Merge branch 'mount-unmount-root-fs' into 'develop-BA-FS26'

if the boot_root_fs contains a /dev directory, vfs mounts the devfs onto the existing directory

See merge request teachos/kernel!33

2 files changed, 44 insertions, 13 deletions

diff --git a/kernel/src/filesystem/vfs.cpp b/kernel/src/filesystem/vfs.cpp
index ee7c262..535f898 100644
--- a/kernel/src/filesystem/vfs.cpp
+++ b/kernel/src/filesystem/vfs.cpp
@@ -41,36 +41,35 @@ namespace kernel::filesystem
 
   auto vfs::init_internal() -> void
   {
+    // mount rootfs at /
     auto root_fs = kstd::make_shared<rootfs::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, nullptr));
 
-    // Mount devfs at /dev in rootfs (temporary, will be shadowed)
+    // mount devfs at /dev (inside rootfs, temporary, will be shadowed)
     auto device_fs = kstd::make_shared<devfs::filesystem>();
     device_fs->mount(nullptr);
-    auto dev_mount_point_dentry = resolve_path("/dev");
-    if (!dev_mount_point_dentry)
+
+    if (auto dev_mount_point_dentry = resolve_path("/dev"))
+    {
+      do_mount_internal(dev_mount_point_dentry, device_fs);
+    }
+    else
     {
       kapi::system::panic("[FILESYSTEM] failed to resolve /dev for initial devfs mount.");
     }
-    do_mount_internal(dev_mount_point_dentry, device_fs);
 
-    // Mount boot filesystem at / (will shadow rootfs)
+    // mount boot fs at / (shadows rootfs), re-graft devfs
     if (auto boot_device_dentry = resolve_path("/dev/ram0"))
     {
       if (auto boot_root_fs = kernel::filesystem::filesystem::probe_and_mount(boot_device_dentry->get_inode()))
       {
-        do_mount_internal(root_fs_root_dentry, boot_root_fs);
-
-        // Resolve / to get the boot root dentry
-        if (auto boot_root_dentry = resolve_path("/"))
+        if (auto root_dentry = resolve_path("/"))
         {
-          auto dev_dentry = kstd::make_shared<dentry>(boot_root_dentry, device_fs->root_inode(), "dev");
-          boot_root_dentry->add_child(dev_dentry);
-
-          do_mount_internal(dev_dentry, device_fs);
+          do_mount_internal(root_dentry, boot_root_fs);
+          graft_persistent_device_fs(device_fs);
         }
       }
     }
@@ -151,6 +150,21 @@ namespace kernel::filesystem
     m_mount_table.add_mount(new_mount);
   }
 
+  auto vfs::graft_persistent_device_fs(kstd::shared_ptr<devfs::filesystem> const & device_fs) -> void
+  {
+    if (auto new_root_dentry = resolve_path("/"))
+    {
+      auto dev_dentry = new_root_dentry->find_child("dev");
+      if (!dev_dentry)
+      {
+        dev_dentry = kstd::make_shared<dentry>(new_root_dentry, device_fs->root_inode(), "dev");
+        new_root_dentry->add_child(dev_dentry);
+      }
+
+      do_mount_internal(dev_dentry, device_fs);
+    }
+  }
+
   auto vfs::resolve_path(std::string_view path) -> kstd::shared_ptr<dentry>
   {
     if (!path::is_valid_absolute_path(path))
diff --git a/kernel/src/filesystem/vfs.tests.cpp b/kernel/src/filesystem/vfs.tests.cpp
index 8e4cb70..add96aa 100644
--- a/kernel/src/filesystem/vfs.tests.cpp
+++ b/kernel/src/filesystem/vfs.tests.cpp
@@ -62,6 +62,23 @@ SCENARIO_METHOD(kernel::tests::filesystem::storage_boot_module_vfs_fixture, "VFS
     }
   }
 
+  GIVEN("a real image file containing a /dev directory")
+  {
+    REQUIRE(std::filesystem::exists(image_path_2));
+    REQUIRE_NOTHROW(setup_modules_from_img_and_init_vfs({"test_img_module_2"}, {image_path_2}));
+
+    THEN("vfs hides the image's /dev behind the devfs mount")
+    {
+      auto & vfs = kernel::filesystem::vfs::get();
+
+      auto image_1 = vfs.open("/dev/image_1.txt");
+      REQUIRE(image_1 == nullptr);
+
+      auto dev = vfs.open("/dev/ram0");
+      REQUIRE(dev != nullptr);
+    }
+  }
+
   GIVEN("three real image files")
   {
     REQUIRE(std::filesystem::exists(image_path_1));