From c09ef501e1baf293d92b166e5e38e29a41cf64c2 Mon Sep 17 00:00:00 2001
From: Lukas Oesch <lukasoesch20@gmail.com>
Date: Tue, 9 Jun 2026 11:06:25 +0200
Subject: implement mkdir and create function in kapi::filesystem that calls
 the vfs and then the underlying filesystem

---
 kapi/kapi/filesystem.hpp                           | 18 +++++++++
 kernel/kapi/filesystem.cpp                         | 12 ++++++
 kernel/kernel/filesystem/devfs/filesystem.cpp      | 10 ++++-
 kernel/kernel/filesystem/devfs/filesystem.hpp      | 12 ++++++
 kernel/kernel/filesystem/error.hpp                 |  5 +++
 kernel/kernel/filesystem/ext2/filesystem.hpp       |  3 +-
 kernel/kernel/filesystem/filesystem.hpp            | 12 ++++++
 kernel/kernel/filesystem/path.hpp                  | 32 +++++++++++++++
 kernel/kernel/filesystem/rootfs/filesystem.cpp     |  9 ++++-
 kernel/kernel/filesystem/rootfs/filesystem.hpp     | 12 ++++++
 kernel/kernel/filesystem/vfs.cpp                   | 46 ++++++++++++++++++++++
 kernel/kernel/filesystem/vfs.hpp                   | 18 +++++++++
 .../kernel/test_support/filesystem/filesystem.cpp  | 12 +++++-
 .../kernel/test_support/filesystem/filesystem.hpp  |  9 ++++-
 14 files changed, 202 insertions(+), 8 deletions(-)

diff --git a/kapi/kapi/filesystem.hpp b/kapi/kapi/filesystem.hpp
index 5346a96d..1656a17f 100644
--- a/kapi/kapi/filesystem.hpp
+++ b/kapi/kapi/filesystem.hpp
@@ -1,6 +1,7 @@
 #ifndef TEACHOS_KAPI_FILESYSTEM_HPP
 #define TEACHOS_KAPI_FILESYSTEM_HPP
 
+#include <kstd/result.hpp>
 #include <kstd/system_error.hpp>
 
 #include <cstddef>
@@ -69,6 +70,23 @@ namespace kapi::filesystem
   @qualifier kernel-defined
   */
   auto write(size_t file_descriptor, void const * buffer, size_t size) -> std::expected<std::size_t, kstd::error_code>;
+
+  /**
+  @brief Creates a new directory at the specified @p path.
+  @param path The path where the new directory should be created.
+  @return 0 on success, -1 on failure.
+  @qualifier kernel-defined
+  */
+  auto mkdir(std::string_view path) -> kstd::result<void>;
+
+  /**
+  @brief Creates a new file at the specified @p path.
+  @param path The path where the new file should be created.
+  @return 0 on success, -1 on failure.
+  @qualifier kernel-defined
+  */
+  // TODO remove again after the open method supports an optional create flag
+  auto create(std::string_view path) -> kstd::result<void>;
 }  // namespace kapi::filesystem
 
 #endif  // TEACHOS_KAPI_FILESYSTEM_HPP
\ No newline at end of file
diff --git a/kernel/kapi/filesystem.cpp b/kernel/kapi/filesystem.cpp
index efde1336..822095e6 100644
--- a/kernel/kapi/filesystem.cpp
+++ b/kernel/kapi/filesystem.cpp
@@ -5,6 +5,7 @@
 #include <kernel/filesystem/vfs.hpp>
 
 #include <kstd/memory.hpp>
+#include <kstd/result.hpp>
 #include <kstd/system_error.hpp>
 
 #include <cstddef>
@@ -53,4 +54,15 @@ namespace kapi::filesystem
       return descriptor->write(buffer, size);
     });
   }
+
+  auto mkdir(std::string_view path) -> kstd::result<void>
+  {
+    return kernel::filesystem::vfs::get().mkdir(path);
+  }
+
+  auto create(std::string_view path) -> kstd::result<void>
+  {
+    return kernel::filesystem::vfs::get().create(path);
+  }
+
 }  // namespace kapi::filesystem
\ No newline at end of file
diff --git a/kernel/kernel/filesystem/devfs/filesystem.cpp b/kernel/kernel/filesystem/devfs/filesystem.cpp
index 7ffcb3c4..66799988 100644
--- a/kernel/kernel/filesystem/devfs/filesystem.cpp
+++ b/kernel/kernel/filesystem/devfs/filesystem.cpp
@@ -1,12 +1,13 @@
 #include <kernel/filesystem/devfs/filesystem.hpp>
 
-#include "kernel/filesystem/filesystem.hpp"
 #include <kernel/devices/storage/management.hpp>
 #include <kernel/filesystem/devfs/inode.hpp>
 #include <kernel/filesystem/device_inode.hpp>
 #include <kernel/filesystem/error.hpp>
+#include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/inode.hpp>
 #include <kernel/filesystem/type.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kapi/devices/device.hpp>
 
@@ -82,6 +83,13 @@ namespace kernel::filesystem::devfs
     return kstd::failure(vfs_errc::no_such_file_or_directory);
   }
 
+  auto filesystem::create_inode(kstd::shared_ptr<kernel::filesystem::inode> const &, std::string_view,
+                                kernel::filesystem::vfs_types::inode_type)
+      -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>>
+  {
+    return kstd::failure(vfs_errc::read_only_file_system);
+  }
+
   auto filesystem::build_device_inode_table() -> void
   {
     m_inodes.clear();
diff --git a/kernel/kernel/filesystem/devfs/filesystem.hpp b/kernel/kernel/filesystem/devfs/filesystem.hpp
index dadeaf7d..be3c119c 100644
--- a/kernel/kernel/filesystem/devfs/filesystem.hpp
+++ b/kernel/kernel/filesystem/devfs/filesystem.hpp
@@ -4,6 +4,7 @@
 #include <kernel/filesystem/device_inode.hpp>
 #include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/result.hpp>
@@ -38,6 +39,17 @@ namespace kernel::filesystem::devfs
     [[nodiscard]] auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name) const
         -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
 
+    /**
+    @brief Creates a new inode with @p name within a @p parent directory.
+    @param parent The parent directory inode.
+    @param name The name of the inode to create.
+    @param inode_type The type of inode to be created.
+    @return Always returns nullptr, as creating new inodes is not supported in devfs.
+    */
+    [[nodiscard]] auto create_inode(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name,
+                                    kernel::filesystem::vfs_types::inode_type inode_type)
+        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
+
   private:
     auto build_device_inode_table() -> void;
 
diff --git a/kernel/kernel/filesystem/error.hpp b/kernel/kernel/filesystem/error.hpp
index 56f56ce4..82ba33b3 100644
--- a/kernel/kernel/filesystem/error.hpp
+++ b/kernel/kernel/filesystem/error.hpp
@@ -24,6 +24,7 @@ namespace kernel::filesystem
     invalid_inode,
     not_a_directory,
     is_a_directory,
+    read_only_file_system,
   };
 
   namespace detail
@@ -65,6 +66,8 @@ namespace kernel::filesystem
             return "not a directory";
           case vfs_errc::is_a_directory:
             return "is a directory";
+          case vfs_errc::read_only_file_system:
+            return "readonly filesystem";
           default:
             return "unknown VFS error";
         }
@@ -95,6 +98,8 @@ namespace kernel::filesystem
             return make_error_condition(kstd::errc::not_a_directory);
           case vfs_errc::is_a_directory:
             return make_error_condition(kstd::errc::is_a_directory);
+          case vfs_errc::read_only_file_system:
+            return make_error_condition(kstd::errc::read_only_file_system);
           default:
             return kstd::error_condition{value, *this};
         }
diff --git a/kernel/kernel/filesystem/ext2/filesystem.hpp b/kernel/kernel/filesystem/ext2/filesystem.hpp
index 03398f00..9af9aeb1 100644
--- a/kernel/kernel/filesystem/ext2/filesystem.hpp
+++ b/kernel/kernel/filesystem/ext2/filesystem.hpp
@@ -16,7 +16,6 @@
 #include <array>
 #include <cstddef>
 #include <cstdint>
-#include <optional>
 #include <string_view>
 
 namespace kernel::filesystem::ext2
@@ -77,7 +76,7 @@ namespace kernel::filesystem::ext2
     */
     [[nodiscard]] auto create_inode(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name,
                                     kernel::filesystem::vfs_types::inode_type inode_type)
-        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>>;  // TODO move into base class and override
+        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
 
     /**
     @brief Gets the size of a block in the filesystem.
diff --git a/kernel/kernel/filesystem/filesystem.hpp b/kernel/kernel/filesystem/filesystem.hpp
index 1264d00d..aa6286bf 100644
--- a/kernel/kernel/filesystem/filesystem.hpp
+++ b/kernel/kernel/filesystem/filesystem.hpp
@@ -2,6 +2,7 @@
 #define TEACH_OS_KERNEL_FILESYSTEM_FILESYSTEM_HPP
 
 #include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/result.hpp>
@@ -53,6 +54,17 @@ namespace kernel::filesystem
     [[nodiscard]] virtual auto lookup(kstd::shared_ptr<inode> const & parent, std::string_view name) const
         -> kstd::result<kstd::shared_ptr<inode>> = 0;
 
+    /**
+    @brief Creates a new inode with @p name within a @p parent directory.
+    @param parent The parent directory inode.
+    @param name The name of the inode to create.
+    @param inode_type The type of inode to be created.
+    @return A pointer to the created inode, or a null pointer if creation failed.
+    */
+    [[nodiscard]] virtual auto create_inode(kstd::shared_ptr<inode> const & parent, std::string_view name,
+                                            vfs_types::inode_type inode_type)
+        -> kstd::result<kstd::shared_ptr<inode>> = 0;
+
     /**
     @brief Returns a reference to the root inode of the filesystem.
     */
diff --git a/kernel/kernel/filesystem/path.hpp b/kernel/kernel/filesystem/path.hpp
index 438c22f3..c2d8e588 100644
--- a/kernel/kernel/filesystem/path.hpp
+++ b/kernel/kernel/filesystem/path.hpp
@@ -7,6 +7,7 @@
 
 #include <ranges>
 #include <string_view>
+#include <utility>
 
 namespace kernel::filesystem::path
 {
@@ -66,6 +67,37 @@ namespace kernel::filesystem::path
                [](auto const & part) { return kstd::string(std::string_view(part.begin(), part.end())); });
   }
 
+  /**
+  @brief Splits the given path into its parent path and filename components.
+  @param path The path to split.
+  @return A pair of string views representing the parent path and filename.
+  */
+  auto inline split_into_path_and_filename(std::string_view path) -> std::pair<std::string_view, std::string_view>
+  {
+    if (path.empty())
+    {
+      return {"", ""};
+    }
+
+    auto search_from = path.length() > 1 ? path.length() - 2 : 0;
+    auto last_separator_index = path.rfind('/', search_from);
+
+    if (last_separator_index == std::string_view::npos)
+    {
+      return {"", path};
+    }
+    else
+    {
+      auto parent_path = path.substr(0, last_separator_index);
+      if (parent_path.empty())
+      {
+        parent_path = "/";
+      }
+      auto filename = path.substr(last_separator_index + 1);
+      return {parent_path, filename};
+    }
+  }
+
 }  // namespace kernel::filesystem::path
 
 #endif  // TEACH_OS_KERNEL_FILESYSTEM_PATH_HPP
\ No newline at end of file
diff --git a/kernel/kernel/filesystem/rootfs/filesystem.cpp b/kernel/kernel/filesystem/rootfs/filesystem.cpp
index fef43e28..5ff56547 100644
--- a/kernel/kernel/filesystem/rootfs/filesystem.cpp
+++ b/kernel/kernel/filesystem/rootfs/filesystem.cpp
@@ -5,6 +5,7 @@
 #include <kernel/filesystem/inode.hpp>
 #include <kernel/filesystem/rootfs/inode.hpp>
 #include <kernel/filesystem/type.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/result.hpp>
@@ -14,7 +15,6 @@
 
 namespace kernel::filesystem::rootfs
 {
-
   struct type final : kernel::filesystem::type
   {
     [[nodiscard]] auto name() const noexcept -> std::string_view override
@@ -47,4 +47,11 @@ namespace kernel::filesystem::rootfs
   {
     return kstd::failure(vfs_errc::no_such_file_or_directory);
   }
+
+  auto filesystem::create_inode(kstd::shared_ptr<kernel::filesystem::inode> const &, std::string_view,
+                                kernel::filesystem::vfs_types::inode_type)
+      -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>>
+  {
+    return kstd::failure(vfs_errc::read_only_file_system);
+  }
 }  // namespace kernel::filesystem::rootfs
diff --git a/kernel/kernel/filesystem/rootfs/filesystem.hpp b/kernel/kernel/filesystem/rootfs/filesystem.hpp
index 8507d8b8..498503c5 100644
--- a/kernel/kernel/filesystem/rootfs/filesystem.hpp
+++ b/kernel/kernel/filesystem/rootfs/filesystem.hpp
@@ -3,6 +3,7 @@
 
 #include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/result.hpp>
@@ -37,6 +38,17 @@ namespace kernel::filesystem::rootfs
     */
     [[nodiscard]] auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name) const
         -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
+
+    /**
+    @brief Creates a new inode with @p name within a @p parent directory.
+    @param parent The parent directory inode.
+    @param name The name of the inode to create.
+    @param inode_type The type of inode to be created.
+    @return Always returns nullptr, as creating new inodes is not supported in devfs.
+    */
+    [[nodiscard]] auto create_inode(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name,
+                                    kernel::filesystem::vfs_types::inode_type inode_type)
+        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
   };
 }  // namespace kernel::filesystem::rootfs
 
diff --git a/kernel/kernel/filesystem/vfs.cpp b/kernel/kernel/filesystem/vfs.cpp
index d128bbf5..2e4145db 100644
--- a/kernel/kernel/filesystem/vfs.cpp
+++ b/kernel/kernel/filesystem/vfs.cpp
@@ -9,6 +9,7 @@
 #include <kernel/filesystem/mount_table.hpp>
 #include <kernel/filesystem/path.hpp>
 #include <kernel/filesystem/rootfs/filesystem.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kapi/system.hpp>
 
@@ -171,6 +172,51 @@ namespace kernel::filesystem
     return kstd::failure(vfs_errc::unmount_failed);
   }
 
+  auto vfs::mkdir(std::string_view path) -> kstd::result<void>
+  {
+    return create_inode(path, vfs_types::inode_type::directory);
+  }
+
+  auto vfs::create(std::string_view path) -> kstd::result<void>
+  {
+    return create_inode(path, vfs_types::inode_type::regular);
+  }
+
+  auto vfs::create_inode(std::string_view path, vfs_types::inode_type type) -> kstd::result<void>
+  {
+    if (!path::is_valid_path(path))
+    {
+      return kstd::failure(vfs_errc::invalid_path);
+    }
+
+    auto [parent_path, name] = path::split_into_path_and_filename(path);
+    if (name.empty())
+    {
+      return kstd::failure(vfs_errc::invalid_path);
+    }
+
+    auto resolved_parent = resolve_path_internal(parent_path);
+    if (!resolved_parent)
+    {
+      return kstd::failure(resolved_parent.error());
+    }
+
+    auto [parent_dentry, mount_context] = *resolved_parent;
+
+    if (auto fs = mount_context->get_filesystem())
+    {
+      if (auto new_inode = fs->create_inode(parent_dentry->get_inode(), name, type))
+      {
+        auto new_dentry = kstd::make_shared<dentry>(parent_dentry, *new_inode, name);
+        parent_dentry->add_child(new_dentry);
+
+        return kstd::success();
+      }
+    }
+
+    return kstd::failure(vfs_errc::no_such_file_or_directory);
+  }
+
   auto vfs::do_mount_internal(dentry_ptr const & mount_point_dentry, mount_ptr const & parent_mount, fs_ptr const & fs,
                               mount_ptr const & source_mount) -> void
   {
diff --git a/kernel/kernel/filesystem/vfs.hpp b/kernel/kernel/filesystem/vfs.hpp
index 9dfd3637..beb336a4 100644
--- a/kernel/kernel/filesystem/vfs.hpp
+++ b/kernel/kernel/filesystem/vfs.hpp
@@ -6,6 +6,7 @@
 #include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/mount.hpp>
 #include <kernel/filesystem/mount_table.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/result.hpp>
@@ -77,6 +78,21 @@ namespace kernel::filesystem
     */
     auto unmount(std::string_view path) -> kstd::result<void>;
 
+    /**
+    @brief Create a new directory at the specified @p path.
+    @param path The path where the new directory should be created.
+    @return The result of the mkdir operation.
+    */
+    auto mkdir(std::string_view path) -> kstd::result<void>;
+
+    /**
+    @brief Create a new file at the specified @p path.
+    @param path The path where the new file should be created.
+    @return The result of the create operation.
+    */
+    // TODO remove again after the open method supports an optional create flag
+    auto create(std::string_view path) -> kstd::result<void>;
+
   private:
     /**
      * Note: Resolving a dentry requires traversing mount points; since the
@@ -100,6 +116,8 @@ namespace kernel::filesystem
 
     auto graft_persistent_device_fs(kstd::shared_ptr<devfs::filesystem> const & device_fs) -> void;
 
+    auto create_inode(std::string_view path, vfs_types::inode_type type) -> kstd::result<void>;
+
     mount_table m_mount_table{};
   };
 }  // namespace kernel::filesystem
diff --git a/kernel/kernel/test_support/filesystem/filesystem.cpp b/kernel/kernel/test_support/filesystem/filesystem.cpp
index 38cea2f1..b48c7935 100644
--- a/kernel/kernel/test_support/filesystem/filesystem.cpp
+++ b/kernel/kernel/test_support/filesystem/filesystem.cpp
@@ -1,18 +1,26 @@
 #include <kernel/test_support/filesystem/filesystem.hpp>
 
 #include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 #include <kernel/test_support/filesystem/inode.hpp>
 
 #include <kstd/memory.hpp>
+#include <kstd/result.hpp>
 #include <kstd/system_error.hpp>
 
-#include <expected>
 #include <string_view>
 
 namespace kernel::tests::filesystem
 {
   auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const &, std::string_view) const
-      -> std::expected<kstd::shared_ptr<kernel::filesystem::inode>, kstd::error_code>
+      -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>>
+  {
+    return kstd::make_shared<inode>();
+  }
+
+  auto filesystem::create_inode(kstd::shared_ptr<kernel::filesystem::inode> const &, std::string_view,
+                                kernel::filesystem::vfs_types::inode_type)
+      -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>>
   {
     return kstd::make_shared<inode>();
   }
diff --git a/kernel/kernel/test_support/filesystem/filesystem.hpp b/kernel/kernel/test_support/filesystem/filesystem.hpp
index e6e0f416..17edd079 100644
--- a/kernel/kernel/test_support/filesystem/filesystem.hpp
+++ b/kernel/kernel/test_support/filesystem/filesystem.hpp
@@ -3,11 +3,12 @@
 
 #include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/vfs_types.hpp>
 
 #include <kstd/memory.hpp>
+#include <kstd/result.hpp>
 #include <kstd/system_error.hpp>
 
-#include <expected>
 #include <string_view>
 
 namespace kernel::tests::filesystem
@@ -17,7 +18,11 @@ namespace kernel::tests::filesystem
     filesystem() = default;
 
     [[nodiscard]] auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name) const
-        -> std::expected<kstd::shared_ptr<kernel::filesystem::inode>, kstd::error_code> override;
+        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
+
+    [[nodiscard]] auto create_inode(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name,
+                                    kernel::filesystem::vfs_types::inode_type inode_type)
+        -> kstd::result<kstd::shared_ptr<kernel::filesystem::inode>> override;
   };
 }  // namespace kernel::tests::filesystem
 
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