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SubjectRe: [PATCH v6 2/5] dma-buf: heaps: Add heap helpers
> +void INIT_HEAP_HELPER_BUFFER(struct heap_helper_buffer *buffer,
> + void (*free)(struct heap_helper_buffer *))

Please use a lower case naming following the naming scheme for the
rest of the file.

> +static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer)
> +{
> + void *vaddr;
> +
> + vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL);
> + if (!vaddr)
> + return ERR_PTR(-ENOMEM);
> +
> + return vaddr;
> +}

Unless I'm misreading the patches this is used for the same pages that
also might be dma mapped. In this case you need to use
flush_kernel_vmap_range and invalidate_kernel_vmap_range in the right
places to ensure coherency between the vmap and device view. Please
also document the buffer ownership, as this really can get complicated.

> +static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
> +{
> + struct vm_area_struct *vma = vmf->vma;
> + struct heap_helper_buffer *buffer = vma->vm_private_data;
> +
> + vmf->page = buffer->pages[vmf->pgoff];
> + get_page(vmf->page);
> +
> + return 0;
> +}

Is there any exlusion between mmap / vmap and the device accessing
the data? Without that you are going to run into a lot of coherency
problems.

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