drm/amdgpu: SDMA update use unlocked iterator

SDMA update page table may be called from unlocked context, this
generate below warning. Use unlocked iterator to handle this case.

WARNING: CPU: 0 PID: 1475 at
drivers/dma-buf/dma-resv.c:483 dma_resv_iter_next
Call Trace:
 dma_resv_iter_first+0x43/0xa0
 amdgpu_vm_sdma_update+0x69/0x2d0 [amdgpu]
 amdgpu_vm_ptes_update+0x29c/0x870 [amdgpu]
 amdgpu_vm_update_range+0x2f6/0x6c0 [amdgpu]
 svm_range_unmap_from_gpus+0x115/0x300 [amdgpu]
 svm_range_cpu_invalidate_pagetables+0x510/0x5e0 [amdgpu]
 __mmu_notifier_invalidate_range_start+0x1d3/0x230
 unmap_vmas+0x140/0x150
 unmap_region+0xa8/0x110
Signed-off-by: NPhilip Yang <Philip.Yang@amd.com>
Suggested-by: NFelix Kuehling <felix.kuehling@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -212,12 +212,15 @@ static int amdgpu_vm_sdma_update(struct amdgpu_vm_update_params *p,
 	int r;
 
 	/* Wait for PD/PT moves to be completed */
-	dma_resv_for_each_fence(&cursor, bo->tbo.base.resv,
-				DMA_RESV_USAGE_KERNEL, fence) {
+	dma_resv_iter_begin(&cursor, bo->tbo.base.resv, DMA_RESV_USAGE_KERNEL);
+	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 		r = amdgpu_sync_fence(&p->job->sync, fence);
-		if (r)
+		if (r) {
+			dma_resv_iter_end(&cursor);
 			return r;
+		}
 	}
+	dma_resv_iter_end(&cursor);
 
 	do {
 		ndw = p->num_dw_left;