static VALUE method_get_children(VALUE self, VALUE reqid, VALUE path, VALUE async, VALUE watch) {
  STANDARD_PREAMBLE(self, zk, reqid, path, async, watch, data_ctx, watch_ctx, call_type);

  struct String_vector strings;
  struct Stat stat;

  int rc;
  switch (call_type) {
    case SYNC:
      rc = zoo_get_children2(zk->zh, RSTRING_PTR(path), 0, &strings, &stat);
      break;

    case SYNC_WATCH:
      rc = zoo_wget_children2(zk->zh, RSTRING_PTR(path), zkrb_state_callback, watch_ctx, &strings, &stat);
      break;

    case ASYNC:
      rc = zoo_aget_children2(zk->zh, RSTRING_PTR(path), 0, zkrb_strings_stat_callback, data_ctx);
      break;

    case ASYNC_WATCH:
      rc = zoo_awget_children2(zk->zh, RSTRING_PTR(path), zkrb_state_callback, watch_ctx, zkrb_strings_stat_callback, data_ctx);
      break;
  }

  VALUE output = rb_ary_new();
  rb_ary_push(output, INT2FIX(rc));
  if (IS_SYNC(call_type) && rc == ZOK) {
    rb_ary_push(output, zkrb_string_vector_to_ruby(&strings));
    rb_ary_push(output, zkrb_stat_to_rarray(&stat));
  }
  return output;
}

static VALUE method_set(VALUE self, VALUE reqid, VALUE path, VALUE data, VALUE async, VALUE version) {
  VALUE watch = Qfalse;
  struct Stat stat;
  const char *data_ptr ;
  size_t      data_len ;
  int rc;
  VALUE output ;
  STANDARD_PREAMBLE(self, zk, reqid, path, async, watch, data_ctx, watch_ctx, call_type);

  if (data != Qnil) Check_Type(data, T_STRING);
  data_ptr = (data == Qnil) ? NULL : RSTRING_PTR(data);
  data_len = (data == Qnil) ? -1   : RSTRING_LEN(data);

  switch (call_type) {
    case SYNC:
      rc = zoo_set2(zk->zh, RSTRING_PTR(path), data_ptr, data_len, FIX2INT(version), &stat);
      break;
    case ASYNC:
      rc = zoo_aset(zk->zh, RSTRING_PTR(path), data_ptr, data_len, FIX2INT(version),
                            zkrb_stat_callback, data_ctx);
      break;
    default:
      /* TODO(wickman) raise proper argument error */
      return Qnil;
      break;
  }

  output = rb_ary_new();
  rb_ary_push(output, INT2FIX(rc));
  if (IS_SYNC(call_type) && rc == ZOK) {
    rb_ary_push(output, zkrb_stat_to_rarray(&stat));
  }
  return output;
}

static VALUE method_get_acl(VALUE self, VALUE reqid, VALUE path, VALUE async) {
  VALUE watch = Qfalse;
  struct ACL_vector acls;
  struct Stat stat;
  int rc;
  VALUE output ;
  STANDARD_PREAMBLE(self, zk, reqid, path, async, watch, data_ctx, watch_ctx, call_type);

  switch (call_type) {
    case SYNC:
      rc = zoo_get_acl(zk->zh, RSTRING_PTR(path), &acls, &stat);
      break;
    case ASYNC:
      rc = zoo_aget_acl(zk->zh, RSTRING_PTR(path), zkrb_acl_callback, data_ctx);
      break;
    default:
      /* TODO(wickman) raise proper argument error */
      return Qnil;
      break;
  }

  output = rb_ary_new();
  rb_ary_push(output, INT2FIX(rc));
  if (IS_SYNC(call_type) && rc == ZOK) {
    rb_ary_push(output, zkrb_acl_vector_to_ruby(&acls));
    rb_ary_push(output, zkrb_stat_to_rarray(&stat));
    deallocate_ACL_vector(&acls);
  }
  return output;
}

void nilfs_evict_inode(struct inode *inode)
{
	struct nilfs_transaction_info ti;
	struct super_block *sb = inode->i_sb;
	struct nilfs_inode_info *ii = NILFS_I(inode);
	int ret;

	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
		truncate_inode_pages_final(&inode->i_data);
		clear_inode(inode);
		nilfs_clear_inode(inode);
		return;
	}
	nilfs_transaction_begin(sb, &ti, 0); /* never fails */

	truncate_inode_pages_final(&inode->i_data);

	/* TODO: some of the following operations may fail.  */
	nilfs_truncate_bmap(ii, 0);
	nilfs_mark_inode_dirty(inode);
	clear_inode(inode);

	ret = nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
	if (!ret)
		atomic64_dec(&ii->i_root->inodes_count);

	nilfs_clear_inode(inode);

	if (IS_SYNC(inode))
		nilfs_set_transaction_flag(NILFS_TI_SYNC);
	nilfs_transaction_commit(sb);
	/* May construct a logical segment and may fail in sync mode.
	   But delete_inode has no return value. */
}

static VALUE method_exists(VALUE self, VALUE reqid, VALUE path, VALUE async, VALUE watch) {
  struct Stat stat;
  int rc;
  VALUE output;
  STANDARD_PREAMBLE(self, zk, reqid, path, async, watch, data_ctx, watch_ctx, call_type);

  switch (call_type) {
    case SYNC:
      rc = zoo_exists(zk->zh, RSTRING_PTR(path), 0, &stat);
      break;

    case SYNC_WATCH:
      rc = zoo_wexists(zk->zh, RSTRING_PTR(path), zkrb_state_callback, watch_ctx, &stat);
      break;

    case ASYNC:
      rc = zoo_aexists(zk->zh, RSTRING_PTR(path), 0, zkrb_stat_callback, data_ctx);
      break;

    case ASYNC_WATCH:
      rc = zoo_awexists(zk->zh, RSTRING_PTR(path), zkrb_state_callback, watch_ctx, zkrb_stat_callback, data_ctx);
      break;
  }

  output = rb_ary_new();
  rb_ary_push(output, INT2FIX(rc));
  if (IS_SYNC(call_type) && rc == ZOK) {
    rb_ary_push(output, zkrb_stat_to_rarray(&stat));
  }
  return output;
}

/**
 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 * @pipe:	pipe info
 * @out:	file to write to
 * @len:	number of bytes to splice
 * @flags:	splice modifier flags
 *
 * Will either move or copy pages (determined by @flags options) from
 * the given pipe inode to the given file. The caller is responsible
 * for acquiring i_mutex on both inodes.
 *
 */
ssize_t
generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
				 loff_t *ppos, size_t len, unsigned int flags)
{
	struct address_space *mapping = out->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;
	int err;

	err = remove_suid(out->f_path.dentry);
	if (unlikely(err))
		return err;

	ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
	if (ret > 0) {
		*ppos += ret;

		/*
		 * If file or inode is SYNC and we actually wrote some data,
		 * sync it.
		 */
		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
			err = generic_osync_inode(inode, mapping,
						  OSYNC_METADATA|OSYNC_DATA);

			if (err)
				ret = err;
		}
	}

	return ret;
}

void nilfs_evict_inode(struct inode *inode)
{
	struct nilfs_transaction_info ti;
	struct super_block *sb = inode->i_sb;
	struct nilfs_inode_info *ii = NILFS_I(inode);
	int ret;

	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
		if (inode->i_data.nrpages)
			truncate_inode_pages(&inode->i_data, 0);
		end_writeback(inode);
		nilfs_clear_inode(inode);
		return;
	}
	nilfs_transaction_begin(sb, &ti, 0); 

	if (inode->i_data.nrpages)
		truncate_inode_pages(&inode->i_data, 0);

	
	nilfs_truncate_bmap(ii, 0);
	nilfs_mark_inode_dirty(inode);
	end_writeback(inode);

	ret = nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
	if (!ret)
		atomic_dec(&ii->i_root->inodes_count);

	nilfs_clear_inode(inode);

	if (IS_SYNC(inode))
		nilfs_set_transaction_flag(NILFS_TI_SYNC);
	nilfs_transaction_commit(sb);
}

static VALUE method_get_acl(VALUE self, VALUE reqid, VALUE path, VALUE async) {
  STANDARD_PREAMBLE(self, zk, reqid, path, async, Qfalse, call_type);

  VALUE output = Qnil;
  struct ACL_vector acls;
  struct Stat stat;

  int rc=ZOK;
  switch (call_type) {

#ifdef THREADED
    case SYNC:
      rc = zkrb_call_zoo_get_acl(zk->zh, RSTRING_PTR(path), &acls, &stat);
      break;
#endif

    case ASYNC:
      rc = zkrb_call_zoo_aget_acl(zk->zh, RSTRING_PTR(path), zkrb_acl_callback, CTX_ALLOC(zk, reqid));
      break;

    default:
      raise_invalid_call_type_err(call_type);
      break;
  }

  output = rb_ary_new();
  rb_ary_push(output, INT2FIX(rc));
  if (IS_SYNC(call_type) && rc == ZOK) {
    rb_ary_push(output, zkrb_acl_vector_to_ruby(&acls));
    rb_ary_push(output, zkrb_stat_to_rarray(&stat));
    deallocate_ACL_vector(&acls);
  }
  return output;
}

void nilfs_truncate(struct inode *inode)
{
	unsigned long blkoff;
	unsigned int blocksize;
	struct nilfs_transaction_info ti;
	struct super_block *sb = inode->i_sb;
	struct nilfs_inode_info *ii = NILFS_I(inode);

	inode_debug(2, "called. (ino=%lu)\n", inode->i_ino);
	if (!test_bit(NILFS_I_BMAP, &ii->i_state))
		return;
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		return;

	blocksize = sb->s_blocksize;
	blkoff = (inode->i_size + blocksize - 1) >> sb->s_blocksize_bits;
	nilfs_transaction_begin(sb, &ti, 0); /* never fails */

	block_truncate_page(inode->i_mapping, inode->i_size, nilfs_get_block);

	nilfs_truncate_bmap(ii, blkoff);

	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	if (IS_SYNC(inode))
		nilfs_set_transaction_flag(NILFS_TI_SYNC);

	nilfs_set_file_dirty(NILFS_SB(sb), inode, 0);
	nilfs_transaction_commit(sb);
	/* May construct a logical segment and may fail in sync mode.
	   But truncate has no return value. */
}

void nilfs_delete_inode(struct inode *inode)
{
	struct nilfs_transaction_info ti;
	struct super_block *sb = inode->i_sb;
	struct nilfs_inode_info *ii = NILFS_I(inode);

	if (unlikely(is_bad_inode(inode))) {
		if (inode->i_data.nrpages)
			truncate_inode_pages(&inode->i_data, 0);
		clear_inode(inode);
		return;
	}
	nilfs_transaction_begin(sb, &ti, 0); /* never fails */

	if (inode->i_data.nrpages)
		truncate_inode_pages(&inode->i_data, 0);

	nilfs_truncate_bmap(ii, 0);
	nilfs_free_inode(inode);
	/* nilfs_free_inode() marks inode buffer dirty */
	if (IS_SYNC(inode))
		nilfs_set_transaction_flag(NILFS_TI_SYNC);
	nilfs_transaction_commit(sb);
	/* May construct a logical segment and may fail in sync mode.
	   But delete_inode has no return value. */
}

static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
{
	mark_buffer_dirty_inode(bh, inode);
	if (IS_SYNC(inode)) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
}

static ssize_t
ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_path.dentry->d_inode;
	ssize_t ret;
	int err;

	ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

	/*
	 * Skip flushing if there was an error, or if nothing was written.
	 */
	if (ret <= 0)
		return ret;

	/*
	 * If the inode is IS_SYNC, or is O_SYNC and we are doing data
	 * journalling then we need to make sure that we force the transaction
	 * to disk to keep all metadata uptodate synchronously.
	 */
	if (file->f_flags & O_SYNC) {
		/*
		 * If we are non-data-journaled, then the dirty data has
		 * already been flushed to backing store by generic_osync_inode,
		 * and the inode has been flushed too if there have been any
		 * modifications other than mere timestamp updates.
		 *
		 * Open question --- do we care about flushing timestamps too
		 * if the inode is IS_SYNC?
		 */
		if (!ext4_should_journal_data(inode))
			return ret;

		goto force_commit;
	}

	/*
	 * So we know that there has been no forced data flush.  If the inode
	 * is marked IS_SYNC, we need to force one ourselves.
	 */
	if (!IS_SYNC(inode))
		return ret;

	/*
	 * Open question #2 --- should we force data to disk here too?  If we
	 * don't, the only impact is that data=writeback filesystems won't
	 * flush data to disk automatically on IS_SYNC, only metadata (but
	 * historically, that is what ext2 has done.)
	 */

force_commit:
	err = ext4_force_commit(inode->i_sb);
	if (err)
		return err;
	return ret;
}

static int ufs_trunc_tindirect(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
	struct ufs_inode_info *ufsi = UFS_I(inode);
	struct ufs_buffer_head * tind_bh;
	u64 tindirect_block, tmp, i;
	void *tind, *p;
	int retry;
	
	UFSD("ENTER: ino %lu\n", inode->i_ino);

	retry = 0;
	
	tindirect_block = (DIRECT_BLOCK > (UFS_NDADDR + uspi->s_apb + uspi->s_2apb))
		? ((DIRECT_BLOCK - UFS_NDADDR - uspi->s_apb - uspi->s_2apb) >> uspi->s_2apbshift) : 0;

	p = ufs_get_direct_data_ptr(uspi, ufsi, UFS_TIND_BLOCK);
	if (!(tmp = ufs_data_ptr_to_cpu(sb, p)))
		return 0;
	tind_bh = ubh_bread (sb, tmp, uspi->s_bsize);
	if (tmp != ufs_data_ptr_to_cpu(sb, p)) {
		ubh_brelse (tind_bh);
		return 1;
	}
	if (!tind_bh) {
		ufs_data_ptr_clear(uspi, p);
		return 0;
	}

	for (i = tindirect_block ; i < uspi->s_apb ; i++) {
		tind = ubh_get_data_ptr(uspi, tind_bh, i);
		retry |= ufs_trunc_dindirect(inode, UFS_NDADDR + 
			uspi->s_apb + ((i + 1) << uspi->s_2apbshift), tind);
		ubh_mark_buffer_dirty(tind_bh);
	}
	for (i = 0; i < uspi->s_apb; i++)
		if (!ufs_is_data_ptr_zero(uspi,
					  ubh_get_data_ptr(uspi, tind_bh, i)))
			break;
	if (i >= uspi->s_apb) {
		tmp = ufs_data_ptr_to_cpu(sb, p);
		ufs_data_ptr_clear(uspi, p);

		ufs_free_blocks(inode, tmp, uspi->s_fpb);
		mark_inode_dirty(inode);
		ubh_bforget(tind_bh);
		tind_bh = NULL;
	}
	if (IS_SYNC(inode) && tind_bh && ubh_buffer_dirty(tind_bh)) {
		ubh_ll_rw_block(SWRITE, tind_bh);
		ubh_wait_on_buffer (tind_bh);
	}
	ubh_brelse (tind_bh);
	
	UFSD("EXIT: ino %lu\n", inode->i_ino);
	return retry;
}

static int ufs_trunc_tindirect (struct inode * inode)
{
    struct ufs_inode_info *ufsi = UFS_I(inode);
    struct super_block * sb;
    struct ufs_sb_private_info * uspi;
    struct ufs_buffer_head * tind_bh;
    unsigned tindirect_block, tmp, i;
    __fs32 * tind, * p;
    int retry;

    UFSD("ENTER\n");

    sb = inode->i_sb;
    uspi = UFS_SB(sb)->s_uspi;
    retry = 0;

    tindirect_block = (DIRECT_BLOCK > (UFS_NDADDR + uspi->s_apb + uspi->s_2apb))
                      ? ((DIRECT_BLOCK - UFS_NDADDR - uspi->s_apb - uspi->s_2apb) >> uspi->s_2apbshift) : 0;
    p = ufsi->i_u1.i_data + UFS_TIND_BLOCK;
    if (!(tmp = fs32_to_cpu(sb, *p)))
        return 0;
    tind_bh = ubh_bread (sb, tmp, uspi->s_bsize);
    if (tmp != fs32_to_cpu(sb, *p)) {
        ubh_brelse (tind_bh);
        return 1;
    }
    if (!tind_bh) {
        *p = 0;
        return 0;
    }

    for (i = tindirect_block ; i < uspi->s_apb ; i++) {
        tind = ubh_get_addr32 (tind_bh, i);
        retry |= ufs_trunc_dindirect(inode, UFS_NDADDR +
                                     uspi->s_apb + ((i + 1) << uspi->s_2apbshift), tind);
        ubh_mark_buffer_dirty(tind_bh);
    }
    for (i = 0; i < uspi->s_apb; i++)
        if (*ubh_get_addr32 (tind_bh, i))
            break;
    if (i >= uspi->s_apb) {
        tmp = fs32_to_cpu(sb, *p);
        *p = 0;

        ufs_free_blocks(inode, tmp, uspi->s_fpb);
        mark_inode_dirty(inode);
        ubh_bforget(tind_bh);
        tind_bh = NULL;
    }
    if (IS_SYNC(inode) && tind_bh && ubh_buffer_dirty(tind_bh)) {
        ubh_ll_rw_block(SWRITE, tind_bh);
        ubh_wait_on_buffer (tind_bh);
    }
    ubh_brelse (tind_bh);

    UFSD("EXIT\n");
    return retry;
}

static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)
{
	struct inode *dir = (struct inode *)page->mapping->host;
	int err = 0;

	page->mapping->a_ops->commit_write(NULL, page, from, to);
	if (IS_SYNC(dir))
		err = waitfor_one_page(page);
	return err;
}

/**
 * generic_write_sync - perform syncing after a write if file / inode is sync
 * @file:	file to which the write happened
 * @pos:	offset where the write started
 * @count:	length of the write
 *
 * This is just a simple wrapper about our general syncing function.
 */
int generic_write_sync(struct file *file, loff_t pos, loff_t count)
{
	//conditional fsync disable
	#ifdef CONFIG_FSYNC_OFF
	  return 0;
	#endif
	if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
		return 0;
	return vfs_fsync_range(file, pos, pos + count - 1,
			       (file->f_flags & __O_SYNC) ? 0 : 1);
}

/**
 * generic_write_sync - perform syncing after a write if file / inode is sync
 * @file:	file to which the write happened
 * @pos:	offset where the write started
 * @count:	length of the write
 *
 * This is just a simple wrapper about our general syncing function.
 */
int generic_write_sync(struct file *file, loff_t pos, loff_t count)
{
#ifdef CONFIG_DYNAMIC_FSYNC
	if (!early_suspend_active)
		return 0;
#endif
	if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
		return 0;
	return vfs_fsync_range(file, pos, pos + count - 1,
			       (file->f_flags & __O_SYNC) ? 0 : 1);
}

static int nfs_need_sync_write(struct file *filp, struct inode *inode)
{
	struct nfs_open_context *ctx;

	if (IS_SYNC(inode) || (filp->f_flags & O_SYNC))
		return 1;
	ctx = nfs_file_open_context(filp);
	if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags))
		return 1;
	return 0;
}

/*
 * Write an mmapped page to the server.
 */
int
nfs_writepage(struct page *page)
{
	struct inode *inode = page->mapping->host;
	unsigned long end_index;
	unsigned offset = PAGE_CACHE_SIZE;
	int inode_referenced = 0;
	int err;

	/*
	 * Note: We need to ensure that we have a reference to the inode
	 *       if we are to do asynchronous writes. If not, waiting
	 *       in nfs_wait_on_request() may deadlock with clear_inode().
	 *
	 *       If igrab() fails here, then it is in any case safe to
	 *       call nfs_wb_page(), since there will be no pending writes.
	 */
	if (igrab(inode) != 0)
		inode_referenced = 1;
	end_index = inode->i_size >> PAGE_CACHE_SHIFT;

	/* Ensure we've flushed out any previous writes */
	nfs_wb_page(inode,page);

	/* easy case */
	if (page->index < end_index)
		goto do_it;
	/* things got complicated... */
	offset = inode->i_size & (PAGE_CACHE_SIZE-1);

	/* OK, are we completely out? */
	err = -EIO;
	if (page->index >= end_index+1 || !offset)
		goto out;
do_it:
	lock_kernel();
	if (NFS_SERVER(inode)->wsize >= PAGE_CACHE_SIZE && !IS_SYNC(inode) &&
			inode_referenced) {
		err = nfs_writepage_async(NULL, inode, page, 0, offset);
		if (err >= 0)
			err = 0;
	} else {
		err = nfs_writepage_sync(NULL, inode, page, 0, offset); 
		if (err == offset)
			err = 0;
	}
	unlock_kernel();
out:
	UnlockPage(page);
	if (inode_referenced)
		iput(inode);
	return err;
}

int ufs_truncate(struct inode *inode, loff_t old_i_size)
{
	struct ufs_inode_info *ufsi = UFS_I(inode);
	struct super_block *sb = inode->i_sb;
	struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
	int retry, err = 0;
	
	UFSD("ENTER: ino %lu, i_size: %llu, old_i_size: %llu\n",
	     inode->i_ino, (unsigned long long)i_size_read(inode),
	     (unsigned long long)old_i_size);

	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
	      S_ISLNK(inode->i_mode)))
		return -EINVAL;
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		return -EPERM;

	err = ufs_alloc_lastblock(inode);

	if (err) {
		i_size_write(inode, old_i_size);
		goto out;
	}

	block_truncate_page(inode->i_mapping, inode->i_size, ufs_getfrag_block);

	lock_kernel();
	while (1) {
		retry = ufs_trunc_direct(inode);
		retry |= ufs_trunc_indirect(inode, UFS_IND_BLOCK,
					    ufs_get_direct_data_ptr(uspi, ufsi,
								    UFS_IND_BLOCK));
		retry |= ufs_trunc_dindirect(inode, UFS_IND_BLOCK + uspi->s_apb,
					     ufs_get_direct_data_ptr(uspi, ufsi,
								     UFS_DIND_BLOCK));
		retry |= ufs_trunc_tindirect (inode);
		if (!retry)
			break;
		if (IS_SYNC(inode) && (inode->i_state & I_DIRTY))
			ufs_sync_inode (inode);
		blk_run_address_space(inode->i_mapping);
		yield();
	}

	inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
	ufsi->i_lastfrag = DIRECT_FRAGMENT;
	unlock_kernel();
	mark_inode_dirty(inode);
out:
	UFSD("EXIT: err %d\n", err);
	return err;
}