On Thu, Feb 19, 2026 at 08:17:28AM +0100, Christian König wrote:
>
>
> On 2/18/26 18:14, 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 <[email protected]>
> > ---
> > 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;
> > };
> >
> > 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) {
>
> Since mem_accounting is a module parameter it is possible to make it
> changeable during runtime.
>
> IIRC it currently is read only, but maybe add a one line comment that the cma
> heap now depends on that.
>
Agreed, while read-only it is easily missed without at least a comment.
Alternatively, should that value be captured in the init callback to
guaranty it is set once and make this requirement clearer?
Thanks,
> Apart from that the series looks totally sane to me.
>
> Regards,
> Christian.
>
> > + ret = dmem_cgroup_try_charge(
> > + cma_get_dmem_cgroup_region(cma_heap->cma), size,
> > + &buffer->pool, NULL);
> > + if (ret)
> > + goto free_buffer;
> > + }
> > +
> > cma_pages = cma_alloc(cma_heap->cma, pagecount, align, false);
> > if (!cma_pages)
> > - goto free_buffer;
> > + goto uncharge_cgroup;
> >
> > /* Clear the cma pages */
> > if (PageHighMem(cma_pages)) {
> > @@ -376,6 +387,8 @@ static struct dma_buf *cma_heap_allocate(struct
> > dma_heap *heap,
> > kfree(buffer->pages);
> > free_cma:
> > cma_release(cma_heap->cma, cma_pages, pagecount);
> > +uncharge_cgroup:
> > + dmem_cgroup_uncharge(buffer->pool, size);
> > free_buffer:
> > kfree(buffer);
> >
> >
>
--
Eric Chanudet
