On Tue, Apr 22, 2025 at 1:24 AM Christian König christian.koenig@amd.com wrote:

Am 17.04.25 um 20:09 schrieb T.J. Mercier:

...

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

I'm not *that* expert for this code, but looks totally reasonable to me.

I noticed this while reviewing Maxime Ripard's recent carveout heap patches, where I was confused about sg_free_table() until I realized it doesn't free the underlying allocation. Then I started looking at other heaps and found that most of them do it this way (including the cma heap), and figured it was a nice cleanup here.

Reviewed-by: Christian König christian.koenig@amd.com

Let me know if I should push that to drm-misc-next.

Regards, Christian.

Thanks, yes please!

...

---

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