Kernel: Fix the search method of free userspace physical pages (#742)

Now the userspace page allocator will search through physical regions,
and stop the search as it finds an available page.

Also remove an "address of" sign since we don't need that when
counting size of physical regions

2 files changed, 12 insertions, 6 deletions

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index 39fa0ad3c6..885cdbd19f 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -144,7 +144,7 @@ void MemoryManager::initialize_paging()
             } else {
                 if (region.is_null() || region_is_super || region->upper().offset(PAGE_SIZE) != addr) {
                     m_user_physical_regions.append(PhysicalRegion::create(addr, addr));
-                    region = &m_user_physical_regions.last();
+                    region = m_user_physical_regions.last();
                     region_is_super = false;
                 } else {
                     region->expand(region->lower(), addr);
@@ -386,16 +386,21 @@ void MemoryManager::deallocate_user_physical_page(PhysicalPage&& page)
     ASSERT_NOT_REACHED();
 }
 
-RefPtr<PhysicalPage> MemoryManager::allocate_user_physical_page(ShouldZeroFill should_zero_fill)
+RefPtr<PhysicalPage> MemoryManager::find_free_user_physical_page()
 {
-    InterruptDisabler disabler;
     RefPtr<PhysicalPage> page;
-
     for (auto& region : m_user_physical_regions) {
         page = region.take_free_page(false);
-        if (page.is_null())
-            continue;
+        if (!page.is_null())
+            break;
     }
+    return page;
+}
+
+RefPtr<PhysicalPage> MemoryManager::allocate_user_physical_page(ShouldZeroFill should_zero_fill)
+{
+    InterruptDisabler disabler;
+    RefPtr<PhysicalPage> page = find_free_user_physical_page();
 
     if (!page) {
         if (m_user_physical_regions.is_empty()) {
diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
index 9a3ffd1018..399d0f1502 100644
--- a/Kernel/VM/MemoryManager.h
+++ b/Kernel/VM/MemoryManager.h
@@ -103,6 +103,7 @@ private:
 
     static Region* region_from_vaddr(VirtualAddress);
 
+    RefPtr<PhysicalPage> find_free_user_physical_page();
     u8* quickmap_page(PhysicalPage&);
     void unquickmap_page();