Re: [RFC PATCH 03/12] staging: android: ion: Duplicate sg_table

[Laura Abbott]

On 03/03/2017 12:18 AM, Hillf Danton wrote:
> 
> On March 03, 2017 5:45 AM Laura Abbott wrote: 
>>
>> +static struct sg_table *dup_sg_table(struct sg_table *table)
>> +{
>> +struct sg_table *new_table;
>> +int ret, i;
>> +struct scatterlist *sg, *new_sg;
>> +
>> +new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
>> +if (!new_table)
>> +return ERR_PTR(-ENOMEM);
>> +
>> +ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
>> +if (ret) {
>> +kfree(table);
> 
> Free new table?
> 
>> +return ERR_PTR(-ENOMEM);
>> +}
>> +
>> +new_sg = new_table->sgl;
>> +for_each_sg(table->sgl, sg, table->nents, i) {
>> +memcpy(new_sg, sg, sizeof(*sg));
>> +sg->dma_address = 0;
>> +new_sg = sg_next(new_sg);
>> +}
>> +
> 
> Do we need a helper, sg_copy_table(dst_table, src_table)?
> 
>> +return new_table;
>> +}
>> +

Yes, that would probably be good since I've seen this
code elsewhere.

Thanks,
Laura

Re: [RFC PATCH 03/12] staging: android: ion: Duplicate sg_table

[Hillf Danton]

On March 03, 2017 5:45 AM Laura Abbott wrote: 
> 
> +static struct sg_table *dup_sg_table(struct sg_table *table)
> +{
> + struct sg_table *new_table;
> + int ret, i;
> + struct scatterlist *sg, *new_sg;
> +
> + new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
> + if (!new_table)
> + return ERR_PTR(-ENOMEM);
> +
> + ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
> + if (ret) {
> + kfree(table);

Free new table?

> + return ERR_PTR(-ENOMEM);
> + }
> +
> + new_sg = new_table->sgl;
> + for_each_sg(table->sgl, sg, table->nents, i) {
> + memcpy(new_sg, sg, sizeof(*sg));
> + sg->dma_address = 0;
> + new_sg = sg_next(new_sg);
> + }
> +

Do we need a helper, sg_copy_table(dst_table, src_table)?

> + return new_table;
> +}
> +

[RFC PATCH 03/12] staging: android: ion: Duplicate sg_table

[Laura Abbott]

Ion currently returns a single sg_table on each dma_map call. This is
incorrect for later usage.

Signed-off-by: Laura Abbott 
---
 drivers/staging/android/ion/ion.c | 30 +-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ion/ion.c 
b/drivers/staging/android/ion/ion.c
index 94a498e..ce4adac 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -799,6 +799,32 @@ static void ion_buffer_sync_for_device(struct ion_buffer 
*buffer,
   struct device *dev,
   enum dma_data_direction direction);
 
+static struct sg_table *dup_sg_table(struct sg_table *table)
+{
+   struct sg_table *new_table;
+   int ret, i;
+   struct scatterlist *sg, *new_sg;
+
+   new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
+   if (!new_table)
+   return ERR_PTR(-ENOMEM);
+
+   ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
+   if (ret) {
+   kfree(table);
+   return ERR_PTR(-ENOMEM);
+   }
+
+   new_sg = new_table->sgl;
+   for_each_sg(table->sgl, sg, table->nents, i) {
+   memcpy(new_sg, sg, sizeof(*sg));
+   sg->dma_address = 0;
+   new_sg = sg_next(new_sg);
+   }
+
+   return new_table;
+}
+
 static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment,
enum dma_data_direction direction)
 {
@@ -806,13 +832,15 @@ static struct sg_table *ion_map_dma_buf(struct 
dma_buf_attachment *attachment,
struct ion_buffer *buffer = dmabuf->priv;
 
ion_buffer_sync_for_device(buffer, attachment->dev, direction);
-   return buffer->sg_table;
+   return dup_sg_table(buffer->sg_table);
 }
 
 static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment,
  struct sg_table *table,
  enum dma_data_direction direction)
 {
+   sg_free_table(table);
+   kfree(table);
 }
 
 void ion_pages_sync_for_device(struct device *dev, struct page *page,
-- 
2.7.4