drm/amdgpu: shrink critical section in amdgpu_amdkfd_gpuvm_free_memory_of_gpu

Reduce the mem->lock`s protected code area, no need to protect pr_debug.
This also simplifies error handling.
Signed-off-by: Bernard Zhao <bernard@vivo.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c

@@ -1284,22 +1284,22 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
 	struct kfd_bo_va_list *entry, *tmp;
 	struct bo_vm_reservation_context ctx;
 	struct ttm_validate_buffer *bo_list_entry;
+	unsigned int mapped_to_gpu_memory;
 	int ret;
 
 	mutex_lock(&mem->lock);
+	mapped_to_gpu_memory = mem->mapped_to_gpu_memory;
+	mutex_unlock(&mem->lock);
+	/* lock is not needed after this, since mem is unused and will
+	 * be freed anyway
+	 */
 
-	if (mem->mapped_to_gpu_memory > 0) {
+	if (mapped_to_gpu_memory > 0) {
 		pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n",
 				mem->va, bo_size);
-		mutex_unlock(&mem->lock);
 		return -EBUSY;
 	}
 
-	mutex_unlock(&mem->lock);
-	/* lock is not needed after this, since mem is unused and will
-	 * be freed anyway
-	 */
-
 	/* No more MMU notifiers */
 	amdgpu_mn_unregister(mem->bo);