ladybird/Kernel/FileSystem/DiskBackedFileSystem.h
Andreas Kling 59ed235c85 Kernel: Implement O_DIRECT open() flag to bypass disk caches
Files opened with O_DIRECT will now bypass the disk cache in read/write
operations (though metadata operations will still hit the disk cache.)

This will allow us to test actual disk performance instead of testing
disk *cache* performance, if that's what we want. :^)

There's room for improvment here, we're very aggressively flushing any
dirty cache entries for the specific block before reading/writing that
block. This is done by walking the entire cache, which may be slow.
2019-11-05 19:35:12 +01:00

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C++

#pragma once
#include "FileSystem.h"
#include <AK/ByteBuffer.h>
class DiskCache;
class DiskBackedFS : public FS {
public:
virtual ~DiskBackedFS() override;
virtual bool is_disk_backed() const override { return true; }
DiskDevice& device() { return *m_device; }
const DiskDevice& device() const { return *m_device; }
virtual void flush_writes() override;
void flush_writes_impl();
protected:
explicit DiskBackedFS(NonnullRefPtr<DiskDevice>&&);
bool read_block(unsigned index, u8* buffer, FileDescription* = nullptr) const;
bool read_blocks(unsigned index, unsigned count, u8* buffer, FileDescription* = nullptr) const;
bool write_block(unsigned index, const u8*, FileDescription* = nullptr);
bool write_blocks(unsigned index, unsigned count, const u8*, FileDescription* = nullptr);
private:
DiskCache& cache() const;
void flush_specific_block_if_needed(unsigned index);
NonnullRefPtr<DiskDevice> m_device;
mutable OwnPtr<DiskCache> m_cache;
};