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Implement the stray marking in PT to ensure serializability

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This commit is contained in:
Zhang Junyang
2025-03-24 11:58:03 +08:00
committed by Tate, Hongliang Tian
parent 5b7637eac3
commit 54fbdcf059
10 changed files with 167 additions and 126 deletions
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17
ostd/src/mm/page_table/node/mod.rs
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@ -191,6 +191,12 @@ impl<'a, E: PageTableEntryTrait, C: PagingConstsTrait> PageTableGuard<'a, E, C>
unsafe { *self.meta().nr_children.get() }
}
/// Returns if the page table node is detached from its parent.
pub(super) fn stray_mut(&mut self) -> &mut bool {
// SAFETY: The lock is held so we have an exclusive access.
unsafe { &mut *self.meta().stray.get() }
}
/// Reads a non-owning PTE at the given index.
///
/// A non-owning PTE means that it does not account for a reference count
@ -258,6 +264,12 @@ impl<E: PageTableEntryTrait, C: PagingConstsTrait> Drop for PageTableGuard<'_, E
pub(in crate::mm) struct PageTablePageMeta<E: PageTableEntryTrait, C: PagingConstsTrait> {
/// The number of valid PTEs. It is mutable if the lock is held.
pub nr_children: SyncUnsafeCell<u16>,
/// If the page table is detached from its parent.
///
/// A page table can be detached from its parent while still being accessed,
/// since we use a RCU scheme to recycle page tables. If this flag is set,
/// it means that the parent is recycling the page table.
pub stray: SyncUnsafeCell<bool>,
/// The level of the page table page. A page table page cannot be
/// referenced by page tables of different levels.
pub level: PagingLevel,
@ -288,6 +300,7 @@ impl<E: PageTableEntryTrait, C: PagingConstsTrait> PageTablePageMeta<E, C> {
pub fn new(level: PagingLevel, is_tracked: MapTrackingStatus) -> Self {
Self {
nr_children: SyncUnsafeCell::new(0),
stray: SyncUnsafeCell::new(false),
level,
lock: AtomicU8::new(0),
is_tracked,
@ -296,8 +309,8 @@ impl<E: PageTableEntryTrait, C: PagingConstsTrait> PageTablePageMeta<E, C> {
}
}
// SAFETY: The layout of the `PageTablePageMeta` is ensured to be the same for
// all possible generic parameters. And the layout fits the requirements.
// SAFETY: We can read the page table node because the page table pages are
// accessed as untyped memory.
unsafe impl<E: PageTableEntryTrait, C: PagingConstsTrait> AnyFrameMeta for PageTablePageMeta<E, C> {
fn on_drop(&mut self, reader: &mut VmReader<Infallible>) {
let nr_children = self.nr_children.get_mut();