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

Increase reference count of source_mount when one of its files is mounted somewhere

See merge request teachos/kernel!42

2 files changed, 15 insertions, 9 deletions

diff --git a/kernel/include/kernel/filesystem/mount.hpp b/kernel/include/kernel/filesystem/mount.hpp
index 4ce374f..53d7f6d 100644
--- a/kernel/include/kernel/filesystem/mount.hpp
+++ b/kernel/include/kernel/filesystem/mount.hpp
@@ -24,11 +24,12 @@ namespace kernel::filesystem
     @param mount_dentry The dentry where the filesystem is mounted.
     @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.
+    @param parent_mount The mount that contains the mount_dentry.
+    @param source_mount The mount that the filesystem originates from.
     */
     mount(kstd::shared_ptr<dentry> const & mount_dentry, kstd::shared_ptr<dentry> const & root_dentry,
-          kstd::shared_ptr<filesystem> const & fs, kstd::shared_ptr<mount> const & parent_mount);
+          kstd::shared_ptr<filesystem> const & fs, kstd::shared_ptr<mount> const & parent_mount,
+          kstd::shared_ptr<mount> const & source_mount);
 
     /**
     @brief Get the dentry where the filesystem is mounted.
@@ -56,15 +57,20 @@ namespace kernel::filesystem
     [[nodiscard]] auto parent_mount() const -> kstd::shared_ptr<mount> const &;
 
     /**
+    @brief Get the source mount where this mount originates from.
+    */
+    [[nodiscard]] auto source_mount() const -> kstd::shared_ptr<mount>;
+
+    /**
     @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.
+    @warning Throws if ref_count is zero.
     */
-    [[nodiscard]] auto decrement_ref_count() -> bool;
+    auto decrement_ref_count() -> void;
 
     /**
     @brief Check if the mount is ready to be unmounted.
@@ -83,6 +89,7 @@ namespace kernel::filesystem
     kstd::shared_ptr<dentry> m_root_dentry;
     kstd::shared_ptr<filesystem> m_filesystem{};
     kstd::shared_ptr<mount> m_parent_mount{};
+    kstd::weak_ptr<mount> m_source_mount{};
     std::atomic_size_t m_ref_count;
   };
 }  // namespace kernel::filesystem
diff --git a/kernel/include/kernel/filesystem/vfs.hpp b/kernel/include/kernel/filesystem/vfs.hpp
index aec8bfe..e6f2327 100644
--- a/kernel/include/kernel/filesystem/vfs.hpp
+++ b/kernel/include/kernel/filesystem/vfs.hpp
@@ -32,8 +32,7 @@ namespace kernel::filesystem
       non_existent_path = -2,
       mount_point_not_found = -3,
       unmount_failed = -4,
-      invalid_filesystem = -5,
-      close_failed = -6
+      invalid_filesystem = -5
     };
 
     /**
@@ -103,8 +102,8 @@ namespace kernel::filesystem
     [[nodiscard]] auto find_mount(std::string_view path) const -> 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;
+                           kstd::shared_ptr<mount> const & parent_mount, kstd::shared_ptr<filesystem> const & fs,
+                           kstd::shared_ptr<mount> const & source_mount = nullptr) -> void;
 
     auto graft_persistent_device_fs(kstd::shared_ptr<devfs::filesystem> const & device_fs) -> void;