drm: Some refactoring and bug fixes to address VM panics

sys/dev/drm/core/drm_vm.c

@@ -370,20 +370,23 @@ static const struct vm_operations_struct drm_vm_ops = {
 	.fault = drm_vm_fault,
 	.open = drm_vm_open,
 	.close = drm_vm_close,
+	.objtype = OBJT_MGTDEVICE,
 };
 
 /** Shared virtual memory operations */
 static const struct vm_operations_struct drm_vm_shm_ops = {
 	.fault = drm_vm_shm_fault,
 	.open = drm_vm_open,
 	.close = drm_vm_shm_close,
+	.objtype = OBJT_MGTDEVICE,
 };
 
 /** DMA virtual memory operations */
 static const struct vm_operations_struct drm_vm_dma_ops = {
 	.fault = drm_vm_dma_fault,
 	.open = drm_vm_open,
 	.close = drm_vm_close,
+	.objtype = OBJT_MGTDEVICE,
 };
 
 /** Scatter-gather virtual memory operations */

sys/dev/drm/drmkpi/include/linux/mm.h

@@ -119,20 +119,18 @@ struct vm_area_struct {
 struct vm_fault {
 	unsigned int flags;
 	pgoff_t	pgoff;
-	union {
-		/* user-space address */
-		void *virtual_address;	/* < 4.11 */
-		unsigned long address;	/* >= 4.11 */
-	};
+	vm_object_t object;
+	vm_pindex_t pindex;	/* fault pindex */
+	int count;		/* pages faulted in */
 	struct page *page;
-	struct vm_area_struct *vma;
 };
 
 struct vm_operations_struct {
 	void    (*open) (struct vm_area_struct *);
 	void    (*close) (struct vm_area_struct *);
-	int     (*fault) (struct vm_area_struct *, struct vm_fault *);
+	int     (*fault) (struct vm_fault *);
 	int	(*access) (struct vm_area_struct *, unsigned long, void *, int, int);
+	int	objtype;
 };
 
 struct sysinfo {

sys/dev/drm/freebsd/drm_gem_cma_helper.c

@@ -156,47 +156,47 @@ drm_gem_cma_alloc(struct drm_device *drm, struct drm_gem_cma_object *bo)
 }
 
 static int
-drm_gem_cma_fault(struct vm_area_struct *dummy, struct vm_fault *vmf)
+drm_gem_cma_fault(struct vm_fault *vmf)
 {
-	struct vm_area_struct *vma;
 	struct drm_gem_object *gem_obj;
 	struct drm_gem_cma_object *bo;
 	vm_object_t obj;
 	vm_pindex_t pidx;
 	struct page *page;
 	int i;
 
-	vma = vmf->vma;
-	gem_obj = vma->vm_private_data;
+	obj = vmf->object;
+	gem_obj = obj->handle;
 	bo = container_of(gem_obj, struct drm_gem_cma_object, gem_obj);
-	obj = vma->vm_obj;
 
 	if (!bo->m)
 		return (VM_FAULT_SIGBUS);
 
-	pidx = OFF_TO_IDX(vmf->address - vma->vm_start);
+	pidx = vmf->pindex;
 	if (pidx >= bo->npages)
 		return (VM_FAULT_SIGBUS);
 
 	VM_OBJECT_WLOCK(obj);
 	for (i = 0; i < bo->npages; i++) {
 		page = bo->m[i];
-		if (vm_page_busied(page))
+		if (!vm_page_tryxbusy(page))
 			goto fail_unlock;
-		if (vm_page_insert(page, obj, i))
+		if (vm_page_insert(page, obj, i)) {
+			vm_page_xunbusy(page);
 			goto fail_unlock;
-		vm_page_tryxbusy(page);
+		}
 		page->valid = VM_PAGE_BITS_ALL;
 	}
 	VM_OBJECT_WUNLOCK(obj);
 
-	vma->vm_pfn_first = 0;
-	vma->vm_pfn_count =  bo->npages;
-	DRM_DEBUG("%s: pidx: %llu, start: 0x%08X, addr: 0x%08lX\n", __func__, pidx, vma->vm_start, vmf->address);
+	vmf->pindex = 0;
+	vmf->count = bo->npages;
 
 	return (VM_FAULT_NOPAGE);
 
 fail_unlock:
+	for (i--; i >= 0; i--)
+		vm_page_xunbusy(bo->m[i]);
 	VM_OBJECT_WUNLOCK(obj);
 	DRM_ERROR("%s: insert failed\n", __func__);
 	return (VM_FAULT_SIGBUS);
@@ -206,6 +206,7 @@ const struct vm_operations_struct drm_gem_cma_vm_ops = {
 	.fault = drm_gem_cma_fault,
 	.open = drm_gem_vm_open,
 	.close = drm_gem_vm_close,
+	.objtype = OBJT_MGTDEVICE,
 };
 
 static int