Kernel: Add for_each_vmobject_of_type<T>

This makes iterating over a specific type of VMObjects a bit nicer.

Kernel/Process.cpp

@@ -671,9 +671,8 @@ int Process::sys$purge(int mode)
         NonnullRefPtrVector<PurgeableVMObject> vmobjects;
         {
             InterruptDisabler disabler;
-            MM.for_each_vmobject([&](auto& vmobject) {
+            MM.for_each_vmobject_of_type<PurgeableVMObject>([&](auto& vmobject) {
-                if (vmobject.is_purgeable())
+                vmobjects.append(vmobject);
-                    vmobjects.append(static_cast<PurgeableVMObject&>(vmobject));
                 return IterationDecision::Continue;
             });
         }
@@ -685,9 +684,8 @@ int Process::sys$purge(int mode)
         NonnullRefPtrVector<InodeVMObject> vmobjects;
         {
             InterruptDisabler disabler;
-            MM.for_each_vmobject([&](auto& vmobject) {
+            MM.for_each_vmobject_of_type<InodeVMObject>([&](auto& vmobject) {
-                if (vmobject.is_inode())
+                vmobjects.append(vmobject);
-                    vmobjects.append(static_cast<InodeVMObject&>(vmobject));
                 return IterationDecision::Continue;
             });
         }

Kernel/VM/AnonymousVMObject.h

@@ -56,4 +56,10 @@ private:
     virtual bool is_anonymous() const override { return true; }
 };
 
+template<>
+inline bool is<AnonymousVMObject>(const VMObject& vmobject)
+{
+    return vmobject.is_anonymous();
+}
+
 }

Kernel/VM/ContiguousVMObject.h

@@ -50,4 +50,11 @@ private:
 
     virtual bool is_contiguous() const override { return true; }
 };
+
+template<>
+inline bool is<ContiguousVMObject>(const VMObject& vmobject)
+{
+    return vmobject.is_contiguous();
+}
+
 }

Kernel/VM/InodeVMObject.h

@@ -66,4 +66,10 @@ protected:
     Bitmap m_dirty_pages;
 };
 
+template<>
+inline bool is<InodeVMObject>(const VMObject& vmobject)
+{
+    return vmobject.is_inode();
+}
+
 }

Kernel/VM/MemoryManager.cpp

@@ -441,16 +441,13 @@ RefPtr<PhysicalPage> MemoryManager::allocate_user_physical_page(ShouldZeroFill s
             klog() << "MM: no user physical regions available (?)";
         }
 
-        for_each_vmobject([&](auto& vmobject) {
+        for_each_vmobject_of_type<PurgeableVMObject>([&](auto& vmobject) {
-            if (vmobject.is_purgeable()) {
+            int purged_page_count = vmobject.purge_with_interrupts_disabled({});
-                auto& purgeable_vmobject = static_cast<PurgeableVMObject&>(vmobject);
+            if (purged_page_count) {
-                int purged_page_count = purgeable_vmobject.purge_with_interrupts_disabled({});
+                klog() << "MM: Purge saved the day! Purged " << purged_page_count << " pages from PurgeableVMObject{" << &vmobject << "}";
-                if (purged_page_count) {
+                page = find_free_user_physical_page();
-                    klog() << "MM: Purge saved the day! Purged " << purged_page_count << " pages from PurgeableVMObject{" << &purgeable_vmobject << "}";
+                ASSERT(page);
-                    page = find_free_user_physical_page();
+                return IterationDecision::Break;
-                    ASSERT(page);
-                    return IterationDecision::Break;
-                }
             }
             return IterationDecision::Continue;
         });

Kernel/VM/MemoryManager.h

@@ -125,6 +125,17 @@ public:
         }
     }
 
+    template<typename T, typename Callback>
+    static void for_each_vmobject_of_type(Callback callback)
+    {
+        for (auto& vmobject : MM.m_vmobjects) {
+            if (!is<T>(vmobject))
+                continue;
+            if (callback(static_cast<T&>(vmobject)) == IterationDecision::Break)
+                break;
+        }
+    }
+
     static Region* region_from_vaddr(Process&, VirtualAddress);
     static const Region* region_from_vaddr(const Process&, VirtualAddress);
 

Kernel/VM/PurgeableVMObject.h

@@ -64,4 +64,10 @@ private:
     bool m_volatile { false };
 };
 
+template<>
+inline bool is<PurgeableVMObject>(const VMObject& vmobject)
+{
+    return vmobject.is_purgeable();
+}
+
 }

Kernel/VM/VMObject.h

@@ -84,4 +84,14 @@ private:
     VMObject(VMObject&&) = delete;
 };
 
+template<typename T>
+inline bool is(const VMObject&) { return false; }
+
+template<typename T>
+inline T& to(VMObject& object)
+{
+    ASSERT(is<typename RemoveConst<T>::Type>(object));
+    return static_cast<T&>(object);
+}
+
 }