gpu: drm: udl: Adding new typedef vm_fault_t

Use new return type vm_fault_t for fault and huge_fault
handler. For now, this is just documenting that the
function returns a VM_FAULT value rather than an errno.
Once all instances are converted, vm_fault_t will become
a distinct type.

Commit 1c8f422059ae ("mm: change return type to vm_fault_t")

Previously vm_insert_page() returns err which driver
mapped into VM_FAULT_* type. The new function vmf_
insert_page() will replace this inefficiency by
returning VM_FAULT_* type.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180425045922.GA21590@jordon-HP-15-Notebook-PC

drivers/gpu/drm/udl/udl_drv.h

@@ -16,6 +16,7 @@
 
 #include <linux/usb.h>
 #include <drm/drm_gem.h>
+#include <linux/mm_types.h>
 
 #define DRIVER_NAME		"udl"
 #define DRIVER_DESC		"DisplayLink"
@@ -136,7 +137,7 @@ void udl_gem_put_pages(struct udl_gem_object *obj);
 int udl_gem_vmap(struct udl_gem_object *obj);
 void udl_gem_vunmap(struct udl_gem_object *obj);
 int udl_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
-int udl_gem_fault(struct vm_fault *vmf);
+vm_fault_t udl_gem_fault(struct vm_fault *vmf);
 
 int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
 		      int width, int height);

drivers/gpu/drm/udl/udl_gem.c

@@ -100,13 +100,12 @@ int udl_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	return ret;
 }
 
-int udl_gem_fault(struct vm_fault *vmf)
+vm_fault_t udl_gem_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct udl_gem_object *obj = to_udl_bo(vma->vm_private_data);
 	struct page *page;
 	unsigned int page_offset;
-	int ret = 0;
 
 	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
 
@@ -114,17 +113,7 @@ int udl_gem_fault(struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 
 	page = obj->pages[page_offset];
-	ret = vm_insert_page(vma, vmf->address, page);
-	switch (ret) {
-	case -EAGAIN:
-	case 0:
-	case -ERESTARTSYS:
-		return VM_FAULT_NOPAGE;
-	case -ENOMEM:
-		return VM_FAULT_OOM;
-	default:
-		return VM_FAULT_SIGBUS;
-	}
+	return vmf_insert_page(vma, vmf->address, page);
 }
 
 int udl_gem_get_pages(struct udl_gem_object *obj)