Re: [PATCH v11 6/8] mm: rust: add VmAreaNew for f_ops->mmap()

[Andreas Hindborg <a.hindborg@kernel.org>]

"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>
> ---
>  rust/kernel/mm/virt.rs | 181 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 180 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs
> index 3a23854e14f4..6d9ba56d4f95 100644
> --- a/rust/kernel/mm/virt.rs
> +++ b/rust/kernel/mm/virt.rs

[cut]

> +    /// Returns whether `VM_READ` is set.
> +    ///
> +    /// This flag indicates whether userspace is mapping this vma as readable.
> +    #[inline]
> +    pub fn get_read(&self) -> bool {
> +        (self.flags() & flags::READ) != 0
> +    }

As an afterthought, should we name these getters according to RFC344 [1]
(remove get_ prefix)?


Best regards,
Andreas Hindborg


[1] https://github.com/rust-lang/rfcs/blob/master/text/0344-conventions-galore.md#gettersetter-apis