static int ext4_dax_writepages(struct address_space *mapping,
			       struct writeback_control *wbc)
{
	int ret;
	long nr_to_write = wbc->nr_to_write;
	struct inode *inode = mapping->host;
	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);

	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
		return -EIO;

	percpu_down_read(&sbi->s_writepages_rwsem);
	trace_ext4_writepages(inode, wbc);

	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
	trace_ext4_writepages_result(inode, wbc, ret,
				     nr_to_write - wbc->nr_to_write);
	percpu_up_read(&sbi->s_writepages_rwsem);
	return ret;
}
static int ext4_dax_writepages(struct address_space *mapping,
			       struct writeback_control *wbc)
{
	int ret;
	long nr_to_write = wbc->nr_to_write;
	struct inode *inode = mapping->host;
	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);

	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
		return -EIO;

	percpu_down_read(&sbi->s_writepages_rwsem);
	trace_ext4_writepages(inode, wbc);

	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
	trace_ext4_writepages_result(inode, wbc, ret,
				     nr_to_write - wbc->nr_to_write);
	percpu_up_read(&sbi->s_writepages_rwsem);
	return ret;
}