serenity/Kernel/FileSystem/MountFile.h
Liav A. cb10f70394 Kernel: Change internal handling of filesystem-specific options
Instead of using a raw `KBuffer` and letting each implementation to
populating the specific flags on its own, we change things so we only
let each FileSystem implementation to validate the flag and its value
but then store it in a HashMap which its key is the flag name and
the value is a special new class called `FileSystemSpecificOption`
which wraps around `AK::Variant<...>`.

This approach has multiple advantages over the previous:
- It allows runtime inspection of what the user has set on a `MountFile`
  description for a specific filesystem.
- It ensures accidental overriding of filesystem specific option that
  was already set is not possible
- It removes ugly casting of a `KBuffer` contents to a strongly-typed
  values. Instead, a strongly-typed `AK::Variant` is used which ensures
  we always get a value without doing any casting.

Please note that we have removed support for ASCII string-oriented flags
as there were no actual use cases, and supporting such type would make
`FileSystemSpecificOption` more complicated unnecessarily for now.
2024-08-03 20:35:06 +02:00

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/*
* Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <Kernel/FileSystem/File.h>
#include <Kernel/FileSystem/FileSystemSpecificOption.h>
#include <Kernel/FileSystem/Initializer.h>
#include <Kernel/Locking/MutexProtected.h>
namespace Kernel {
class MountFile final : public File {
public:
static ErrorOr<NonnullLockRefPtr<MountFile>> create(FileSystemInitializer const&, int flags);
virtual ~MountFile() override;
virtual bool can_read(OpenFileDescription const&, u64) const override { return true; }
virtual bool can_write(OpenFileDescription const&, u64) const override { return true; }
virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override { return ENOTSUP; }
virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override { return ENOTSUP; }
virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override;
virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(OpenFileDescription const&) const override;
virtual StringView class_name() const override { return "MountFile"sv; }
int mount_flags() const { return m_flags; }
MutexProtected<FileSystemSpecificOptions>& filesystem_specific_options() { return m_filesystem_specific_options; }
FileSystemInitializer const& file_system_initializer() const { return m_file_system_initializer; }
private:
virtual bool is_mount_file() const override { return true; }
MountFile(FileSystemInitializer const&, int flags);
int const m_flags;
FileSystemInitializer const& m_file_system_initializer;
MutexProtected<FileSystemSpecificOptions> m_filesystem_specific_options;
};
}