staging: android: ion: use the manged version of DMA memory allocation

From: Hari Prasath Gujulan Elango <[email protected]>

Use the managed version of the dma_alloc_coherent() i.e. the dmam_alloc_coherent() & accordingly cleanup the error handling part.Also,remove the references to dma_free_coherent

Signed-off-by Hari Prasath Gujulan Elango <[email protected]>

---
v2:kbuild test robot reported warnings on ununsed
variables.Those warnings are fixed.

---
  drivers/staging/android/ion/ion_cma_heap.c | 11 ++---------
  1 file changed, 2 insertions(+), 9 deletions(-)

drivers/staging/android/ion/ion_cma_heap.c +2 -9

index a3446da..8cd720b 100644
@@ -61,7 +61,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
  	if (!info)
  		return ION_CMA_ALLOCATE_FAILED;
 
-	info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle),
+	info->cpu_addr = dmam_alloc_coherent(dev, len, &(info->handle),
  						GFP_HIGHUSER | __GFP_ZERO);
 
  	if (!info->cpu_addr) {

@@ -71,7 +71,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
  	info->table = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
  	if (!info->table)
-		goto free_mem;
+		goto err;
 
  	if (dma_get_sgtable(dev, info->table, info->cpu_addr, info->handle,
  			    len))

@@ -83,8 +83,6 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
  free_table:
  	kfree(info->table);
-free_mem:
-	dma_free_coherent(dev, len, info->cpu_addr, info->handle);
  err:
  	kfree(info);
  	return ION_CMA_ALLOCATE_FAILED;

@@ -92,13 +90,8 @@ err:
 
  static void ion_cma_free(struct ion_buffer *buffer)
  {
-	struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);
-	struct device *dev = cma_heap->dev;
  	struct ion_cma_buffer_info *info = buffer->priv_virt;
 
-	dev_dbg(dev, "Release buffer %p\n", buffer);
-	/* release memory */
-	dma_free_coherent(dev, buffer->size, info->cpu_addr, info->handle);
  	/* release sg table */
  	sg_free_table(info->table);
  	kfree(info->table);

Quoted 5 lines · Hari Prasath (H.)

From: Hari Prasath Gujulan Elango <[email protected]>

Use the managed version of the dma_alloc_coherent() i.e. the dmam_alloc_coherent() & accordingly cleanup the error handling part.Also,remove the references to dma_free_coherent

That last aspect looks a bit off to me - the heaps don't seem to be something that exist for the lifetime of the ION "device", given that these are specific runtime alloc and free calls, rather than the probe and remove routines. I don't know if CMA heaps are among those which ION creates and destroys frequently (enough that it apparently kicks off a whole background thread to manage the freeing), but this looks like a recipe for leaks. If the free call doesn't actually free the buffer, it's going to remain hanging around consuming precious CMA area until the ION device itself is torn down, which is likely never.

I wouldn't say it's necessarily inappropriate to use managed DMA resources here to cover unexpected failure cases for the ION device itself (I see the comment in ion_device_remove()), but that means still using dmam_free_coherent() when naturally releasing allocations for other reasons (i.e. both cases here). Think Java finalisers, rather than C++ destructors.

Robin.

Quoted 54 lines

Signed-off-by Hari Prasath Gujulan Elango <[email protected]>

---
v2:kbuild test robot reported warnings on ununsed
variables.Those warnings are fixed.

---
  drivers/staging/android/ion/ion_cma_heap.c | 11 ++---------
  1 file changed, 2 insertions(+), 9 deletions(-)

drivers/staging/android/ion/ion_cma_heap.c +2 -9

index a3446da..8cd720b 100644
@@ -61,7 +61,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
      if (!info)
          return ION_CMA_ALLOCATE_FAILED;
 
-    info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle),
+    info->cpu_addr = dmam_alloc_coherent(dev, len, &(info->handle),
                          GFP_HIGHUSER | __GFP_ZERO);
 
      if (!info->cpu_addr) {

@@ -71,7 +71,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
      info->table = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
      if (!info->table)
-        goto free_mem;
+        goto err;
 
      if (dma_get_sgtable(dev, info->table, info->cpu_addr, info->handle,
                  len))

@@ -83,8 +83,6 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
  free_table:
      kfree(info->table);
-free_mem:
-    dma_free_coherent(dev, len, info->cpu_addr, info->handle);
  err:
      kfree(info);
      return ION_CMA_ALLOCATE_FAILED;

@@ -92,13 +90,8 @@ err:
 
  static void ion_cma_free(struct ion_buffer *buffer)
  {
-    struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);
-    struct device *dev = cma_heap->dev;
      struct ion_cma_buffer_info *info = buffer->priv_virt;
 
-    dev_dbg(dev, "Release buffer %p\n", buffer);
-    /* release memory */
-    dma_free_coherent(dev, buffer->size, info->cpu_addr, info->handle);
      /* release sg table */
      sg_free_table(info->table);
      kfree(info->table);

Quoted 7 lines · Robin Murphy

Quoted 5 lines · Hari Prasath (H.)

From: Hari Prasath Gujulan Elango <[email protected]>

Use the managed version of the dma_alloc_coherent() i.e. the dmam_alloc_coherent() & accordingly cleanup the error handling part.Also,remove the references to dma_free_coherent

Quoted 6 lines

That last aspect looks a bit off to me - the heaps don't seem to be something that exist for the lifetime of the ION "device", given that these are specific runtime alloc and free calls, rather than the probe and remove routines. I don't know if CMA heaps are among those which ION creates and destroys frequently (enough that it apparently kicks off a whole background thread to manage the freeing), but this looks like a recipe for leaks. If the free call doesn't actually free the buffer, it's going to remain hanging around consuming precious CMA area until the ION device itself is torn down, which is likely never.

I wouldn't say it's necessarily inappropriate to use managed DMA resources here to cover unexpected failure cases for the ION device itself (I see the comment in ion_device_remove()), but that means still using dmam_free_coherent() when naturally releasing allocations for other reasons (i.e. both cases here). Think Java finalisers, rather than C++ destructors.

Robin.

Yes, Robin is correct. These allocations are not tied to the lifetime of the device so it is incorrect to move to the manged APIs. The dma_alloc_coherent allocations are done on request.

Ion isn't a good candidate to look at to switch APIs over to the devm interface since it does many things in a non-standard way. You should probably focus devm efforts outside of Ion (although if you find a potential patch I'll certainly review it)

Thanks,
Laura

Quoted 55 lines

Quoted 54 lines

Signed-off-by Hari Prasath Gujulan Elango <[email protected]>

---
v2:kbuild test robot reported warnings on ununsed
variables.Those warnings are fixed.

---
 drivers/staging/android/ion/ion_cma_heap.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

drivers/staging/android/ion/ion_cma_heap.c +2 -9

index a3446da..8cd720b 100644
@@ -61,7 +61,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
     if (!info)
         return ION_CMA_ALLOCATE_FAILED;
 
-    info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle),
+    info->cpu_addr = dmam_alloc_coherent(dev, len, &(info->handle),
                         GFP_HIGHUSER | __GFP_ZERO);
 
     if (!info->cpu_addr) {

@@ -71,7 +71,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
     info->table = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
     if (!info->table)
-        goto free_mem;
+        goto err;
 
     if (dma_get_sgtable(dev, info->table, info->cpu_addr, info->handle,
                 len))

@@ -83,8 +83,6 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
 free_table:
     kfree(info->table);
-free_mem:
-    dma_free_coherent(dev, len, info->cpu_addr, info->handle);
 err:
     kfree(info);
     return ION_CMA_ALLOCATE_FAILED;

@@ -92,13 +90,8 @@ err:
 
 static void ion_cma_free(struct ion_buffer *buffer)
 {
-    struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);
-    struct device *dev = cma_heap->dev;
     struct ion_cma_buffer_info *info = buffer->priv_virt;
 
-    dev_dbg(dev, "Release buffer %p\n", buffer);
-    /* release memory */
-    dma_free_coherent(dev, buffer->size, info->cpu_addr, info->handle);
     /* release sg table */
     sg_free_table(info->table);
     kfree(info->table);