Re: [PATCH v12 6/8] mm: rust: add VmAreaNew for f_ops->mmap()

Andreas Hindborg
2025-01-20T13:58:59Z

"Alice Ryhl" <aliceryhl@google.com> writes:

> This type will be used when setting up a new vma in an f_ops->mmap()
> hook. Using a separate type from VmAreaRef allows us to have a separate
> set of operations that you are only able to use during the mmap() hook.
> For example, the VM_MIXEDMAP flag must not be changed after the initial
> setup that happens during the f_ops->mmap() hook.
>
> To avoid setting invalid flag values, the methods for clearing
> VM_MAYWRITE and similar involve a check of VM_WRITE, and return an error
> if VM_WRITE is set. Trying to use `try_clear_maywrite` without checking
> the return value results in a compilation error because the `Result`
> type is marked #[must_use].
>
> For now, there's only a method for VM_MIXEDMAP and not VM_PFNMAP. When
> we add a VM_PFNMAP method, we will need some way to prevent you from
> setting both VM_MIXEDMAP and VM_PFNMAP on the same vma.
>
> Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> (for mm bits)
> Reviewed-by: Jann Horn <jannh@google.com>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>

Best regards,
Andreas Hindborg