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302 lines
9.8 KiB
C++
302 lines
9.8 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/IntrusiveList.h>
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#include <Kernel/Debug.h>
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#include <Kernel/FileSystem/BlockBasedFileSystem.h>
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#include <Kernel/Process.h>
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namespace Kernel {
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struct CacheEntry {
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IntrusiveListNode<CacheEntry> list_node;
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BlockBasedFileSystem::BlockIndex block_index { 0 };
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u8* data { nullptr };
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bool has_data { false };
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};
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class DiskCache {
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public:
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explicit DiskCache(BlockBasedFileSystem& fs)
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: m_fs(fs)
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, m_cached_block_data(KBuffer::create_with_size(m_entry_count * m_fs.block_size()))
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, m_entries(KBuffer::create_with_size(m_entry_count * sizeof(CacheEntry)))
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{
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for (size_t i = 0; i < m_entry_count; ++i) {
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entries()[i].data = m_cached_block_data.data() + i * m_fs.block_size();
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m_clean_list.append(entries()[i]);
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}
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}
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~DiskCache() = default;
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bool is_dirty() const { return m_dirty; }
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void set_dirty(bool b) { m_dirty = b; }
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void mark_all_clean()
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{
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while (auto* entry = m_dirty_list.first())
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m_clean_list.prepend(*entry);
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m_dirty = false;
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}
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void mark_dirty(CacheEntry& entry)
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{
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m_dirty_list.prepend(entry);
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m_dirty = true;
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}
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void mark_clean(CacheEntry& entry)
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{
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m_clean_list.prepend(entry);
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}
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CacheEntry& get(BlockBasedFileSystem::BlockIndex block_index) const
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{
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if (auto it = m_hash.find(block_index); it != m_hash.end()) {
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auto& entry = const_cast<CacheEntry&>(*it->value);
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VERIFY(entry.block_index == block_index);
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return entry;
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}
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if (m_clean_list.is_empty()) {
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// Not a single clean entry! Flush writes and try again.
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// NOTE: We want to make sure we only call FileBackedFileSystem flush here,
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// not some FileBackedFileSystem subclass flush!
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m_fs.flush_writes_impl();
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return get(block_index);
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}
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VERIFY(m_clean_list.last());
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auto& new_entry = *m_clean_list.last();
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m_clean_list.prepend(new_entry);
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m_hash.remove(new_entry.block_index);
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m_hash.set(block_index, &new_entry);
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new_entry.block_index = block_index;
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new_entry.has_data = false;
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return new_entry;
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}
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const CacheEntry* entries() const { return (const CacheEntry*)m_entries.data(); }
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CacheEntry* entries() { return (CacheEntry*)m_entries.data(); }
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template<typename Callback>
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void for_each_dirty_entry(Callback callback)
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{
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for (auto& entry : m_dirty_list)
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callback(entry);
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}
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private:
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BlockBasedFileSystem& m_fs;
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size_t m_entry_count { 10000 };
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mutable HashMap<BlockBasedFileSystem::BlockIndex, CacheEntry*> m_hash;
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mutable IntrusiveList<CacheEntry, RawPtr<CacheEntry>, &CacheEntry::list_node> m_clean_list;
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mutable IntrusiveList<CacheEntry, RawPtr<CacheEntry>, &CacheEntry::list_node> m_dirty_list;
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KBuffer m_cached_block_data;
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KBuffer m_entries;
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bool m_dirty { false };
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};
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BlockBasedFileSystem::BlockBasedFileSystem(FileDescription& file_description)
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: FileBackedFileSystem(file_description)
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{
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VERIFY(file_description.file().is_seekable());
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}
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BlockBasedFileSystem::~BlockBasedFileSystem()
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{
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}
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KResult BlockBasedFileSystem::write_block(BlockIndex index, const UserOrKernelBuffer& data, size_t count, size_t offset, bool allow_cache)
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{
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VERIFY(m_logical_block_size);
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VERIFY(offset + count <= block_size());
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dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::write_block {}, size={}", index, count);
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MutexLocker locker(m_cache_lock);
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if (!allow_cache) {
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flush_specific_block_if_needed(index);
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auto base_offset = index.value() * block_size() + offset;
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auto nwritten = file_description().write(base_offset, data, count);
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if (nwritten.is_error())
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return nwritten.error();
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VERIFY(nwritten.value() == count);
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return KSuccess;
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}
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auto& entry = cache().get(index);
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if (count < block_size()) {
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// Fill the cache first.
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auto result = read_block(index, nullptr, block_size());
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if (result.is_error())
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return result;
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}
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if (!data.read(entry.data + offset, count))
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return EFAULT;
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cache().mark_dirty(entry);
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entry.has_data = true;
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return KSuccess;
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}
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bool BlockBasedFileSystem::raw_read(BlockIndex index, UserOrKernelBuffer& buffer)
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{
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auto base_offset = index.value() * m_logical_block_size;
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auto nread = file_description().read(buffer, base_offset, m_logical_block_size);
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VERIFY(!nread.is_error());
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VERIFY(nread.value() == m_logical_block_size);
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return true;
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}
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bool BlockBasedFileSystem::raw_write(BlockIndex index, const UserOrKernelBuffer& buffer)
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{
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auto base_offset = index.value() * m_logical_block_size;
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auto nwritten = file_description().write(base_offset, buffer, m_logical_block_size);
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VERIFY(!nwritten.is_error());
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VERIFY(nwritten.value() == m_logical_block_size);
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return true;
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}
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bool BlockBasedFileSystem::raw_read_blocks(BlockIndex index, size_t count, UserOrKernelBuffer& buffer)
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{
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auto current = buffer;
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for (auto block = index.value(); block < (index.value() + count); block++) {
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if (!raw_read(BlockIndex { block }, current))
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return false;
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current = current.offset(logical_block_size());
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}
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return true;
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}
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bool BlockBasedFileSystem::raw_write_blocks(BlockIndex index, size_t count, const UserOrKernelBuffer& buffer)
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{
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auto current = buffer;
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for (auto block = index.value(); block < (index.value() + count); block++) {
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if (!raw_write(block, current))
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return false;
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current = current.offset(logical_block_size());
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}
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return true;
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}
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KResult BlockBasedFileSystem::write_blocks(BlockIndex index, unsigned count, const UserOrKernelBuffer& data, bool allow_cache)
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{
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VERIFY(m_logical_block_size);
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dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::write_blocks {}, count={}", index, count);
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for (unsigned i = 0; i < count; ++i) {
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auto result = write_block(BlockIndex { index.value() + i }, data.offset(i * block_size()), block_size(), 0, allow_cache);
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if (result.is_error())
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return result;
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}
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return KSuccess;
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}
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KResult BlockBasedFileSystem::read_block(BlockIndex index, UserOrKernelBuffer* buffer, size_t count, size_t offset, bool allow_cache) const
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{
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VERIFY(m_logical_block_size);
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VERIFY(offset + count <= block_size());
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dbgln_if(BBFS_DEBUG, "BlockBasedFileSystem::read_block {}", index);
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MutexLocker locker(m_cache_lock);
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if (!allow_cache) {
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const_cast<BlockBasedFileSystem*>(this)->flush_specific_block_if_needed(index);
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auto base_offset = index.value() * block_size() + offset;
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auto nread = file_description().read(*buffer, base_offset, count);
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if (nread.is_error())
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return nread.error();
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VERIFY(nread.value() == count);
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return KSuccess;
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}
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auto& entry = cache().get(index);
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if (!entry.has_data) {
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auto base_offset = index.value() * block_size();
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auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
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auto nread = file_description().read(entry_data_buffer, base_offset, block_size());
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if (nread.is_error())
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return nread.error();
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VERIFY(nread.value() == block_size());
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entry.has_data = true;
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}
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if (buffer && !buffer->write(entry.data + offset, count))
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return EFAULT;
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return KSuccess;
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}
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KResult BlockBasedFileSystem::read_blocks(BlockIndex index, unsigned count, UserOrKernelBuffer& buffer, bool allow_cache) const
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{
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VERIFY(m_logical_block_size);
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if (!count)
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return EINVAL;
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if (count == 1)
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return read_block(index, &buffer, block_size(), 0, allow_cache);
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auto out = buffer;
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for (unsigned i = 0; i < count; ++i) {
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auto result = read_block(BlockIndex { index.value() + i }, &out, block_size(), 0, allow_cache);
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if (result.is_error())
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return result;
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out = out.offset(block_size());
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}
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return KSuccess;
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}
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void BlockBasedFileSystem::flush_specific_block_if_needed(BlockIndex index)
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{
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MutexLocker locker(m_cache_lock);
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if (!cache().is_dirty())
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return;
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Vector<CacheEntry*, 32> cleaned_entries;
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cache().for_each_dirty_entry([&](CacheEntry& entry) {
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if (entry.block_index != index) {
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size_t base_offset = entry.block_index.value() * block_size();
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auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
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[[maybe_unused]] auto rc = file_description().write(base_offset, entry_data_buffer, block_size());
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cleaned_entries.append(&entry);
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}
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});
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// NOTE: We make a separate pass to mark entries clean since marking them clean
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// moves them out of the dirty list which would disturb the iteration above.
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for (auto* entry : cleaned_entries)
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cache().mark_clean(*entry);
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}
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void BlockBasedFileSystem::flush_writes_impl()
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{
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MutexLocker locker(m_cache_lock);
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if (!cache().is_dirty())
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return;
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u32 count = 0;
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cache().for_each_dirty_entry([&](CacheEntry& entry) {
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auto base_offset = entry.block_index.value() * block_size();
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auto entry_data_buffer = UserOrKernelBuffer::for_kernel_buffer(entry.data);
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[[maybe_unused]] auto rc = file_description().write(base_offset, entry_data_buffer, block_size());
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++count;
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});
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cache().mark_all_clean();
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dbgln("{}: Flushed {} blocks to disk", class_name(), count);
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}
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void BlockBasedFileSystem::flush_writes()
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{
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flush_writes_impl();
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}
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DiskCache& BlockBasedFileSystem::cache() const
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{
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if (!m_cache)
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m_cache = make<DiskCache>(const_cast<BlockBasedFileSystem&>(*this));
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return *m_cache;
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}
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}
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