refactor: promote new architecture to repository root

Archive the deprecated implementation under lume-legacy, make the new kernel the default root-level build, and update repository entry points without changing kernel behavior.

1 files changed, 90 insertions, 0 deletions

diff --git a/fs/fs_struct.cc b/fs/fs_struct.cc
new file mode 100644
index 0000000..090819f
--- /dev/null
+++ b/fs/fs_struct.cc
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * fs_struct.cc — Per-task filesystem context (cwd, root)
+ */
+
+#include <lume/fs_struct.h>
+#include <lume/slab.h>
+
+/* ================================================================== */
+/*  alloc_fs_struct                                                   */
+/* ================================================================== */
+
+fs_struct* alloc_fs_struct()
+{
+    auto* fs = new fs_struct{};
+    if (!fs) return nullptr;
+
+    fs->count.store(1);
+    fs->umask = 022;
+    fs->root = {nullptr, nullptr};
+    fs->pwd  = {nullptr, nullptr};
+
+    return fs;
+}
+
+/* ================================================================== */
+/*  put_fs_struct                                                     */
+/* ================================================================== */
+
+void put_fs_struct(fs_struct* fs)
+{
+    if (!fs) return;
+
+    int old = fs->count.fetch_sub(1);
+    if (old > 1) return;
+
+    path_put(&fs->root);
+    path_put(&fs->pwd);
+    delete fs;
+}
+
+/* ================================================================== */
+/*  copy_fs_struct — for fork without CLONE_FS                        */
+/* ================================================================== */
+
+fs_struct* copy_fs_struct(const fs_struct* old_fs)
+{
+    auto* fs = alloc_fs_struct();
+    if (!fs) return nullptr;
+
+    fs->umask = old_fs->umask;
+
+    fs->root = old_fs->root;
+    path_get(&fs->root);
+
+    fs->pwd = old_fs->pwd;
+    path_get(&fs->pwd);
+
+    return fs;
+}
+
+/* ================================================================== */
+/*  set_fs_root / set_fs_pwd                                          */
+/* ================================================================== */
+
+void set_fs_root(fs_struct* fs, const path* p)
+{
+    path old_root;
+    {
+        LockGuard guard(fs->lock);
+        old_root = fs->root;
+        fs->root = *p;
+        path_get(p);
+    }
+    path_put(&old_root);
+}
+
+void set_fs_pwd(fs_struct* fs, const path* p)
+{
+    path old_pwd;
+    {
+        LockGuard guard(fs->lock);
+        old_pwd = fs->pwd;
+        fs->pwd = *p;
+        path_get(p);
+    }
+    path_put(&old_pwd);
+}