drm/amdgpu: check userptrs mm earlier

Instead of when we try to bind it check the usermm when
we try to use it in the IOCTLs.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 100bfd4a..cdb393db 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -499,9 +499,6 @@
 	enum dma_data_direction direction = write ?
 		DMA_BIDIRECTIONAL : DMA_TO_DEVICE;
 
-	if (current->mm != gtt->usermm)
-		return -EPERM;
-
 	if (gtt->userflags & AMDGPU_GEM_USERPTR_ANONONLY) {
 		/* check that we only pin down anonymous memory
 		   to prevent problems with writeback */
@@ -773,14 +770,14 @@
 	return 0;
 }
 
-bool amdgpu_ttm_tt_has_userptr(struct ttm_tt *ttm)
+struct mm_struct *amdgpu_ttm_tt_get_usermm(struct ttm_tt *ttm)
 {
 	struct amdgpu_ttm_tt *gtt = (void *)ttm;
 
 	if (gtt == NULL)
-		return false;
+		return NULL;
 
-	return !!gtt->userptr;
+	return gtt->usermm;
 }
 
 bool amdgpu_ttm_tt_affect_userptr(struct ttm_tt *ttm, unsigned long start,