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Kernel: Tweak FileBackedFS API to avoid intermediary copies

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read_block() and write_block() now accept the count (how many bytes to read
or write) and offset (where in the block to start; defaults to 0). Using these
new APIs, we can avoid doing copies between intermediary buffers in a lot more
cases. Hopefully this improves performance or something.
This commit is contained in:
Sergey Bugaev 2020-05-18 21:55:08 +03:00 • committed by Andreas Kling
parent de4b7d9c21
commit 88e23113ae
4 changed files with 68 additions and 85 deletions
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14
Kernel/FileSystem/FileBackedFileSystem.h
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@ -36,8 +36,6 @@ 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(); }
@ -52,8 +50,8 @@ public:
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 read_block(unsigned index, u8* buffer, size_t count, size_t offset = 0, bool allow_cache = true) const;
bool read_blocks(unsigned index, unsigned count, u8* buffer, bool allow_cache = true) const;
bool raw_read(unsigned index, u8* buffer);
bool raw_write(unsigned index, const u8* buffer);
@ -61,16 +59,18 @@ protected:
bool raw_read_blocks(unsigned index, size_t count, u8* buffer);
bool raw_write_blocks(unsigned index, size_t count, const u8* buffer);
bool write_block(unsigned index, const u8*, FileDescription* = nullptr);
bool write_blocks(unsigned index, unsigned count, const u8*, FileDescription* = nullptr);
bool write_block(unsigned index, const u8* buffer, size_t count, size_t offset = 0, bool allow_cache = true);
bool write_blocks(unsigned index, unsigned count, const u8*, bool allow_cache = true);
size_t m_logical_block_size { 512 };
private:
virtual bool is_file_backed() const override { return true; }
DiskCache& cache() const;
void flush_specific_block_if_needed(unsigned index);
NonnullRefPtr<FileDescription> m_file_description;
mutable NonnullRefPtr<FileDescription> m_file_description;
mutable OwnPtr<DiskCache> m_cache;
};