implement unmount, improve error codes

8 files changed, 121 insertions, 32 deletions

diff --git a/kernel/src/filesystem/devfs/filesystem.cpp b/kernel/src/filesystem/devfs/filesystem.cpp
index 9043ac5..03b4218 100644
--- a/kernel/src/filesystem/devfs/filesystem.cpp
+++ b/kernel/src/filesystem/devfs/filesystem.cpp
@@ -1,6 +1,7 @@
 #include "kernel/filesystem/devfs/filesystem.hpp"
 
 #include "kapi/devices/device.hpp"
+
 #include "kernel/devices/storage/management.hpp"
 #include "kernel/filesystem/devfs/inode.hpp"
 #include "kernel/filesystem/device_inode.hpp"
@@ -13,12 +14,12 @@
 
 namespace kernel::filesystem::devfs
 {
-  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const &) -> int
+  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const &) -> operation_result
   {
     m_root_inode = kstd::make_shared<inode>();
     build_device_inode_table();
 
-    return 0;
+    return operation_result::success;
   }
 
   auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index 7ee1072..6d5960e 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -36,10 +36,6 @@ namespace kernel::filesystem::ext2
     constexpr uint16_t S_IFREG = 0x8000;
     constexpr uint16_t S_IFDIR = 0x4000;
 
-    // Error codes
-    constexpr int INVALID_MAGIC_NUMBER = -1;
-    constexpr int INVALID_ROOT_INODE = -2;
-
     auto S_ISREG(uint16_t mode) -> bool
     {
       return (mode & S_IFMT) == S_IFREG;
@@ -51,7 +47,7 @@ namespace kernel::filesystem::ext2
     }
   }  // namespace
 
-  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int
+  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result
   {
     kernel::filesystem::filesystem::mount(device);
 
@@ -59,7 +55,7 @@ namespace kernel::filesystem::ext2
 
     if (m_superblock.magic != MAGIC_NUMBER)
     {
-      return INVALID_MAGIC_NUMBER;
+      return operation_result::invalid_magic_number;
     }
 
     auto const block_size = get_block_size();
@@ -77,9 +73,9 @@ namespace kernel::filesystem::ext2
 
     if (!m_root_inode || !m_root_inode->is_directory())
     {
-      return INVALID_ROOT_INODE;
+      return operation_result::invalid_root_inode;
     }
-    return 0;
+    return operation_result::success;
   }
 
   auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
diff --git a/kernel/src/filesystem/filesystem.cpp b/kernel/src/filesystem/filesystem.cpp
index b08b520..da2838d 100644
--- a/kernel/src/filesystem/filesystem.cpp
+++ b/kernel/src/filesystem/filesystem.cpp
@@ -30,7 +30,7 @@ namespace kernel::filesystem
     for (auto & factory : filesystem_factories)
     {
       auto fs = factory();
-      if (fs->mount(device) == 0)
+      if (fs->mount(device) == operation_result::success)
       {
         return fs;
       }
@@ -39,11 +39,11 @@ namespace kernel::filesystem
     return nullptr;
   }
 
-  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int
+  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const & device) -> operation_result
   {
     // TODO BA-FS26 maybe check if device is null and panic here already?
     m_device = device;
-    return 0;
+    return operation_result::success;
   }
 
   auto filesystem::root_inode() const -> kstd::shared_ptr<inode> const &
diff --git a/kernel/src/filesystem/mount.cpp b/kernel/src/filesystem/mount.cpp
index a6d2f7e..d165385 100644
--- a/kernel/src/filesystem/mount.cpp
+++ b/kernel/src/filesystem/mount.cpp
@@ -13,11 +13,13 @@
 namespace kernel::filesystem
 {
   mount::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)
       : m_mount_path(mount_path)
       , m_mount_dentry(mount_dentry)
       , m_root_dentry(root_dentry)
       , m_filesystem(fs)
+      , m_parent_mount(parent_mount)
   {
     if (!m_filesystem)
     {
@@ -44,4 +46,9 @@ namespace kernel::filesystem
   {
     return m_mount_path.view();
   }
+
+  auto mount::get_parent_mount() const -> kstd::shared_ptr<mount> const &
+  {
+    return m_parent_mount;
+  }
 }  // namespace kernel::filesystem
\ No newline at end of file
diff --git a/kernel/src/filesystem/mount_table.cpp b/kernel/src/filesystem/mount_table.cpp
index 195f48a..3b1dee3 100644
--- a/kernel/src/filesystem/mount_table.cpp
+++ b/kernel/src/filesystem/mount_table.cpp
@@ -1,17 +1,83 @@
 #include "kernel/filesystem/mount_table.hpp"
 
+#include "kernel/filesystem/dentry.hpp"
 #include "kernel/filesystem/mount.hpp"
 
 #include <kstd/memory>
+#include <kstd/vector>
 
+#include <algorithm>
 #include <cstddef>
+#include <ranges>
 #include <string_view>
 
 namespace kernel::filesystem
 {
+  namespace
+  {
+    auto is_descendant_of(kstd::shared_ptr<mount> const & candidate, kstd::shared_ptr<mount> const & ancestor) -> bool
+    {
+      for (auto current = candidate; current; current = current->get_parent_mount())
+      {
+        if (current == ancestor)
+        {
+          return true;
+        }
+      }
+
+      return false;
+    }
+
+    auto is_strict_prefix(std::string_view prefix, std::string_view path) -> bool
+    {
+      return prefix != "/" && path.starts_with(prefix) && path.size() > prefix.size() && path[prefix.size()] == '/';
+    }
+
+    auto is_visible_mount(kstd::shared_ptr<mount> const & candidate,
+                          kstd::vector<kstd::shared_ptr<mount>> const & mounts) -> bool
+    {
+      return std::ranges::none_of(mounts, [&](auto const & other) {
+        return other != candidate && is_strict_prefix(other->get_mount_path(), candidate->get_mount_path()) &&
+               !is_descendant_of(candidate, other);
+      });
+    }
+  }  // namespace
+
+  auto mount_table::has_child_mounts(kstd::shared_ptr<mount> const & parent_mount) const -> bool
+  {
+    return std::ranges::any_of(
+        m_mounts, [&parent_mount](auto const & mount) { return mount->get_parent_mount() == parent_mount; });
+  }
+
   void mount_table::add_mount(kstd::shared_ptr<mount> const & mount)
   {
     m_mounts.push_back(mount);
+    if (auto mount_dentry = mount->get_mount_dentry())
+    {
+      mount_dentry->set_flag(dentry::dentry_flags::dcache_mounted);
+    }
+  }
+
+  auto mount_table::remove_mount(std::string_view path) -> operation_result
+  {
+    auto mount_it = std::ranges::find_if(std::ranges::reverse_view(m_mounts), [&](auto const & mount) {
+      return mount->get_mount_path() == path && is_visible_mount(mount, m_mounts);
+    });
+
+    if (mount_it == std::ranges::reverse_view(m_mounts).end())
+    {
+      return operation_result::mount_not_found;
+    }
+
+    auto const & mount = *mount_it;
+    if (has_child_mounts(mount))
+    {
+      return operation_result::has_child_mounts;
+    }
+
+    mount->get_mount_dentry()->unset_flag(dentry::dentry_flags::dcache_mounted);
+    m_mounts.erase(std::ranges::find(m_mounts, mount));
+    return operation_result::removed;
   }
 
   auto mount_table::find_longest_prefix_mount(std::string_view path) const -> kstd::shared_ptr<mount>
@@ -25,8 +91,9 @@ namespace kernel::filesystem
 
       // /a/b/c should match /a/b but not /a/bb or /a/b/c/d, / should match everything
       bool is_prefix = path.starts_with(mp) && (mp == "/" || path.size() == mp.size() || path[mp.size()] == '/');
+      bool visible = is_visible_mount(mount, m_mounts);
 
-      if (is_prefix && mp.size() >= best_len)
+      if (is_prefix && visible && mp.size() >= best_len)
       {
         mount_with_longest_prefix = mount;
         best_len = mp.size();
diff --git a/kernel/src/filesystem/rootfs/filesystem.cpp b/kernel/src/filesystem/rootfs/filesystem.cpp
index a7c746e..dffef99 100644
--- a/kernel/src/filesystem/rootfs/filesystem.cpp
+++ b/kernel/src/filesystem/rootfs/filesystem.cpp
@@ -11,13 +11,13 @@
 
 namespace kernel::filesystem::rootfs
 {
-  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const &) -> int
+  auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const &) -> operation_result
   {
     auto rfs_inode = kstd::make_shared<inode>();
     rfs_inode->add_child("dev");
     m_root_inode = rfs_inode;
 
-    return 0;
+    return operation_result::success;
   }
 
   auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
diff --git a/kernel/src/filesystem/vfs.cpp b/kernel/src/filesystem/vfs.cpp
index 2578036..45ae053 100644
--- a/kernel/src/filesystem/vfs.cpp
+++ b/kernel/src/filesystem/vfs.cpp
@@ -7,6 +7,7 @@
 #include "kernel/filesystem/devfs/filesystem.hpp"
 #include "kernel/filesystem/filesystem.hpp"
 #include "kernel/filesystem/mount.hpp"
+#include "kernel/filesystem/mount_table.hpp"
 #include "kernel/filesystem/open_file_description.hpp"
 #include "kernel/filesystem/rootfs/filesystem.hpp"
 
@@ -21,11 +22,6 @@ namespace kernel::filesystem
   namespace
   {
     constinit auto static active_vfs = std::optional<vfs>{};
-
-    // Error codes
-    constexpr int INVALID_PATH = -1;
-    constexpr int MOUNT_POINT_NOT_FOUND = -2;
-    constexpr int FILESYSTEM_NULL = -3;
   }  // namespace
 
   auto vfs::init() -> void
@@ -45,7 +41,7 @@ namespace kernel::filesystem
     root_fs->mount(nullptr);
 
     auto root_fs_root_dentry = kstd::make_shared<dentry>(nullptr, root_fs->root_inode());
-    m_mount_table.add_mount(kstd::make_shared<mount>(nullptr, root_fs_root_dentry, root_fs, ""));
+    m_mount_table.add_mount(kstd::make_shared<mount>(nullptr, root_fs_root_dentry, root_fs, "", nullptr));
 
     auto storage_mgmt = devices::storage::management::get();
     if (auto boot_device = storage_mgmt.determine_boot_device())
@@ -79,36 +75,55 @@ namespace kernel::filesystem
     return nullptr;
   }
 
-  // TODO BA-FS26 implement unmount
-  auto vfs::do_mount(std::string_view path, kstd::shared_ptr<filesystem> const & filesystem) -> int
+  auto vfs::do_mount(std::string_view path, kstd::shared_ptr<filesystem> const & filesystem) -> operation_result
   {
     if (!filesystem)
     {
-      return FILESYSTEM_NULL;
+      return operation_result::filesystem_null;
     }
 
     if (path.empty() || path.front() != '/' || (path.size() > 1 && path.back() == '/'))
     {
-      return INVALID_PATH;
+      return operation_result::invalid_path;
     }
 
     if (auto mount_point_dentry = resolve_path(path))
     {
       do_mount_internal(path, mount_point_dentry, filesystem);
-      return 0;
+      return operation_result::success;
+    }
+
+    return operation_result::mount_point_not_found;
+  }
+
+  auto vfs::unmount(std::string_view path) -> operation_result
+  {
+    if (path.empty() || path.front() != '/' || (path.size() > 1 && path.back() == '/'))
+    {
+      return operation_result::invalid_path;
+    }
+
+    auto remove_result = m_mount_table.remove_mount(path);
+    if (remove_result == mount_table::operation_result::removed)
+    {
+      return operation_result::success;
+    }
+
+    if (remove_result == mount_table::operation_result::has_child_mounts)
+    {
+      return operation_result::unmount_failed;
     }
 
-    return MOUNT_POINT_NOT_FOUND;
+    return operation_result::mount_point_not_found;
   }
 
   auto vfs::do_mount_internal(std::string_view path, kstd::shared_ptr<dentry> const & mount_point_dentry,
                               kstd::shared_ptr<filesystem> const & fs) -> void
   {
-    // TODO BA-FS26 check if mount point is already mounted and handle it (unmount old fs, fail, etc.)
+    auto parent_mount = m_mount_table.find_longest_prefix_mount(path);
     auto new_fs_root = kstd::make_shared<dentry>(mount_point_dentry, fs->root_inode());
-    auto new_mount = kstd::make_shared<mount>(mount_point_dentry, new_fs_root, fs, path);
+    auto new_mount = kstd::make_shared<mount>(mount_point_dentry, new_fs_root, fs, path, parent_mount);
     m_mount_table.add_mount(new_mount);
-    mount_point_dentry->set_flag(dentry::dentry_flags::dcache_mounted);
   }
 
   auto vfs::resolve_path(std::string_view path) -> kstd::shared_ptr<dentry>
diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index 1893b84..1d73e20 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -145,6 +145,9 @@ auto test_file_lookup() -> void
   vfs.do_mount("/enclosures/aquarium", new_filesystem);
   read_and_write_file("/enclosures/aquarium/closed.txt");
   read_and_write_file("/enclosures/aquarium/information/info_2.txt");
+
+  vfs.unmount("/enclosures/aquarium");
+  read_and_write_file("/enclosures/aquarium/tank_1/fish_4.txt");
 }
 
 auto run_test_code() -> void