From 5a78977262f47dd52a4880689a2ca3d21dbf149a Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Fri, 16 May 2025 19:32:19 +0000 Subject: [PATCH] mm: rust: make CONFIG_MMU ifdefs more narrow Currently the entire kernel::mm module is ifdef'd out when CONFIG_MMU=n. However, there are some downstream users of the module in rust/kernel/task.rs and rust/kernel/miscdevice.rs. Thus, update the cfgs so that only MmWithUserAsync is removed with CONFIG_MMU=n. The code is moved into a new file, since the #[cfg()] annotation otherwise has to be duplicated several times. Link: https://lkml.kernel.org/r/20250516193219.2987032-1-aliceryhl@google.com Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202505071753.kldNHYVQ-lkp@intel.com/ Closes: https://lore.kernel.org/oe-kbuild-all/202505072116.eSYC8igT-lkp@intel.com/ Fixes: 5bb9ed6cdfeb ("mm: rust: add abstraction for struct mm_struct") Signed-off-by: Alice Ryhl Reviewed-by: Boqun Feng Cc: Boqun Feng Cc: Liam Howlett Cc: Lorenzo Stoakes Signed-off-by: Andrew Morton --- rust/kernel/mm.rs | 56 +++-------------------------- rust/kernel/mm/mmput_async.rs | 68 +++++++++++++++++++++++++++++++++++ 2 files changed, 72 insertions(+), 52 deletions(-) create mode 100644 rust/kernel/mm/mmput_async.rs diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs index 615907a0f3b4..43f525c0d16c 100644 --- a/rust/kernel/mm.rs +++ b/rust/kernel/mm.rs @@ -10,7 +10,6 @@ //! control what happens when userspace reads or writes to that region of memory. //! //! C header: [`include/linux/mm.h`](srctree/include/linux/mm.h) -#![cfg(CONFIG_MMU)] use crate::{ bindings, @@ -21,6 +20,10 @@ use core::{ops::Deref, ptr::NonNull}; pub mod virt; use virt::VmaRef; +#[cfg(CONFIG_MMU)] +pub use mmput_async::MmWithUserAsync; +mod mmput_async; + /// A wrapper for the kernel's `struct mm_struct`. /// /// This represents the address space of a userspace process, so each process has one `Mm` @@ -111,50 +114,6 @@ impl Deref for MmWithUser { } } -/// A wrapper for the kernel's `struct mm_struct`. -/// -/// This type is identical to `MmWithUser` except that it uses `mmput_async` when dropping a -/// refcount. This means that the destructor of `ARef` is safe to call in atomic -/// context. -/// -/// # Invariants -/// -/// Values of this type are always refcounted using `mmget`. The value of `mm_users` is non-zero. -#[repr(transparent)] -pub struct MmWithUserAsync { - mm: MmWithUser, -} - -// SAFETY: It is safe to call `mmput_async` on another thread than where `mmget` was called. -unsafe impl Send for MmWithUserAsync {} -// SAFETY: All methods on `MmWithUserAsync` can be called in parallel from several threads. -unsafe impl Sync for MmWithUserAsync {} - -// SAFETY: By the type invariants, this type is always refcounted. -unsafe impl AlwaysRefCounted for MmWithUserAsync { - #[inline] - fn inc_ref(&self) { - // SAFETY: The pointer is valid since self is a reference. - unsafe { bindings::mmget(self.as_raw()) }; - } - - #[inline] - unsafe fn dec_ref(obj: NonNull) { - // SAFETY: The caller is giving up their refcount. - unsafe { bindings::mmput_async(obj.cast().as_ptr()) }; - } -} - -// Make all `MmWithUser` methods available on `MmWithUserAsync`. -impl Deref for MmWithUserAsync { - type Target = MmWithUser; - - #[inline] - fn deref(&self) -> &MmWithUser { - &self.mm - } -} - // These methods are safe to call even if `mm_users` is zero. impl Mm { /// Returns a raw pointer to the inner `mm_struct`. @@ -206,13 +165,6 @@ impl MmWithUser { unsafe { &*ptr.cast() } } - /// Use `mmput_async` when dropping this refcount. - #[inline] - pub fn into_mmput_async(me: ARef) -> ARef { - // SAFETY: The layouts and invariants are compatible. - unsafe { ARef::from_raw(ARef::into_raw(me).cast()) } - } - /// Attempt to access a vma using the vma read lock. /// /// This is an optimistic trylock operation, so it may fail if there is contention. In that diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs new file mode 100644 index 000000000000..9289e05f7a67 --- /dev/null +++ b/rust/kernel/mm/mmput_async.rs @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Version of `MmWithUser` using `mmput_async`. +//! +//! This is a separate file from `mm.rs` due to the dependency on `CONFIG_MMU=y`. +#![cfg(CONFIG_MMU)] + +use crate::{ + bindings, + mm::MmWithUser, + types::{ARef, AlwaysRefCounted}, +}; +use core::{ops::Deref, ptr::NonNull}; + +/// A wrapper for the kernel's `struct mm_struct`. +/// +/// This type is identical to `MmWithUser` except that it uses `mmput_async` when dropping a +/// refcount. This means that the destructor of `ARef` is safe to call in atomic +/// context. +/// +/// # Invariants +/// +/// Values of this type are always refcounted using `mmget`. The value of `mm_users` is non-zero. +#[repr(transparent)] +pub struct MmWithUserAsync { + mm: MmWithUser, +} + +// SAFETY: It is safe to call `mmput_async` on another thread than where `mmget` was called. +unsafe impl Send for MmWithUserAsync {} +// SAFETY: All methods on `MmWithUserAsync` can be called in parallel from several threads. +unsafe impl Sync for MmWithUserAsync {} + +// SAFETY: By the type invariants, this type is always refcounted. +unsafe impl AlwaysRefCounted for MmWithUserAsync { + #[inline] + fn inc_ref(&self) { + // SAFETY: The pointer is valid since self is a reference. + unsafe { bindings::mmget(self.as_raw()) }; + } + + #[inline] + unsafe fn dec_ref(obj: NonNull) { + // SAFETY: The caller is giving up their refcount. + unsafe { bindings::mmput_async(obj.cast().as_ptr()) }; + } +} + +// Make all `MmWithUser` methods available on `MmWithUserAsync`. +impl Deref for MmWithUserAsync { + type Target = MmWithUser; + + #[inline] + fn deref(&self) -> &MmWithUser { + &self.mm + } +} + +impl MmWithUser { + /// Use `mmput_async` when dropping this refcount. + #[inline] + pub fn into_mmput_async(me: ARef) -> ARef { + // SAFETY: The layouts and invariants are compatible. + unsafe { ARef::from_raw(ARef::into_raw(me).cast()) } + } +} -- 2.20.1