From 81e23617d6525663c11619a9c330a62654671155 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Wed, 29 Dec 2021 00:23:25 +0200
Subject: [PATCH] Kernel: Port Custody to ListedRefCounted

Custody's unref is one of many implementions of ListedRefCounted's
behaviour in the Kernel, which results in avoidable bugs caused by
the fragmentation of the implementations. This commit starts the work
of replacing all custom implementations with ListedRefCounted by
porting Custody to it.
---
 Kernel/FileSystem/Custody.cpp | 23 ++++-------------------
 Kernel/FileSystem/Custody.h   |  8 ++++----
 2 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/Kernel/FileSystem/Custody.cpp b/Kernel/FileSystem/Custody.cpp
index 84b7479c33..81532d731f 100644
--- a/Kernel/FileSystem/Custody.cpp
+++ b/Kernel/FileSystem/Custody.cpp
@@ -10,20 +10,19 @@
 #include <AK/Vector.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/Inode.h>
-#include <Kernel/Locking/MutexProtected.h>
 
 namespace Kernel {
 
-static Singleton<MutexProtected<Custody::AllCustodiesList>> s_all_custodies;
+static Singleton<MutexProtected<Custody::AllCustodiesList>> s_all_instances;
 
-static MutexProtected<Custody::AllCustodiesList>& all_custodies()
+MutexProtected<Custody::AllCustodiesList>& Custody::all_instances()
 {
-    return s_all_custodies;
+    return s_all_instances;
 }
 
 ErrorOr<NonnullRefPtr<Custody>> Custody::try_create(Custody* parent, StringView name, Inode& inode, int mount_flags)
 {
-    return all_custodies().with_exclusive([&](auto& all_custodies) -> ErrorOr<NonnullRefPtr<Custody>> {
+    return all_instances().with_exclusive([&](auto& all_custodies) -> ErrorOr<NonnullRefPtr<Custody>> {
         for (Custody& custody : all_custodies) {
             if (custody.parent() == parent
                 && custody.name() == name
@@ -40,20 +39,6 @@ ErrorOr<NonnullRefPtr<Custody>> Custody::try_create(Custody* parent, StringView
     });
 }
 
-bool Custody::unref() const
-{
-    bool should_destroy = all_custodies().with_exclusive([&](auto&) {
-        if (deref_base())
-            return false;
-        m_all_custodies_list_node.remove();
-        return true;
-    });
-
-    if (should_destroy)
-        delete this;
-    return should_destroy;
-}
-
 Custody::Custody(Custody* parent, NonnullOwnPtr<KString> name, Inode& inode, int mount_flags)
     : m_parent(parent)
     , m_name(move(name))
diff --git a/Kernel/FileSystem/Custody.h b/Kernel/FileSystem/Custody.h
index 64a4c4dae1..b688ae660c 100644
--- a/Kernel/FileSystem/Custody.h
+++ b/Kernel/FileSystem/Custody.h
@@ -8,20 +8,19 @@
 
 #include <AK/Error.h>
 #include <AK/IntrusiveList.h>
-#include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
 #include <AK/String.h>
 #include <Kernel/Forward.h>
 #include <Kernel/KString.h>
+#include <Kernel/Library/ListedRefCounted.h>
+#include <Kernel/Locking/MutexProtected.h>
 
 namespace Kernel {
 
 // FIXME: Custody needs some locking.
 
-class Custody : public RefCountedBase {
+class Custody : public ListedRefCounted<Custody, LockType::Mutex> {
 public:
-    bool unref() const;
-
     static ErrorOr<NonnullRefPtr<Custody>> try_create(Custody* parent, StringView name, Inode&, int mount_flags);
 
     ~Custody();
@@ -49,6 +48,7 @@ private:
 
 public:
     using AllCustodiesList = IntrusiveList<&Custody::m_all_custodies_list_node>;
+    static MutexProtected<Custody::AllCustodiesList>& all_instances();
 };
 
 }