Kernel: Use KResultOr and TRY() for FIFO

Kernel/FileSystem/FIFO.cpp

@@ -16,12 +16,10 @@ namespace Kernel {
 
 static Atomic<int> s_next_fifo_id = 1;
 
-RefPtr<FIFO> FIFO::try_create(UserID uid)
+KResultOr<NonnullRefPtr<FIFO>> FIFO::try_create(UserID uid)
 {
-    auto buffer_or_error = DoubleBuffer::try_create();
-    if (buffer_or_error.is_error())
-        return {};
-    return adopt_ref_if_nonnull(new (nothrow) FIFO(uid, buffer_or_error.release_value()));
+    auto buffer = TRY(DoubleBuffer::try_create());
+    return adopt_nonnull_ref_or_enomem(new (nothrow) FIFO(uid, move(buffer)));
 }
 
 KResultOr<NonnullRefPtr<OpenFileDescription>> FIFO::open_direction(FIFO::Direction direction)

Kernel/FileSystem/FIFO.h

@@ -24,7 +24,7 @@ public:
         Writer
     };
 
-    static RefPtr<FIFO> try_create(UserID);
+    static KResultOr<NonnullRefPtr<FIFO>> try_create(UserID);
     virtual ~FIFO() override;
 
     UserID uid() const { return m_uid; }

Kernel/FileSystem/Inode.cpp

@@ -163,19 +163,15 @@ void Inode::unregister_watcher(Badge<InodeWatcher>, InodeWatcher& watcher)
     m_watchers.remove(&watcher);
 }
 
-NonnullRefPtr<FIFO> Inode::fifo()
+KResultOr<NonnullRefPtr<FIFO>> Inode::fifo()
 {
     MutexLocker locker(m_inode_lock);
     VERIFY(metadata().is_fifo());
 
     // FIXME: Release m_fifo when it is closed by all readers and writers
-    if (!m_fifo) {
-        m_fifo = FIFO::try_create(metadata().uid);
-        // FIXME: We need to be able to observe OOM here.
-        VERIFY(!m_fifo.is_null());
-    }
+    if (!m_fifo)
+        m_fifo = TRY(FIFO::try_create(metadata().uid));
 
-    VERIFY(m_fifo);
     return *m_fifo;
 }
 

Kernel/FileSystem/Inode.h

@@ -94,7 +94,7 @@ public:
     void register_watcher(Badge<InodeWatcher>, InodeWatcher&);
     void unregister_watcher(Badge<InodeWatcher>, InodeWatcher&);
 
-    NonnullRefPtr<FIFO> fifo();
+    KResultOr<NonnullRefPtr<FIFO>> fifo();
 
     KResult can_apply_flock(OpenFileDescription const&, flock const&) const;
     KResult apply_flock(Process const&, OpenFileDescription const&, Userspace<flock const*>);

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -250,7 +250,7 @@ KResultOr<NonnullRefPtr<OpenFileDescription>> VirtualFileSystem::open(StringView
         return *preopen_fd;
 
     if (metadata.is_fifo()) {
-        auto fifo = inode.fifo();
+        auto fifo = TRY(inode.fifo());
         if (options & O_WRONLY) {
             auto description = TRY(fifo->open_direction_blocking(FIFO::Direction::Writer));
             description->set_rw_mode(options);

Kernel/Syscalls/pipe.cpp

@@ -20,9 +20,7 @@ KResultOr<FlatPtr> Process::sys$pipe(int pipefd[2], int flags)
         return EINVAL;
 
     u32 fd_flags = (flags & O_CLOEXEC) ? FD_CLOEXEC : 0;
-    auto fifo = FIFO::try_create(uid());
-    if (!fifo)
-        return ENOMEM;
+    auto fifo = TRY(FIFO::try_create(uid()));
 
     auto reader_fd_allocation = TRY(m_fds.allocate());
     auto writer_fd_allocation = TRY(m_fds.allocate());