Re: [PATCH v6 08/39] mm: add mmap action for discontiguous kernel page mapping

["David Hildenbrand (Arm)" <david@kernel.org>]

On 10/13/26 17:04, Lorenzo Stoakes (ARM) wrote:
> The existing kernel page mapping mmap actions allow for partial and full
> mapping of an array of struct page pointers.
> 
> However some drivers require the mapping of discontiguous ranges. Permit
> this by providing discontig_kernel_page_ops which allows a driver to
> specify how the operation should begin and how batches of pages should be
> retrieved.
> 
> It uses the minimum exposed interface to do so, providing address, page
> offset and both vm_private_data state and a local private state object.
> 
> ops->init can establish state for the operation, and ops->get outputs the
> pages to map and their count. Should an error arise the core unmaps the
> VMA, invoking vm_ops->close, which is therefore where any state established
> by ops->init is released.
> 
> Also update the compatibility layer to do this too via
> compat_mmap_action_abort().
> 
> Batches may not exceed the VMA, but may map less than its full range in
> case the driver wishes to allow the user to map an area larger than the
> available data.
> 
> To use it, users invoke mmap_action_map_discontig_kernel_pages() with
> initial local private state and a set of operations.
> 
> Users can then use one of the provided helper functions to perform an
> action:
> 
> * discontig_kernel_map_abort() - Abort and leave the mapping as it has
>   been accumulated so far.
> * discontig_kernel_map_page() - Map a single page, or a compound page given
>   its head page, as 1..N contiguous pages.
> * discontig_kernel_map_pages() - Map a struct page ** array of a specified
>   count, mapping only those pages which fit in the VMA.
> 
> The userland VMA tests are updated accordingly.
> 
> Acked-by: Zi Yan <ziy@nvidia.com>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> ---


[...]

> +
> +int map_discontig_kernel_pages_complete(struct vm_area_struct *vma,
> +					struct mmap_action *action)

... indentation ;)

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David