Re: [PATCH v3 3/5] mm: introduce VM_FAULT_UFFD_MINOR fault reason

[David Hildenbrand (Red Hat)]

On 11/30/25 12:18, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@xxxxxxxxxx>
>
> When a VMA is registered with userfaulfd in minor mode, its ->fault()
> method should check if a folio exists in the page cache and if yes
> ->fault() should call handle_userfault(VM_UFFD_MINOR).
>
> Instead of calling handle_userfault() directly from a specific ->fault()
> implementation introduce new fault reason VM_FAULT_UFFD_MINOR that will
> notify the core page fault handler that it should call
> handle_userfaultfd(VM_UFFD_MINOR) to complete a page fault.
>
> Replace a call to handle_userfault(VM_UFFD_MINOR) in shmem and use the
> new VM_FAULT_UFFD_MINOR there instead.
>
> For configurations that don't enable CONFIG_USERFAULTFD,
> VM_FAULT_UFFD_MINOR is set to 0.
>
> Suggested-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> ---

LGTM and does not look too invasive for me.

Acked-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>

--
Cheers

David