Re: [PATCH v3 15/40] mm/vma: add vma[_flags]_is_kernel_owned() predicates

[Zi Yan]

On Thu Sep 17, 2026 at 12:22 PM EDT, Lorenzo Stoakes (ARM) wrote:
> Rather than referring to VMA flags with uncertain meaning, add a new
> predicate that explicitly describes what possession of the VMA_PFNMAP_BIT
> or VMA_MIXEDMAP_BIT flags mean, and then refer to that function for
> determining VMA mergeability.
>
> Either flag means the contents of the mapping are owned by the kernel,
> usually a driver, rather than by the core mm: the memory may be MMIO,
> kernel-allocated pages or even ordinary pages the driver maps itself, but
> the core must not populate, reclaim, migrate, copy-on-write or merge the
> range on its own initiative.
>
> We initially also include VMA_IO_BIT here, as by implication, these must be
> kernel-owned. (mlock() also sets VMA_IO_BIT transiently on ordinary VMAs
> while locking them, which is addressed later in this series.)
>
> However the intent is to in future remove this, as no mapping should be
> marked as an I/O mapping without also being marked with VMA_PFNMAP_BIT.
>
> This forms the basis of further work intended to improve how we express VMA
> properties such as this.
>
> Also update the VMA userland tests to reflect the change.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  include/linux/mm.h              | 56 ++++++++++++++++++++++++++++++++++++++++-
>  tools/testing/vma/include/dup.h | 29 ++++++++++++++++++++-
>  2 files changed, 83 insertions(+), 2 deletions(-)
>

LGTM.

Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>


-- 
Best Regards,
Yan, Zi