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

[Alice Ryhl <aliceryhl@google.com>]

On Thu, Jan 9, 2025 at 9:23 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> "Alice Ryhl" <aliceryhl@google.com> writes:
>
> > On Tue, Dec 17, 2024 at 10:31 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
> >>
> >> "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)?
> >
> > Well, perhaps is_readable?
>
> Why not just `readable() -> bool`? That would match the guidelines.

I guess that could work.

Alice