Merge branch 'mount-reference-count' into 'develop-BA-FS26'

Mount reference count

See merge request teachos/kernel!37

7 files changed, 75 insertions, 46 deletions

diff --git a/kernel/include/kernel/filesystem/dentry.hpp b/kernel/include/kernel/filesystem/dentry.hpp
index 7eef693..925768a 100644
--- a/kernel/include/kernel/filesystem/dentry.hpp
+++ b/kernel/include/kernel/filesystem/dentry.hpp
@@ -24,8 +24,7 @@ namespace kernel::filesystem
     */
     enum class dentry_flags : uint32_t
     {
-      is_mount_point = 1 << 0,
-      is_mount_root = 1 << 1,
+      is_mount_point = 1 << 0
     };
 
     /**
@@ -62,12 +61,6 @@ namespace kernel::filesystem
     [[nodiscard]] auto get_absolute_path() const -> kstd::string;
 
     /**
-    @brief traverse parent dentries until dentry with is_mount_root flag is found.
-    @return The found dentry.
-    */
-    [[nodiscard]] auto find_mount_root_dentry() const -> kstd::shared_ptr<dentry>;
-
-    /**
     @brief Add a @p child dentry.
     @param child The child dentry to add.
     */
@@ -104,7 +97,7 @@ namespace kernel::filesystem
     kstd::shared_ptr<dentry> m_parent;
     kstd::vector<kstd::shared_ptr<dentry>> m_children;
     kstd::shared_ptr<inode> m_inode;
-    uint32_t m_flags{0};
+    uint32_t m_flags;
   };
 }  // namespace kernel::filesystem
 
diff --git a/kernel/include/kernel/filesystem/mount.hpp b/kernel/include/kernel/filesystem/mount.hpp
index f920891..5d8ea69 100644
--- a/kernel/include/kernel/filesystem/mount.hpp
+++ b/kernel/include/kernel/filesystem/mount.hpp
@@ -8,6 +8,7 @@
 #include <kstd/string>
 
 #include <atomic>
+#include <cstddef>
 
 namespace kernel::filesystem
 {
@@ -54,12 +55,35 @@ namespace kernel::filesystem
     */
     [[nodiscard]] auto get_parent_mount() const -> kstd::shared_ptr<mount> const &;
 
+    /**
+    @brief Increment the reference count for this mount.
+    */
+    auto increment_ref_count() -> void;
+
+    /**
+    @brief Decrement the reference count for this mount.
+    @return True if the reference count reached zero, false otherwise.
+    */
+    auto decrement_ref_count() -> bool;
+
+    /**
+    @brief Check if the mount is ready to be unmounted.
+    @return True if the mount is ready to be unmounted, false otherwise.
+    */
+    [[nodiscard]] auto is_ready_to_unmount() const -> bool;
+
+    /**
+    @brief Get the current reference count for this mount.
+    @return The current reference count.
+    */
+    [[nodiscard]] auto get_ref_count() const -> size_t;
+
   private:
     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{};
-    std::atomic_uint32_t m_ref_count{0};  // TODO BA-FS26
+    std::atomic_size_t m_ref_count;
   };
 }  // namespace kernel::filesystem
 
diff --git a/kernel/include/kernel/filesystem/mount_table.hpp b/kernel/include/kernel/filesystem/mount_table.hpp
index 59b9503..4f2d1b7 100644
--- a/kernel/include/kernel/filesystem/mount_table.hpp
+++ b/kernel/include/kernel/filesystem/mount_table.hpp
@@ -22,7 +22,8 @@ namespace kernel::filesystem
     {
       removed = 0,
       has_child_mounts = -1,
-      mount_not_found = -2
+      mount_not_found = -2,
+      cannot_be_unmounted = -3
     };
 
     /**
@@ -43,10 +44,12 @@ namespace kernel::filesystem
     @param path The path to match against the mount paths in the table.
     @return A pointer to the mount with the exact matching path, or a null pointer if no mount matches the path.
     */
-    [[nodiscard]] auto find_exact_mount(std::string_view path) const -> kstd::shared_ptr<mount>;
+    [[nodiscard]] auto find_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;
+    [[nodiscard]] auto find_mount_iterator(std::string_view path) const
+        -> kstd::vector<kstd::shared_ptr<mount>>::const_iterator;
 
     kstd::vector<kstd::shared_ptr<mount>> m_mounts;
   };
diff --git a/kernel/include/kernel/filesystem/open_file_descriptor.hpp b/kernel/include/kernel/filesystem/open_file_descriptor.hpp
index 036dcf0..7ca7350 100644
--- a/kernel/include/kernel/filesystem/open_file_descriptor.hpp
+++ b/kernel/include/kernel/filesystem/open_file_descriptor.hpp
@@ -1,7 +1,7 @@
 #ifndef TEACH_OS_KERNEL_FILESYSTEM_OPEN_FILE_DESCRIPTOR_HPP
 #define TEACH_OS_KERNEL_FILESYSTEM_OPEN_FILE_DESCRIPTOR_HPP
 
-#include <kernel/filesystem/inode.hpp>
+#include <kernel/filesystem/dentry.hpp>
 
 #include <kstd/memory>
 
@@ -11,15 +11,15 @@ namespace kernel::filesystem
 {
   /**
   @brief Represents an open file descriptor in the filesystem. This class encapsulates the state of an open file,
-  including a reference to the associated inode and the current file offset.
+  including a reference to the associated dentry and the current file offset.
   */
   struct open_file_descriptor
   {
     /**
-    @brief Constructs an open file descriptor for the given @p inode.
-    @param inode The inode to associate with the open file descriptor.
+    @brief Constructs an open file descriptor for the given @p dentry.
+    @param dentry The dentry to associate with the open file descriptor.
     */
-    explicit open_file_descriptor(kstd::shared_ptr<inode> const & inode);
+    explicit open_file_descriptor(kstd::shared_ptr<dentry> const & dentry);
 
     /**
     @brief Destructor for the open file descriptor.
@@ -50,10 +50,16 @@ namespace kernel::filesystem
     @brief Returns the current file offset for this open file descriptor.
     @return The current file offset in bytes.
      */
-    [[nodiscard]] auto offset() const -> size_t;
+    [[nodiscard]] auto get_offset() const -> size_t;
+
+    /**
+    @brief Return a reference to the dentry associated with this open file descriptor.
+    @return A reference to the associated dentry.
+     */
+    [[nodiscard]] auto get_dentry() const -> kstd::shared_ptr<dentry> const &;
 
   private:
-    kstd::shared_ptr<inode> m_inode;
+    kstd::shared_ptr<dentry> m_dentry;
     size_t m_offset;
   };
 
diff --git a/kernel/include/kernel/filesystem/rootfs/filesystem.hpp b/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
index cc778d8..f99440b 100644
--- a/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/rootfs/filesystem.hpp
@@ -31,7 +31,7 @@ namespace kernel::filesystem::rootfs
     @brief Looks up an inode by @p name within a @p parent directory.
     @param parent The parent directory inode.
     @param name The name of the inode to look up.
-    @return A pointer to the found inode, or a null pointer if not found.
+    @return Always returns nullptr.
     */
     auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
         -> kstd::shared_ptr<kernel::filesystem::inode> override;
diff --git a/kernel/include/kernel/filesystem/rootfs/inode.hpp b/kernel/include/kernel/filesystem/rootfs/inode.hpp
index 58035ea..2671207 100644
--- a/kernel/include/kernel/filesystem/rootfs/inode.hpp
+++ b/kernel/include/kernel/filesystem/rootfs/inode.hpp
@@ -8,16 +8,10 @@
 #include <kstd/vector>
 
 #include <cstddef>
-#include <string_view>
-#include <utility>
-
 namespace kernel::filesystem::rootfs
 {
   /**
-  @brief Represents an inode in the rootfs filesystem. This inode represents a directory in the root filesystem and
-  maintains a list of child inodes corresponding to files and subdirectories within the root directory. The rootfs inode
-  provides methods for reading and writing data (which are no-ops for the root directory), as well as adding and looking
-  up child inodes by name.
+  @brief Represents an inode in the rootfs filesystem.
   */
   struct inode : kernel::filesystem::inode
   {
@@ -40,26 +34,10 @@ namespace kernel::filesystem::rootfs
     auto write(void const * buffer, size_t offset, size_t size) -> size_t override;
 
     /**
-    @brief Adds a child inode to the rootfs directory inode with the specified @p name.
-    @param name The name of the child inode.
-    */
-    auto add_child(std::string_view name) -> void;
-
-    /**
-    @brief Looks up a child inode by @p name.
-    @param name The name of the child inode to look up.
-    @return A pointer to the found child inode, or a null pointer if not found.
-    */
-    auto lookup_child(std::string_view name) -> kstd::shared_ptr<inode>;
-
-    /**
     @brief Check if this inode represents a directory.
-    @return returns true, since this inode represents the root directory in the rootfs filesystem.
+    @return returns true, since this inode represents the / directory in the rootfs filesystem.
     */
     [[nodiscard]] auto is_directory() const -> bool override;
-
-  private:
-    kstd::vector<std::pair<kstd::string, kstd::shared_ptr<inode>>> m_children;
   };
 }  // namespace kernel::filesystem::rootfs
 
diff --git a/kernel/include/kernel/filesystem/vfs.hpp b/kernel/include/kernel/filesystem/vfs.hpp
index b5053a2..0058d04 100644
--- a/kernel/include/kernel/filesystem/vfs.hpp
+++ b/kernel/include/kernel/filesystem/vfs.hpp
@@ -1,14 +1,16 @@
 #ifndef TEACH_OS_KERNEL_FILESYSTEM_VFS_HPP
 #define TEACH_OS_KERNEL_FILESYSTEM_VFS_HPP
 
-#include "kernel/filesystem/devfs/filesystem.hpp"
 #include <kernel/filesystem/dentry.hpp>
+#include <kernel/filesystem/devfs/filesystem.hpp>
 #include <kernel/filesystem/filesystem.hpp>
+#include <kernel/filesystem/mount.hpp>
 #include <kernel/filesystem/mount_table.hpp>
 
 #include <kstd/memory>
 
 #include <string_view>
+#include <utility>
 
 namespace kernel::filesystem
 {
@@ -31,6 +33,7 @@ namespace kernel::filesystem
       mount_point_not_found = -3,
       unmount_failed = -4,
       invalid_filesystem = -5,
+      close_failed = -6
     };
 
     /**
@@ -59,6 +62,13 @@ namespace kernel::filesystem
     auto open(std::string_view path) -> kstd::shared_ptr<dentry>;
 
     /**
+    @brief Close a file by its associated @p path.
+    @param path The path to the file to close.
+    @return The result of the close operation.
+    */
+    auto close(std::string_view path) -> operation_result;
+
+    /**
     @brief Mount a @p source path to a specific @p target path.
     @param source The source of the filesystem to mount.
     @param target The path where the filesystem should be mounted.
@@ -77,8 +87,23 @@ namespace kernel::filesystem
     vfs() = default;
     auto init_internal() -> void;
 
+    /**
+     * Note: Resolving a dentry requires traversing mount points; since the
+     * associated 'mount' object is discovered as a byproduct of this
+     * traversal, we return it alongside the dentry to avoid redundant
+     * lookups in callers that require mount context.
+     *
+     * If only one component is needed, the convenience wrappers can be used:
+     * - resolve_path() for the dentry only.
+     * - find_mount() for the mount context only.
+     */
+    [[nodiscard]] auto resolve_path_internal(std::string_view path)
+        -> std::pair<kstd::shared_ptr<dentry>, kstd::shared_ptr<mount>>;
     [[nodiscard]] auto resolve_path(std::string_view path) -> kstd::shared_ptr<dentry>;
-    auto do_mount_internal(kstd::shared_ptr<dentry> const & mount_point_dentry, kstd::shared_ptr<filesystem> const & fs)
+    [[nodiscard]] auto find_mount(std::string_view path) -> kstd::shared_ptr<mount>;
+
+    auto do_mount_internal(kstd::shared_ptr<dentry> const & mount_point_dentry,
+                           kstd::shared_ptr<mount> const & parent_mount, kstd::shared_ptr<filesystem> const & fs)
         -> void;
 
     auto graft_persistent_device_fs(kstd::shared_ptr<devfs::filesystem> const & device_fs) -> void;