/* Also.. Note that bforget() doesn't lock the buffer. So there can be writeout I/O going on against recently-freed buffers. We don't wait on that I/O in bforget() - it's more efficient to wait on the I/O only if we really need to. That happens here.  */
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
/* Also.. Note that bforget() doesn't lock the buffer. So there can be writeout I/O going on against recently-freed buffers. We don't wait on that I/O in bforget() - it's more efficient to wait on the I/O only if we really need to. That happens here.  */
void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
{
	struct buffer_head *old_bh;
	might_sleep();
	old_bh = __find_get_block_slow(bdev, block);
	if (old_bh) {
		clear_buffer_dirty(old_bh);
		wait_on_buffer(old_bh);
		clear_buffer_req(old_bh);
		__brelse(old_bh);
	}
}