Kernel: Remove FIFO::{attach,detach}(Direction)

These functions would have caused a `-Woverloaded-virtual` warning with
GCC 13, as they shadow `File::{attach,detach}(OpenFileDescription&)`.

Both of these functions had a single call site. This commit inlines
`attach` into its only caller, `FIFO::open_direction`.

Instead of explicitly checking `is_fifo()` in `~OpenFileDescription`
before running the `detach(Direction)` overload, let's just override the
regular `detach(OpenFileDescription&)` for `FIFO` to perform this action
instead.

Kernel/FileSystem/FIFO.cpp

@@ -25,7 +25,12 @@ ErrorOr<NonnullRefPtr<FIFO>> FIFO::try_create(UserID uid)
 ErrorOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction(FIFO::Direction direction)
 {
     auto description = TRY(OpenFileDescription::try_create(*this));
-    attach(direction);
+    if (direction == Direction::Reader) {
+        ++m_readers;
+    } else if (direction == Direction::Writer) {
+        ++m_writers;
+    }
+    evaluate_block_conditions();
     description->set_fifo_direction({}, direction);
     return description;
 }
@@ -73,19 +78,11 @@ FIFO::FIFO(UserID uid, NonnullOwnPtr<DoubleBuffer> buffer)
 
 FIFO::~FIFO() = default;
 
-void FIFO::attach(Direction direction)
+void FIFO::detach(OpenFileDescription& description)
 {
-    if (direction == Direction::Reader) {
+    File::detach(description);
-        ++m_readers;
-    } else if (direction == Direction::Writer) {
-        ++m_writers;
-    }
 
-    evaluate_block_conditions();
+    auto direction = description.fifo_direction();
-}
-
-void FIFO::detach(Direction direction)
-{
     if (direction == Direction::Reader) {
         VERIFY(m_readers);
         --m_readers;

Kernel/FileSystem/FIFO.h

@@ -32,17 +32,12 @@ public:
     ErrorOr<NonnullRefPtr<OpenFileDescription>> open_direction(Direction);
     ErrorOr<NonnullRefPtr<OpenFileDescription>> open_direction_blocking(Direction);
 
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Woverloaded-virtual"
-    void attach(Direction);
-    void detach(Direction);
-#pragma GCC diagnostic pop
-
 private:
     // ^File
     virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override;
     virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
     virtual ErrorOr<struct stat> stat() const override;
+    virtual void detach(OpenFileDescription&) override;
     virtual bool can_read(OpenFileDescription const&, u64) const override;
     virtual bool can_write(OpenFileDescription const&, u64) const override;
     virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(OpenFileDescription const&) const override;

Kernel/FileSystem/OpenFileDescription.cpp

@@ -53,8 +53,6 @@ OpenFileDescription::OpenFileDescription(File& file)
 OpenFileDescription::~OpenFileDescription()
 {
     m_file->detach(*this);
-    if (is_fifo())
-        static_cast<FIFO*>(m_file.ptr())->detach(fifo_direction());
     // FIXME: Should this error path be observed somehow?
     (void)m_file->close();
     if (m_inode)