The reference counts for ZONE_DEVICE private pages should be
initialised by the driver when the page is actually allocated by the
driver allocator, not when they are first created. This is currently
the case for MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_COHERENT pages
but not MEMORY_DEVICE_PCI_P2PDMA pages so fix that up.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
 drivers/pci/p2pdma.c |  6 ++++++
 mm/memremap.c        | 17 +++++++++++++----
 mm/mm_init.c         | 22 ++++++++++++++++++----
 3 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 4f47a13..210b9f4 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c

@@ -129,6 +129,12 @@ static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj,
 	}
 
 	/*
+	 * Initialise the refcount for the freshly allocated page. As we have
+	 * just allocated the page no one else should be using it.
+	 */
+	set_page_count(virt_to_page(kaddr), 1);