[PATCH v1 1/2] udmabuf: Use vmf_insert_pfn and VM_PFNMAP for handling mmap

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

Add VM_PFNMAP to vm_flags in the mmap handler to ensure that
the mappings would be managed without using struct page.

And, in the vm_fault handler, use vmf_insert_pfn to share the
page's pfn to userspace instead of directly sharing the page
(via struct page *).

Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Junxiao Chang <junxiao.chang@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 drivers/dma-buf/udmabuf.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 12cf6bb2e3ce..6de40c51d895 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -35,12 +35,13 @@ static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	struct udmabuf *ubuf = vma->vm_private_data;
 	pgoff_t pgoff = vmf->pgoff;
+	unsigned long pfn;
 
 	if (pgoff >= ubuf->pagecount)
 		return VM_FAULT_SIGBUS;
-	vmf->page = ubuf->pages[pgoff];
-	get_page(vmf->page);
-	return 0;
+
+	pfn = page_to_pfn(ubuf->pages[pgoff]);
+	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
 static const struct vm_operations_struct udmabuf_vm_ops = {
@@ -58,6 +59,7 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
 
 	vma->vm_ops = &udmabuf_vm_ops;
 	vma->vm_private_data = ubuf;
+	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
 	return 0;
 }
 
-- 
2.39.2