[PATCH] dma-buf: system_heap: No separate allocation for attachment sg_tables

["T.J. Mercier" <tjmercier@google.com>]

struct dma_heap_attachment is a separate allocation from the struct
sg_table it contains, but there is no reason for this. Let's use the
slab allocator just once instead of twice for dma_heap_attachment.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
 drivers/dma-buf/heaps/system_heap.c | 43 ++++++++++++-----------------
 1 file changed, 17 insertions(+), 26 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 26d5dc89ea16..bee10c400cf0 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -35,7 +35,7 @@ struct system_heap_buffer {
 
 struct dma_heap_attachment {
 	struct device *dev;
-	struct sg_table *table;
+	struct sg_table table;
 	struct list_head list;
 	bool mapped;
 };
@@ -54,29 +54,22 @@ static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
 static const unsigned int orders[] = {8, 4, 0};
 #define NUM_ORDERS ARRAY_SIZE(orders)
 
-static struct sg_table *dup_sg_table(struct sg_table *table)
+static int dup_sg_table(struct sg_table *from, struct sg_table *to)
 {
-	struct sg_table *new_table;
-	int ret, i;
 	struct scatterlist *sg, *new_sg;
+	int ret, i;
 
-	new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
-	if (!new_table)
-		return ERR_PTR(-ENOMEM);
-
-	ret = sg_alloc_table(new_table, table->orig_nents, GFP_KERNEL);
-	if (ret) {
-		kfree(new_table);
-		return ERR_PTR(-ENOMEM);
-	}
+	ret = sg_alloc_table(to, from->orig_nents, GFP_KERNEL);
+	if (ret)
+		return ret;
 
-	new_sg = new_table->sgl;
-	for_each_sgtable_sg(table, sg, i) {
+	new_sg = to->sgl;
+	for_each_sgtable_sg(from, sg, i) {
 		sg_set_page(new_sg, sg_page(sg), sg->length, sg->offset);
 		new_sg = sg_next(new_sg);
 	}
 
-	return new_table;
+	return 0;
 }
 
 static int system_heap_attach(struct dma_buf *dmabuf,
@@ -84,19 +77,18 @@ static int system_heap_attach(struct dma_buf *dmabuf,
 {
 	struct system_heap_buffer *buffer = dmabuf->priv;
 	struct dma_heap_attachment *a;
-	struct sg_table *table;
+	int ret;
 
 	a = kzalloc(sizeof(*a), GFP_KERNEL);
 	if (!a)
 		return -ENOMEM;
 
-	table = dup_sg_table(&buffer->sg_table);
-	if (IS_ERR(table)) {
+	ret = dup_sg_table(&buffer->sg_table, &a->table);
+	if (ret) {
 		kfree(a);
-		return -ENOMEM;
+		return ret;
 	}
 
-	a->table = table;
 	a->dev = attachment->dev;
 	INIT_LIST_HEAD(&a->list);
 	a->mapped = false;
@@ -120,8 +112,7 @@ static void system_heap_detach(struct dma_buf *dmabuf,
 	list_del(&a->list);
 	mutex_unlock(&buffer->lock);
 
-	sg_free_table(a->table);
-	kfree(a->table);
+	sg_free_table(&a->table);
 	kfree(a);
 }
 
@@ -129,7 +120,7 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac
 						enum dma_data_direction direction)
 {
 	struct dma_heap_attachment *a = attachment->priv;
-	struct sg_table *table = a->table;
+	struct sg_table *table = &a->table;
 	int ret;
 
 	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
@@ -164,7 +155,7 @@ static int system_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
 	list_for_each_entry(a, &buffer->attachments, list) {
 		if (!a->mapped)
 			continue;
-		dma_sync_sgtable_for_cpu(a->dev, a->table, direction);
+		dma_sync_sgtable_for_cpu(a->dev, &a->table, direction);
 	}
 	mutex_unlock(&buffer->lock);
 
@@ -185,7 +176,7 @@ static int system_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
 	list_for_each_entry(a, &buffer->attachments, list) {
 		if (!a->mapped)
 			continue;
-		dma_sync_sgtable_for_device(a->dev, a->table, direction);
+		dma_sync_sgtable_for_device(a->dev, &a->table, direction);
 	}
 	mutex_unlock(&buffer->lock);
 

base-commit: 8ffd015db85fea3e15a77027fda6c02ced4d2444
-- 
2.49.0.805.g082f7c87e0-goog