[PATCH v2 06/22] PCI/P2PDMA: Attempt to set map_type if it has not been set

[Logan Gunthorpe]

Attempt to find the mapping type for P2PDMA pages on the first
DMA map attempt if it has not been done ahead of time.

Previously, the mapping type was expected to be calculated ahead of
time, but if pages are to come from userspace then there's no
way to ensure the path was checked ahead of time.

With this change it's no longer invalid to call pci_p2pdma_map_sg()
before the mapping type is calculated so drop the WARN_ON when that
is the case.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 drivers/pci/p2pdma.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 0e0b2218eacd..4034ffa0eb06 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -847,11 +847,17 @@ EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct pci_dev *provider,
 						    struct pci_dev *client)
 {
+	enum pci_p2pdma_map_type ret;
+
 	if (!provider->p2pdma)
 		return PCI_P2PDMA_MAP_NOT_SUPPORTED;
 
-	return xa_to_value(xa_load(&provider->p2pdma->map_types,
-				   map_types_idx(client)));
+	ret = xa_to_value(xa_load(&provider->p2pdma->map_types,
+				  map_types_idx(client)));
+	if (ret == PCI_P2PDMA_MAP_UNKNOWN)
+		return calc_map_type_and_dist_warn(provider, client, NULL);
+
+	return ret;
 }
 
 static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
@@ -899,7 +905,6 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	case PCI_P2PDMA_MAP_BUS_ADDR:
 		return __pci_p2pdma_map_sg(p2p_pgmap, dev, sg, nents);
 	default:
-		WARN_ON_ONCE(1);
 		return 0;
 	}
 }
-- 
2.20.1