[PATCH 07/13] PCI/P2PDMA: create compound page for aligned p2pdma memory

[Hou Tao]

From: Hou Tao <houtao1 at huawei.com>

Commit c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound
pages") has already supported compound page for ZONE_DEVICE memory. It
not only decreases the memory overhead of ZONE_DEVICE memory through
the deduplication of vmemmap pages, it also optimize the performance of
get_user_pages when the memory is used for IO.

As for now, the alignment of p2p dma memory is already known, setting
vmemmap_shift accordingly to create compound page for p2pdma memory.

Signed-off-by: Hou Tao <houtao1 at huawei.com>
---
 drivers/pci/p2pdma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 70482e240304..7180dea4855c 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -447,6 +447,8 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
 	pgmap->nr_range = 1;
 	pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;
 	pgmap->ops = &p2pdma_pgmap_ops;
+	if (align > PAGE_SIZE)
+		pgmap->vmemmap_shift = ilog2(align) - PAGE_SHIFT;
 	p2p_pgmap->mem = mem;
 
 	addr = devm_memremap_pages(&pdev->dev, pgmap);
-- 
2.29.2