On Mon Dec 15, 2025 at 5:34 PM JST, Brendan Shephard wrote:
> Use page::page_align for GEM object memory allocation to ensure the
> allocation is page aligned. This is important on systems where the
> default page size is not 4k. Such as 16k or 64k aarch64 systems.
>
> This change uses the updated page_align() function which returns
> Option<usize> for overflow safety. (See "rust: Return Option from
> page_align and ensure no usize overflow").
>
> Signed-off-by: Brendan Shephard <[email protected]>
> ---
> Changes in v2:
> - Updated to use the new page_align() Option<usize> return value
> - Prerequisite patch:
>
> https://lore.kernel.org/rust-for-linux/[email protected]/T/#u
> - Link to v1:
> https://lore.kernel.org/rust-for-linux/[email protected]/
>
> Changes in v3:
> - Add back missing semi-colon after ok_or().
> - Reword commit message to be more concise.
> - Link to v2:
> https://lore.kernel.org/rust-for-linux/[email protected]/T/#u
>
> Changes in v4:
> - Add back the size == 0 check;
> - Rebase on latest drm-next branch
> - Link to v3:
> https://lore.kernel.org/rust-for-linux/[email protected]/T/#u
>
> drivers/gpu/drm/nova/gem.rs | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
> index 2760ba4f3450..3a3a41e8d4bc 100644
> --- a/drivers/gpu/drm/nova/gem.rs
> +++ b/drivers/gpu/drm/nova/gem.rs
> @@ -3,6 +3,7 @@
> use kernel::{
> drm,
> drm::{gem, gem::BaseObject},
> + page::page_align,
> prelude::*,
> sync::aref::ARef,
> };
> @@ -27,11 +28,10 @@ fn new(_dev: &NovaDevice, _size: usize) -> impl
> PinInit<Self, Error> {
> impl NovaObject {
> /// Create a new DRM GEM object.
> pub(crate) fn new(dev: &NovaDevice, size: usize) ->
> Result<ARef<gem::Object<Self>>> {
> - let aligned_size = size.next_multiple_of(1 << 12);
> -
> - if size == 0 || size > aligned_size {
> + if size == 0 {
> return Err(EINVAL);
> }
> + let aligned_size = page_align(size).ok_or(EINVAL)?;
nit, but it's a good practice to always leave an empty line before a
block of variable declarations.
>
> gem::Object::new(dev, aligned_size)
... or if you prefer to avoid the variable altogether:
page_align(size)
.ok_or(EINVAL)
.and_then(|size| gem::Object::new(dev, size))
