Kernel/Devices: Defer creation of SysFS component after the constructor

Instead of doing so in the constructor, let's do immediately after the
constructor, so we can safely pass a reference of a Device, so the
SysFSDeviceComponent constructor can use that object to identify whether
it's a block device or a character device.
This allows to us to not hold a device in SysFSDeviceComponent with a
RefPtr.
Also, we also call the before_removing method in both SlavePTY::unref
and File::unref, so because Device has that method being overrided, it
can ensure the device is removed always cleanly.

41 files changed, 141 insertions, 56 deletions

diff --git a/Kernel/ConsoleDevice.cpp b/Kernel/ConsoleDevice.cpp
index 69d1ceff84..2bb5569a0c 100644
--- a/Kernel/ConsoleDevice.cpp
+++ b/Kernel/ConsoleDevice.cpp
@@ -20,6 +20,7 @@ static Kernel::Spinlock g_console_lock;
 UNMAP_AFTER_INIT void ConsoleDevice::initialize()
 {
     s_the.ensure_instance();
+    s_the->after_inserting();
 }
 
 ConsoleDevice& ConsoleDevice::the()
diff --git a/Kernel/Devices/Device.cpp b/Kernel/Devices/Device.cpp
index e74365e2d0..e3b809cb4e 100644
--- a/Kernel/Devices/Device.cpp
+++ b/Kernel/Devices/Device.cpp
@@ -26,8 +26,9 @@ NonnullRefPtr<SysFSDeviceComponent> SysFSDeviceComponent::must_create(Device con
 }
 SysFSDeviceComponent::SysFSDeviceComponent(Device const& device)
     : SysFSComponent(String::formatted("{}:{}", device.major(), device.minor()))
-    , m_associated_device(device)
+    , m_block_device(device.is_block_device())
 {
+    VERIFY(device.is_block_device() || device.is_character_device());
 }
 
 UNMAP_AFTER_INIT NonnullRefPtr<SysFSDevicesDirectory> SysFSDevicesDirectory::must_create(SysFSRootDirectory const& root_directory)
@@ -58,7 +59,7 @@ KResult SysFSBlockDevicesDirectory::traverse_as_directory(unsigned fsid, Functio
 
     SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
         for (auto& exposed_device : list) {
-            if (!exposed_device.device().is_block_device())
+            if (!exposed_device.is_block_device())
                 continue;
             callback({ exposed_device.name(), { fsid, exposed_device.component_index() }, 0 });
         }
@@ -69,7 +70,7 @@ RefPtr<SysFSComponent> SysFSBlockDevicesDirectory::lookup(StringView name)
 {
     return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> RefPtr<SysFSComponent> {
         for (auto& exposed_device : list) {
-            if (!exposed_device.device().is_block_device())
+            if (!exposed_device.is_block_device())
                 continue;
             if (exposed_device.name() == name)
                 return exposed_device;
@@ -94,7 +95,7 @@ KResult SysFSCharacterDevicesDirectory::traverse_as_directory(unsigned fsid, Fun
 
     SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
         for (auto& exposed_device : list) {
-            if (!exposed_device.device().is_character_device())
+            if (exposed_device.is_block_device())
                 continue;
             callback({ exposed_device.name(), { fsid, exposed_device.component_index() }, 0 });
         }
@@ -105,7 +106,7 @@ RefPtr<SysFSComponent> SysFSCharacterDevicesDirectory::lookup(StringView name)
 {
     return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> RefPtr<SysFSComponent> {
         for (auto& exposed_device : list) {
-            if (!exposed_device.device().is_character_device())
+            if (exposed_device.is_block_device())
                 continue;
             if (exposed_device.name() == name)
                 return exposed_device;
@@ -145,6 +146,11 @@ Device::Device(unsigned major, unsigned minor)
         VERIFY(!map.contains(device_id));
         map.set(device_id, this);
     });
+}
+
+void Device::after_inserting()
+{
+    VERIFY(!m_sysfs_component);
     auto sys_fs_component = SysFSDeviceComponent::must_create(*this);
     m_sysfs_component = sys_fs_component;
     SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
@@ -154,12 +160,11 @@ Device::Device(unsigned major, unsigned minor)
 
 void Device::before_removing()
 {
-    auto sys_fs_component = m_sysfs_component.strong_ref();
-    VERIFY(sys_fs_component);
+    m_state = State::BeingRemoved;
+    VERIFY(m_sysfs_component);
     SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
-        list.remove(*sys_fs_component);
+        list.remove(*m_sysfs_component);
     });
-    m_state = State::BeingRemoved;
 }
 
 Device::~Device()
diff --git a/Kernel/Devices/Device.h b/Kernel/Devices/Device.h
index cc1fc51827..e981d76d73 100644
--- a/Kernel/Devices/Device.h
+++ b/Kernel/Devices/Device.h
@@ -18,6 +18,7 @@
 #include <AK/Function.h>
 #include <AK/HashMap.h>
 #include <AK/RefPtr.h>
+#include <Kernel/API/KResult.h>
 #include <Kernel/Devices/AsyncDeviceRequest.h>
 #include <Kernel/FileSystem/File.h>
 #include <Kernel/FileSystem/SysFS.h>
@@ -26,6 +27,14 @@
 
 namespace Kernel {
 
+template<typename DeviceType, typename... Args>
+inline KResultOr<NonnullRefPtr<DeviceType>> try_create_device(Args&&... args)
+{
+    auto device = TRY(adopt_nonnull_ref_or_enomem(new DeviceType(forward<Args>(args)...)));
+    device->after_inserting();
+    return device;
+}
+
 class Device : public File {
 protected:
     enum class State {
@@ -46,7 +55,8 @@ public:
     GroupID gid() const { return m_gid; }
 
     virtual bool is_device() const override { return true; }
-    virtual void before_removing();
+    virtual void before_removing() override;
+    virtual void after_inserting();
 
     static void for_each(Function<void(Device&)>);
     static Device* get_device(unsigned major, unsigned minor);
@@ -82,7 +92,7 @@ private:
 
     Spinlock m_requests_lock;
     DoublyLinkedList<RefPtr<AsyncDeviceRequest>> m_requests;
-    WeakPtr<SysFSDeviceComponent> m_sysfs_component;
+    RefPtr<SysFSDeviceComponent> m_sysfs_component;
 };
 
 }
diff --git a/Kernel/Devices/FullDevice.cpp b/Kernel/Devices/FullDevice.cpp
index b8b0488722..df425cfcea 100644
--- a/Kernel/Devices/FullDevice.cpp
+++ b/Kernel/Devices/FullDevice.cpp
@@ -13,7 +13,10 @@ namespace Kernel {
 
 UNMAP_AFTER_INIT NonnullRefPtr<FullDevice> FullDevice::must_create()
 {
-    return adopt_ref(*new FullDevice);
+    auto full_device_or_error = try_create_device<FullDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!full_device_or_error.is_error());
+    return full_device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT FullDevice::FullDevice()
diff --git a/Kernel/Devices/FullDevice.h b/Kernel/Devices/FullDevice.h
index ded36209de..3a3f7e09b9 100644
--- a/Kernel/Devices/FullDevice.h
+++ b/Kernel/Devices/FullDevice.h
@@ -16,9 +16,10 @@ public:
     static NonnullRefPtr<FullDevice> must_create();
     virtual ~FullDevice() override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     FullDevice();
 
+private:
     // ^CharacterDevice
     virtual KResultOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
     virtual KResultOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
diff --git a/Kernel/Devices/HID/HIDManagement.cpp b/Kernel/Devices/HID/HIDManagement.cpp
index 3461e3f7d6..0fdc78839b 100644
--- a/Kernel/Devices/HID/HIDManagement.cpp
+++ b/Kernel/Devices/HID/HIDManagement.cpp
@@ -112,6 +112,7 @@ UNMAP_AFTER_INIT void HIDManagement::enumerate()
     m_i8042_controller->detect_devices();
     if (m_i8042_controller->mouse())
         m_hid_devices.append(m_i8042_controller->mouse().release_nonnull());
+
     if (m_i8042_controller->keyboard())
         m_hid_devices.append(m_i8042_controller->keyboard().release_nonnull());
 }
diff --git a/Kernel/Devices/HID/PS2KeyboardDevice.cpp b/Kernel/Devices/HID/PS2KeyboardDevice.cpp
index e81ea7fa0c..0b569b632f 100644
--- a/Kernel/Devices/HID/PS2KeyboardDevice.cpp
+++ b/Kernel/Devices/HID/PS2KeyboardDevice.cpp
@@ -83,9 +83,11 @@ bool PS2KeyboardDevice::handle_irq(const RegisterState&)
 
 UNMAP_AFTER_INIT RefPtr<PS2KeyboardDevice> PS2KeyboardDevice::try_to_initialize(const I8042Controller& ps2_controller)
 {
-    auto device = adopt_ref(*new PS2KeyboardDevice(ps2_controller));
-    if (device->initialize())
-        return device;
+    auto keyboard_device_or_error = try_create_device<PS2KeyboardDevice>(ps2_controller);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!keyboard_device_or_error.is_error());
+    if (keyboard_device_or_error.value()->initialize())
+        return keyboard_device_or_error.release_value();
     return nullptr;
 }
 
diff --git a/Kernel/Devices/HID/PS2KeyboardDevice.h b/Kernel/Devices/HID/PS2KeyboardDevice.h
index 8fb9c285cd..cd8feca328 100644
--- a/Kernel/Devices/HID/PS2KeyboardDevice.h
+++ b/Kernel/Devices/HID/PS2KeyboardDevice.h
@@ -35,9 +35,10 @@ public:
         enable_irq();
     }
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     explicit PS2KeyboardDevice(const I8042Controller&);
 
+private:
     // ^IRQHandler
     virtual bool handle_irq(const RegisterState&) override;
 
diff --git a/Kernel/Devices/HID/PS2MouseDevice.cpp b/Kernel/Devices/HID/PS2MouseDevice.cpp
index 15dec13ae1..fce0609e2c 100644
--- a/Kernel/Devices/HID/PS2MouseDevice.cpp
+++ b/Kernel/Devices/HID/PS2MouseDevice.cpp
@@ -174,9 +174,11 @@ void PS2MouseDevice::set_sample_rate(u8 rate)
 
 UNMAP_AFTER_INIT RefPtr<PS2MouseDevice> PS2MouseDevice::try_to_initialize(const I8042Controller& ps2_controller)
 {
-    auto device = adopt_ref(*new PS2MouseDevice(ps2_controller));
-    if (device->initialize())
-        return device;
+    auto mouse_device_or_error = try_create_device<PS2MouseDevice>(ps2_controller);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!mouse_device_or_error.is_error());
+    if (mouse_device_or_error.value()->initialize())
+        return mouse_device_or_error.release_value();
     return nullptr;
 }
 
diff --git a/Kernel/Devices/HID/PS2MouseDevice.h b/Kernel/Devices/HID/PS2MouseDevice.h
index 1182ce2946..fc3b84cd00 100644
--- a/Kernel/Devices/HID/PS2MouseDevice.h
+++ b/Kernel/Devices/HID/PS2MouseDevice.h
@@ -32,8 +32,10 @@ public:
         enable_irq();
     }
 
-protected:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     explicit PS2MouseDevice(const I8042Controller&);
+
+protected:
     // ^IRQHandler
     virtual bool handle_irq(const RegisterState&) override;
 
diff --git a/Kernel/Devices/HID/VMWareMouseDevice.cpp b/Kernel/Devices/HID/VMWareMouseDevice.cpp
index 46ca4b3984..291cde6a78 100644
--- a/Kernel/Devices/HID/VMWareMouseDevice.cpp
+++ b/Kernel/Devices/HID/VMWareMouseDevice.cpp
@@ -16,9 +16,11 @@ UNMAP_AFTER_INIT RefPtr<VMWareMouseDevice> VMWareMouseDevice::try_to_initialize(
         return {};
     if (!VMWareBackdoor::the()->vmmouse_is_absolute())
         return {};
-    auto device = adopt_ref(*new VMWareMouseDevice(ps2_controller));
-    if (device->initialize())
-        return device;
+    auto mouse_device_or_error = try_create_device<VMWareMouseDevice>(ps2_controller);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!mouse_device_or_error.is_error());
+    if (mouse_device_or_error.value()->initialize())
+        return mouse_device_or_error.release_value();
     return {};
 }
 
diff --git a/Kernel/Devices/HID/VMWareMouseDevice.h b/Kernel/Devices/HID/VMWareMouseDevice.h
index 60749639bb..7f17e27392 100644
--- a/Kernel/Devices/HID/VMWareMouseDevice.h
+++ b/Kernel/Devices/HID/VMWareMouseDevice.h
@@ -23,7 +23,7 @@ public:
     // ^I8042Device
     virtual void irq_handle_byte_read(u8 byte) override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     explicit VMWareMouseDevice(const I8042Controller&);
 };
 
diff --git a/Kernel/Devices/KCOVDevice.cpp b/Kernel/Devices/KCOVDevice.cpp
index 712d5df7b9..0d3dc59674 100644
--- a/Kernel/Devices/KCOVDevice.cpp
+++ b/Kernel/Devices/KCOVDevice.cpp
@@ -20,7 +20,10 @@ HashMap<ThreadID, KCOVInstance*>* KCOVDevice::thread_instance;
 
 UNMAP_AFTER_INIT NonnullRefPtr<KCOVDevice> KCOVDevice::must_create()
 {
-    return adopt_ref(*new KCOVDevice);
+    auto kcov_device_or_error = try_create_device<KCOVDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!kcov_device_or_error.is_error());
+    return kcov_device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT KCOVDevice::KCOVDevice()
diff --git a/Kernel/Devices/KCOVDevice.h b/Kernel/Devices/KCOVDevice.h
index 56002ac545..0b7fcc8799 100644
--- a/Kernel/Devices/KCOVDevice.h
+++ b/Kernel/Devices/KCOVDevice.h
@@ -25,6 +25,9 @@ public:
     KResultOr<Memory::Region*> mmap(Process&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
     KResultOr<NonnullRefPtr<OpenFileDescription>> open(int options) override;
 
+    // FIXME: We expose this constructor to make try_create_device helper to work
+    KCOVDevice();
+
 protected:
     virtual StringView class_name() const override { return "KCOVDevice"; }
 
@@ -34,9 +37,6 @@ protected:
     virtual KResultOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override { return EINVAL; }
     virtual KResultOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override { return EINVAL; }
     virtual KResult ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override;
-
-private:
-    KCOVDevice();
 };
 
 }
diff --git a/Kernel/Devices/MemoryDevice.cpp b/Kernel/Devices/MemoryDevice.cpp
index eb5df7ea02..80020f22ab 100644
--- a/Kernel/Devices/MemoryDevice.cpp
+++ b/Kernel/Devices/MemoryDevice.cpp
@@ -15,7 +15,10 @@ namespace Kernel {
 
 UNMAP_AFTER_INIT NonnullRefPtr<MemoryDevice> MemoryDevice::must_create()
 {
-    return adopt_ref(*new MemoryDevice);
+    auto memory_device_or_error = try_create_device<MemoryDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!memory_device_or_error.is_error());
+    return memory_device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT MemoryDevice::MemoryDevice()
diff --git a/Kernel/Devices/MemoryDevice.h b/Kernel/Devices/MemoryDevice.h
index 875ff434de..0f40d26a4f 100644
--- a/Kernel/Devices/MemoryDevice.h
+++ b/Kernel/Devices/MemoryDevice.h
@@ -21,8 +21,10 @@ public:
 
     virtual KResultOr<Memory::Region*> mmap(Process&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     MemoryDevice();
+
+private:
     virtual StringView class_name() const override { return "MemoryDevice"; }
     virtual bool can_read(const OpenFileDescription&, size_t) const override { return true; }
     virtual bool can_write(const OpenFileDescription&, size_t) const override { return false; }
diff --git a/Kernel/Devices/NullDevice.cpp b/Kernel/Devices/NullDevice.cpp
index 240f90d3f0..ae20bcfeba 100644
--- a/Kernel/Devices/NullDevice.cpp
+++ b/Kernel/Devices/NullDevice.cpp
@@ -15,6 +15,7 @@ static Singleton<NullDevice> s_the;
 UNMAP_AFTER_INIT void NullDevice::initialize()
 {
     s_the.ensure_instance();
+    s_the->after_inserting();
 }
 
 NullDevice& NullDevice::the()
diff --git a/Kernel/Devices/RandomDevice.cpp b/Kernel/Devices/RandomDevice.cpp
index d8116ca0dc..1d2ab995e4 100644
--- a/Kernel/Devices/RandomDevice.cpp
+++ b/Kernel/Devices/RandomDevice.cpp
@@ -12,7 +12,10 @@ namespace Kernel {
 
 UNMAP_AFTER_INIT NonnullRefPtr<RandomDevice> RandomDevice::must_create()
 {
-    return adopt_ref(*new RandomDevice);
+    auto random_device_or_error = try_create_device<RandomDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!random_device_or_error.is_error());
+    return random_device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT RandomDevice::RandomDevice()
diff --git a/Kernel/Devices/RandomDevice.h b/Kernel/Devices/RandomDevice.h
index 52dfcce0bd..8e915cd1c5 100644
--- a/Kernel/Devices/RandomDevice.h
+++ b/Kernel/Devices/RandomDevice.h
@@ -16,9 +16,10 @@ public:
     static NonnullRefPtr<RandomDevice> must_create();
     virtual ~RandomDevice() override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     RandomDevice();
 
+private:
     // ^CharacterDevice
     virtual KResultOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
     virtual KResultOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
diff --git a/Kernel/Devices/SB16.cpp b/Kernel/Devices/SB16.cpp
index b0ef199a13..219d77f7bb 100644
--- a/Kernel/Devices/SB16.cpp
+++ b/Kernel/Devices/SB16.cpp
@@ -89,6 +89,7 @@ UNMAP_AFTER_INIT void SB16::detect()
 UNMAP_AFTER_INIT void SB16::create()
 {
     s_the.ensure_instance();
+    s_the->after_inserting();
 }
 
 SB16& SB16::the()
diff --git a/Kernel/Devices/ZeroDevice.cpp b/Kernel/Devices/ZeroDevice.cpp
index 880db84502..fad3113f1a 100644
--- a/Kernel/Devices/ZeroDevice.cpp
+++ b/Kernel/Devices/ZeroDevice.cpp
@@ -12,7 +12,10 @@ namespace Kernel {
 
 UNMAP_AFTER_INIT NonnullRefPtr<ZeroDevice> ZeroDevice::must_create()
 {
-    return adopt_ref(*new ZeroDevice);
+    auto zero_device_or_error = try_create_device<ZeroDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!zero_device_or_error.is_error());
+    return zero_device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT ZeroDevice::ZeroDevice()
diff --git a/Kernel/Devices/ZeroDevice.h b/Kernel/Devices/ZeroDevice.h
index cf68501324..e5a2b6dea2 100644
--- a/Kernel/Devices/ZeroDevice.h
+++ b/Kernel/Devices/ZeroDevice.h
@@ -16,8 +16,10 @@ public:
     static NonnullRefPtr<ZeroDevice> must_create();
     virtual ~ZeroDevice() override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     ZeroDevice();
+
+private:
     // ^CharacterDevice
     virtual KResultOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
     virtual KResultOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
diff --git a/Kernel/FileSystem/File.cpp b/Kernel/FileSystem/File.cpp
index ac03665b9c..fd98a3a629 100644
--- a/Kernel/FileSystem/File.cpp
+++ b/Kernel/FileSystem/File.cpp
@@ -24,6 +24,7 @@ bool File::unref() const
 {
     if (deref_base())
         return false;
+    const_cast<File&>(*this).before_removing();
     delete this;
     return true;
 }
diff --git a/Kernel/FileSystem/File.h b/Kernel/FileSystem/File.h
index 52e495411d..2740516000 100644
--- a/Kernel/FileSystem/File.h
+++ b/Kernel/FileSystem/File.h
@@ -75,6 +75,7 @@ class File
     , public Weakable<File> {
 public:
     virtual bool unref() const;
+    virtual void before_removing() { }
     virtual ~File();
 
     virtual KResultOr<NonnullRefPtr<OpenFileDescription>> open(int options);
diff --git a/Kernel/FileSystem/SysFS.h b/Kernel/FileSystem/SysFS.h
index 08a5c82135..886c31eeb9 100644
--- a/Kernel/FileSystem/SysFS.h
+++ b/Kernel/FileSystem/SysFS.h
@@ -34,12 +34,12 @@ class SysFSDeviceComponent final
 public:
     static NonnullRefPtr<SysFSDeviceComponent> must_create(Device const&);
 
-    Device const& device() const { return *m_associated_device; }
+    bool is_block_device() { return m_block_device; }
 
 private:
     explicit SysFSDeviceComponent(Device const&);
     IntrusiveListNode<SysFSDeviceComponent, NonnullRefPtr<SysFSDeviceComponent>> m_list_node;
-    RefPtr<Device> m_associated_device;
+    bool m_block_device;
 };
 
 class SysFSDevicesDirectory final : public SysFSDirectory {
diff --git a/Kernel/Graphics/FramebufferDevice.cpp b/Kernel/Graphics/FramebufferDevice.cpp
index 03b8b760eb..0d36a3400e 100644
--- a/Kernel/Graphics/FramebufferDevice.cpp
+++ b/Kernel/Graphics/FramebufferDevice.cpp
@@ -22,7 +22,10 @@ namespace Kernel {
 
 NonnullRefPtr<FramebufferDevice> FramebufferDevice::create(const GraphicsDevice& adapter, size_t output_port_index, PhysicalAddress paddr, size_t width, size_t height, size_t pitch)
 {
-    return adopt_ref(*new FramebufferDevice(adapter, output_port_index, paddr, width, height, pitch));
+    auto framebuffer_device_or_error = try_create_device<FramebufferDevice>(adapter, output_port_index, paddr, width, height, pitch);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!framebuffer_device_or_error.is_error());
+    return framebuffer_device_or_error.release_value();
 }
 
 KResultOr<Memory::Region*> FramebufferDevice::mmap(Process& process, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
diff --git a/Kernel/Graphics/FramebufferDevice.h b/Kernel/Graphics/FramebufferDevice.h
index 00b57226c6..2b4e958bbf 100644
--- a/Kernel/Graphics/FramebufferDevice.h
+++ b/Kernel/Graphics/FramebufferDevice.h
@@ -32,6 +32,9 @@ public:
     virtual ~FramebufferDevice() {};
     KResult initialize();
 
+    // FIXME: We expose this constructor to make try_create_device helper to work
+    FramebufferDevice(const GraphicsDevice&, size_t, PhysicalAddress, size_t, size_t, size_t);
+
 private:
     // ^File
     virtual StringView class_name() const override { return "FramebufferDevice"; }
@@ -42,8 +45,6 @@ private:
     virtual KResultOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override { return EINVAL; }
     virtual KResultOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override { return EINVAL; }
 
-    FramebufferDevice(const GraphicsDevice&, size_t, PhysicalAddress, size_t, size_t, size_t);
-
     PhysicalAddress m_framebuffer_address;
     size_t m_framebuffer_pitch { 0 };
     size_t m_framebuffer_width { 0 };
diff --git a/Kernel/Graphics/VirtIOGPU/GPU.cpp b/Kernel/Graphics/VirtIOGPU/GPU.cpp
index 36b50f217f..e5b2140bd8 100644
--- a/Kernel/Graphics/VirtIOGPU/GPU.cpp
+++ b/Kernel/Graphics/VirtIOGPU/GPU.cpp
@@ -64,6 +64,7 @@ void GPU::create_framebuffer_devices()
     for (size_t i = 0; i < min(m_num_scanouts, VIRTIO_GPU_MAX_SCANOUTS); i++) {
         auto& scanout = m_scanouts[i];
         scanout.framebuffer = adopt_ref(*new VirtIOGPU::FrameBufferDevice(*this, i));
+        scanout.framebuffer->after_inserting();
         scanout.console = Kernel::Graphics::VirtIOGPU::Console::initialize(scanout.framebuffer);
     }
 }
diff --git a/Kernel/Storage/PATADiskDevice.cpp b/Kernel/Storage/PATADiskDevice.cpp
index 015ff71d9c..d4aab035b0 100644
--- a/Kernel/Storage/PATADiskDevice.cpp
+++ b/Kernel/Storage/PATADiskDevice.cpp
@@ -15,7 +15,10 @@ namespace Kernel {
 
 UNMAP_AFTER_INIT NonnullRefPtr<PATADiskDevice> PATADiskDevice::create(const IDEController& controller, IDEChannel& channel, DriveType type, InterfaceType interface_type, u16 capabilities, u64 max_addressable_block)
 {
-    return adopt_ref(*new PATADiskDevice(controller, channel, type, interface_type, capabilities, max_addressable_block));
+    auto device_or_error = try_create_device<PATADiskDevice>(controller, channel, type, interface_type, capabilities, max_addressable_block);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!device_or_error.is_error());
+    return device_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT PATADiskDevice::PATADiskDevice(const IDEController& controller, IDEChannel& channel, DriveType type, InterfaceType interface_type, u16 capabilities, u64 max_addressable_block)
diff --git a/Kernel/Storage/PATADiskDevice.h b/Kernel/Storage/PATADiskDevice.h
index 4aadb24893..9de2561b36 100644
--- a/Kernel/Storage/PATADiskDevice.h
+++ b/Kernel/Storage/PATADiskDevice.h
@@ -44,9 +44,10 @@ public:
     virtual void start_request(AsyncBlockDeviceRequest&) override;
     virtual String storage_name() const override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     PATADiskDevice(const IDEController&, IDEChannel&, DriveType, InterfaceType, u16, u64);
 
+private:
     // ^DiskDevice
     virtual StringView class_name() const override;
 
diff --git a/Kernel/Storage/Partition/DiskPartition.cpp b/Kernel/Storage/Partition/DiskPartition.cpp
index 17d474f011..5352528773 100644
--- a/Kernel/Storage/Partition/DiskPartition.cpp
+++ b/Kernel/Storage/Partition/DiskPartition.cpp
@@ -12,7 +12,10 @@ namespace Kernel {
 
 NonnullRefPtr<DiskPartition> DiskPartition::create(BlockDevice& device, unsigned minor_number, DiskPartitionMetadata metadata)
 {
-    return adopt_ref(*new DiskPartition(device, minor_number, metadata));
+    auto partition_or_error = try_create_device<DiskPartition>(device, minor_number, metadata);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!partition_or_error.is_error());
+    return partition_or_error.release_value();
 }
 
 DiskPartition::DiskPartition(BlockDevice& device, unsigned minor_number, DiskPartitionMetadata metadata)
diff --git a/Kernel/Storage/Partition/DiskPartition.h b/Kernel/Storage/Partition/DiskPartition.h
index 46f99a1fcd..1d4bae1c75 100644
--- a/Kernel/Storage/Partition/DiskPartition.h
+++ b/Kernel/Storage/Partition/DiskPartition.h
@@ -28,11 +28,12 @@ public:
 
     const DiskPartitionMetadata& metadata() const;
 
+    // FIXME: We expose this constructor to make try_create_device helper to work
+    DiskPartition(BlockDevice&, unsigned, DiskPartitionMetadata);
+
 private:
     virtual StringView class_name() const override;
 
-    DiskPartition(BlockDevice&, unsigned, DiskPartitionMetadata);
-
     WeakPtr<BlockDevice> m_device;
     DiskPartitionMetadata m_metadata;
 };
diff --git a/Kernel/Storage/RamdiskDevice.cpp b/Kernel/Storage/RamdiskDevice.cpp
index 283767b148..5d831edae2 100644
--- a/Kernel/Storage/RamdiskDevice.cpp
+++ b/Kernel/Storage/RamdiskDevice.cpp
@@ -14,7 +14,10 @@ namespace Kernel {
 
 NonnullRefPtr<RamdiskDevice> RamdiskDevice::create(const RamdiskController& controller, NonnullOwnPtr<Memory::Region>&& region, int major, int minor)
 {
-    return adopt_ref(*new RamdiskDevice(controller, move(region), major, minor));
+    auto device_or_error = try_create_device<RamdiskDevice>(controller, move(region), major, minor);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!device_or_error.is_error());
+    return device_or_error.release_value();
 }
 
 RamdiskDevice::RamdiskDevice(const RamdiskController& controller, NonnullOwnPtr<Memory::Region>&& region, int major, int minor)
diff --git a/Kernel/Storage/SATADiskDevice.cpp b/Kernel/Storage/SATADiskDevice.cpp
index 87effd650e..0e7c7bd8d4 100644
--- a/Kernel/Storage/SATADiskDevice.cpp
+++ b/Kernel/Storage/SATADiskDevice.cpp
@@ -14,7 +14,10 @@ namespace Kernel {
 
 NonnullRefPtr<SATADiskDevice> SATADiskDevice::create(const AHCIController& controller, const AHCIPort& port, size_t sector_size, u64 max_addressable_block)
 {
-    return adopt_ref(*new SATADiskDevice(controller, port, sector_size, max_addressable_block));
+    auto device_or_error = try_create_device<SATADiskDevice>(controller, port, sector_size, max_addressable_block);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!device_or_error.is_error());
+    return device_or_error.release_value();
 }
 
 SATADiskDevice::SATADiskDevice(const AHCIController& controller, const AHCIPort& port, size_t sector_size, u64 max_addressable_block)
diff --git a/Kernel/Storage/SATADiskDevice.h b/Kernel/Storage/SATADiskDevice.h
index 8c1138b121..97776b4500 100644
--- a/Kernel/Storage/SATADiskDevice.h
+++ b/Kernel/Storage/SATADiskDevice.h
@@ -32,9 +32,10 @@ public:
     virtual void start_request(AsyncBlockDeviceRequest&) override;
     virtual String storage_name() const override;
 
-private:
+    // FIXME: We expose this constructor to make try_create_device helper to work
     SATADiskDevice(const AHCIController&, const AHCIPort&, size_t sector_size, u64 max_addressable_block);
 
+private:
     // ^DiskDevice
     virtual StringView class_name() const override;
     WeakPtr<AHCIPort> m_port;
diff --git a/Kernel/TTY/MasterPTY.cpp b/Kernel/TTY/MasterPTY.cpp
index bb6ad80228..d669ea60b7 100644
--- a/Kernel/TTY/MasterPTY.cpp
+++ b/Kernel/TTY/MasterPTY.cpp
@@ -22,6 +22,8 @@ KResultOr<NonnullRefPtr<MasterPTY>> MasterPTY::try_create(unsigned int index)
     auto master_pty = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) MasterPTY(index, move(buffer))));
     auto slave_pty = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) SlavePTY(*master_pty, index)));
     master_pty->m_slave = slave_pty;
+    master_pty->after_inserting();
+    slave_pty->after_inserting();
     return master_pty;
 }
 
diff --git a/Kernel/TTY/PTYMultiplexer.cpp b/Kernel/TTY/PTYMultiplexer.cpp
index 4cb2e2c10c..22ae1312c0 100644
--- a/Kernel/TTY/PTYMultiplexer.cpp
+++ b/Kernel/TTY/PTYMultiplexer.cpp
@@ -35,6 +35,11 @@ UNMAP_AFTER_INIT PTYMultiplexer::~PTYMultiplexer()
 {
 }
 
+void PTYMultiplexer::initialize()
+{
+    the().after_inserting();
+}
+
 KResultOr<NonnullRefPtr<OpenFileDescription>> PTYMultiplexer::open(int options)
 {
     return m_freelist.with_exclusive([&](auto& freelist) -> KResultOr<NonnullRefPtr<OpenFileDescription>> {
diff --git a/Kernel/TTY/PTYMultiplexer.h b/Kernel/TTY/PTYMultiplexer.h
index 9401f3c7e3..8db52a121b 100644
--- a/Kernel/TTY/PTYMultiplexer.h
+++ b/Kernel/TTY/PTYMultiplexer.h
@@ -20,10 +20,7 @@ public:
     PTYMultiplexer();
     virtual ~PTYMultiplexer() override;
 
-    static void initialize()
-    {
-        the();
-    }
+    static void initialize();
     static PTYMultiplexer& the();
 
     // ^CharacterDevice
diff --git a/Kernel/TTY/SlavePTY.cpp b/Kernel/TTY/SlavePTY.cpp
index 5a4e63ef96..e06ff6949c 100644
--- a/Kernel/TTY/SlavePTY.cpp
+++ b/Kernel/TTY/SlavePTY.cpp
@@ -28,8 +28,10 @@ bool SlavePTY::unref() const
         m_list_node.remove();
         return true;
     });
-    if (did_hit_zero)
+    if (did_hit_zero) {
+        const_cast<SlavePTY&>(*this).before_removing();
         delete this;
+    }
     return did_hit_zero;
 }
 
diff --git a/Kernel/TTY/VirtualConsole.cpp b/Kernel/TTY/VirtualConsole.cpp
index 69935ad69a..58361a3a79 100644
--- a/Kernel/TTY/VirtualConsole.cpp
+++ b/Kernel/TTY/VirtualConsole.cpp
@@ -103,12 +103,18 @@ void VirtualConsole::set_graphical(bool graphical)
 
 UNMAP_AFTER_INIT NonnullRefPtr<VirtualConsole> VirtualConsole::create(size_t index)
 {
-    return adopt_ref(*new VirtualConsole(index));
+    auto virtual_console_or_error = try_create_device<VirtualConsole>(index);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!virtual_console_or_error.is_error());
+    return virtual_console_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT NonnullRefPtr<VirtualConsole> VirtualConsole::create_with_preset_log(size_t index, const CircularQueue<char, 16384>& log)
 {
-    return adopt_ref(*new VirtualConsole(index, log));
+    auto virtual_console_or_error = try_create_device<VirtualConsole>(index, log);
+    // FIXME: Find a way to propagate errors
+    VERIFY(!virtual_console_or_error.is_error());
+    return virtual_console_or_error.release_value();
 }
 
 UNMAP_AFTER_INIT void VirtualConsole::initialize()
diff --git a/Kernel/TTY/VirtualConsole.h b/Kernel/TTY/VirtualConsole.h
index 7f1e17db96..d90e718cbe 100644
--- a/Kernel/TTY/VirtualConsole.h
+++ b/Kernel/TTY/VirtualConsole.h
@@ -84,9 +84,11 @@ public:
 
     void emit_char(char);
 
-private:
+    // FIXME: We expose these constructors to make try_create_device helper to work
     explicit VirtualConsole(const unsigned index);
     VirtualConsole(const unsigned index, const CircularQueue<char, 16384>&);
+
+private:
     // ^KeyboardClient
     virtual void on_key_pressed(KeyEvent) override;