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Kernel: Change Ext2FS to be backed by a file instead of a block device

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In contrast to the previous patchset that was reverted, this time we use
a "special" method to access a file with block size of 512 bytes (like
a harddrive essentially).
This commit is contained in:
Liav A 2020-04-06 11:54:21 +03:00 • committed by Andreas Kling
parent 1d6c8724b9
commit ecee76b741
10 changed files with 104 additions and 77 deletions
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74
Kernel/FileSystem/FileBackedFileSystem.h Normal file
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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <Kernel/FileSystem/FileDescription.h>
#include <Kernel/FileSystem/FileSystem.h>
#include <Kernel/Forward.h>
namespace Kernel {
class FileBackedFS : public FS {
public:
virtual ~FileBackedFS() override;
virtual bool is_file_backed() const override { return true; }
File& file() { return m_file_description->file(); }
FileDescription& file_description() { return *m_file_description; }
const File& file() const { return m_file_description->file(); }
const FileDescription& file_description() const { return *m_file_description; }
virtual void flush_writes() override;
void flush_writes_impl();
size_t logical_block_size() const { return m_logical_block_size; };
protected:
explicit FileBackedFS(FileDescription&);
bool read_block(unsigned index, u8* buffer, FileDescription* = nullptr) const;
bool read_blocks(unsigned index, unsigned count, u8* buffer, FileDescription* = nullptr) const;
bool raw_read(unsigned index, u8* buffer);
bool raw_write(unsigned index, const u8* buffer);
bool write_block(unsigned index, const u8*, FileDescription* = nullptr);
bool write_blocks(unsigned index, unsigned count, const u8*, FileDescription* = nullptr);
size_t m_logical_block_size { 512 };
private:
DiskCache& cache() const;
void flush_specific_block_if_needed(unsigned index);
NonnullRefPtr<FileDescription> m_file_description;
mutable OwnPtr<DiskCache> m_cache;
};
}