static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
{
	struct inode *inode = mpd->inode;
	struct ext4_map_blocks *map = &mpd->map;
	int get_blocks_flags;
	int err, dioread_nolock;

	trace_ext4_da_write_pages_extent(inode, map);
	/*
	 * Call ext4_map_blocks() to allocate any delayed allocation blocks, or
	 * to convert an unwritten extent to be initialized (in the case
	 * where we have written into one or more preallocated blocks).  It is
	 * possible that we're going to need more metadata blocks than
	 * previously reserved. However we must not fail because we're in
	 * writeback and there is nothing we can do about it so it might result
	 * in data loss.  So use reserved blocks to allocate metadata if
	 * possible.
	 *
	 * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE if
	 * the blocks in question are delalloc blocks.  This indicates
	 * that the blocks and quotas has already been checked when
	 * the data was copied into the page cache.
	 */
	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
			   EXT4_GET_BLOCKS_METADATA_NOFAIL |
			   EXT4_GET_BLOCKS_IO_SUBMIT;
	dioread_nolock = ext4_should_dioread_nolock(inode);
	if (dioread_nolock)
		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
	if (map->m_flags & (1 << BH_Delay))
		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;

	err = ext4_map_blocks(handle, inode, map, get_blocks_flags);
	if (err < 0)
		return err;
	if (dioread_nolock && (map->m_flags & EXT4_MAP_UNWRITTEN)) {
		if (!mpd->io_submit.io_end->handle &&
		    ext4_handle_valid(handle)) {
			mpd->io_submit.io_end->handle = handle->h_rsv_handle;
			handle->h_rsv_handle = NULL;
		}
		ext4_set_io_unwritten_flag(inode, mpd->io_submit.io_end);
	}

	BUG_ON(map->m_len == 0);
	if (map->m_flags & EXT4_MAP_NEW) {
		clean_bdev_aliases(inode->i_sb->s_bdev, map->m_pblk,
				   map->m_len);
	}
	return 0;
}
Unknown