From 251b17085b4390c00a979f7abd1cb5c0f7cc18d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?kleines=20Filmr=C3=B6llchen?= <filmroellchen@serenityos.org>
Date: Sun, 2 Jul 2023 14:25:16 +0200
Subject: [PATCH] Kernel/Ext2: Check and set file system state

This is supposed to detect whether a file system was unmounted
cleanly or not.
---
 Kernel/FileSystem/Ext2FS/FileSystem.cpp | 32 ++++++++++++++++++++++---
 Kernel/FileSystem/FileSystem.cpp        |  1 +
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/Kernel/FileSystem/Ext2FS/FileSystem.cpp b/Kernel/FileSystem/Ext2FS/FileSystem.cpp
index 359e1a1213..597aaa17a0 100644
--- a/Kernel/FileSystem/Ext2FS/FileSystem.cpp
+++ b/Kernel/FileSystem/Ext2FS/FileSystem.cpp
@@ -65,6 +65,9 @@ ErrorOr<void> Ext2FS::initialize_while_locked()
         return EINVAL;
     }
 
+    if (super_block.s_state == EXT2_ERROR_FS)
+        dmesgln("Ext2FS: Was not unmounted cleanly, file system may be erroneous!");
+
     if constexpr (EXT2_DEBUG) {
         dmesgln("Ext2FS: {} inodes, {} blocks", super_block.s_inodes_count, super_block.s_blocks_count);
         dmesgln("Ext2FS: Block size: {}", EXT2_BLOCK_SIZE(&super_block));
@@ -105,6 +108,12 @@ ErrorOr<void> Ext2FS::initialize_while_locked()
     }
 
     m_root_inode = TRY(build_root_inode());
+
+    // Set filesystem to "error" state until we unmount cleanly.
+    dmesgln("Ext2FS: Mount successful, setting superblock to error state.");
+    m_super_block.s_state = EXT2_ERROR_FS;
+    TRY(flush_super_block());
+
     return {};
 }
 
@@ -534,16 +543,33 @@ unsigned Ext2FS::free_inode_count() const
 
 ErrorOr<void> Ext2FS::prepare_to_clear_last_mount(Inode& mount_guest_inode)
 {
-    (void)mount_guest_inode;
     MutexLocker locker(m_lock);
+    bool any_inode_busy = false;
     for (auto& it : m_inode_cache) {
-        if (it.value->ref_count() > 1)
-            return EBUSY;
+        // We hold the last reference to the root inode, and the VFS Mount object holds the last reference to the mount_guest_inode,
+        // so they are allowed to have one more reference.
+        if ((it.value == m_root_inode || it.value->identifier() == mount_guest_inode.identifier()) && it.value->ref_count() > 2) {
+            dbgln_if(EXT2_DEBUG, "Ext2FS: Ignoring root or mount point inode's last reference");
+            continue;
+        }
+        // The Inode::all_instances list always holds one reference to all inodes, which we disregard.
+        if (it.value->ref_count() > 1) {
+            dbgln_if(EXT2_DEBUG, "Ext2FS: Busy inode {} ({} refs)", it.value->index(), it.value->ref_count());
+            any_inode_busy = true;
+        }
     }
+    if (any_inode_busy)
+        return EBUSY;
 
     BlockBasedFileSystem::remove_disk_cache_before_last_unmount();
     m_inode_cache.clear();
     m_root_inode = nullptr;
+
+    // Mark filesystem as valid before unmount.
+    dmesgln("Ext2FS: Clean unmount, setting superblock to valid state");
+    m_super_block.s_state = EXT2_VALID_FS;
+    TRY(flush_super_block());
+
     return {};
 }
 
diff --git a/Kernel/FileSystem/FileSystem.cpp b/Kernel/FileSystem/FileSystem.cpp
index fa1a363470..42c1f9c8c8 100644
--- a/Kernel/FileSystem/FileSystem.cpp
+++ b/Kernel/FileSystem/FileSystem.cpp
@@ -30,6 +30,7 @@ FileSystem::~FileSystem()
 ErrorOr<void> FileSystem::prepare_to_unmount(Inode& mount_guest_inode)
 {
     return m_attach_count.with([&](auto& attach_count) -> ErrorOr<void> {
+        dbgln_if(VFS_DEBUG, "VFS: File system {} (id {}) is attached {} time(s)", class_name(), m_fsid.value(), attach_count);
         if (attach_count == 1)
             return prepare_to_clear_last_mount(mount_guest_inode);
         return {};