implement unmount, improve error codes

7 files changed, 66 insertions, 12 deletions

diff --git a/kernel/include/kernel/filesystem/devfs/filesystem.hpp b/kernel/include/kernel/filesystem/devfs/filesystem.hpp
index 60c39cf..137eca3 100644
--- a/kernel/include/kernel/filesystem/devfs/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/devfs/filesystem.hpp
@@ -24,9 +24,9 @@ namespace kernel::filesystem::devfs
     /**
     @brief Initializes the devfs instance and builds the device inode table.
     @param device Backing device passed by the generic filesystem interface (not required by devfs).
-    @return 0 on success, -1 on failure.
+    @return The result of the mount operation.
     */
-    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int override;
+    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result override;
 
     /**
     @brief Looks up an inode by @p name within a @p parent directory.
diff --git a/kernel/include/kernel/filesystem/ext2/filesystem.hpp b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
index 32374dc..65324c8 100644
--- a/kernel/include/kernel/filesystem/ext2/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
@@ -27,9 +27,9 @@ namespace kernel::filesystem::ext2
     /**
     @brief Initializes the ext2 filesystem with the given @p device.
     @param device The device to mount.
-    @return 0 on success, negative error code on failure.
+    @return The result of the mount operation.
     */
-    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int override;
+    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result override;
 
     /**
     @brief Looks up an inode by @p name within a @p parent directory.
diff --git a/kernel/include/kernel/filesystem/filesystem.hpp b/kernel/include/kernel/filesystem/filesystem.hpp
index f855380..ef6929a 100644
--- a/kernel/include/kernel/filesystem/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/filesystem.hpp
@@ -18,6 +18,14 @@ namespace kernel::filesystem
   */
   struct filesystem
   {
+    enum class operation_result : int
+    {
+      success = 0,
+      invalid_magic_number = -1,
+      invalid_root_inode = -2,
+      unmount_failed = -3
+    };
+
     /**
     @brief Virtual destructor for the filesystem.
     */
@@ -37,9 +45,9 @@ namespace kernel::filesystem
     /**
     @brief Initializes the filesystem with the given @p device.
     @param device The device to mount.
-    @return 0 on success, or a negative error code on failure.
+    @return The result of the mount operation.
     */
-    virtual auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int;
+    virtual auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result;
 
     /**
     @brief Looks up a child inode within the given @p parent inode with the specified @p name. This method must be
diff --git a/kernel/include/kernel/filesystem/mount.hpp b/kernel/include/kernel/filesystem/mount.hpp
index 3e3c69f..0ac6b2f 100644
--- a/kernel/include/kernel/filesystem/mount.hpp
+++ b/kernel/include/kernel/filesystem/mount.hpp
@@ -24,9 +24,11 @@ namespace kernel::filesystem
     @param root_dentry The root dentry of the mounted filesystem.
     @param fs The filesystem instance being mounted.
     @param mount_path The path at which the filesystem is mounted.
+    @param parent_mount The parent mount that this mount is attached beneath.
     */
     mount(kstd::shared_ptr<dentry> const & mount_dentry, kstd::shared_ptr<dentry> const & root_dentry,
-          kstd::shared_ptr<filesystem> const & fs, std::string_view mount_path);
+          kstd::shared_ptr<filesystem> const & fs, std::string_view mount_path,
+          kstd::shared_ptr<mount> const & parent_mount);
 
     /**
     @brief Get the dentry where the filesystem is mounted.
@@ -48,11 +50,17 @@ namespace kernel::filesystem
     */
     [[nodiscard]] auto get_mount_path() const -> std::string_view;
 
+    /**
+    @brief Get the parent mount that this mount was attached beneath.
+    */
+    [[nodiscard]] auto get_parent_mount() const -> kstd::shared_ptr<mount> const &;
+
   private:
     kstd::string m_mount_path;
     kstd::shared_ptr<dentry> m_mount_dentry;
     kstd::shared_ptr<dentry> m_root_dentry;
     kstd::shared_ptr<filesystem> m_filesystem{};
+    kstd::shared_ptr<mount> m_parent_mount{};
   };
 }  // namespace kernel::filesystem
 
diff --git a/kernel/include/kernel/filesystem/mount_table.hpp b/kernel/include/kernel/filesystem/mount_table.hpp
index a8ef59e..a5cdde6 100644
--- a/kernel/include/kernel/filesystem/mount_table.hpp
+++ b/kernel/include/kernel/filesystem/mount_table.hpp
@@ -16,10 +16,27 @@ namespace kernel::filesystem
   struct mount_table
   {
     /**
+    @brief Results for mount table operations.
+    */
+    enum class operation_result : int
+    {
+      removed = 0,
+      has_child_mounts = -1,
+      mount_not_found = -2
+    };
+
+    /**
     @brief Adds a mount to the table.
     @param mount The mount to add.
     */
-    void add_mount(kstd::shared_ptr<mount> const & mount);
+    auto add_mount(kstd::shared_ptr<mount> const & mount) -> void;
+
+    /**
+    @brief Removes the topmost mount at the given @p path.
+    @param path The mount path to remove.
+    @return The result of the removal operation.
+    */
+    [[nodiscard]] auto remove_mount(std::string_view path) -> operation_result;
 
     /**
     @brief Finds the mount with the longest prefix matching the given @p path. This method is used to determine which
@@ -30,6 +47,8 @@ namespace kernel::filesystem
     [[nodiscard]] auto find_longest_prefix_mount(std::string_view path) const -> kstd::shared_ptr<mount>;
 
   private:
+    [[nodiscard]] auto has_child_mounts(kstd::shared_ptr<mount> const & parent_mount) const -> bool;
+
     kstd::vector<kstd::shared_ptr<mount>> m_mounts;
   };
 }  // namespace kernel::filesystem
diff --git a/kernel/include/kernel/filesystem/rootfs/filesystem.hpp b/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
index b7e7c6f..0155c41 100644
--- a/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
@@ -25,9 +25,9 @@ namespace kernel::filesystem::rootfs
     /**
     @brief Initializes the rootfs filesystem with the given @p device.
     @param device The device to mount (not required by rootfs).
-    @return 0 on success, negative error code on failure.
+    @return The result of the mount operation.
     */
-    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int override;
+    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result override;
 
     /**
     @brief Looks up an inode by @p name within a @p parent directory.
diff --git a/kernel/include/kernel/filesystem/vfs.hpp b/kernel/include/kernel/filesystem/vfs.hpp
index 2d05765..4dd2a83 100644
--- a/kernel/include/kernel/filesystem/vfs.hpp
+++ b/kernel/include/kernel/filesystem/vfs.hpp
@@ -21,6 +21,18 @@ namespace kernel::filesystem
   struct vfs
   {
     /**
+    @brief Results for VFS operations.
+    */
+    enum class operation_result : int
+    {
+      success = 0,
+      invalid_path = -1,
+      mount_point_not_found = -2,
+      filesystem_null = -3,
+      unmount_failed = -4
+    };
+
+    /**
     @brief Initialize the virtual filesystem.
     @warning Panics if the VFS has already been initialized.
     */
@@ -49,9 +61,16 @@ namespace kernel::filesystem
     @brief Mount a @p filesystem at a specific @p path.
     @param path The path where the filesystem should be mounted.
     @param filesystem The filesystem to mount.
-    @return 0 on success, or a negative error code on failure.
+    @return The result of the mount operation.
+    */
+    auto do_mount(std::string_view path, kstd::shared_ptr<filesystem> const & filesystem) -> operation_result;
+
+    /**
+    @brief Unmount the filesystem mounted at the specified @p path.
+    @param path The path where the filesystem is mounted.
+    @return The result of the unmount operation.
     */
-    auto do_mount(std::string_view path, kstd::shared_ptr<filesystem> const & filesystem) -> int;
+    auto unmount(std::string_view path) -> operation_result;
 
   private:
     vfs() = default;