[RFC V2 36/37] vfio: support dmempage refcount for vfio

[yulei . kernel]

From: Yulei Zhang <yuleixzh...@tencent.com>

Add get/put_dmem_pfn(), each time when vfio module reference/release
dmempages.

Signed-off-by: Chen Zhuo <sagazc...@tencent.com>
Signed-off-by: Yulei Zhang <yuleixzh...@tencent.com>
---
 drivers/vfio/vfio_iommu_type1.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c465d1a..4856a89 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -39,6 +39,7 @@
 #include <linux/notifier.h>
 #include <linux/dma-iommu.h>
 #include <linux/irqdomain.h>
+#include <linux/dmem.h>
 
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <alex.william...@redhat.com>"
@@ -411,7 +412,10 @@ static int put_pfn(unsigned long pfn, int prot)
 
                unpin_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE);
                return 1;
-       }
+       } else if (is_dmem_pfn(pfn))
+               put_dmem_pfn(pfn);
+
+       /* Dmem page is not counted against user. */
        return 0;
 }
 
@@ -477,6 +481,9 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned 
long vaddr,
 
                if (!ret && !is_invalid_reserved_pfn(*pfn))
                        ret = -EFAULT;
+
+               if (!ret && is_dmem_pfn(*pfn))
+                       get_dmem_pfn(*pfn);
        }
 done:
        mmap_read_unlock(mm);
-- 
1.8.3.1