Merge tag 'mm-stable-2025-06-01-14-06' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more MM updates from Andrew Morton:

 - "zram: support algorithm-specific parameters" from Sergey Senozhatsky
   adds infrastructure for passing algorithm-specific parameters into
   zram. A single parameter `winbits' is implemented at this time.

 - "memcg: nmi-safe kmem charging" from Shakeel Butt makes memcg
   charging nmi-safe, which is required by BFP, which can operate in NMI
   context.

 - "Some random fixes and cleanup to shmem" from Kemeng Shi implements
   small fixes and cleanups in the shmem code.

 - "Skip mm selftests instead when kernel features are not present" from
   Zi Yan fixes some issues in the MM selftest code.

 - "mm/damon: build-enable essential DAMON components by default" from
   SeongJae Park reworks DAMON Kconfig to make it easier to enable
   CONFIG_DAMON.

 - "sched/numa: add statistics of numa balance task migration" from Libo
   Chen adds more info into sysfs and procfs files to improve visibility
   into the NUMA balancer's task migration activity.

 - "selftests/mm: cow and gup_longterm cleanups" from Mark Brown
   provides various updates to some of the MM selftests to make them
   play better with the overall containing framework.

* tag 'mm-stable-2025-06-01-14-06' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (43 commits)
  mm/khugepaged: clean up refcount check using folio_expected_ref_count()
  selftests/mm: fix test result reporting in gup_longterm
  selftests/mm: report unique test names for each cow test
  selftests/mm: add helper for logging test start and results
  selftests/mm: use standard ksft_finished() in cow and gup_longterm
  selftests/damon/_damon_sysfs: skip testcases if CONFIG_DAMON_SYSFS is disabled
  sched/numa: add statistics of numa balance task
  sched/numa: fix task swap by skipping kernel threads
  tools/testing: check correct variable in open_procmap()
  tools/testing/vma: add missing function stub
  mm/gup: update comment explaining why gup_fast() disables IRQs
  selftests/mm: two fixes for the pfnmap test
  mm/khugepaged: fix race with folio split/free using temporary reference
  mm: add CONFIG_PAGE_BLOCK_ORDER to select page block order
  mmu_notifiers: remove leftover stub macros
  selftests/mm: deduplicate test names in madv_populate
  kcov: rust: add flags for KCOV with Rust
  mm: rust: make CONFIG_MMU ifdefs more narrow
  mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free_pgtables()
  mm/damon/Kconfig: enable CONFIG_DAMON by default
  ...

1 files changed, 4 insertions, 52 deletions

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<MmWithUserAsync>` 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<Self>) {
-        // 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<MmWithUser>) -> ARef<MmWithUserAsync> {
-        // 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