[PATCH v2] rust: page:: optimize rust symbol generation for Page

[PATCH v2] rust: page:: optimize rust symbol generation for Page

[Kunwu Chan]

From: Kunwu Chan <kunwu.chan@hotmail.com>

When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
with ARCH=arm64, the following symbols are generated:

$nm vmlinux | grep ' _R'.*Page | rustfilt
ffff8000805b6f98 T <kernel::page::Page>::alloc_page
ffff8000805b715c T <kernel::page::Page>::fill_zero_raw
ffff8000805b720c T <kernel::page::Page>::copy_from_user_slice_raw
ffff8000805b6fb4 T <kernel::page::Page>::read_raw
ffff8000805b7088 T <kernel::page::Page>::write_raw
ffff8000805b72fc T <kernel::page::Page as core::ops::drop::Drop>::drop

These Rust symbols(alloc_page and drop) are trivial wrappers around the C
functions alloc_pages and __free_pages. It doesn't make sense to go
through a trivial wrapper for these functions, so mark them inline.

Link: https://github.com/Rust-for-Linux/linux/issues/1145
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>

---
Changes in v2:
- mark inline only for 'alloc_page' and 'drop'
- reword commit msg
---
 rust/kernel/page.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index f6126aca33a6..7c1b17246ed5 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -69,6 +69,7 @@ impl Page {
     /// let page = Page::alloc_page(GFP_KERNEL | __GFP_ZERO)?;
     /// # Ok::<(), kernel::alloc::AllocError>(())
     /// ```
+    #[inline]
     pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
         // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
         // is always safe to call this method.
@@ -251,6 +252,7 @@ pub unsafe fn copy_from_user_slice_raw(
 }
 
 impl Drop for Page {
+    #[inline]
     fn drop(&mut self) {
         // SAFETY: By the type invariants, we have ownership of the page and can free it.
         unsafe { bindings::__free_pages(self.page.as_ptr(), 0) };
-- 
2.43.0

Re: [PATCH v2] rust: page:: optimize rust symbol generation for Page

[Alice Ryhl]

On Fri, Mar 21, 2025 at 9:02 AM Kunwu Chan <kunwu.chan@linux.dev> wrote:
>
> From: Kunwu Chan <kunwu.chan@hotmail.com>
>
> When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
> with ARCH=arm64, the following symbols are generated:
>
> $nm vmlinux | grep ' _R'.*Page | rustfilt
> ffff8000805b6f98 T <kernel::page::Page>::alloc_page
> ffff8000805b715c T <kernel::page::Page>::fill_zero_raw
> ffff8000805b720c T <kernel::page::Page>::copy_from_user_slice_raw
> ffff8000805b6fb4 T <kernel::page::Page>::read_raw
> ffff8000805b7088 T <kernel::page::Page>::write_raw
> ffff8000805b72fc T <kernel::page::Page as core::ops::drop::Drop>::drop
>
> These Rust symbols(alloc_page and drop) are trivial wrappers around the C
> functions alloc_pages and __free_pages. It doesn't make sense to go
> through a trivial wrapper for these functions, so mark them inline.
>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
> Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
> Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v2] rust: page:: optimize rust symbol generation for Page

[Miguel Ojeda]

On Fri, Mar 21, 2025 at 9:02 AM Kunwu Chan <kunwu.chan@linux.dev> wrote:
>
> When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
> with ARCH=arm64, the following symbols are generated:
>
> $nm vmlinux | grep ' _R'.*Page | rustfilt
> ffff8000805b6f98 T <kernel::page::Page>::alloc_page
> ffff8000805b715c T <kernel::page::Page>::fill_zero_raw
> ffff8000805b720c T <kernel::page::Page>::copy_from_user_slice_raw
> ffff8000805b6fb4 T <kernel::page::Page>::read_raw
> ffff8000805b7088 T <kernel::page::Page>::write_raw
> ffff8000805b72fc T <kernel::page::Page as core::ops::drop::Drop>::drop
>
> These Rust symbols(alloc_page and drop) are trivial wrappers around the C
> functions alloc_pages and __free_pages. It doesn't make sense to go
> through a trivial wrapper for these functions, so mark them inline.
>
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
> Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
> Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>

Applied to `rust-next` -- thanks!

    [ Removed spurious colon in title. - Miguel ]

Cheers,
Miguel