1 files changed, 285 insertions, 243 deletions

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 4deea75c0b9c..e3885c90a3ac 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -34,6 +34,7 @@
  */
 
 #include <linux/dma-resv.h>
+#include <linux/dma-fence-array.h>
 #include <linux/export.h>
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
@@ -43,12 +44,12 @@
 /**
  * DOC: Reservation Object Overview
  *
- * The reservation object provides a mechanism to manage shared and
- * exclusive fences associated with a buffer.  A reservation object
- * can have attached one exclusive fence (normally associated with
- * write operations) or N shared fences (read operations).  The RCU
- * mechanism is used to protect read access to fences from locked
- * write-side updates.
+ * The reservation object provides a mechanism to manage a container of
+ * dma_fence object associated with a resource. A reservation object
+ * can have any number of fences attaches to it. Each fence carries an usage
+ * parameter determining how the operation represented by the fence is using the
+ * resource. The RCU mechanism is used to protect read access to fences from
+ * locked write-side updates.
  *
  * See struct dma_resv for more details.
  */
@@ -56,33 +57,59 @@
 DEFINE_WD_CLASS(reservation_ww_class);
 EXPORT_SYMBOL(reservation_ww_class);
 
-/**
- * dma_resv_list_alloc - allocate fence list
- * @shared_max: number of fences we need space for
- *
+/* Mask for the lower fence pointer bits */
+#define DMA_RESV_LIST_MASK	0x3
+
+struct dma_resv_list {
+	struct rcu_head rcu;
+	u32 num_fences, max_fences;
+	struct dma_fence __rcu *table[];
+};
+
+/* Extract the fence and usage flags from an RCU protected entry in the list. */
+static void dma_resv_list_entry(struct dma_resv_list *list, unsigned int index,
+				struct dma_resv *resv, struct dma_fence **fence,
+				enum dma_resv_usage *usage)
+{
+	long tmp;
+
+	tmp = (long)rcu_dereference_check(list->table[index],
+					  resv ? dma_resv_held(resv) : true);
+	*fence = (struct dma_fence *)(tmp & ~DMA_RESV_LIST_MASK);
+	if (usage)
+		*usage = tmp & DMA_RESV_LIST_MASK;
+}
+
+/* Set the fence and usage flags at the specific index in the list. */
+static void dma_resv_list_set(struct dma_resv_list *list,
+			      unsigned int index,
+			      struct dma_fence *fence,
+			      enum dma_resv_usage usage)
+{
+	long tmp = ((long)fence) | usage;
+
+	RCU_INIT_POINTER(list->table[index], (struct dma_fence *)tmp);
+}
+
+/*
  * Allocate a new dma_resv_list and make sure to correctly initialize
- * shared_max.
+ * max_fences.
  */
-static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
+static struct dma_resv_list *dma_resv_list_alloc(unsigned int max_fences)
 {
 	struct dma_resv_list *list;
 
-	list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
+	list = kmalloc(struct_size(list, table, max_fences), GFP_KERNEL);
 	if (!list)
 		return NULL;
 
-	list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
-		sizeof(*list->shared);
+	list->max_fences = (ksize(list) - offsetof(typeof(*list), table)) /
+		sizeof(*list->table);
 
 	return list;
 }
 
-/**
- * dma_resv_list_free - free fence list
- * @list: list to free
- *
- * Free a dma_resv_list and make sure to drop all references.
- */
+/* Free a dma_resv_list and make sure to drop all references. */
 static void dma_resv_list_free(struct dma_resv_list *list)
 {
 	unsigned int i;
@@ -90,9 +117,12 @@ static void dma_resv_list_free(struct dma_resv_list *list)
 	if (!list)
 		return;
 
-	for (i = 0; i < list->shared_count; ++i)
-		dma_fence_put(rcu_dereference_protected(list->shared[i], true));
+	for (i = 0; i < list->num_fences; ++i) {
+		struct dma_fence *fence;
 
+		dma_resv_list_entry(list, i, NULL, &fence, NULL);
+		dma_fence_put(fence);
+	}
 	kfree_rcu(list, rcu);
 }
 
@@ -103,10 +133,8 @@ static void dma_resv_list_free(struct dma_resv_list *list)
 void dma_resv_init(struct dma_resv *obj)
 {
 	ww_mutex_init(&obj->lock, &reservation_ww_class);
-	seqcount_ww_mutex_init(&obj->seq, &obj->lock);
 
-	RCU_INIT_POINTER(obj->fence, NULL);
-	RCU_INIT_POINTER(obj->fence_excl, NULL);
+	RCU_INIT_POINTER(obj->fences, NULL);
 }
 EXPORT_SYMBOL(dma_resv_init);
 
@@ -116,51 +144,48 @@ EXPORT_SYMBOL(dma_resv_init);
  */
 void dma_resv_fini(struct dma_resv *obj)
 {
-	struct dma_resv_list *fobj;
-	struct dma_fence *excl;
-
 	/*
 	 * This object should be dead and all references must have
 	 * been released to it, so no need to be protected with rcu.
 	 */
-	excl = rcu_dereference_protected(obj->fence_excl, 1);
-	if (excl)
-		dma_fence_put(excl);
-
-	fobj = rcu_dereference_protected(obj->fence, 1);
-	dma_resv_list_free(fobj);
+	dma_resv_list_free(rcu_dereference_protected(obj->fences, true));
 	ww_mutex_destroy(&obj->lock);
 }
 EXPORT_SYMBOL(dma_resv_fini);
 
+/* Dereference the fences while ensuring RCU rules */
+static inline struct dma_resv_list *dma_resv_fences_list(struct dma_resv *obj)
+{
+	return rcu_dereference_check(obj->fences, dma_resv_held(obj));
+}
+
 /**
- * dma_resv_reserve_shared - Reserve space to add shared fences to
- * a dma_resv.
+ * dma_resv_reserve_fences - Reserve space to add fences to a dma_resv object.
  * @obj: reservation object
  * @num_fences: number of fences we want to add
  *
- * Should be called before dma_resv_add_shared_fence().  Must
- * be called with @obj locked through dma_resv_lock().
+ * Should be called before dma_resv_add_fence().  Must be called with @obj
+ * locked through dma_resv_lock().
  *
  * Note that the preallocated slots need to be re-reserved if @obj is unlocked
- * at any time before calling dma_resv_add_shared_fence(). This is validated
- * when CONFIG_DEBUG_MUTEXES is enabled.
+ * at any time before calling dma_resv_add_fence(). This is validated when
+ * CONFIG_DEBUG_MUTEXES is enabled.
  *
  * RETURNS
  * Zero for success, or -errno
  */
-int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
+int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences)
 {
 	struct dma_resv_list *old, *new;
 	unsigned int i, j, k, max;
 
 	dma_resv_assert_held(obj);
 
-	old = dma_resv_shared_list(obj);
-	if (old && old->shared_max) {
-		if ((old->shared_count + num_fences) <= old->shared_max)
+	old = dma_resv_fences_list(obj);
+	if (old && old->max_fences) {
+		if ((old->num_fences + num_fences) <= old->max_fences)
 			return 0;
-		max = max(old->shared_count + num_fences, old->shared_max * 2);
+		max = max(old->num_fences + num_fences, old->max_fences * 2);
 	} else {
 		max = max(4ul, roundup_pow_of_two(num_fences));
 	}
@@ -175,27 +200,27 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 	 * references from the old struct are carried over to
 	 * the new.
 	 */
-	for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
+	for (i = 0, j = 0, k = max; i < (old ? old->num_fences : 0); ++i) {
+		enum dma_resv_usage usage;
 		struct dma_fence *fence;
 
-		fence = rcu_dereference_protected(old->shared[i],
-						  dma_resv_held(obj));
+		dma_resv_list_entry(old, i, obj, &fence, &usage);
 		if (dma_fence_is_signaled(fence))
-			RCU_INIT_POINTER(new->shared[--k], fence);
+			RCU_INIT_POINTER(new->table[--k], fence);
 		else
-			RCU_INIT_POINTER(new->shared[j++], fence);
+			dma_resv_list_set(new, j++, fence, usage);
 	}
-	new->shared_count = j;
+	new->num_fences = j;
 
 	/*
 	 * We are not changing the effective set of fences here so can
 	 * merely update the pointer to the new array; both existing
 	 * readers and new readers will see exactly the same set of
-	 * active (unsignaled) shared fences. Individual fences and the
+	 * active (unsignaled) fences. Individual fences and the
 	 * old array are protected by RCU and so will not vanish under
 	 * the gaze of the rcu_read_lock() readers.
 	 */
-	rcu_assign_pointer(obj->fence, new);
+	rcu_assign_pointer(obj->fences, new);
 
 	if (!old)
 		return 0;
@@ -204,7 +229,7 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 	for (i = k; i < max; ++i) {
 		struct dma_fence *fence;
 
-		fence = rcu_dereference_protected(new->shared[i],
+		fence = rcu_dereference_protected(new->table[i],
 						  dma_resv_held(obj));
 		dma_fence_put(fence);
 	}
@@ -212,41 +237,43 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 
 	return 0;
 }
-EXPORT_SYMBOL(dma_resv_reserve_shared);
+EXPORT_SYMBOL(dma_resv_reserve_fences);
 
 #ifdef CONFIG_DEBUG_MUTEXES
 /**
- * dma_resv_reset_shared_max - reset shared fences for debugging
+ * dma_resv_reset_max_fences - reset fences for debugging
  * @obj: the dma_resv object to reset
  *
- * Reset the number of pre-reserved shared slots to test that drivers do
- * correct slot allocation using dma_resv_reserve_shared(). See also
- * &dma_resv_list.shared_max.
+ * Reset the number of pre-reserved fence slots to test that drivers do
+ * correct slot allocation using dma_resv_reserve_fences(). See also
+ * &dma_resv_list.max_fences.
  */
-void dma_resv_reset_shared_max(struct dma_resv *obj)
+void dma_resv_reset_max_fences(struct dma_resv *obj)
 {
-	struct dma_resv_list *fences = dma_resv_shared_list(obj);
+	struct dma_resv_list *fences = dma_resv_fences_list(obj);
 
 	dma_resv_assert_held(obj);
 
-	/* Test shared fence slot reservation */
+	/* Test fence slot reservation */
 	if (fences)
-		fences->shared_max = fences->shared_count;
+		fences->max_fences = fences->num_fences;
 }
-EXPORT_SYMBOL(dma_resv_reset_shared_max);
+EXPORT_SYMBOL(dma_resv_reset_max_fences);
 #endif
 
 /**
- * dma_resv_add_shared_fence - Add a fence to a shared slot
+ * dma_resv_add_fence - Add a fence to the dma_resv obj
  * @obj: the reservation object
- * @fence: the shared fence to add
+ * @fence: the fence to add
+ * @usage: how the fence is used, see enum dma_resv_usage
  *
- * Add a fence to a shared slot, @obj must be locked with dma_resv_lock(), and
- * dma_resv_reserve_shared() has been called.
+ * Add a fence to a slot, @obj must be locked with dma_resv_lock(), and
+ * dma_resv_reserve_fences() has been called.
  *
  * See also &dma_resv.fence for a discussion of the semantics.
  */
-void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
+void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
+			enum dma_resv_usage usage)
 {
 	struct dma_resv_list *fobj;
 	struct dma_fence *old;
@@ -256,129 +283,111 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
 
 	dma_resv_assert_held(obj);
 
-	fobj = dma_resv_shared_list(obj);
-	count = fobj->shared_count;
+	/* Drivers should not add containers here, instead add each fence
+	 * individually.
+	 */
+	WARN_ON(dma_fence_is_container(fence));
 
-	write_seqcount_begin(&obj->seq);
+	fobj = dma_resv_fences_list(obj);
+	count = fobj->num_fences;
 
 	for (i = 0; i < count; ++i) {
-
-		old = rcu_dereference_protected(fobj->shared[i],
-						dma_resv_held(obj));
-		if (old->context == fence->context ||
-		    dma_fence_is_signaled(old))
-			goto replace;
+		enum dma_resv_usage old_usage;
+
+		dma_resv_list_entry(fobj, i, obj, &old, &old_usage);
+		if ((old->context == fence->context && old_usage >= usage &&
+		     dma_fence_is_later(fence, old)) ||
+		    dma_fence_is_signaled(old)) {
+			dma_resv_list_set(fobj, i, fence, usage);
+			dma_fence_put(old);
+			return;
+		}
 	}
 
-	BUG_ON(fobj->shared_count >= fobj->shared_max);
-	old = NULL;
+	BUG_ON(fobj->num_fences >= fobj->max_fences);
 	count++;
 
-replace:
-	RCU_INIT_POINTER(fobj->shared[i], fence);
-	/* pointer update must be visible before we extend the shared_count */
-	smp_store_mb(fobj->shared_count, count);
-
-	write_seqcount_end(&obj->seq);
-	dma_fence_put(old);
+	dma_resv_list_set(fobj, i, fence, usage);
+	/* pointer update must be visible before we extend the num_fences */
+	smp_store_mb(fobj->num_fences, count);
 }
-EXPORT_SYMBOL(dma_resv_add_shared_fence);
+EXPORT_SYMBOL(dma_resv_add_fence);
 
 /**
- * dma_resv_add_excl_fence - Add an exclusive fence.
+ * dma_resv_replace_fences - replace fences in the dma_resv obj
  * @obj: the reservation object
- * @fence: the exclusive fence to add
+ * @context: the context of the fences to replace
+ * @replacement: the new fence to use instead
+ * @usage: how the new fence is used, see enum dma_resv_usage
+ *
+ * Replace fences with a specified context with a new fence. Only valid if the
+ * operation represented by the original fence has no longer access to the
+ * resources represented by the dma_resv object when the new fence completes.
  *
- * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock().
- * Note that this function replaces all fences attached to @obj, see also
- * &dma_resv.fence_excl for a discussion of the semantics.
+ * And example for using this is replacing a preemption fence with a page table
+ * update fence which makes the resource inaccessible.
  */
-void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
+void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
+			     struct dma_fence *replacement,
+			     enum dma_resv_usage usage)
 {
-	struct dma_fence *old_fence = dma_resv_excl_fence(obj);
-	struct dma_resv_list *old;
-	u32 i = 0;
+	struct dma_resv_list *list;
+	unsigned int i;
 
 	dma_resv_assert_held(obj);
 
-	old = dma_resv_shared_list(obj);
-	if (old)
-		i = old->shared_count;
-
-	dma_fence_get(fence);
-
-	write_seqcount_begin(&obj->seq);
-	/* write_seqcount_begin provides the necessary memory barrier */
-	RCU_INIT_POINTER(obj->fence_excl, fence);
-	if (old)
-		old->shared_count = 0;
-	write_seqcount_end(&obj->seq);
+	list = dma_resv_fences_list(obj);
+	for (i = 0; list && i < list->num_fences; ++i) {
+		struct dma_fence *old;
 
-	/* inplace update, no shared fences */
-	while (i--)
-		dma_fence_put(rcu_dereference_protected(old->shared[i],
-						dma_resv_held(obj)));
+		dma_resv_list_entry(list, i, obj, &old, NULL);
+		if (old->context != context)
+			continue;
 
-	dma_fence_put(old_fence);
+		dma_resv_list_set(list, i, dma_fence_get(replacement), usage);
+		dma_fence_put(old);
+	}
 }
-EXPORT_SYMBOL(dma_resv_add_excl_fence);
+EXPORT_SYMBOL(dma_resv_replace_fences);
 
-/**
- * dma_resv_iter_restart_unlocked - restart the unlocked iterator
- * @cursor: The dma_resv_iter object to restart
- *
- * Restart the unlocked iteration by initializing the cursor object.
- */
+/* Restart the unlocked iteration by initializing the cursor object. */
 static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor)
 {
-	cursor->seq = read_seqcount_begin(&cursor->obj->seq);
-	cursor->index = -1;
-	cursor->shared_count = 0;
-	if (cursor->all_fences) {
-		cursor->fences = dma_resv_shared_list(cursor->obj);
-		if (cursor->fences)
-			cursor->shared_count = cursor->fences->shared_count;
-	} else {
-		cursor->fences = NULL;
-	}
+	cursor->index = 0;
+	cursor->num_fences = 0;
+	cursor->fences = dma_resv_fences_list(cursor->obj);
+	if (cursor->fences)
+		cursor->num_fences = cursor->fences->num_fences;
 	cursor->is_restarted = true;
 }
 
-/**
- * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj
- * @cursor: cursor to record the current position
- *
- * Return all the fences in the dma_resv object which are not yet signaled.
- * The returned fence has an extra local reference so will stay alive.
- * If a concurrent modify is detected the whole iteration is started over again.
- */
+/* Walk to the next not signaled fence and grab a reference to it */
 static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
 {
-	struct dma_resv *obj = cursor->obj;
+	if (!cursor->fences)
+		return;
 
 	do {
 		/* Drop the reference from the previous round */
 		dma_fence_put(cursor->fence);
 
-		if (cursor->index == -1) {
-			cursor->fence = dma_resv_excl_fence(obj);
-			cursor->index++;
-			if (!cursor->fence)
-				continue;
-
-		} else if (!cursor->fences ||
-			   cursor->index >= cursor->shared_count) {
+		if (cursor->index >= cursor->num_fences) {
 			cursor->fence = NULL;
 			break;
 
-		} else {
-			struct dma_resv_list *fences = cursor->fences;
-			unsigned int idx = cursor->index++;
-
-			cursor->fence = rcu_dereference(fences->shared[idx]);
 		}
+
+		dma_resv_list_entry(cursor->fences, cursor->index++,
+				    cursor->obj, &cursor->fence,
+				    &cursor->fence_usage);
 		cursor->fence = dma_fence_get_rcu(cursor->fence);
-		if (!cursor->fence || !dma_fence_is_signaled(cursor->fence))
+		if (!cursor->fence) {
+			dma_resv_iter_restart_unlocked(cursor);
+			continue;
+		}
+
+		if (!dma_fence_is_signaled(cursor->fence) &&
+		    cursor->usage >= cursor->fence_usage)
 			break;
 	} while (true);
 }
@@ -387,6 +396,12 @@ static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
  * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj.
  * @cursor: the cursor with the current position
  *
+ * Subsequent fences are iterated with dma_resv_iter_next_unlocked().
+ *
+ * Beware that the iterator can be restarted.  Code which accumulates statistics
+ * or similar needs to check for this with dma_resv_iter_is_restarted(). For
+ * this reason prefer the locked dma_resv_iter_first() whenver possible.
+ *
  * Returns the first fence from an unlocked dma_resv obj.
  */
 struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
@@ -395,7 +410,7 @@ struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
 	do {
 		dma_resv_iter_restart_unlocked(cursor);
 		dma_resv_iter_walk_unlocked(cursor);
-	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+	} while (dma_resv_fences_list(cursor->obj) != cursor->fences);
 	rcu_read_unlock();
 
 	return cursor->fence;
@@ -406,6 +421,10 @@ EXPORT_SYMBOL(dma_resv_iter_first_unlocked);
  * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj.
  * @cursor: the cursor with the current position
  *
+ * Beware that the iterator can be restarted.  Code which accumulates statistics
+ * or similar needs to check for this with dma_resv_iter_is_restarted(). For
+ * this reason prefer the locked dma_resv_iter_next() whenver possible.
+ *
  * Returns the next fence from an unlocked dma_resv obj.
  */
 struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
@@ -414,13 +433,13 @@ struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
 
 	rcu_read_lock();
 	cursor->is_restarted = false;
-	restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
+	restart = dma_resv_fences_list(cursor->obj) != cursor->fences;
 	do {
 		if (restart)
 			dma_resv_iter_restart_unlocked(cursor);
 		dma_resv_iter_walk_unlocked(cursor);
 		restart = true;
-	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+	} while (dma_resv_fences_list(cursor->obj) != cursor->fences);
 	rcu_read_unlock();
 
 	return cursor->fence;
@@ -431,6 +450,8 @@ EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
  * dma_resv_iter_first - first fence from a locked dma_resv object
  * @cursor: cursor to record the current position
  *
+ * Subsequent fences are iterated with dma_resv_iter_next_unlocked().
+ *
  * Return the first fence in the dma_resv object while holding the
  * &dma_resv.lock.
  */
@@ -441,15 +462,9 @@ struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor)
 	dma_resv_assert_held(cursor->obj);
 
 	cursor->index = 0;
-	if (cursor->all_fences)
-		cursor->fences = dma_resv_shared_list(cursor->obj);
-	else
-		cursor->fences = NULL;
-
-	fence = dma_resv_excl_fence(cursor->obj);
-	if (!fence)
-		fence = dma_resv_iter_next(cursor);
+	cursor->fences = dma_resv_fences_list(cursor->obj);
 
+	fence = dma_resv_iter_next(cursor);
 	cursor->is_restarted = true;
 	return fence;
 }
@@ -464,17 +479,22 @@ EXPORT_SYMBOL_GPL(dma_resv_iter_first);
  */
 struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor)
 {
-	unsigned int idx;
+	struct dma_fence *fence;
 
 	dma_resv_assert_held(cursor->obj);
 
 	cursor->is_restarted = false;
-	if (!cursor->fences || cursor->index >= cursor->fences->shared_count)
-		return NULL;
 
-	idx = cursor->index++;
-	return rcu_dereference_protected(cursor->fences->shared[idx],
-					 dma_resv_held(cursor->obj));
+	do {
+		if (!cursor->fences ||
+		    cursor->index >= cursor->fences->num_fences)
+			return NULL;
+
+		dma_resv_list_entry(cursor->fences, cursor->index++,
+				    cursor->obj, &fence, &cursor->fence_usage);
+	} while (cursor->fence_usage > cursor->usage);
+
+	return fence;
 }
 EXPORT_SYMBOL_GPL(dma_resv_iter_next);
 
@@ -489,110 +509,81 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 {
 	struct dma_resv_iter cursor;
 	struct dma_resv_list *list;
-	struct dma_fence *f, *excl;
+	struct dma_fence *f;
 
 	dma_resv_assert_held(dst);
 
 	list = NULL;
-	excl = NULL;
 
-	dma_resv_iter_begin(&cursor, src, true);
+	dma_resv_iter_begin(&cursor, src, DMA_RESV_USAGE_BOOKKEEP);
 	dma_resv_for_each_fence_unlocked(&cursor, f) {
 
 		if (dma_resv_iter_is_restarted(&cursor)) {
 			dma_resv_list_free(list);
-			dma_fence_put(excl);
-
-			if (cursor.shared_count) {
-				list = dma_resv_list_alloc(cursor.shared_count);
-				if (!list) {
-					dma_resv_iter_end(&cursor);
-					return -ENOMEM;
-				}
-
-				list->shared_count = 0;
 
-			} else {
-				list = NULL;
+			list = dma_resv_list_alloc(cursor.num_fences);
+			if (!list) {
+				dma_resv_iter_end(&cursor);
+				return -ENOMEM;
 			}
-			excl = NULL;
+			list->num_fences = 0;
 		}
 
 		dma_fence_get(f);
-		if (dma_resv_iter_is_exclusive(&cursor))
-			excl = f;
-		else
-			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
+		dma_resv_list_set(list, list->num_fences++, f,
+				  dma_resv_iter_usage(&cursor));
 	}
 	dma_resv_iter_end(&cursor);
 
-	write_seqcount_begin(&dst->seq);
-	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
-	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
-	write_seqcount_end(&dst->seq);
-
+	list = rcu_replace_pointer(dst->fences, list, dma_resv_held(dst));
 	dma_resv_list_free(list);
-	dma_fence_put(excl);
-
 	return 0;
 }
 EXPORT_SYMBOL(dma_resv_copy_fences);
 
 /**
- * dma_resv_get_fences - Get an object's shared and exclusive
+ * dma_resv_get_fences - Get an object's fences
  * fences without update side lock held
  * @obj: the reservation object
- * @fence_excl: the returned exclusive fence (or NULL)
- * @shared_count: the number of shared fences returned
- * @shared: the array of shared fence ptrs returned (array is krealloc'd to
- * the required size, and must be freed by caller)
- *
- * Retrieve all fences from the reservation object. If the pointer for the
- * exclusive fence is not specified the fence is put into the array of the
- * shared fences as well. Returns either zero or -ENOMEM.
+ * @usage: controls which fences to include, see enum dma_resv_usage.
+ * @num_fences: the number of fences returned
+ * @fences: the array of fence ptrs returned (array is krealloc'd to the
+ * required size, and must be freed by caller)
+ *
+ * Retrieve all fences from the reservation object.
+ * Returns either zero or -ENOMEM.
  */
-int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl,
-			unsigned int *shared_count, struct dma_fence ***shared)
+int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
+			unsigned int *num_fences, struct dma_fence ***fences)
 {
 	struct dma_resv_iter cursor;
 	struct dma_fence *fence;
 
-	*shared_count = 0;
-	*shared = NULL;
+	*num_fences = 0;
+	*fences = NULL;
 
-	if (fence_excl)
-		*fence_excl = NULL;
-
-	dma_resv_iter_begin(&cursor, obj, true);
+	dma_resv_iter_begin(&cursor, obj, usage);
 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 
 		if (dma_resv_iter_is_restarted(&cursor)) {
 			unsigned int count;
 
-			while (*shared_count)
-				dma_fence_put((*shared)[--(*shared_count)]);
-
-			if (fence_excl)
-				dma_fence_put(*fence_excl);
+			while (*num_fences)
+				dma_fence_put((*fences)[--(*num_fences)]);
 
-			count = cursor.shared_count;
-			count += fence_excl ? 0 : 1;
+			count = cursor.num_fences + 1;
 
 			/* Eventually re-allocate the array */
-			*shared = krealloc_array(*shared, count,
+			*fences = krealloc_array(*fences, count,
 						 sizeof(void *),
 						 GFP_KERNEL);
-			if (count && !*shared) {
+			if (count && !*fences) {
 				dma_resv_iter_end(&cursor);
 				return -ENOMEM;
 			}
 		}
 
-		dma_fence_get(fence);
-		if (dma_resv_iter_is_exclusive(&cursor) && fence_excl)
-			*fence_excl = fence;
-		else
-			(*shared)[(*shared_count)++] = fence;
+		(*fences)[(*num_fences)++] = dma_fence_get(fence);
 	}
 	dma_resv_iter_end(&cursor);
 
@@ -601,10 +592,62 @@ int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl,
 EXPORT_SYMBOL_GPL(dma_resv_get_fences);
 
 /**
- * dma_resv_wait_timeout - Wait on reservation's objects
- * shared and/or exclusive fences.
+ * dma_resv_get_singleton - Get a single fence for all the fences
+ * @obj: the reservation object
+ * @usage: controls which fences to include, see enum dma_resv_usage.
+ * @fence: the resulting fence
+ *
+ * Get a single fence representing all the fences inside the resv object.
+ * Returns either 0 for success or -ENOMEM.
+ *
+ * Warning: This can't be used like this when adding the fence back to the resv
+ * object since that can lead to stack corruption when finalizing the
+ * dma_fence_array.
+ *
+ * Returns 0 on success and negative error values on failure.
+ */
+int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
+			   struct dma_fence **fence)
+{
+	struct dma_fence_array *array;
+	struct dma_fence **fences;
+	unsigned count;
+	int r;
+
+	r = dma_resv_get_fences(obj, usage, &count, &fences);
+        if (r)
+		return r;
+
+	if (count == 0) {
+		*fence = NULL;
+		return 0;
+	}
+
+	if (count == 1) {
+		*fence = fences[0];
+		kfree(fences);
+		return 0;
+	}
+
+	array = dma_fence_array_create(count, fences,
+				       dma_fence_context_alloc(1),
+				       1, false);
+	if (!array) {
+		while (count--)
+			dma_fence_put(fences[count]);
+		kfree(fences);
+		return -ENOMEM;
+	}
+
+	*fence = &array->base;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dma_resv_get_singleton);
+
+/**
+ * dma_resv_wait_timeout - Wait on reservation's objects fences
  * @obj: the reservation object
- * @wait_all: if true, wait on all fences, else wait on just exclusive fence
+ * @usage: controls which fences to include, see enum dma_resv_usage.
  * @intr: if true, do interruptible wait
  * @timeout: timeout value in jiffies or zero to return immediately
  *
@@ -614,14 +657,14 @@ EXPORT_SYMBOL_GPL(dma_resv_get_fences);
  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
  * greater than zer on success.
  */
-long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
-			   unsigned long timeout)
+long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage,
+			   bool intr, unsigned long timeout)
 {
 	long ret = timeout ? timeout : 1;
 	struct dma_resv_iter cursor;
 	struct dma_fence *fence;
 
-	dma_resv_iter_begin(&cursor, obj, wait_all);
+	dma_resv_iter_begin(&cursor, obj, usage);
 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 
 		ret = dma_fence_wait_timeout(fence, intr, ret);
@@ -641,8 +684,7 @@ EXPORT_SYMBOL_GPL(dma_resv_wait_timeout);
  * dma_resv_test_signaled - Test if a reservation object's fences have been
  * signaled.
  * @obj: the reservation object
- * @test_all: if true, test all fences, otherwise only test the exclusive
- * fence
+ * @usage: controls which fences to include, see enum dma_resv_usage.
  *
  * Callers are not required to hold specific locks, but maybe hold
  * dma_resv_lock() already.
@@ -651,12 +693,12 @@ EXPORT_SYMBOL_GPL(dma_resv_wait_timeout);
  *
  * True if all fences signaled, else false.
  */
-bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all)
+bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage)
 {
 	struct dma_resv_iter cursor;
 	struct dma_fence *fence;
 
-	dma_resv_iter_begin(&cursor, obj, test_all);
+	dma_resv_iter_begin(&cursor, obj, usage);
 	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 		dma_resv_iter_end(&cursor);
 		return false;
@@ -676,13 +718,13 @@ EXPORT_SYMBOL_GPL(dma_resv_test_signaled);
  */
 void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq)
 {
+	static const char *usage[] = { "kernel", "write", "read", "bookkeep" };
 	struct dma_resv_iter cursor;
 	struct dma_fence *fence;
 
-	dma_resv_for_each_fence(&cursor, obj, true, fence) {
+	dma_resv_for_each_fence(&cursor, obj, DMA_RESV_USAGE_READ, fence) {
 		seq_printf(seq, "\t%s fence:",
-			   dma_resv_iter_is_exclusive(&cursor) ?
-				"Exclusive" : "Shared");
+			   usage[dma_resv_iter_usage(&cursor)]);
 		dma_fence_describe(fence, seq);
 	}
 }