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.

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;
 }
 

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>> {

Kernel/TTY/PTYMultiplexer.h

@@ -20,10 +20,7 @@ public:
     PTYMultiplexer();
     virtual ~PTYMultiplexer() override;
 
-    static void initialize()
-    {
-        the();
-    }
+    static void initialize();
     static PTYMultiplexer& the();
 
     // ^CharacterDevice

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;
 }
 

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()

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;