[01/24] dma-buf: add dma_resv_replace_fences

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 4deea75c0b9c..a688dbded3d3 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -284,6 +284,49 @@  void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
 }
 EXPORT_SYMBOL(dma_resv_add_shared_fence);
 
+/**
+ * dma_resv_replace_fences - replace fences in the dma_resv obj
+ * @obj: the reservation object
+ * @context: the context of the fences to replace
+ * @replacement: the new fence to use instead
+ *
+ * Replace fences with a specified context with a new fence. Only valid if the
+ * operation represented by the original fences is completed or has no longer
+ * access to the resources protected by the dma_resv object when the new fence
+ * completes.
+ */
+void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
+			     struct dma_fence *replacement)
+{
+	struct dma_resv_list *list;
+	struct dma_fence *old;
+	unsigned int i;
+
+	dma_resv_assert_held(obj);
+
+	write_seqcount_begin(&obj->seq);
+
+	old = dma_resv_excl_fence(obj);
+	if (old->context == context) {
+		RCU_INIT_POINTER(obj->fence_excl, dma_fence_get(replacement));
+		dma_fence_put(old);
+	}
+
+	list = dma_resv_shared_list(obj);
+	for (i = 0; list && i < list->shared_count; ++i) {
+		old = rcu_dereference_protected(list->shared[i],
+						dma_resv_held(obj));
+		if (old->context != context)
+			continue;
+
+		rcu_assign_pointer(list->shared[i], dma_fence_get(replacement));
+		dma_fence_put(old);
+	}
+
+	write_seqcount_end(&obj->seq);
+}
+EXPORT_SYMBOL(dma_resv_replace_fences);
+
 /**
  * dma_resv_add_excl_fence - Add an exclusive fence.
  * @obj: the reservation object
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 71acd577803e..b558ef0f8c4a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -236,53 +236,18 @@  void amdgpu_amdkfd_release_notify(struct amdgpu_bo *bo)
 static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo,
 					struct amdgpu_amdkfd_fence *ef)
 {
-	struct dma_resv *resv = bo->tbo.base.resv;
-	struct dma_resv_list *old, *new;
-	unsigned int i, j, k;
+	struct dma_fence *replacement;
 
 	if (!ef)
 		return -EINVAL;
 
-	old = dma_resv_shared_list(resv);
-	if (!old)
-		return 0;
-
-	new = kmalloc(struct_size(new, shared, old->shared_max), GFP_KERNEL);
-	if (!new)
-		return -ENOMEM;
-
-	/* Go through all the shared fences in the resevation object and sort
-	 * the interesting ones to the end of the list.
+	/* TODO: Instead of block before we should use the fence of the page
+	 * table update and TLB flush here directly.
 	 */
-	for (i = 0, j = old->shared_count, k = 0; i < old->shared_count; ++i) {
-		struct dma_fence *f;
-
-		f = rcu_dereference_protected(old->shared[i],
-					      dma_resv_held(resv));
-
-		if (f->context == ef->base.context)
-			RCU_INIT_POINTER(new->shared[--j], f);
-		else
-			RCU_INIT_POINTER(new->shared[k++], f);
-	}
-	new->shared_max = old->shared_max;
-	new->shared_count = k;
-
-	/* Install the new fence list, seqcount provides the barriers */
-	write_seqcount_begin(&resv->seq);
-	RCU_INIT_POINTER(resv->fence, new);
-	write_seqcount_end(&resv->seq);
-
-	/* Drop the references to the removed fences or move them to ef_list */
-	for (i = j; i < old->shared_count; ++i) {
-		struct dma_fence *f;
-
-		f = rcu_dereference_protected(new->shared[i],
-					      dma_resv_held(resv));
-		dma_fence_put(f);
-	}
-	kfree_rcu(old, rcu);
-
+	replacement = dma_fence_get_stub();
+	dma_resv_replace_fences(bo->tbo.base.resv, ef->base.context,
+				replacement);
+	dma_fence_put(replacement);
 	return 0;
 }
 
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index eebf04325b34..e0be34265eae 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -457,6 +457,8 @@  void dma_resv_init(struct dma_resv *obj);
 void dma_resv_fini(struct dma_resv *obj);
 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences);
 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence);
+void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
+			     struct dma_fence *fence);
 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence);
 int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl,
 			unsigned *pshared_count, struct dma_fence ***pshared);