[PATCH v6 30/39] mm/vma: introduce vma[_flags]_is_mm_backed()

[David Hildenbrand (Arm)]

On 10/13/26 17:05, Lorenzo Stoakes (ARM) wrote:
> Introduce vma[_flags]_is_mm_backed() for the purposes of identifying
> mappings which are mm-managed and whose contents were placed there by core
> mm's own fault path - rather than a custom ->fault handler.
> 
> Mappings not managed by core mm do not fall into this category, as they are
> populated by their owner, and nor of course does memory-mapped I/O.
> 
> We exclude fixed mappings as these have a layout core mm cannot assume
> ordinary fault semantics over.
> 
> hugetlb mappings are fixed mappings, but core mm owns them entirely, so
> they are explicitly carved out as mm-backed, as the MADV_DODUMP check
> already does.
> 
> Use this functionality to update the madvise MADV_DODUMP check to test for
> this rather than open-coding it.
> 
> Also update vma_flags_can_merge() so it is written in terms of
> vma_flags_is_mm_backed() - all mm-backed mappings can be merged except
> hugetlb mappings, whose flags and fields do not completely describe them.
> 
> Also update __thp_vma_allowable_orders() to use vma_is_mm_backed() rather
> than testing for mergeability, which is irrelevant to this function.
> 
> This replaces the VM_SPECIAL check which means it no longer checks for
> VMA_IO_BIT, however this is safe as we have established the invariant that
> mm-managed mappings may not set VMA_IO_BIT, so we implicitly include
> these.
> 
> No functional change intended.
> 
> Acked-by: Zi Yan <ziy at nvidia.com>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
> ---

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

-- 
Cheers,

David