From 118cb391dddb33ca528309e1526464bd824b7e72 Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@gmail.com>
Date: Fri, 14 Jun 2019 14:56:21 +0300
Subject: [PATCH] VM: Pass a PhysicalPage by rvalue reference when returning it
 to the freelist.

This makes no functional difference, but it makes it clear that
MemoryManager and PhysicalRegion take over the actual physical
page represented by this PhysicalPage instance.
---
 Kernel/VM/MemoryManager.cpp | 8 ++++----
 Kernel/VM/MemoryManager.h   | 4 ++--
 Kernel/VM/PhysicalPage.cpp  | 6 +++---
 Kernel/VM/PhysicalPage.h    | 4 ++--
 Kernel/VM/PhysicalRegion.h  | 2 +-
 5 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index 3f1fd93753..d45fcda41f 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -458,7 +458,7 @@ RetainPtr<Region> MemoryManager::allocate_kernel_region(size_t size, String&& na
     return region;
 }
 
-void MemoryManager::deallocate_user_physical_page(PhysicalPage& page)
+void MemoryManager::deallocate_user_physical_page(PhysicalPage&& page)
 {
     for (auto& region : m_user_physical_regions) {
         if (!region->contains(page)) {
@@ -468,7 +468,7 @@ void MemoryManager::deallocate_user_physical_page(PhysicalPage& page)
             continue;
         }
 
-        region->return_page(page);
+        region->return_page(move(page));
         m_user_physical_pages_used--;
 
         return;
@@ -515,7 +515,7 @@ RetainPtr<PhysicalPage> MemoryManager::allocate_user_physical_page(ShouldZeroFil
     return page;
 }
 
-void MemoryManager::deallocate_supervisor_physical_page(PhysicalPage& page)
+void MemoryManager::deallocate_supervisor_physical_page(PhysicalPage&& page)
 {
     for (auto& region : m_super_physical_regions) {
         if (!region->contains(page)) {
@@ -525,7 +525,7 @@ void MemoryManager::deallocate_supervisor_physical_page(PhysicalPage& page)
             continue;
         }
 
-        region->return_page(page);
+        region->return_page(move(page));
         m_super_physical_pages_used--;
 
         return;
diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
index 29a985adc1..efa291e41c 100644
--- a/Kernel/VM/MemoryManager.h
+++ b/Kernel/VM/MemoryManager.h
@@ -63,8 +63,8 @@ public:
 
     RetainPtr<PhysicalPage> allocate_user_physical_page(ShouldZeroFill);
     RetainPtr<PhysicalPage> allocate_supervisor_physical_page();
-    void deallocate_user_physical_page(PhysicalPage&);
-    void deallocate_supervisor_physical_page(PhysicalPage&);
+    void deallocate_user_physical_page(PhysicalPage&&);
+    void deallocate_supervisor_physical_page(PhysicalPage&&);
 
     void remap_region(PageDirectory&, Region&);
 
diff --git a/Kernel/VM/PhysicalPage.cpp b/Kernel/VM/PhysicalPage.cpp
index 43d014a0c8..2ddb1d02a5 100644
--- a/Kernel/VM/PhysicalPage.cpp
+++ b/Kernel/VM/PhysicalPage.cpp
@@ -23,7 +23,7 @@ PhysicalPage::PhysicalPage(PhysicalAddress paddr, bool supervisor, bool may_retu
 {
 }
 
-void PhysicalPage::return_to_freelist()
+void PhysicalPage::return_to_freelist() &&
 {
     ASSERT((paddr().get() & ~PAGE_MASK) == 0);
 
@@ -32,9 +32,9 @@ void PhysicalPage::return_to_freelist()
     m_retain_count = 1;
 
     if (m_supervisor)
-        MM.deallocate_supervisor_physical_page(*this);
+        MM.deallocate_supervisor_physical_page(move(*this));
     else
-        MM.deallocate_user_physical_page(*this);
+        MM.deallocate_user_physical_page(move(*this));
 
 #ifdef MM_DEBUG
     dbgprintf("MM: P%x released to freelist\n", m_paddr.get());
diff --git a/Kernel/VM/PhysicalPage.h b/Kernel/VM/PhysicalPage.h
index bf2726bcef..5ac8ad7aac 100644
--- a/Kernel/VM/PhysicalPage.h
+++ b/Kernel/VM/PhysicalPage.h
@@ -23,7 +23,7 @@ public:
         ASSERT(m_retain_count);
         if (!--m_retain_count) {
             if (m_may_return_to_freelist)
-                return_to_freelist();
+                move(*this).return_to_freelist();
             else
                 delete this;
         }
@@ -38,7 +38,7 @@ private:
     PhysicalPage(PhysicalAddress paddr, bool supervisor, bool may_return_to_freelist = true);
     ~PhysicalPage() {}
 
-    void return_to_freelist();
+    void return_to_freelist() &&;
 
     word m_retain_count { 1 };
     bool m_may_return_to_freelist { true };
diff --git a/Kernel/VM/PhysicalRegion.h b/Kernel/VM/PhysicalRegion.h
index d4f4fb1934..b14b6daf1a 100644
--- a/Kernel/VM/PhysicalRegion.h
+++ b/Kernel/VM/PhysicalRegion.h
@@ -25,7 +25,7 @@ public:
 
     RetainPtr<PhysicalPage> take_free_page(bool supervisor);
     void return_page_at(PhysicalAddress addr);
-    void return_page(PhysicalPage& page) { return_page_at(page.paddr()); }
+    void return_page(PhysicalPage&& page) { return_page_at(page.paddr()); }
 
 private:
     PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper);