Luna/kernel/src/fs/ext2/FileSystem.h

#pragma once
#include "fs/VFS.h"
#include "fs/devices/DeviceRegistry.h"
#include <luna/HashMap.h>

#define EXT2_MAGIC 0xef53

namespace Ext2
{
    struct [[gnu::packed]] Superblock
    {
        u32 nr_inodes;
        u32 nr_blocks;
        u32 nr_reserved;
        u32 nr_free_inodes;
        u32 nr_free_blocks;
        u32 superblock_block;
        u32 log_block_size;
        u32 log_fragment_size;
        u32 blocks_per_block_group;
        u32 fragments_per_block_group;
        u32 inodes_per_block_group;
        u32 last_mount_time;
        u32 last_write_time;
        u16 mounts_since_last_fsck;
        u16 mounts_allowed_before_fsck;
        u16 signature;
        u16 fs_state;
        u16 error_action;
        u16 minor_version;
        u32 last_fsck_time;
        u32 fsck_time_interval;
        u32 os_id;
        u32 major_version;
        u16 reserved_block_uid;
        u16 reserved_block_gid;
        u8 padding[1024 - 84];
    };

    static_assert(sizeof(Superblock) == 1024);

    class FileSystem : public VFS::FileSystem
    {
      public:
        SharedPtr<VFS::Inode> root_inode() const override
        {
            return m_root_inode;
        }

        Result<SharedPtr<VFS::Inode>> create_file_inode() override
        {
            return err(EROFS);
        }

        Result<SharedPtr<VFS::Inode>> create_dir_inode(SharedPtr<VFS::Inode>) override
        {
            return err(EROFS);
        }

        Result<SharedPtr<VFS::Inode>> create_device_inode(u32, u32) override
        {
            return err(EROFS);
        }

        Result<SharedPtr<VFS::Inode>> create_symlink_inode(StringView) override
        {
            return err(EROFS);
        }

        Result<void> set_mount_dir(SharedPtr<VFS::Inode>) override
        {
            return {};
        }

        static Result<SharedPtr<VFS::FileSystem>> create(SharedPtr<Device> host_device);

        dev_t host_device_id() const override
        {
            return m_host_device_id;
        }

        Result<SharedPtr<VFS::Inode>> find_inode_by_number(ino_t inode);

        virtual ~FileSystem() = default;

      private:
        FileSystem();

        SharedPtr<VFS::Inode> m_root_inode;

        SharedPtr<Device> m_host_device;
        dev_t m_host_device_id;

        Superblock m_superblock;

        // FIXME: This inode cache will keep all inodes in it alive despite having no other references to it, but we're
        // not worrying about that as for now the filesystem implementation is read-only.
        HashMap<ino_t, SharedPtr<VFS::Inode>> m_inode_cache;
    };
}