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rust: page:: optimize rust symbol generation for Page

PATCH Applied Kunwu Chan 3 participants 3 messages Mar 21, 2025 – May 12, 2025

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Rust Memory management - Rust
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Kunwu Chan

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#0 lore raw

PATCH v2 1/1 rust: page:: optimize rust symbol generation for Page

From: Kunwu Chan <[email protected]>

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 <[email protected]>
Co-developed-by Grace Deng <[email protected]>
Signed-off-by Grace Deng <[email protected]>
Signed-off-by Kunwu Chan <[email protected]>

---
Changes in v2:
- mark inline only for 'alloc_page' and 'drop'
- reword commit msg

---
 rust/kernel/page.rs | 2 ++
 1 file changed, 2 insertions(+)
rust/kernel/page.rs +2 -0
index f6126aca33a6..7c1b17246ed5 100644
@@ -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) };
Signature · 1 line
2.43.0
maintainer Reviewed-by on v2 1/1
#1 lore raw
Quoted 18 lines · Kunwu Chan

From: Kunwu Chan <[email protected]>

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.

Quoted 5 lines
Link https://github.com/Rust-for-Linux/linux/issues/1145
Suggested-by Alice Ryhl <[email protected]>
Co-developed-by Grace Deng <[email protected]>
Signed-off-by Grace Deng <[email protected]>
Signed-off-by Kunwu Chan <[email protected]>
Reviewed-by Alice Ryhl <[email protected]>
Applied
#2 lore raw
In reply to Kunwu Chan
Quoted 16 lines · Kunwu Chan

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.

Quoted 5 lines
Link https://github.com/Rust-for-Linux/linux/issues/1145
Suggested-by Alice Ryhl <[email protected]>
Co-developed-by Grace Deng <[email protected]>
Signed-off-by Grace Deng <[email protected]>
Signed-off-by Kunwu Chan <[email protected]>

Applied to rust-next -- thanks!

[ Removed spurious colon in title. - Miguel ]

Cheers,
Miguel