pci_unmap_sg
pci_unmap_sg(dev->persist->pdev, chunk->mem, chunk->npages,
pci_unmap_sg(dev->pdev, &db_tab->page[i].mem, 1, PCI_DMA_TODEVICE);
pci_unmap_sg(dev->pdev, &db_tab->page[i].mem, 1, PCI_DMA_TODEVICE);
pci_unmap_sg(dev->pdev, chunk->mem, chunk->npages,