#include <linux/compiler.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/linkage.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/sched.h>
  #include <linux/stat.h>
  #include <linux/utime.h>
  #include <linux/syscalls.h>
  #include <asm/uaccess.h>
  #include <asm/unistd.h>
  
  #ifdef __ARCH_WANT_SYS_UTIME
  
  /*
   * sys_utime() can be implemented in user-level using sys_utimes().
   * Is this for backwards compatibility?  If so, why not move it
   * into the appropriate arch directory (for those architectures that
   * need it).
   */
  
  /* If times==NULL, set access and modification to current time,
   * must be owner or have write permission.
   * Else, update from *times, must be owner or super user.
   */
  SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
  {
  	struct timespec tv[2];
  
  	if (times) {
  		if (get_user(tv[0].tv_sec, &times->actime) ||
  		    get_user(tv[1].tv_sec, &times->modtime))
  			return -EFAULT;
  		tv[0].tv_nsec = 0;
  		tv[1].tv_nsec = 0;
  	}
  	return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
  }
  
  #endif
  
  static bool nsec_valid(long nsec)
  {
  	if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
  		return true;
  
  	return nsec >= 0 && nsec <= 999999999;
  }
  
  static int utimes_common(struct path *path, struct timespec *times)
  {
  	int error;
  	struct iattr newattrs;
  	struct inode *inode = path->dentry->d_inode;
  	struct inode *delegated_inode = NULL;
  
  	error = mnt_want_write(path->mnt);
  	if (error)
  		goto out;
  
  	if (times && times[0].tv_nsec == UTIME_NOW &&
  		     times[1].tv_nsec == UTIME_NOW)
  		times = NULL;
  
  	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
  	if (times) {
  		if (times[0].tv_nsec == UTIME_OMIT)
  			newattrs.ia_valid &= ~ATTR_ATIME;
  		else if (times[0].tv_nsec != UTIME_NOW) {
  			newattrs.ia_atime.tv_sec = times[0].tv_sec;
  			newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
  			newattrs.ia_valid |= ATTR_ATIME_SET;
  		}
  
  		if (times[1].tv_nsec == UTIME_OMIT)
  			newattrs.ia_valid &= ~ATTR_MTIME;
  		else if (times[1].tv_nsec != UTIME_NOW) {
  			newattrs.ia_mtime.tv_sec = times[1].tv_sec;
  			newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
  			newattrs.ia_valid |= ATTR_MTIME_SET;
  		}
  		/*
  		 * Tell inode_change_ok(), that this is an explicit time
  		 * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
  		 * were used.
  		 */
  		newattrs.ia_valid |= ATTR_TIMES_SET;
  	} else {
  		/*
  		 * If times is NULL (or both times are UTIME_NOW),
  		 * then we need to check permissions, because
  		 * inode_change_ok() won't do it.
  		 */
  		error = -EACCES;
                  if (IS_IMMUTABLE(inode))
  			goto mnt_drop_write_and_out;
  
  		if (!inode_owner_or_capable(inode)) {
  			error = inode_permission(inode, MAY_WRITE);
  			if (error)
  				goto mnt_drop_write_and_out;
  		}
  	}
  retry_deleg:
  	mutex_lock(&inode->i_mutex);
  	error = notify_change(path->dentry, &newattrs, &delegated_inode);
  	mutex_unlock(&inode->i_mutex);
  	if (delegated_inode) {
  		error = break_deleg_wait(&delegated_inode);
  		if (!error)
  			goto retry_deleg;
  	}
  
  mnt_drop_write_and_out:
  	mnt_drop_write(path->mnt);
  out:
  	return error;
  }
  
  /*
   * do_utimes - change times on filename or file descriptor
   * @dfd: open file descriptor, -1 or AT_FDCWD
   * @filename: path name or NULL
   * @times: new times or NULL
   * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
   *
   * If filename is NULL and dfd refers to an open file, then operate on
   * the file.  Otherwise look up filename, possibly using dfd as a
   * starting point.
   *
   * If times==NULL, set access and modification to current time,
   * must be owner or have write permission.
   * Else, update from *times, must be owner or super user.
   */
  long do_utimes(int dfd, const char __user *filename, struct timespec *times,
  	       int flags)
  {
  	int error = -EINVAL;
  
  	if (times && (!nsec_valid(times[0].tv_nsec) ||
  		      !nsec_valid(times[1].tv_nsec))) {
  		goto out;
  	}
  
  	if (flags & ~AT_SYMLINK_NOFOLLOW)
  		goto out;
  
  	if (filename == NULL && dfd != AT_FDCWD) {
  		struct fd f;
  
  		if (flags & AT_SYMLINK_NOFOLLOW)
  			goto out;
  
  		f = fdget(dfd);
  		error = -EBADF;
  		if (!f.file)
  			goto out;
  
  		error = utimes_common(&f.file->f_path, times);
  		fdput(f);
  	} else {
  		struct path path;
  		int lookup_flags = 0;
  
  		if (!(flags & AT_SYMLINK_NOFOLLOW))
  			lookup_flags |= LOOKUP_FOLLOW;
  retry:
  		error = user_path_at(dfd, filename, lookup_flags, &path);
  		if (error)
  			goto out;
  
  		error = utimes_common(&path, times);
  		path_put(&path);
  		if (retry_estale(error, lookup_flags)) {
  			lookup_flags |= LOOKUP_REVAL;
  			goto retry;
  		}
  	}
  
  out:
  	return error;
  }
  
  SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
  		struct timespec __user *, utimes, int, flags)
  {
  	struct timespec tstimes[2];
  
  	if (utimes) {
  		if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
  			return -EFAULT;
  
  		/* Nothing to do, we must not even check the path.  */
  		if (tstimes[0].tv_nsec == UTIME_OMIT &&
  		    tstimes[1].tv_nsec == UTIME_OMIT)
  			return 0;
  	}
  
  	return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
  }
  
  SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
  		struct timeval __user *, utimes)
  {
  	struct timeval times[2];
  	struct timespec tstimes[2];
  
  	if (utimes) {
  		if (copy_from_user(&times, utimes, sizeof(times)))
  			return -EFAULT;
  
  		/* This test is needed to catch all invalid values.  If we
  		   would test only in do_utimes we would miss those invalid
  		   values truncated by the multiplication with 1000.  Note
  		   that we also catch UTIME_{NOW,OMIT} here which are only
  		   valid for utimensat.  */
  		if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
  		    times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
  			return -EINVAL;
  
  		tstimes[0].tv_sec = times[0].tv_sec;
  		tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
  		tstimes[1].tv_sec = times[1].tv_sec;
  		tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
  	}
  
  	return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
  }
  
  SYSCALL_DEFINE2(utimes, char __user *, filename,
  		struct timeval __user *, utimes)
  {
  	return sys_futimesat(AT_FDCWD, filename, utimes);
  }