PCI/P2PDMA: Factor out __pci_p2pdma_map_sg()

Factor out the bus-only mapping into its own static function.  No
functional changes. The original pci_p2pdma_map_sg_attrs() will be used to
decide whether this is an appropriate way to map.

Link: https://lore.kernel.org/r/20190730163545.4915-11-logang@deltatee.com
Link: https://lore.kernel.org/r/20190812173048.9186-11-logang@deltatee.comSigned-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

drivers/pci/p2pdma.c

@@ -792,23 +792,9 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 
-/**
- * pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA
- * @dev: device doing the DMA request
- * @sg: scatter list to map
- * @nents: elements in the scatterlist
- * @dir: DMA direction
- * @attrs: DMA attributes passed to dma_map_sg() (if called)
- *
- * Scatterlists mapped with this function should be unmapped using
- * pci_p2pdma_unmap_sg_attrs().
- *
- * Returns the number of SG entries mapped or 0 on error.
- */
-int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
+static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
+		struct device *dev, struct scatterlist *sg, int nents)
 {
-	struct pci_p2pdma_pagemap *p2p_pgmap;
 	struct scatterlist *s;
 	phys_addr_t paddr;
 	int i;
@@ -824,7 +810,6 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 		return 0;
 
 	for_each_sg(sg, s, nents, i) {
-		p2p_pgmap = to_p2p_pgmap(sg_page(s)->pgmap);
 		paddr = sg_phys(s);
 
 		s->dma_address = paddr - p2p_pgmap->bus_offset;
@@ -833,6 +818,28 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 
 	return nents;
 }
+
+/**
+ * pci_p2pdma_map_sg - map a PCI peer-to-peer scatterlist for DMA
+ * @dev: device doing the DMA request
+ * @sg: scatter list to map
+ * @nents: elements in the scatterlist
+ * @dir: DMA direction
+ * @attrs: DMA attributes passed to dma_map_sg() (if called)
+ *
+ * Scatterlists mapped with this function should be unmapped using
+ * pci_p2pdma_unmap_sg_attrs().
+ *
+ * Returns the number of SG entries mapped or 0 on error.
+ */
+int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
+		int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+	struct pci_p2pdma_pagemap *p2p_pgmap =
+		to_p2p_pgmap(sg_page(sg)->pgmap);
+
+	return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
+}
 EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg_attrs);
 
 /**