Re: [PATCH v2 3/3] dma-buf: heaps: cma: charge each cma heap's dmem

[Eric Chanudet <echanude@redhat.com>]

On Thu, Feb 19, 2026 at 10:16:37AM +0100, Maxime Ripard wrote:
> Hi,
> 
> On Wed, Feb 18, 2026 at 12:14:12PM -0500, Eric Chanudet wrote:
> > The cma dma-buf heaps let userspace allocate buffers in CMA regions
> > without enforcing limits. Since each cma region registers in dmem,
> > charge against it when allocating a buffer in a cma heap.
> > 
> > Signed-off-by: Eric Chanudet <echanude@redhat.com>
> > ---
> >  drivers/dma-buf/heaps/cma_heap.c | 15 ++++++++++++++-
> >  1 file changed, 14 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> > index 49cc45fb42dd7200c3c14384bcfdbe85323454b1..bbd4f9495808da19256d97bd6a4dca3e1b0a30a0 100644
> > --- a/drivers/dma-buf/heaps/cma_heap.c
> > +++ b/drivers/dma-buf/heaps/cma_heap.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/scatterlist.h>
> >  #include <linux/slab.h>
> >  #include <linux/vmalloc.h>
> > +#include <linux/cgroup_dmem.h>
> >  
> >  #define DEFAULT_CMA_NAME "default_cma_region"
> >  
> > @@ -58,6 +59,7 @@ struct cma_heap_buffer {
> >  	pgoff_t pagecount;
> >  	int vmap_cnt;
> >  	void *vaddr;
> > +	struct dmem_cgroup_pool_state *pool;
> 
> I guess we should add an #if IS_ENABLED #endif guard for dmem?
> 

Sure, I saw the other user (ttm) didn't, but that makes sense as the
field is useless if dmem is not enabled.

> >  };
> >  
> >  struct dma_heap_attachment {
> > @@ -276,6 +278,7 @@ static void cma_heap_dma_buf_release(struct dma_buf *dmabuf)
> >  	kfree(buffer->pages);
> >  	/* release memory */
> >  	cma_release(cma_heap->cma, buffer->cma_pages, buffer->pagecount);
> > +	dmem_cgroup_uncharge(buffer->pool, buffer->len);
> >  	kfree(buffer);
> >  }
> >  
> > @@ -319,9 +322,17 @@ static struct dma_buf *cma_heap_allocate(struct dma_heap *heap,
> >  	if (align > CONFIG_CMA_ALIGNMENT)
> >  		align = CONFIG_CMA_ALIGNMENT;
> >  
> > +	if (mem_accounting) {
> > +		ret = dmem_cgroup_try_charge(
> > +			cma_get_dmem_cgroup_region(cma_heap->cma), size,
> > +			&buffer->pool, NULL);
> 
> This alone doesn't call for a new version, but adhering to the kernel
> coding style would look like this:
> 
> +		ret = dmem_cgroup_try_charge(cma_get_dmem_cgroup_region(cma_heap->cma),
> +					     size, &buffer->pool, NULL);

Will add to v3 with the other changes.

Thanks,

> 
> It looks good to me otherwise,
> Acked-by: Maxime Ripard <mripard@kernel.org>
> 
> Maxime



-- 
Eric Chanudet