From a0ec6873157136d0b4ce053d62f9dd712b85ee4f Mon Sep 17 00:00:00 2001
From: rikosellic <wanxinyi825@gmail.com>
Date: Fri, 30 Aug 2024 17:32:50 +0800
Subject: [PATCH] Page::inc_ref_count conforms to the reference counting
 invariant

format code

Add detailed annotations

Typo fixed
---
 ostd/src/mm/page/mod.rs | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/ostd/src/mm/page/mod.rs b/ostd/src/mm/page/mod.rs
index 458b8f9a..d3663e6a 100644
--- a/ostd/src/mm/page/mod.rs
+++ b/ostd/src/mm/page/mod.rs
@@ -123,11 +123,18 @@ impl<M: PageMeta> Page<M> {
     ///
     /// # Safety
     ///
-    /// The physical address must represent a valid page and the caller must already hold one
-    /// reference count.
+    /// The physical address must represent a valid page and the caller must ensure the corresponding
+    /// virtual address points to an initialized metadata slot by holding a reference count priorly.
     pub(in crate::mm) unsafe fn inc_ref_count(paddr: Paddr) {
-        let page = unsafe { ManuallyDrop::new(Self::from_raw(paddr)) };
-        let _page = page.clone();
+        debug_assert!(paddr % PAGE_SIZE == 0);
+        debug_assert!(paddr < MAX_PADDR.load(Ordering::Relaxed) as Paddr);
+        let vaddr: Vaddr = mapping::page_to_meta::<PagingConsts>(paddr);
+        // SAFETY: The virtual address points to an initialized metadata slot. The caller can ensure
+        // it is initialized by holding a reference count before calling this function, preventing
+        // adding a reference count to an unused page.
+        (*(vaddr as *const MetaSlot))
+            .ref_count
+            .fetch_add(1, Ordering::Relaxed);
     }
 
     /// Get the physical address.
@@ -229,11 +236,18 @@ impl DynPage {
     ///
     /// # Safety
     ///
-    /// The physical address must represent a valid page and the caller must already hold one
-    /// reference count.
+    /// The physical address must represent a valid page and the caller must ensure the corresponding
+    /// virtual address points to an initialized metadata slot by holding a reference count priorly.
     pub(in crate::mm) unsafe fn inc_ref_count(paddr: Paddr) {
-        let page = unsafe { ManuallyDrop::new(Self::from_raw(paddr)) };
-        let _page = page.clone();
+        debug_assert!(paddr % PAGE_SIZE == 0);
+        debug_assert!(paddr < MAX_PADDR.load(Ordering::Relaxed) as Paddr);
+        let vaddr: Vaddr = mapping::page_to_meta::<PagingConsts>(paddr);
+        // SAFETY: The virtual address points to an initialized metadata slot. The caller can ensure
+        // it is initialized by holding a reference count before calling this function, preventing
+        // adding a reference count to an unused page.
+        (*(vaddr as *const MetaSlot))
+            .ref_count
+            .fetch_add(1, Ordering::Relaxed);
     }
 
     /// Get the physical address of the start of the page