Kernel: Rewrite DiskCache
We now cache only clean pages since I don't want to think about syncing the disk later.
This commit is contained in:
Bananymous
parent
6c0f864a6e
commit
a9cf9bceef
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@ -7,16 +7,14 @@
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namespace Kernel
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{
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class StorageDevice;
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class DiskCache
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{
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public:
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DiskCache(StorageDevice&);
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DiskCache(size_t sector_size);
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~DiskCache();
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BAN::ErrorOr<void> read_sector(uint64_t sector, uint8_t* buffer);
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BAN::ErrorOr<void> write_sector(uint64_t sector, const uint8_t* buffer);
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bool read_from_cache(uint64_t sector, uint8_t* buffer);
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BAN::ErrorOr<void> write_to_cache(uint64_t sector, const uint8_t* buffer, bool dirty);
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void sync();
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size_t release_clean_pages(size_t);
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@ -30,16 +28,11 @@ namespace Kernel
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uint64_t first_sector { 0 };
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uint8_t sector_mask { 0 };
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uint8_t dirty_mask { 0 };
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void sync(StorageDevice&);
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BAN::ErrorOr<void> read_sector(StorageDevice&, uint64_t sector, uint8_t* buffer);
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BAN::ErrorOr<void> write_sector(StorageDevice&, uint64_t sector, const uint8_t* buffer);
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};
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private:
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SpinLock m_lock;
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StorageDevice& m_device;
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BAN::Vector<PageCache> m_cache;
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const size_t m_sector_size;
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BAN::Vector<PageCache> m_cache;
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};
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}
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@ -81,8 +81,8 @@ namespace Kernel
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void add_disk_cache();
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private:
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DiskCache* m_disk_cache { nullptr };
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BAN::Vector<Partition*> m_partitions;
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BAN::Optional<DiskCache> m_disk_cache;
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BAN::Vector<Partition*> m_partitions;
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friend class DiskCache;
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};
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@ -8,105 +8,121 @@
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namespace Kernel
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{
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DiskCache::DiskCache(StorageDevice& device)
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: m_device(device)
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{ }
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DiskCache::DiskCache(size_t sector_size)
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: m_sector_size(sector_size)
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{
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ASSERT(PAGE_SIZE % m_sector_size == 0);
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ASSERT(PAGE_SIZE / m_sector_size <= sizeof(PageCache::sector_mask) * 8);
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ASSERT(PAGE_SIZE / m_sector_size <= sizeof(PageCache::dirty_mask) * 8);
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}
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DiskCache::~DiskCache()
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{
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release_all_pages();
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}
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BAN::ErrorOr<void> DiskCache::read_sector(uint64_t sector, uint8_t* buffer)
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bool DiskCache::read_from_cache(uint64_t sector, uint8_t* buffer)
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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uint64_t sectors_per_page = PAGE_SIZE / m_sector_size;
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uint64_t page_cache_offset = sector % sectors_per_page;
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uint64_t page_cache_start = sector - page_cache_offset;
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LockGuard _(m_lock);
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PageTable& page_table = PageTable::current();
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LockGuard page_table_locker(page_table);
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ASSERT(page_table.is_page_free(0));
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uint64_t sectors_per_page = PAGE_SIZE / m_device.sector_size();
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ASSERT(sectors_per_page <= sizeof(PageCache::sector_mask) * 8);
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CriticalScope _;
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for (auto& cache : m_cache)
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{
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if (cache.first_sector < page_cache_start)
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continue;
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if (cache.first_sector > page_cache_start)
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break;
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uint64_t page_cache_start = sector / sectors_per_page * sectors_per_page;
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if (!(cache.sector_mask & (1 << page_cache_offset)))
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continue;
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page_table.map_page_at(cache.paddr, 0, PageTable::Flags::Present);
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memcpy(buffer, (void*)(page_cache_offset * m_sector_size), m_sector_size);
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page_table.unmap_page(0);
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return true;
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}
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return false;
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};
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BAN::ErrorOr<void> DiskCache::write_to_cache(uint64_t sector, const uint8_t* buffer, bool dirty)
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{
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uint64_t sectors_per_page = PAGE_SIZE / m_sector_size;
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uint64_t page_cache_offset = sector % sectors_per_page;
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uint64_t page_cache_start = sector - page_cache_offset;
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PageTable& page_table = PageTable::current();
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LockGuard page_table_locker(page_table);
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ASSERT(page_table.is_page_free(0));
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CriticalScope _;
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// Check if we already have a cache for this page
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// FIXME: binary search
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size_t index = 0;
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// Search the cache if the have this sector in memory
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for (; index < m_cache.size(); index++)
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{
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if (m_cache[index].first_sector < page_cache_start)
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auto& cache = m_cache[index];
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if (cache.first_sector < page_cache_start)
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continue;
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if (m_cache[index].first_sector > page_cache_start)
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if (cache.first_sector > page_cache_start)
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break;
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TRY(m_cache[index].read_sector(m_device, sector, buffer));
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page_table.map_page_at(cache.paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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memcpy((void*)(page_cache_offset * m_sector_size), buffer, m_sector_size);
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page_table.unmap_page(0);
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cache.sector_mask |= 1 << page_cache_offset;
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if (dirty)
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cache.dirty_mask |= 1 << page_cache_offset;
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return {};
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}
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// Try to allocate new cache
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if (paddr_t paddr = Heap::get().take_free_page())
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// Try to add new page to the cache
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paddr_t paddr = Heap::get().take_free_page();
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if (paddr == 0)
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return BAN::Error::from_errno(ENOMEM);
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PageCache cache;
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cache.paddr = paddr;
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cache.first_sector = page_cache_start;
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cache.sector_mask = 1 << page_cache_offset;
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cache.dirty_mask = dirty ? cache.sector_mask : 0;
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if (auto ret = m_cache.insert(index, cache); ret.is_error())
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{
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MUST(m_cache.insert(index, { .paddr = paddr, .first_sector = page_cache_start }));
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TRY(m_cache[index].read_sector(m_device, sector, buffer));
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return {};
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Heap::get().release_page(paddr);
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return ret.error();
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}
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// Could not allocate new cache, read from disk
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TRY(m_device.read_sectors_impl(sector, 1, buffer));
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return {};
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}
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page_table.map_page_at(cache.paddr, 0, PageTable::Flags::Present);
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memcpy((void*)(page_cache_offset * m_sector_size), buffer, m_sector_size);
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page_table.unmap_page(0);
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BAN::ErrorOr<void> DiskCache::write_sector(uint64_t sector, const uint8_t* buffer)
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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LockGuard _(m_lock);
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uint64_t sectors_per_page = PAGE_SIZE / m_device.sector_size();
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ASSERT(sectors_per_page <= sizeof(PageCache::sector_mask) * 8);
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uint64_t page_cache_start = sector / sectors_per_page * sectors_per_page;
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// Check if we already have a cache for this page
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// FIXME: binary search
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size_t index = 0;
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for (; index < m_cache.size(); index++)
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{
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if (m_cache[index].first_sector < page_cache_start)
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continue;
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if (m_cache[index].first_sector > page_cache_start)
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break;
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TRY(m_cache[index].write_sector(m_device, sector, buffer));
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return {};
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}
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// Try to allocate new cache
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if (paddr_t paddr = Heap::get().take_free_page())
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{
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MUST(m_cache.insert(index, { .paddr = paddr, .first_sector = page_cache_start }));
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TRY(m_cache[index].write_sector(m_device, sector, buffer));
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return {};
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}
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// Could not allocate new cache, write to disk
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TRY(m_device.write_sectors_impl(sector, 1, buffer));
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return {};
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}
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void DiskCache::sync()
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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LockGuard _(m_lock);
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for (auto& cache_block : m_cache)
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cache_block.sync(m_device);
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CriticalScope _;
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for (auto& cache : m_cache)
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ASSERT(cache.dirty_mask == 0);
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}
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size_t DiskCache::release_clean_pages(size_t page_count)
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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// NOTE: There might not actually be page_count pages after this
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// function returns. The synchronization must be done elsewhere.
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LockGuard _(m_lock);
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CriticalScope _;
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size_t released = 0;
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for (size_t i = 0; i < m_cache.size() && released < page_count;)
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@ -128,138 +144,16 @@ namespace Kernel
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size_t DiskCache::release_pages(size_t page_count)
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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size_t released = release_clean_pages(page_count);
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if (released >= page_count)
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return released;
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// NOTE: There might not actually be page_count pages after this
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// function returns. The synchronization must be done elsewhere.
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LockGuard _(m_lock);
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while (!m_cache.empty() && released < page_count)
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{
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m_cache.back().sync(m_device);
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Heap::get().release_page(m_cache.back().paddr);
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m_cache.pop_back();
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released++;
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}
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(void)m_cache.shrink_to_fit();
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return released;
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ASSERT_NOT_REACHED();
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}
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void DiskCache::release_all_pages()
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{
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ASSERT(m_device.sector_size() <= PAGE_SIZE);
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LockGuard _(m_lock);
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for (auto& cache_block : m_cache)
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{
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cache_block.sync(m_device);
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Heap::get().release_page(cache_block.paddr);
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}
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m_cache.clear();
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}
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void DiskCache::PageCache::sync(StorageDevice& device)
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{
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if (this->dirty_mask == 0)
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return;
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ASSERT(device.sector_size() <= PAGE_SIZE);
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PageTable& page_table = PageTable::current();
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page_table.lock();
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(this->paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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for (size_t i = 0; i < PAGE_SIZE / device.sector_size(); i++)
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{
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if (!(this->dirty_mask & (1 << i)))
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continue;
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MUST(device.write_sectors_impl(this->first_sector + i, 1, (const uint8_t*)(i * device.sector_size())));
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// FIXME: race condition between here :)
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this->dirty_mask &= ~(1 << i);
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}
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page_table.unmap_page(0);
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page_table.unlock();
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}
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BAN::ErrorOr<void> DiskCache::PageCache::read_sector(StorageDevice& device, uint64_t sector, uint8_t* buffer)
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{
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ASSERT(device.sector_size() <= PAGE_SIZE);
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uint64_t sectors_per_page = PAGE_SIZE / device.sector_size();
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uint64_t sector_offset = sector - this->first_sector;
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ASSERT(sector_offset < sectors_per_page);
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PageTable& page_table = PageTable::current();
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page_table.lock();
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(this->paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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// Sector not yet cached
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if (!(this->sector_mask & (1 << sector_offset)))
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{
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TRY(device.read_sectors_impl(sector, 1, buffer));
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CriticalScope _;
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memcpy((void*)(sector_offset * device.sector_size()), buffer, device.sector_size());
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this->sector_mask |= 1 << sector_offset;
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}
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else
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{
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CriticalScope _;
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memcpy(buffer, (const void*)(sector_offset * device.sector_size()), device.sector_size());
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}
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page_table.unmap_page(0);
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page_table.unlock();
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return {};
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}
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BAN::ErrorOr<void> DiskCache::PageCache::write_sector(StorageDevice& device, uint64_t sector, const uint8_t* buffer)
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{
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ASSERT(device.sector_size() <= PAGE_SIZE);
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uint64_t sectors_per_page = PAGE_SIZE / device.sector_size();
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uint64_t sector_offset = sector - this->first_sector;
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ASSERT(sector_offset < sectors_per_page);
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PageTable& page_table = PageTable::current();
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page_table.lock();
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(this->paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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{
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CriticalScope _;
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memcpy((void*)(sector_offset * device.sector_size()), buffer, device.sector_size());
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this->sector_mask |= 1 << sector_offset;
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this->dirty_mask |= 1 << sector_offset;
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}
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page_table.unmap_page(0);
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page_table.unlock();
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return {};
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release_pages(m_cache.size());
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}
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}
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@ -251,35 +251,41 @@ namespace Kernel
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StorageDevice::~StorageDevice()
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{
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if (m_disk_cache)
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delete m_disk_cache;
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m_disk_cache = nullptr;
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}
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void StorageDevice::add_disk_cache()
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{
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ASSERT(m_disk_cache == nullptr);
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m_disk_cache = new DiskCache(*this);
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ASSERT(m_disk_cache);
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ASSERT(!m_disk_cache.has_value());
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m_disk_cache = DiskCache(sector_size());
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}
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BAN::ErrorOr<void> StorageDevice::read_sectors(uint64_t lba, uint8_t sector_count, uint8_t* buffer)
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{
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if (!m_disk_cache)
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return read_sectors_impl(lba, sector_count, buffer);
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for (uint8_t sector = 0; sector < sector_count; sector++)
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TRY(m_disk_cache->read_sector(lba + sector, buffer + sector * sector_size()));
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for (uint8_t offset = 0; offset < sector_count; offset++)
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{
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uint8_t* buffer_ptr = buffer + offset * sector_size();
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if (m_disk_cache.has_value())
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if (m_disk_cache->read_from_cache(lba + offset, buffer_ptr))
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continue;
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TRY(read_sectors_impl(lba + offset, 1, buffer_ptr));
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if (m_disk_cache.has_value())
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(void)m_disk_cache->write_to_cache(lba + offset, buffer_ptr, false);
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}
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return {};
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}
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BAN::ErrorOr<void> StorageDevice::write_sectors(uint64_t lba, uint8_t sector_count, const uint8_t* buffer)
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{
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if (!m_disk_cache)
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return write_sectors_impl(lba, sector_count, buffer);
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// TODO: use disk cache for dirty pages. I don't wanna think about how to do it safely now
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for (uint8_t sector = 0; sector < sector_count; sector++)
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TRY(m_disk_cache->write_sector(lba + sector, buffer + sector * sector_size()));
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{
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TRY(write_sectors_impl(lba + sector, 1, buffer));
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if (m_disk_cache.has_value())
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(void)m_disk_cache->write_to_cache(lba + sector, buffer + sector * sector_size(), false);
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}
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return {};
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}
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}
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