ends the main loop */
  
  last_with_slashes:
  		lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
  last_component:

  		/* Clear LOOKUP_CONTINUE iff it was previously unset */
  		nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;

  		if (lookup_flags & LOOKUP_PARENT)
  			goto lookup_parent;
  		if (this.name[0] == '.') switch (this.len) {
  			default:
  				break;
  			case 2:	
  				if (this.name[1] != '.')
  					break;

  				follow_dotdot(nd);

  				inode = nd->dentry->d_inode;
  				/* fallthrough */
  			case 1:
  				goto return_reval;
  		}
  		if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
  			err = nd->dentry->d_op->d_hash(nd->dentry, &this);
  			if (err < 0)
  				break;
  		}
  		err = do_lookup(nd, &this, &next);
  		if (err)
  			break;

  		inode = next.dentry->d_inode;
  		if ((lookup_flags & LOOKUP_FOLLOW)
  		    && inode && inode->i_op && inode->i_op->follow_link) {

  			err = do_follow_link(&next, nd);

  			if (err)
  				goto return_err;
  			inode = nd->dentry->d_inode;

  		} else
  			path_to_nameidata(&next, nd);

  		err = -ENOENT;
  		if (!inode)
  			break;
  		if (lookup_flags & LOOKUP_DIRECTORY) {
  			err = -ENOTDIR; 
  			if (!inode->i_op || !inode->i_op->lookup)
  				break;
  		}
  		goto return_base;
  lookup_parent:
  		nd->last = this;
  		nd->last_type = LAST_NORM;
  		if (this.name[0] != '.')
  			goto return_base;
  		if (this.len == 1)
  			nd->last_type = LAST_DOT;
  		else if (this.len == 2 && this.name[1] == '.')
  			nd->last_type = LAST_DOTDOT;
  		else
  			goto return_base;
  return_reval:
  		/*
  		 * We bypassed the ordinary revalidation routines.
  		 * We may need to check the cached dentry for staleness.
  		 */
  		if (nd->dentry && nd->dentry->d_sb &&
  		    (nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
  			err = -ESTALE;
  			/* Note: we do not d_invalidate() */
  			if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
  				break;
  		}
  return_base:
  		return 0;
  out_dput:

  		dput_path(&next, nd);

  		break;
  	}
  	path_release(nd);
  return_err:
  	return err;
  }
  
  /*
   * Wrapper to retry pathname resolution whenever the underlying
   * file system returns an ESTALE.
   *
   * Retry the whole path once, forcing real lookup requests
   * instead of relying on the dcache.
   */

  static int link_path_walk(const char *name, struct nameidata *nd)

  {
  	struct nameidata save = *nd;
  	int result;
  
  	/* make sure the stuff we saved doesn't go away */
  	dget(save.dentry);
  	mntget(save.mnt);
  
  	result = __link_path_walk(name, nd);
  	if (result == -ESTALE) {
  		*nd = save;
  		dget(nd->dentry);
  		mntget(nd->mnt);
  		nd->flags |= LOOKUP_REVAL;
  		result = __link_path_walk(name, nd);
  	}
  
  	dput(save.dentry);
  	mntput(save.mnt);
  
  	return result;
  }

  static int path_walk(const char *name, struct nameidata *nd)

  {
  	current->total_link_count = 0;
  	return link_path_walk(name, nd);
  }

  /* 
   * SMP-safe: Returns 1 and nd will have valid dentry and mnt, if
   * everything is done. Returns 0 and drops input nd, if lookup failed;
   */

  static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
  {
  	if (path_walk(name, nd))
  		return 0;		/* something went wrong... */
  
  	if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
  		struct dentry *old_dentry = nd->dentry;
  		struct vfsmount *old_mnt = nd->mnt;
  		struct qstr last = nd->last;
  		int last_type = nd->last_type;

  		struct fs_struct *fs = current->fs;

  		/*

  		 * NAME was not found in alternate root or it's a directory.
  		 * Try to find it in the normal root:

  		 */
  		nd->last_type = LAST_ROOT;

  		read_lock(&fs->lock);
  		nd->mnt = mntget(fs->rootmnt);
  		nd->dentry = dget(fs->root);
  		read_unlock(&fs->lock);

  		if (path_walk(name, nd) == 0) {
  			if (nd->dentry->d_inode) {
  				dput(old_dentry);
  				mntput(old_mnt);
  				return 1;
  			}
  			path_release(nd);
  		}
  		nd->dentry = old_dentry;
  		nd->mnt = old_mnt;
  		nd->last = last;
  		nd->last_type = last_type;
  	}
  	return 1;
  }
  
  void set_fs_altroot(void)
  {
  	char *emul = __emul_prefix();
  	struct nameidata nd;
  	struct vfsmount *mnt = NULL, *oldmnt;
  	struct dentry *dentry = NULL, *olddentry;
  	int err;

  	struct fs_struct *fs = current->fs;

  
  	if (!emul)
  		goto set_it;
  	err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
  	if (!err) {
  		mnt = nd.mnt;
  		dentry = nd.dentry;
  	}
  set_it:

  	write_lock(&fs->lock);
  	oldmnt = fs->altrootmnt;
  	olddentry = fs->altroot;
  	fs->altrootmnt = mnt;
  	fs->altroot = dentry;
  	write_unlock(&fs->lock);

  	if (olddentry) {
  		dput(olddentry);
  		mntput(oldmnt);
  	}
  }

  /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */

  static int do_path_lookup(int dfd, const char *name,

  				unsigned int flags, struct nameidata *nd)

  {

  	int retval = 0;

  	int fput_needed;
  	struct file *file;

  	struct fs_struct *fs = current->fs;

  
  	nd->last_type = LAST_ROOT; /* if there are only slashes... */
  	nd->flags = flags;
  	nd->depth = 0;

  	if (*name=='/') {

  		read_lock(&fs->lock);
  		if (fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
  			nd->mnt = mntget(fs->altrootmnt);
  			nd->dentry = dget(fs->altroot);
  			read_unlock(&fs->lock);

  			if (__emul_lookup_dentry(name,nd))

  				goto out; /* found in altroot */

  			read_lock(&fs->lock);

  		}

  		nd->mnt = mntget(fs->rootmnt);
  		nd->dentry = dget(fs->root);
  		read_unlock(&fs->lock);

  	} else if (dfd == AT_FDCWD) {

  		read_lock(&fs->lock);
  		nd->mnt = mntget(fs->pwdmnt);
  		nd->dentry = dget(fs->pwd);
  		read_unlock(&fs->lock);

  	} else {

  		struct dentry *dentry;
  
  		file = fget_light(dfd, &fput_needed);

  		retval = -EBADF;
  		if (!file)

  			goto out_fail;

  		dentry = file->f_path.dentry;

  		retval = -ENOTDIR;
  		if (!S_ISDIR(dentry->d_inode->i_mode))

  			goto fput_fail;

  
  		retval = file_permission(file, MAY_EXEC);

  		if (retval)

  			goto fput_fail;

  		nd->mnt = mntget(file->f_path.mnt);

  		nd->dentry = dget(dentry);
  
  		fput_light(file, fput_needed);

  	}

  
  	retval = path_walk(name, nd);

  out:

  	if (unlikely(!retval && !audit_dummy_context() && nd->dentry &&

  				nd->dentry->d_inode))

  		audit_inode(name, nd->dentry);

  out_fail:

  	return retval;

  fput_fail:

  	fput_light(file, fput_needed);

  	goto out_fail;

  }

  int path_lookup(const char *name, unsigned int flags,

  			struct nameidata *nd)
  {
  	return do_path_lookup(AT_FDCWD, name, flags, nd);
  }

  /**
   * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
   * @dentry:  pointer to dentry of the base directory
   * @mnt: pointer to vfs mount of the base directory
   * @name: pointer to file name
   * @flags: lookup flags
   * @nd: pointer to nameidata
   */
  int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
  		    const char *name, unsigned int flags,
  		    struct nameidata *nd)
  {
  	int retval;
  
  	/* same as do_path_lookup */
  	nd->last_type = LAST_ROOT;
  	nd->flags = flags;
  	nd->depth = 0;
  
  	nd->mnt = mntget(mnt);
  	nd->dentry = dget(dentry);
  
  	retval = path_walk(name, nd);
  	if (unlikely(!retval && !audit_dummy_context() && nd->dentry &&
  				nd->dentry->d_inode))

  		audit_inode(name, nd->dentry);

  
  	return retval;
  
  }

  static int __path_lookup_intent_open(int dfd, const char *name,
  		unsigned int lookup_flags, struct nameidata *nd,
  		int open_flags, int create_mode)

  {
  	struct file *filp = get_empty_filp();
  	int err;
  
  	if (filp == NULL)
  		return -ENFILE;
  	nd->intent.open.file = filp;
  	nd->intent.open.flags = open_flags;
  	nd->intent.open.create_mode = create_mode;

  	err = do_path_lookup(dfd, name, lookup_flags|LOOKUP_OPEN, nd);

  	if (IS_ERR(nd->intent.open.file)) {
  		if (err == 0) {
  			err = PTR_ERR(nd->intent.open.file);
  			path_release(nd);
  		}
  	} else if (err != 0)
  		release_open_intent(nd);
  	return err;
  }
  
  /**
   * path_lookup_open - lookup a file path with open intent

   * @dfd: the directory to use as base, or AT_FDCWD

   * @name: pointer to file name
   * @lookup_flags: lookup intent flags
   * @nd: pointer to nameidata
   * @open_flags: open intent flags
   */

  int path_lookup_open(int dfd, const char *name, unsigned int lookup_flags,

  		struct nameidata *nd, int open_flags)
  {

  	return __path_lookup_intent_open(dfd, name, lookup_flags, nd,

  			open_flags, 0);
  }
  
  /**
   * path_lookup_create - lookup a file path with open + create intent

   * @dfd: the directory to use as base, or AT_FDCWD

   * @name: pointer to file name
   * @lookup_flags: lookup intent flags
   * @nd: pointer to nameidata
   * @open_flags: open intent flags
   * @create_mode: create intent flags
   */

  static int path_lookup_create(int dfd, const char *name,
  			      unsigned int lookup_flags, struct nameidata *nd,
  			      int open_flags, int create_mode)

  {

  	return __path_lookup_intent_open(dfd, name, lookup_flags|LOOKUP_CREATE,
  			nd, open_flags, create_mode);

  }
  
  int __user_path_lookup_open(const char __user *name, unsigned int lookup_flags,
  		struct nameidata *nd, int open_flags)
  {
  	char *tmp = getname(name);
  	int err = PTR_ERR(tmp);
  
  	if (!IS_ERR(tmp)) {

  		err = __path_lookup_intent_open(AT_FDCWD, tmp, lookup_flags, nd, open_flags, 0);

  		putname(tmp);
  	}
  	return err;
  }

  static struct dentry *__lookup_hash(struct qstr *name,
  		struct dentry *base, struct nameidata *nd)

  {

  	struct dentry *dentry;

  	struct inode *inode;
  	int err;
  
  	inode = base->d_inode;

  
  	/*
  	 * See if the low-level filesystem might want
  	 * to use its own hash..
  	 */
  	if (base->d_op && base->d_op->d_hash) {
  		err = base->d_op->d_hash(base, name);
  		dentry = ERR_PTR(err);
  		if (err < 0)
  			goto out;
  	}
  
  	dentry = cached_lookup(base, name, nd);
  	if (!dentry) {
  		struct dentry *new = d_alloc(base, name);
  		dentry = ERR_PTR(-ENOMEM);
  		if (!new)
  			goto out;
  		dentry = inode->i_op->lookup(inode, new, nd);
  		if (!dentry)
  			dentry = new;
  		else
  			dput(new);
  	}
  out:
  	return dentry;
  }

  /*
   * Restricted form of lookup. Doesn't follow links, single-component only,
   * needs parent already locked. Doesn't follow mounts.
   * SMP-safe.
   */

  static struct dentry *lookup_hash(struct nameidata *nd)

  {

  	int err;

  	err = permission(nd->dentry->d_inode, MAY_EXEC, nd);

  	if (err)

  		return ERR_PTR(err);

  	return __lookup_hash(&nd->last, nd->dentry, nd);

  }

  static int __lookup_one_len(const char *name, struct qstr *this,
  		struct dentry *base, int len)

  {
  	unsigned long hash;

  	unsigned int c;

  	this->name = name;
  	this->len = len;

  	if (!len)

  		return -EACCES;

  
  	hash = init_name_hash();
  	while (len--) {
  		c = *(const unsigned char *)name++;
  		if (c == '/' || c == '\0')

  			return -EACCES;

  		hash = partial_name_hash(c, hash);
  	}

  	this->hash = end_name_hash(hash);
  	return 0;
  }

  /**
   * lookup_one_len:  filesystem helper to lookup single pathname component
   * @name:	pathname component to lookup
   * @base:	base directory to lookup from
   * @len:	maximum length @len should be interpreted to
   *
   * Note that this routine is purely a helper for filesystem useage and should
   * not be called by generic code.  Also note that by using this function to
   * nameidata argument is passed to the filesystem methods and a filesystem
   * using this helper needs to be prepared for that.
   */

  struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
  {
  	int err;
  	struct qstr this;
  
  	err = __lookup_one_len(name, &this, base, len);
  	if (err)
  		return ERR_PTR(err);

  
  	err = permission(base->d_inode, MAY_EXEC, NULL);
  	if (err)
  		return ERR_PTR(err);

  	return __lookup_hash(&this, base, NULL);

  }

  /**
   * lookup_one_noperm - bad hack for sysfs
   * @name:	pathname component to lookup
   * @base:	base directory to lookup from
   *
   * This is a variant of lookup_one_len that doesn't perform any permission
   * checks.   It's a horrible hack to work around the braindead sysfs
   * architecture and should not be used anywhere else.
   *
   * DON'T USE THIS FUNCTION EVER, thanks.
   */
  struct dentry *lookup_one_noperm(const char *name, struct dentry *base)

  {
  	int err;
  	struct qstr this;

  	err = __lookup_one_len(name, &this, base, strlen(name));

  	if (err)
  		return ERR_PTR(err);

  	return __lookup_hash(&this, base, NULL);

  }

  int __user_walk_fd(int dfd, const char __user *name, unsigned flags,

  			    struct nameidata *nd)

  {
  	char *tmp = getname(name);
  	int err = PTR_ERR(tmp);
  
  	if (!IS_ERR(tmp)) {

  		err = do_path_lookup(dfd, tmp, flags, nd);

  		putname(tmp);
  	}
  	return err;
  }

  int __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)

  {
  	return __user_walk_fd(AT_FDCWD, name, flags, nd);
  }

  /*
   * It's inline, so penalty for filesystems that don't use sticky bit is
   * minimal.
   */
  static inline int check_sticky(struct inode *dir, struct inode *inode)
  {
  	if (!(dir->i_mode & S_ISVTX))
  		return 0;
  	if (inode->i_uid == current->fsuid)
  		return 0;
  	if (dir->i_uid == current->fsuid)
  		return 0;
  	return !capable(CAP_FOWNER);
  }
  
  /*
   *	Check whether we can remove a link victim from directory dir, check
   *  whether the type of victim is right.
   *  1. We can't do it if dir is read-only (done in permission())
   *  2. We should have write and exec permissions on dir
   *  3. We can't remove anything from append-only dir
   *  4. We can't do anything with immutable dir (done in permission())
   *  5. If the sticky bit on dir is set we should either
   *	a. be owner of dir, or
   *	b. be owner of victim, or
   *	c. have CAP_FOWNER capability
   *  6. If the victim is append-only or immutable we can't do antyhing with
   *     links pointing to it.
   *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
   *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
   *  9. We can't remove a root or mountpoint.
   * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
   *     nfs_async_unlink().
   */

  static int may_delete(struct inode *dir,struct dentry *victim,int isdir)

  {
  	int error;
  
  	if (!victim->d_inode)
  		return -ENOENT;
  
  	BUG_ON(victim->d_parent->d_inode != dir);

  	audit_inode_child(victim->d_name.name, victim, dir);

  
  	error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
  	if (error)
  		return error;
  	if (IS_APPEND(dir))
  		return -EPERM;
  	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
  	    IS_IMMUTABLE(victim->d_inode))
  		return -EPERM;
  	if (isdir) {
  		if (!S_ISDIR(victim->d_inode->i_mode))
  			return -ENOTDIR;
  		if (IS_ROOT(victim))
  			return -EBUSY;
  	} else if (S_ISDIR(victim->d_inode->i_mode))
  		return -EISDIR;
  	if (IS_DEADDIR(dir))
  		return -ENOENT;
  	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
  		return -EBUSY;
  	return 0;
  }
  
  /*	Check whether we can create an object with dentry child in directory
   *  dir.
   *  1. We can't do it if child already exists (open has special treatment for
   *     this case, but since we are inlined it's OK)
   *  2. We can't do it if dir is read-only (done in permission())
   *  3. We should have write and exec permissions on dir
   *  4. We can't do it if dir is immutable (done in permission())
   */
  static inline int may_create(struct inode *dir, struct dentry *child,
  			     struct nameidata *nd)
  {
  	if (child->d_inode)
  		return -EEXIST;
  	if (IS_DEADDIR(dir))
  		return -ENOENT;
  	return permission(dir,MAY_WRITE | MAY_EXEC, nd);
  }
  
  /* 

   * O_DIRECTORY translates into forcing a directory lookup.
   */
  static inline int lookup_flags(unsigned int f)
  {
  	unsigned long retval = LOOKUP_FOLLOW;
  
  	if (f & O_NOFOLLOW)
  		retval &= ~LOOKUP_FOLLOW;
  	

  	if (f & O_DIRECTORY)
  		retval |= LOOKUP_DIRECTORY;
  
  	return retval;
  }
  
  /*
   * p1 and p2 should be directories on the same fs.
   */
  struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
  {
  	struct dentry *p;
  
  	if (p1 == p2) {

  		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);

  		return NULL;
  	}

  	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

  
  	for (p = p1; p->d_parent != p; p = p->d_parent) {
  		if (p->d_parent == p2) {

  			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
  			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);

  			return p;
  		}
  	}
  
  	for (p = p2; p->d_parent != p; p = p->d_parent) {
  		if (p->d_parent == p1) {

  			mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
  			mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);

  			return p;
  		}
  	}

  	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
  	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);

  	return NULL;
  }
  
  void unlock_rename(struct dentry *p1, struct dentry *p2)
  {

  	mutex_unlock(&p1->d_inode->i_mutex);

  	if (p1 != p2) {

  		mutex_unlock(&p2->d_inode->i_mutex);

  		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

  	}
  }
  
  int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
  		struct nameidata *nd)
  {
  	int error = may_create(dir, dentry, nd);
  
  	if (error)
  		return error;
  
  	if (!dir->i_op || !dir->i_op->create)
  		return -EACCES;	/* shouldn't it be ENOSYS? */
  	mode &= S_IALLUGO;
  	mode |= S_IFREG;
  	error = security_inode_create(dir, dentry, mode);
  	if (error)
  		return error;
  	DQUOT_INIT(dir);
  	error = dir->i_op->create(dir, dentry, mode, nd);

  	if (!error)

  		fsnotify_create(dir, dentry);

  	return error;
  }
  
  int may_open(struct nameidata *nd, int acc_mode, int flag)
  {
  	struct dentry *dentry = nd->dentry;
  	struct inode *inode = dentry->d_inode;
  	int error;
  
  	if (!inode)
  		return -ENOENT;
  
  	if (S_ISLNK(inode->i_mode))
  		return -ELOOP;
  	

  	if (S_ISDIR(inode->i_mode) && (acc_mode & MAY_WRITE))

  		return -EISDIR;

  	/*
  	 * FIFO's, sockets and device files are special: they don't
  	 * actually live on the filesystem itself, and as such you
  	 * can write to them even if the filesystem is read-only.
  	 */
  	if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
  	    	flag &= ~O_TRUNC;
  	} else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
  		if (nd->mnt->mnt_flags & MNT_NODEV)
  			return -EACCES;
  
  		flag &= ~O_TRUNC;

  	} else if (IS_RDONLY(inode) && (acc_mode & MAY_WRITE))

  		return -EROFS;

  
  	error = vfs_permission(nd, acc_mode);
  	if (error)
  		return error;

  	/*
  	 * An append-only file must be opened in append mode for writing.
  	 */
  	if (IS_APPEND(inode)) {
  		if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))
  			return -EPERM;
  		if (flag & O_TRUNC)
  			return -EPERM;
  	}
  
  	/* O_NOATIME can only be set by the owner or superuser */
  	if (flag & O_NOATIME)

  		if (!is_owner_or_cap(inode))

  			return -EPERM;
  
  	/*
  	 * Ensure there are no outstanding leases on the file.
  	 */
  	error = break_lease(inode, flag);
  	if (error)
  		return error;
  
  	if (flag & O_TRUNC) {
  		error = get_write_access(inode);
  		if (error)
  			return error;
  
  		/*
  		 * Refuse to truncate files with mandatory locks held on them.
  		 */
  		error = locks_verify_locked(inode);
  		if (!error) {
  			DQUOT_INIT(inode);

  
  			error = do_truncate(dentry, 0,
  					    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
  					    NULL);

  		}
  		put_write_access(inode);
  		if (error)
  			return error;
  	} else
  		if (flag & FMODE_WRITE)
  			DQUOT_INIT(inode);
  
  	return 0;
  }

  static int open_namei_create(struct nameidata *nd, struct path *path,
  				int flag, int mode)
  {
  	int error;
  	struct dentry *dir = nd->dentry;
  
  	if (!IS_POSIXACL(dir->d_inode))
  		mode &= ~current->fs->umask;
  	error = vfs_create(dir->d_inode, path->dentry, mode, nd);
  	mutex_unlock(&dir->d_inode->i_mutex);
  	dput(nd->dentry);
  	nd->dentry = path->dentry;
  	if (error)
  		return error;
  	/* Don't check for write permission, don't truncate */
  	return may_open(nd, 0, flag & ~O_TRUNC);
  }

  /*
   *	open_namei()
   *
   * namei for open - this is in fact almost the whole open-routine.
   *
   * Note that the low bits of "flag" aren't the same as in the open
   * system call - they are 00 - no permissions needed
   *			  01 - read permission needed
   *			  10 - write permission needed
   *			  11 - read/write permissions needed
   * which is a lot more logical, and also allows the "no perm" needed
   * for symlinks (where the permissions are checked later).
   * SMP-safe
   */

  int open_namei(int dfd, const char *pathname, int flag,
  		int mode, struct nameidata *nd)

  {

  	int acc_mode, error;

  	struct path path;

  	struct dentry *dir;
  	int count = 0;
  
  	acc_mode = ACC_MODE(flag);

  	/* O_TRUNC implies we need access checks for write permissions */
  	if (flag & O_TRUNC)
  		acc_mode |= MAY_WRITE;

  	/* Allow the LSM permission hook to distinguish append 
  	   access from general write access. */
  	if (flag & O_APPEND)
  		acc_mode |= MAY_APPEND;

  	/*
  	 * The simplest case - just a plain lookup.
  	 */
  	if (!(flag & O_CREAT)) {

  		error = path_lookup_open(dfd, pathname, lookup_flags(flag),
  					 nd, flag);

  		if (error)
  			return error;
  		goto ok;
  	}
  
  	/*
  	 * Create - we need to know the parent.
  	 */

  	error = path_lookup_create(dfd,pathname,LOOKUP_PARENT,nd,flag,mode);

  	if (error)
  		return error;
  
  	/*
  	 * We have the parent and last component. First of all, check
  	 * that we are not asked to creat(2) an obvious directory - that
  	 * will not do.
  	 */
  	error = -EISDIR;
  	if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
  		goto exit;
  
  	dir = nd->dentry;
  	nd->flags &= ~LOOKUP_PARENT;

  	mutex_lock(&dir->d_inode->i_mutex);

  	path.dentry = lookup_hash(nd);

  	path.mnt = nd->mnt;

  
  do_last:

  	error = PTR_ERR(path.dentry);
  	if (IS_ERR(path.dentry)) {

  		mutex_unlock(&dir->d_inode->i_mutex);

  		goto exit;
  	}

  	if (IS_ERR(nd->intent.open.file)) {
  		mutex_unlock(&dir->d_inode->i_mutex);
  		error = PTR_ERR(nd->intent.open.file);
  		goto exit_dput;
  	}

  	/* Negative dentry, just create the file */

  	if (!path.dentry->d_inode) {

  		error = open_namei_create(nd, &path, flag, mode);

  		if (error)
  			goto exit;

  		return 0;

  	}
  
  	/*
  	 * It already exists.
  	 */

  	mutex_unlock(&dir->d_inode->i_mutex);

  	audit_inode(pathname, path.dentry);

  
  	error = -EEXIST;
  	if (flag & O_EXCL)
  		goto exit_dput;

  	if (__follow_mount(&path)) {

  		error = -ELOOP;

  		if (flag & O_NOFOLLOW)
  			goto exit_dput;

  	}

  	error = -ENOENT;

  	if (!path.dentry->d_inode)

  		goto exit_dput;

  	if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link)

  		goto do_link;

  	path_to_nameidata(&path, nd);

  	error = -EISDIR;

  	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))

  		goto exit;
  ok:
  	error = may_open(nd, acc_mode, flag);
  	if (error)
  		goto exit;
  	return 0;
  
  exit_dput:

  	dput_path(&path, nd);

  exit:

  	if (!IS_ERR(nd->intent.open.file))
  		release_open_intent(nd);

  	path_release(nd);
  	return error;
  
  do_link:
  	error = -ELOOP;
  	if (flag & O_NOFOLLOW)
  		goto exit_dput;
  	/*
  	 * This is subtle. Instead of calling do_follow_link() we do the
  	 * thing by hands. The reason is that this way we have zero link_count
  	 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
  	 * After that we have the parent and last component, i.e.
  	 * we are in the same situation as after the first path_walk().
  	 * Well, almost - if the last component is normal we get its copy
  	 * stored in nd->last.name and we will have to putname() it when we
  	 * are done. Procfs-like symlinks just set LAST_BIND.
  	 */
  	nd->flags |= LOOKUP_PARENT;

  	error = security_inode_follow_link(path.dentry, nd);

  	if (error)
  		goto exit_dput;

  	error = __do_follow_link(&path, nd);

  	if (error) {
  		/* Does someone understand code flow here? Or it is only
  		 * me so stupid? Anathema to whoever designed this non-sense
  		 * with "intent.open".
  		 */
  		release_open_intent(nd);

  		return error;

  	}

  	nd->flags &= ~LOOKUP_PARENT;

  	if (nd->last_type == LAST_BIND)

  		goto ok;

  	error = -EISDIR;
  	if (nd->last_type != LAST_NORM)
  		goto exit;
  	if (nd->last.name[nd->last.len]) {

  		__putname(nd->last.name);

  		goto exit;
  	}
  	error = -ELOOP;
  	if (count++==32) {

  		__putname(nd->last.name);

  		goto exit;
  	}
  	dir = nd->dentry;

  	mutex_lock(&dir->d_inode->i_mutex);

  	path.dentry = lookup_hash(nd);

  	path.mnt = nd->mnt;

  	__putname(nd->last.name);

  	goto do_last;
  }
  
  /**
   * lookup_create - lookup a dentry, creating it if it doesn't exist
   * @nd: nameidata info
   * @is_dir: directory flag
   *
   * Simple function to lookup and return a dentry and create it
   * if it doesn't exist.  Is SMP-safe.

   *

   * Returns with nd->dentry->d_inode->i_mutex locked.

   */
  struct dentry *lookup_create(struct nameidata *nd, int is_dir)
  {

  	struct dentry *dentry = ERR_PTR(-EEXIST);

  	mutex_lock_nested(&nd->dentry->d_inode->i_mutex, I_MUTEX_PARENT);

  	/*
  	 * Yucky last component or no last component at all?
  	 * (foo/., foo/.., /////)
  	 */

  	if (nd->last_type != LAST_NORM)
  		goto fail;
  	nd->flags &= ~LOOKUP_PARENT;

  	nd->flags |= LOOKUP_CREATE;
  	nd->intent.open.flags = O_EXCL;

  
  	/*
  	 * Do the final lookup.
  	 */

  	dentry = lookup_hash(nd);

  	if (IS_ERR(dentry))
  		goto fail;

  
  	/*
  	 * Special case - lookup gave negative, but... we had foo/bar/
  	 * From the vfs_mknod() POV we just have a negative dentry -
  	 * all is fine. Let's be bastards - you had / on the end, you've
  	 * been asking for (non-existent) directory. -ENOENT for you.
  	 */

  	if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
  		goto enoent;
  	return dentry;
  enoent:
  	dput(dentry);
  	dentry = ERR_PTR(-ENOENT);
  fail:
  	return dentry;
  }

  EXPORT_SYMBOL_GPL(lookup_create);

  
  int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  {
  	int error = may_create(dir, dentry, NULL);
  
  	if (error)
  		return error;
  
  	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
  		return -EPERM;
  
  	if (!dir->i_op || !dir->i_op->mknod)
  		return -EPERM;
  
  	error = security_inode_mknod(dir, dentry, mode, dev);
  	if (error)
  		return error;
  
  	DQUOT_INIT(dir);
  	error = dir->i_op->mknod(dir, dentry, mode, dev);

  	if (!error)

  		fsnotify_create(dir, dentry);

  	return error;
  }

  asmlinkage long sys_mknodat(int dfd, const char __user *filename, int mode,
  				unsigned dev)

  {
  	int error = 0;
  	char * tmp;
  	struct dentry * dentry;
  	struct nameidata nd;
  
  	if (S_ISDIR(mode))
  		return -EPERM;
  	tmp = getname(filename);
  	if (IS_ERR(tmp))
  		return PTR_ERR(tmp);

  	error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);

  	if (error)
  		goto out;
  	dentry = lookup_create(&nd, 0);
  	error = PTR_ERR(dentry);
  
  	if (!IS_POSIXACL(nd.dentry->d_inode))
  		mode &= ~current->fs->umask;
  	if (!IS_ERR(dentry)) {
  		switch (mode & S_IFMT) {
  		case 0: case S_IFREG:
  			error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
  			break;
  		case S_IFCHR: case S_IFBLK:
  			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
  					new_decode_dev(dev));
  			break;
  		case S_IFIFO: case S_IFSOCK:
  			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
  			break;
  		case S_IFDIR:
  			error = -EPERM;
  			break;
  		default:
  			error = -EINVAL;
  		}
  		dput(dentry);
  	}

  	mutex_unlock(&nd.dentry->d_inode->i_mutex);

  	path_release(&nd);
  out:
  	putname(tmp);
  
  	return error;
  }

  asmlinkage long sys_mknod(const char __user *filename, int mode, unsigned dev)
  {
  	return sys_mknodat(AT_FDCWD, filename, mode, dev);
  }

  int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  {
  	int error = may_create(dir, dentry, NULL);
  
  	if (error)
  		return error;
  
  	if (!dir->i_op || !dir->i_op->mkdir)
  		return -EPERM;
  
  	mode &= (S_IRWXUGO|S_ISVTX);
  	error = security_inode_mkdir(dir, dentry, mode);
  	if (error)
  		return error;
  
  	DQUOT_INIT(dir);
  	error = dir->i_op->mkdir(dir, dentry, mode);

  	if (!error)

  		fsnotify_mkdir(dir, dentry);

  	return error;
  }

  asmlinkage long sys_mkdirat(int dfd, const char __user *pathname, int mode)

  {
  	int error = 0;
  	char * tmp;

  	struct dentry *dentry;
  	struct nameidata nd;

  
  	tmp = getname(pathname);
  	error = PTR_ERR(tmp);

  	if (IS_ERR(tmp))
  		goto out_err;

  	error = do_path_lookup(dfd, tmp, LOOKUP_PARENT, &nd);
  	if (error)
  		goto out;
  	dentry = lookup_create(&nd, 1);
  	error = PTR_ERR(dentry);
  	if (IS_ERR(dentry))
  		goto out_unlock;

  	if (!IS_POSIXACL(nd.dentry->d_inode))
  		mode &= ~current->fs->umask;
  	error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
  	dput(dentry);
  out_unlock:
  	mutex_unlock(&nd.dentry->d_inode->i_mutex);
  	path_release(&nd);
  out:
  	putname(tmp);
  out_err:

  	return error;
  }

  asmlinkage long sys_mkdir(const char __user *pathname, int mode)
  {
  	return sys_mkdirat(AT_FDCWD, pathname, mode);
  }

  /*
   * We try to drop the dentry early: we should have
   * a usage count of 2 if we're the only user of this
   * dentry, and if that is true (possibly after pruning
   * the dcache), then we drop the dentry now.
   *
   * A low-level filesystem can, if it choses, legally
   * do a
   *
   *	if (!d_unhashed(dentry))
   *		return -EBUSY;
   *
   * if it cannot handle the case of removing a directory
   * that is still in use by something else..
   */
  void dentry_unhash(struct dentry *dentry)
  {
  	dget(dentry);

  	shrink_dcache_parent(dentry);

  	spin_lock(&dcache_lock);
  	spin_lock(&dentry->d_lock);
  	if (atomic_read(&dentry->d_count) == 2)
  		__d_drop(dentry);
  	spin_unlock(&dentry->d_lock);
  	spin_unlock(&dcache_lock);
  }
  
  int vfs_rmdir(struct inode *dir, struct dentry *dentry)
  {
  	int error = may_delete(dir, dentry, 1);
  
  	if (error)
  		return error;
  
  	if (!dir->i_op || !dir->i_op->rmdir)
  		return -EPERM;
  
  	DQUOT_INIT(dir);

  	mutex_lock(&dentry->d_inode->i_mutex);

  	dentry_unhash(dentry);
  	if (d_mountpoint(dentry))
  		error = -EBUSY;
  	else {
  		error = security_inode_rmdir(dir, dentry);
  		if (!error) {
  			error = dir->i_op->rmdir(dir, dentry);
  			if (!error)
  				dentry->d_inode->i_flags |= S_DEAD;
  		}
  	}

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

  	if (!error) {

  		d_delete(dentry);
  	}
  	dput(dentry);
  
  	return error;
  }

  static long do_rmdir(int dfd, const char __user *pathname)

  {
  	int error = 0;
  	char * name;
  	struct dentry *dentry;
  	struct nameidata nd;
  
  	name = getname(pathname);
  	if(IS_ERR(name))
  		return PTR_ERR(name);

  	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);

  	if (error)
  		goto exit;
  
  	switch(nd.last_type) {
  		case LAST_DOTDOT:
  			error = -ENOTEMPTY;
  			goto exit1;
  		case LAST_DOT:
  			error = -EINVAL;
  			goto exit1;
  		case LAST_ROOT:
  			error = -EBUSY;
  			goto exit1;
  	}

  	mutex_lock_nested(&nd.dentry->d_inode->i_mutex, I_MUTEX_PARENT);

  	dentry = lookup_hash(&nd);

  	error = PTR_ERR(dentry);

  	if (IS_ERR(dentry))
  		goto exit2;
  	error = vfs_rmdir(nd.dentry->d_inode, dentry);
  	dput(dentry);
  exit2:

  	mutex_unlock(&nd.dentry->d_inode->i_mutex);

  exit1:
  	path_release(&nd);
  exit:
  	putname(name);
  	return error;
  }

  asmlinkage long sys_rmdir(const char __user *pathname)
  {
  	return do_rmdir(AT_FDCWD, pathname);
  }

  int vfs_unlink(struct inode *dir, struct dentry *dentry)
  {
  	int error = may_delete(dir, dentry, 0);
  
  	if (error)
  		return error;
  
  	if (!dir->i_op || !dir->i_op->unlink)
  		return -EPERM;
  
  	DQUOT_INIT(dir);

  	mutex_lock(&dentry->d_inode->i_mutex);

  	if (d_mountpoint(dentry))
  		error = -EBUSY;
  	else {
  		error = security_inode_unlink(dir, dentry);
  		if (!error)
  			error = dir->i_op->unlink(dir, dentry);
  	}

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

  
  	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
  	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {

  		fsnotify_link_count(dentry->d_inode);

  		d_delete(dentry);

  	}

  	return error;
  }
  
  /*
   * Make sure that the actual truncation of the file will occur outside its

   * directory's i_mutex.  Truncate can take a long time if there is a lot of

   * writeout happening, and we don't want to prevent access to the directory
   * while waiting on the I/O.
   */

  static long do_unlinkat(int dfd, const char __user *pathname)

  {
  	int error = 0;
  	char * name;
  	struct dentry *dentry;
  	struct nameidata nd;
  	struct inode *inode = NULL;
  
  	name = getname(pathname);
  	if(IS_ERR(name))
  		return PTR_ERR(name);

  	error = do_path_lookup(dfd, name, LOOKUP_PARENT, &nd);

  	if (error)
  		goto exit;
  	error = -EISDIR;
  	if (nd.last_type != LAST_NORM)
  		goto exit1;

  	mutex_lock_nested(&nd.dentry->d_inode->i_mutex, I_MUTEX_PARENT);

  	dentry = lookup_hash(&nd);

  	error = PTR_ERR(dentry);
  	if (!IS_ERR(dentry)) {
  		/* Why not before? Because we want correct error value */
  		if (nd.last.name[nd.last.len])
  			goto slashes;
  		inode = dentry->d_inode;
  		if (inode)
  			atomic_inc(&inode->i_count);
  		error = vfs_unlink(nd.dentry->d_inode, dentry);
  	exit2:
  		dput(dentry);
  	}

  	mutex_unlock(&nd.dentry->d_inode->i_mutex);

  	if (inode)
  		iput(inode);	/* truncate the inode here */
  exit1:
  	path_release(&nd);
  exit:
  	putname(name);
  	return error;
  
  slashes:
  	error = !dentry->d_inode ? -ENOENT :
  		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
  	goto exit2;
  }

  asmlinkage long sys_unlinkat(int dfd, const char __user *pathname, int flag)
  {
  	if ((flag & ~AT_REMOVEDIR) != 0)
  		return -EINVAL;
  
  	if (flag & AT_REMOVEDIR)
  		return do_rmdir(dfd, pathname);
  
  	return do_unlinkat(dfd, pathname);
  }
  
  asmlinkage long sys_unlink(const char __user *pathname)
  {
  	return do_unlinkat(AT_FDCWD, pathname);
  }

  int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
  {
  	int error = may_create(dir, dentry, NULL);
  
  	if (error)
  		return error;
  
  	if (!dir->i_op || !dir->i_op->symlink)
  		return -EPERM;
  
  	error = security_inode_symlink(dir, dentry, oldname);
  	if (error)
  		return error;
  
  	DQUOT_INIT(dir);
  	error = dir->i_op->symlink(dir, dentry, oldname);

  	if (!error)

  		fsnotify_create(dir, dentry);

  	return error;
  }

  asmlinkage long sys_symlinkat(const char __user *oldname,
  			      int newdfd, const char __user *newname)

  {
  	int error = 0;
  	char * from;
  	char * to;

  	struct dentry *dentry;
  	struct nameidata nd;

  
  	from = getname(oldname);
  	if(IS_ERR(from))
  		return PTR_ERR(from);
  	to = getname(newname);
  	error = PTR_ERR(to);

  	if (IS_ERR(to))
  		goto out_putname;

  	error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);
  	if (error)
  		goto out;
  	dentry = lookup_create(&nd, 0);
  	error = PTR_ERR(dentry);
  	if (IS_ERR(dentry))
  		goto out_unlock;
  
  	error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
  	dput(dentry);
  out_unlock:
  	mutex_unlock(&nd.dentry->d_inode->i_mutex);
  	path_release(&nd);

  out:

  	putname(to);
  out_putname:

  	putname(from);
  	return error;
  }

  asmlinkage long sys_symlink(const char __user *oldname, const char __user *newname)
  {
  	return sys_symlinkat(oldname, AT_FDCWD, newname);
  }

  int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
  {
  	struct inode *inode = old_dentry->d_inode;
  	int error;
  
  	if (!inode)
  		return -ENOENT;
  
  	error = may_create(dir, new_dentry, NULL);
  	if (error)
  		return error;
  
  	if (dir->i_sb != inode->i_sb)
  		return -EXDEV;
  
  	/*
  	 * A link to an append-only or immutable file cannot be created.
  	 */
  	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
  		return -EPERM;
  	if (!dir->i_op || !dir->i_op->link)
  		return -EPERM;
  	if (S_ISDIR(old_dentry->d_inode->i_mode))
  		return -EPERM;
  
  	error = security_inode_link(old_dentry, dir, new_dentry);
  	if (error)
  		return error;

  	mutex_lock(&old_dentry->d_inode->i_mutex);

  	DQUOT_INIT(dir);
  	error = dir->i_op->link(old_dentry, dir, new_dentry);

  	mutex_unlock(&old_dentry->d_inode->i_mutex);

  	if (!error)

  		fsnotify_link(dir, old_dentry->d_inode, new_dentry);

  	return error;
  }
  
  /*
   * Hardlinks are often used in delicate situations.  We avoid
   * security-related surprises by not following symlinks on the
   * newname.  --KAB
   *
   * We don't follow them on the oldname either to be compatible
   * with linux 2.0, and to avoid hard-linking to directories
   * and other special files.  --ADM
   */

  asmlinkage long sys_linkat(int olddfd, const char __user *oldname,

  			   int newdfd, const char __user *newname,
  			   int flags)

  {
  	struct dentry *new_dentry;
  	struct nameidata nd, old_nd;
  	int error;
  	char * to;

  	if ((flags & ~AT_SYMLINK_FOLLOW) != 0)

  		return -EINVAL;

  	to = getname(newname);
  	if (IS_ERR(to))
  		return PTR_ERR(to);

  	error = __user_walk_fd(olddfd, oldname,
  			       flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
  			       &old_nd);

  	if (error)
  		goto exit;

  	error = do_path_lookup(newdfd, to, LOOKUP_PARENT, &nd);

  	if (error)
  		goto out;
  	error = -EXDEV;
  	if (old_nd.mnt != nd.mnt)
  		goto out_release;
  	new_dentry = lookup_create(&nd, 0);
  	error = PTR_ERR(new_dentry);

  	if (IS_ERR(new_dentry))
  		goto out_unlock;
  	error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
  	dput(new_dentry);
  out_unlock:

  	mutex_unlock(&nd.dentry->d_inode->i_mutex);

  out_release:
  	path_release(&nd);
  out:
  	path_release(&old_nd);
  exit:
  	putname(to);
  
  	return error;
  }

  asmlinkage long sys_link(const char __user *oldname, const char __user *newname)
  {

  	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);

  }

  /*
   * The worst of all namespace operations - renaming directory. "Perverted"
   * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
   * Problems:
   *	a) we can get into loop creation. Check is done in is_subdir().
   *	b) race potential - two innocent renames can create a loop together.
   *	   That's where 4.4 screws up. Current fix: serialization on

   *	   sb->s_vfs_rename_mutex. We might be more accurate, but that's another

   *	   story.
   *	c) we have to lock _three_ objects - parents and victim (if it exists).

   *	   And that - after we got ->i_mutex on parents (until then we don't know

   *	   whether the target exists).  Solution: try to be smart with locking
   *	   order for inodes.  We rely on the fact that tree topology may change

   *	   only under ->s_vfs_rename_mutex _and_ that parent of the object we

   *	   move will be locked.  Thus we can rank directories by the tree
   *	   (ancestors first) and rank all non-directories after them.
   *	   That works since everybody except rename does "lock parent, lookup,

   *	   lock child" and rename is under ->s_vfs_rename_mutex.

   *	   HOWEVER, it relies on the assumption that any object with ->lookup()
   *	   has no more than 1 dentry.  If "hybrid" objects will ever appear,
   *	   we'd better make sure that there's no link(2) for them.
   *	d) some filesystems don't support opened-but-unlinked directories,
   *	   either because of layout or because they are not ready to deal with
   *	   all cases correctly. The latter will be fixed (taking this sort of
   *	   stuff into VFS), but the former is not going away. Solution: the same
   *	   trick as in rmdir().
   *	e) conversion from fhandle to dentry may come in the wrong moment - when

   *	   we are removing the target. Solution: we will have to grab ->i_mutex

   *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on

   *	   ->i_mutex on parents, which works but leads to some truely excessive

   *	   locking].
   */

  static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
  			  struct inode *new_dir, struct dentry *new_dentry)

  {
  	int error = 0;
  	struct inode *target;
  
  	/*
  	 * If we are going to change the parent - check write permissions,
  	 * we'll need to flip '..'.
  	 */
  	if (new_dir != old_dir) {
  		error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
  		if (error)
  			return error;
  	}
  
  	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
  	if (error)
  		return error;
  
  	target = new_dentry->d_inode;
  	if (target) {

  		mutex_lock(&target->i_mutex);

  		dentry_unhash(new_dentry);
  	}
  	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
  		error = -EBUSY;
  	else 
  		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
  	if (target) {
  		if (!error)
  			target->i_flags |= S_DEAD;

  		mutex_unlock(&target->i_mutex);

  		if (d_unhashed(new_dentry))
  			d_rehash(new_dentry);
  		dput(new_dentry);
  	}

  	if (!error)

  		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
  			d_move(old_dentry,new_dentry);

  	return error;
  }

  static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
  			    struct inode *new_dir, struct dentry *new_dentry)

  {
  	struct inode *target;
  	int error;
  
  	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
  	if (error)
  		return error;
  
  	dget(new_dentry);
  	target = new_dentry->d_inode;
  	if (target)

  		mutex_lock(&target->i_mutex);

  	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
  		error = -EBUSY;
  	else
  		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
  	if (!error) {

  		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))

  			d_move(old_dentry, new_dentry);

  	}
  	if (target)

  		mutex_unlock(&target->i_mutex);

  	dput(new_dentry);
  	return error;
  }
  
  int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
  	       struct inode *new_dir, struct dentry *new_dentry)
  {
  	int error;
  	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);

  	const char *old_name;

  
  	if (old_dentry->d_inode == new_dentry->d_inode)
   		return 0;
   
  	error = may_delete(old_dir, old_dentry, is_dir);
  	if (error)
  		return error;
  
  	if (!new_dentry->d_inode)
  		error = may_create(new_dir, new_dentry, NULL);
  	else
  		error = may_delete(new_dir, new_dentry, is_dir);
  	if (error)
  		return error;
  
  	if (!old_dir->i_op || !old_dir->i_op->rename)
  		return -EPERM;
  
  	DQUOT_INIT(old_dir);
  	DQUOT_INIT(new_dir);

  	old_name = fsnotify_oldname_init(old_dentry->d_name.name);

  	if (is_dir)
  		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
  	else
  		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
  	if (!error) {

  		const char *new_name = old_dentry->d_name.name;

  		fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,

  			      new_dentry->d_inode, old_dentry);

  	}

  	fsnotify_oldname_free(old_name);

  	return error;
  }

  static int do_rename(int olddfd, const char *oldname,
  			int newdfd, const char *newname)

  {
  	int error = 0;
  	struct dentry * old_dir, * new_dir;
  	struct dentry * old_dentry, *new_dentry;
  	struct dentry * trap;
  	struct nameidata oldnd, newnd;

  	error = do_path_lookup(olddfd, oldname, LOOKUP_PARENT, &oldnd);

  	if (error)
  		goto exit;

  	error = do_path_lookup(newdfd, newname, LOOKUP_PARENT, &newnd);

  	if (error)
  		goto exit1;
  
  	error = -EXDEV;
  	if (oldnd.mnt != newnd.mnt)
  		goto exit2;
  
  	old_dir = oldnd.dentry;
  	error = -EBUSY;
  	if (oldnd.last_type != LAST_NORM)
  		goto exit2;
  
  	new_dir = newnd.dentry;
  	if (newnd.last_type != LAST_NORM)
  		goto exit2;
  
  	trap = lock_rename(new_dir, old_dir);

  	old_dentry = lookup_hash(&oldnd);

  	error = PTR_ERR(old_dentry);
  	if (IS_ERR(old_dentry))
  		goto exit3;
  	/* source must exist */
  	error = -ENOENT;
  	if (!old_dentry->d_inode)
  		goto exit4;
  	/* unless the source is a directory trailing slashes give -ENOTDIR */
  	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
  		error = -ENOTDIR;
  		if (oldnd.last.name[oldnd.last.len])
  			goto exit4;
  		if (newnd.last.name[newnd.last.len])
  			goto exit4;
  	}
  	/* source should not be ancestor of target */
  	error = -EINVAL;
  	if (old_dentry == trap)
  		goto exit4;

  	new_dentry = lookup_hash(&newnd);

  	error = PTR_ERR(new_dentry);
  	if (IS_ERR(new_dentry))
  		goto exit4;
  	/* target should not be an ancestor of source */
  	error = -ENOTEMPTY;
  	if (new_dentry == trap)
  		goto exit5;
  
  	error = vfs_rename(old_dir->d_inode, old_dentry,
  				   new_dir->d_inode, new_dentry);
  exit5:
  	dput(new_dentry);
  exit4:
  	dput(old_dentry);
  exit3:
  	unlock_rename(new_dir, old_dir);
  exit2:
  	path_release(&newnd);
  exit1:
  	path_release(&oldnd);
  exit:
  	return error;
  }

  asmlinkage long sys_renameat(int olddfd, const char __user *oldname,
  			     int newdfd, const char __user *newname)

  {
  	int error;
  	char * from;
  	char * to;
  
  	from = getname(oldname);
  	if(IS_ERR(from))
  		return PTR_ERR(from);
  	to = getname(newname);
  	error = PTR_ERR(to);
  	if (!IS_ERR(to)) {

  		error = do_rename(olddfd, from, newdfd, to);

  		putname(to);
  	}
  	putname(from);
  	return error;
  }

  asmlinkage long sys_rename(const char __user *oldname, const char __user *newname)
  {
  	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
  }

  int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
  {
  	int len;
  
  	len = PTR_ERR(link);
  	if (IS_ERR(link))
  		goto out;
  
  	len = strlen(link);
  	if (len > (unsigned) buflen)
  		len = buflen;
  	if (copy_to_user(buffer, link, len))
  		len = -EFAULT;
  out:
  	return len;
  }
  
  /*
   * A helper for ->readlink().  This should be used *ONLY* for symlinks that
   * have ->follow_link() touching nd only in nd_set_link().  Using (or not
   * using) it for any given inode is up to filesystem.
   */
  int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
  {
  	struct nameidata nd;

  	void *cookie;

  	nd.depth = 0;

  	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
  	if (!IS_ERR(cookie)) {
  		int res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));

  		if (dentry->d_inode->i_op->put_link)

  			dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
  		cookie = ERR_PTR(res);

  	}

  	return PTR_ERR(cookie);

  }
  
  int vfs_follow_link(struct nameidata *nd, const char *link)
  {
  	return __vfs_follow_link(nd, link);
  }
  
  /* get the link contents into pagecache */
  static char *page_getlink(struct dentry * dentry, struct page **ppage)
  {
  	struct page * page;
  	struct address_space *mapping = dentry->d_inode->i_mapping;

  	page = read_mapping_page(mapping, 0, NULL);

  	if (IS_ERR(page))

  		return (char*)page;

  	*ppage = page;
  	return kmap(page);

  }
  
  int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
  {
  	struct page *page = NULL;
  	char *s = page_getlink(dentry, &page);
  	int res = vfs_readlink(dentry,buffer,buflen,s);
  	if (page) {
  		kunmap(page);
  		page_cache_release(page);
  	}
  	return res;
  }

  void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)

  {

  	struct page *page = NULL;

  	nd_set_link(nd, page_getlink(dentry, &page));

  	return page;

  }

  void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)

  {

  	struct page *page = cookie;
  
  	if (page) {

  		kunmap(page);
  		page_cache_release(page);

  	}
  }

  int __page_symlink(struct inode *inode, const char *symname, int len,
  		gfp_t gfp_mask)

  {
  	struct address_space *mapping = inode->i_mapping;

  	struct page *page;

  	void *fsdata;

  	int err;

  	char *kaddr;

  retry:

  	err = pagecache_write_begin(NULL, mapping, 0, len-1,
  				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);

  	if (err)

  		goto fail;

  	kaddr = kmap_atomic(page, KM_USER0);
  	memcpy(kaddr, symname, len-1);
  	kunmap_atomic(kaddr, KM_USER0);

  
  	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
  							page, fsdata);

  	if (err < 0)
  		goto fail;

  	if (err < len-1)
  		goto retry;

  	mark_inode_dirty(inode);
  	return 0;

  fail:
  	return err;
  }

  int page_symlink(struct inode *inode, const char *symname, int len)
  {
  	return __page_symlink(inode, symname, len,
  			mapping_gfp_mask(inode->i_mapping));
  }

  const struct inode_operations page_symlink_inode_operations = {

  	.readlink	= generic_readlink,
  	.follow_link	= page_follow_link_light,
  	.put_link	= page_put_link,
  };
  
  EXPORT_SYMBOL(__user_walk);

  EXPORT_SYMBOL(__user_walk_fd);

  EXPORT_SYMBOL(follow_down);
  EXPORT_SYMBOL(follow_up);
  EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
  EXPORT_SYMBOL(getname);
  EXPORT_SYMBOL(lock_rename);

  EXPORT_SYMBOL(lookup_one_len);
  EXPORT_SYMBOL(page_follow_link_light);
  EXPORT_SYMBOL(page_put_link);
  EXPORT_SYMBOL(page_readlink);

  EXPORT_SYMBOL(__page_symlink);

  EXPORT_SYMBOL(page_symlink);
  EXPORT_SYMBOL(page_symlink_inode_operations);
  EXPORT_SYMBOL(path_lookup);

  EXPORT_SYMBOL(vfs_path_lookup);

  EXPORT_SYMBOL(path_release);

  EXPORT_SYMBOL(permission);

  EXPORT_SYMBOL(vfs_permission);

  EXPORT_SYMBOL(file_permission);

  EXPORT_SYMBOL(unlock_rename);
  EXPORT_SYMBOL(vfs_create);
  EXPORT_SYMBOL(vfs_follow_link);
  EXPORT_SYMBOL(vfs_link);
  EXPORT_SYMBOL(vfs_mkdir);
  EXPORT_SYMBOL(vfs_mknod);
  EXPORT_SYMBOL(generic_permission);
  EXPORT_SYMBOL(vfs_readlink);
  EXPORT_SYMBOL(vfs_rename);
  EXPORT_SYMBOL(vfs_rmdir);
  EXPORT_SYMBOL(vfs_symlink);
  EXPORT_SYMBOL(vfs_unlink);
  EXPORT_SYMBOL(dentry_unhash);
  EXPORT_SYMBOL(generic_readlink);