blob: 10798dae2bfe97beed1ed812b60364b5565f1410 [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/disk_cache/blockfile/block_files.h"
#include <limits>
#include "base/atomicops.h"
#include "base/files/file_path.h"
#include "base/metrics/histogram_macros.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "net/disk_cache/blockfile/file_lock.h"
#include "net/disk_cache/blockfile/stress_support.h"
#include "net/disk_cache/blockfile/trace.h"
#include "net/disk_cache/cache_util.h"
using base::TimeTicks;
namespace {
const char kBlockName[] = "data_";
// This array is used to perform a fast lookup of the nibble bit pattern to the
// type of entry that can be stored there (number of consecutive blocks).
const char s_types[16] = {4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0};
// Returns the type of block (number of consecutive blocks that can be stored)
// for a given nibble of the bitmap.
inline int GetMapBlockType(uint32_t value) {
value &= 0xf;
return s_types[value];
}
} // namespace
namespace disk_cache {
BlockHeader::BlockHeader() : header_(NULL) {
}
BlockHeader::BlockHeader(BlockFileHeader* header) : header_(header) {
}
BlockHeader::BlockHeader(MappedFile* file)
: header_(reinterpret_cast<BlockFileHeader*>(file->buffer())) {
}
BlockHeader::BlockHeader(const BlockHeader& other) : header_(other.header_) {
}
BlockHeader::~BlockHeader() {
}
bool BlockHeader::CreateMapBlock(int size, int* index) {
DCHECK(size > 0 && size <= kMaxNumBlocks);
int target = 0;
for (int i = size; i <= kMaxNumBlocks; i++) {
if (header_->empty[i - 1]) {
target = i;
break;
}
}
if (!target) {
STRESS_NOTREACHED();
return false;
}
TimeTicks start = TimeTicks::Now();
// We are going to process the map on 32-block chunks (32 bits), and on every
// chunk, iterate through the 8 nibbles where the new block can be located.
int current = header_->hints[target - 1];
for (int i = 0; i < header_->max_entries / 32; i++, current++) {
if (current == header_->max_entries / 32)
current = 0;
uint32_t map_block = header_->allocation_map[current];
for (int j = 0; j < 8; j++, map_block >>= 4) {
if (GetMapBlockType(map_block) != target)
continue;
disk_cache::FileLock lock(header_);
int index_offset = j * 4 + 4 - target;
*index = current * 32 + index_offset;
STRESS_DCHECK(*index / 4 == (*index + size - 1) / 4);
uint32_t to_add = ((1 << size) - 1) << index_offset;
header_->num_entries++;
// Note that there is no race in the normal sense here, but if we enforce
// the order of memory accesses between num_entries and allocation_map, we
// can assert that even if we crash here, num_entries will never be less
// than the actual number of used blocks.
base::subtle::MemoryBarrier();
header_->allocation_map[current] |= to_add;
header_->hints[target - 1] = current;
header_->empty[target - 1]--;
STRESS_DCHECK(header_->empty[target - 1] >= 0);
if (target != size) {
header_->empty[target - size - 1]++;
}
LOCAL_HISTOGRAM_TIMES("DiskCache.CreateBlock", TimeTicks::Now() - start);
return true;
}
}
// It is possible to have an undetected corruption (for example when the OS
// crashes), fix it here.
LOG(ERROR) << "Failing CreateMapBlock";
FixAllocationCounters();
return false;
}
void BlockHeader::DeleteMapBlock(int index, int size) {
if (size < 0 || size > kMaxNumBlocks) {
NOTREACHED();
return;
}
TimeTicks start = TimeTicks::Now();
int byte_index = index / 8;
uint8_t* byte_map = reinterpret_cast<uint8_t*>(header_->allocation_map);
uint8_t map_block = byte_map[byte_index];
if (index % 8 >= 4)
map_block >>= 4;
// See what type of block will be available after we delete this one.
int bits_at_end = 4 - size - index % 4;
uint8_t end_mask = (0xf << (4 - bits_at_end)) & 0xf;
bool update_counters = (map_block & end_mask) == 0;
uint8_t new_value = map_block & ~(((1 << size) - 1) << (index % 4));
int new_type = GetMapBlockType(new_value);
disk_cache::FileLock lock(header_);
STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
uint8_t to_clear = ((1 << size) - 1) << (index % 8);
STRESS_DCHECK((byte_map[byte_index] & to_clear) == to_clear);
byte_map[byte_index] &= ~to_clear;
if (update_counters) {
if (bits_at_end)
header_->empty[bits_at_end - 1]--;
header_->empty[new_type - 1]++;
STRESS_DCHECK(header_->empty[bits_at_end - 1] >= 0);
}
base::subtle::MemoryBarrier();
header_->num_entries--;
STRESS_DCHECK(header_->num_entries >= 0);
LOCAL_HISTOGRAM_TIMES("DiskCache.DeleteBlock", TimeTicks::Now() - start);
}
// Note that this is a simplified version of DeleteMapBlock().
bool BlockHeader::UsedMapBlock(int index, int size) {
if (size < 0 || size > kMaxNumBlocks)
return false;
int byte_index = index / 8;
uint8_t* byte_map = reinterpret_cast<uint8_t*>(header_->allocation_map);
uint8_t map_block = byte_map[byte_index];
if (index % 8 >= 4)
map_block >>= 4;
STRESS_DCHECK((((1 << size) - 1) << (index % 8)) < 0x100);
uint8_t to_clear = ((1 << size) - 1) << (index % 8);
return ((byte_map[byte_index] & to_clear) == to_clear);
}
void BlockHeader::FixAllocationCounters() {
for (int i = 0; i < kMaxNumBlocks; i++) {
header_->hints[i] = 0;
header_->empty[i] = 0;
}
for (int i = 0; i < header_->max_entries / 32; i++) {
uint32_t map_block = header_->allocation_map[i];
for (int j = 0; j < 8; j++, map_block >>= 4) {
int type = GetMapBlockType(map_block);
if (type)
header_->empty[type -1]++;
}
}
}
bool BlockHeader::NeedToGrowBlockFile(int block_count) const {
bool have_space = false;
int empty_blocks = 0;
for (int i = 0; i < kMaxNumBlocks; i++) {
empty_blocks += header_->empty[i] * (i + 1);
if (i >= block_count - 1 && header_->empty[i])
have_space = true;
}
if (header_->next_file && (empty_blocks < kMaxBlocks / 10)) {
// This file is almost full but we already created another one, don't use
// this file yet so that it is easier to find empty blocks when we start
// using this file again.
return true;
}
return !have_space;
}
bool BlockHeader::CanAllocate(int block_count) const {
DCHECK_GT(block_count, 0);
for (int i = block_count - 1; i < kMaxNumBlocks; i++) {
if (header_->empty[i])
return true;
}
return false;
}
int BlockHeader::EmptyBlocks() const {
int empty_blocks = 0;
for (int i = 0; i < kMaxNumBlocks; i++) {
empty_blocks += header_->empty[i] * (i + 1);
if (header_->empty[i] < 0)
return 0;
}
return empty_blocks;
}
int BlockHeader::MinimumAllocations() const {
return header_->empty[kMaxNumBlocks - 1];
}
int BlockHeader::Capacity() const {
return header_->max_entries;
}
bool BlockHeader::ValidateCounters() const {
if (header_->max_entries < 0 || header_->max_entries > kMaxBlocks ||
header_->num_entries < 0)
return false;
int empty_blocks = EmptyBlocks();
if (empty_blocks + header_->num_entries > header_->max_entries)
return false;
return true;
}
int BlockHeader::FileId() const {
return header_->this_file;
}
int BlockHeader::NextFileId() const {
return header_->next_file;
}
int BlockHeader::Size() const {
return static_cast<int>(sizeof(*header_));
}
BlockFileHeader* BlockHeader::Header() {
return header_;
}
// ------------------------------------------------------------------------
BlockFiles::BlockFiles(const base::FilePath& path)
: init_(false), zero_buffer_(NULL), path_(path) {
}
BlockFiles::~BlockFiles() {
if (zero_buffer_)
delete[] zero_buffer_;
CloseFiles();
}
bool BlockFiles::Init(bool create_files) {
DCHECK(!init_);
if (init_)
return false;
thread_checker_.reset(new base::ThreadChecker);
block_files_.resize(kFirstAdditionalBlockFile);
for (int16_t i = 0; i < kFirstAdditionalBlockFile; i++) {
if (create_files)
if (!CreateBlockFile(i, static_cast<FileType>(i + 1), true))
return false;
if (!OpenBlockFile(i))
return false;
// Walk this chain of files removing empty ones.
if (!RemoveEmptyFile(static_cast<FileType>(i + 1)))
return false;
}
init_ = true;
return true;
}
MappedFile* BlockFiles::GetFile(Addr address) {
DCHECK(thread_checker_->CalledOnValidThread());
DCHECK_GE(block_files_.size(),
static_cast<size_t>(kFirstAdditionalBlockFile));
DCHECK(address.is_block_file() || !address.is_initialized());
if (!address.is_initialized())
return NULL;
int file_index = address.FileNumber();
if (static_cast<unsigned int>(file_index) >= block_files_.size() ||
!block_files_[file_index]) {
// We need to open the file
if (!OpenBlockFile(file_index))
return NULL;
}
DCHECK_GE(block_files_.size(), static_cast<unsigned int>(file_index));
return block_files_[file_index];
}
bool BlockFiles::CreateBlock(FileType block_type, int block_count,
Addr* block_address) {
DCHECK(thread_checker_->CalledOnValidThread());
DCHECK_NE(block_type, EXTERNAL);
DCHECK_NE(block_type, BLOCK_FILES);
DCHECK_NE(block_type, BLOCK_ENTRIES);
DCHECK_NE(block_type, BLOCK_EVICTED);
if (block_count < 1 || block_count > kMaxNumBlocks)
return false;
if (!init_)
return false;
MappedFile* file = FileForNewBlock(block_type, block_count);
if (!file)
return false;
ScopedFlush flush(file);
BlockHeader file_header(file);
int index;
if (!file_header.CreateMapBlock(block_count, &index))
return false;
Addr address(block_type, block_count, file_header.FileId(), index);
block_address->set_value(address.value());
Trace("CreateBlock 0x%x", address.value());
return true;
}
void BlockFiles::DeleteBlock(Addr address, bool deep) {
DCHECK(thread_checker_->CalledOnValidThread());
if (!address.is_initialized() || address.is_separate_file())
return;
if (!zero_buffer_) {
zero_buffer_ = new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4];
memset(zero_buffer_, 0, Addr::BlockSizeForFileType(BLOCK_4K) * 4);
}
MappedFile* file = GetFile(address);
if (!file)
return;
Trace("DeleteBlock 0x%x", address.value());
size_t size = address.BlockSize() * address.num_blocks();
size_t offset = address.start_block() * address.BlockSize() +
kBlockHeaderSize;
if (deep)
file->Write(zero_buffer_, size, offset);
BlockHeader file_header(file);
file_header.DeleteMapBlock(address.start_block(), address.num_blocks());
file->Flush();
if (!file_header.Header()->num_entries) {
// This file is now empty. Let's try to delete it.
FileType type = Addr::RequiredFileType(file_header.Header()->entry_size);
if (Addr::BlockSizeForFileType(RANKINGS) ==
file_header.Header()->entry_size) {
type = RANKINGS;
}
RemoveEmptyFile(type); // Ignore failures.
}
}
void BlockFiles::CloseFiles() {
if (init_) {
DCHECK(thread_checker_->CalledOnValidThread());
}
init_ = false;
for (unsigned int i = 0; i < block_files_.size(); i++) {
if (block_files_[i]) {
block_files_[i]->Release();
block_files_[i] = NULL;
}
}
block_files_.clear();
}
void BlockFiles::ReportStats() {
DCHECK(thread_checker_->CalledOnValidThread());
int used_blocks[kFirstAdditionalBlockFile];
int load[kFirstAdditionalBlockFile];
for (int i = 0; i < kFirstAdditionalBlockFile; i++) {
GetFileStats(i, &used_blocks[i], &load[i]);
}
UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_0", used_blocks[0]);
UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_1", used_blocks[1]);
UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_2", used_blocks[2]);
UMA_HISTOGRAM_COUNTS("DiskCache.Blocks_3", used_blocks[3]);
UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_0", load[0], 101);
UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_1", load[1], 101);
UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_2", load[2], 101);
UMA_HISTOGRAM_ENUMERATION("DiskCache.BlockLoad_3", load[3], 101);
}
bool BlockFiles::IsValid(Addr address) {
#ifdef NDEBUG
return true;
#else
if (!address.is_initialized() || address.is_separate_file())
return false;
MappedFile* file = GetFile(address);
if (!file)
return false;
BlockHeader header(file);
bool rv = header.UsedMapBlock(address.start_block(), address.num_blocks());
DCHECK(rv);
static bool read_contents = false;
if (read_contents) {
std::unique_ptr<char[]> buffer;
buffer.reset(new char[Addr::BlockSizeForFileType(BLOCK_4K) * 4]);
size_t size = address.BlockSize() * address.num_blocks();
size_t offset = address.start_block() * address.BlockSize() +
kBlockHeaderSize;
bool ok = file->Read(buffer.get(), size, offset);
DCHECK(ok);
}
return rv;
#endif
}
bool BlockFiles::CreateBlockFile(int index, FileType file_type, bool force) {
base::FilePath name = Name(index);
int flags = force ? base::File::FLAG_CREATE_ALWAYS : base::File::FLAG_CREATE;
flags |= base::File::FLAG_WRITE | base::File::FLAG_EXCLUSIVE_WRITE;
scoped_refptr<File> file(new File(base::File(name, flags)));
if (!file->IsValid())
return false;
BlockFileHeader header;
memset(&header, 0, sizeof(header));
header.magic = kBlockMagic;
header.version = kBlockVersion2;
header.entry_size = Addr::BlockSizeForFileType(file_type);
header.this_file = static_cast<int16_t>(index);
DCHECK(index <= std::numeric_limits<int16_t>::max() && index >= 0);
return file->Write(&header, sizeof(header), 0);
}
bool BlockFiles::OpenBlockFile(int index) {
if (block_files_.size() - 1 < static_cast<unsigned int>(index)) {
DCHECK(index > 0);
int to_add = index - static_cast<int>(block_files_.size()) + 1;
block_files_.resize(block_files_.size() + to_add);
}
base::FilePath name = Name(index);
scoped_refptr<MappedFile> file(new MappedFile());
if (!file->Init(name, kBlockHeaderSize)) {
LOG(ERROR) << "Failed to open " << name.value();
return false;
}
size_t file_len = file->GetLength();
if (file_len < static_cast<size_t>(kBlockHeaderSize)) {
LOG(ERROR) << "File too small " << name.value();
return false;
}
BlockHeader file_header(file.get());
BlockFileHeader* header = file_header.Header();
if (kBlockMagic != header->magic || kBlockVersion2 != header->version) {
LOG(ERROR) << "Invalid file version or magic " << name.value();
return false;
}
if (header->updating || !file_header.ValidateCounters()) {
// Last instance was not properly shutdown, or counters are out of sync.
if (!FixBlockFileHeader(file.get())) {
LOG(ERROR) << "Unable to fix block file " << name.value();
return false;
}
}
if (static_cast<int>(file_len) <
header->max_entries * header->entry_size + kBlockHeaderSize) {
LOG(ERROR) << "File too small " << name.value();
return false;
}
if (index == 0) {
// Load the links file into memory.
if (!file->Preload())
return false;
}
ScopedFlush flush(file.get());
DCHECK(!block_files_[index]);
file.swap(&block_files_[index]);
return true;
}
bool BlockFiles::GrowBlockFile(MappedFile* file, BlockFileHeader* header) {
if (kMaxBlocks == header->max_entries)
return false;
ScopedFlush flush(file);
DCHECK(!header->empty[3]);
int new_size = header->max_entries + 1024;
if (new_size > kMaxBlocks)
new_size = kMaxBlocks;
int new_size_bytes = new_size * header->entry_size + sizeof(*header);
if (!file->SetLength(new_size_bytes)) {
// Most likely we are trying to truncate the file, so the header is wrong.
if (header->updating < 10 && !FixBlockFileHeader(file)) {
// If we can't fix the file increase the lock guard so we'll pick it on
// the next start and replace it.
header->updating = 100;
return false;
}
return (header->max_entries >= new_size);
}
FileLock lock(header);
header->empty[3] = (new_size - header->max_entries) / 4; // 4 blocks entries
header->max_entries = new_size;
return true;
}
MappedFile* BlockFiles::FileForNewBlock(FileType block_type, int block_count) {
static_assert(RANKINGS == 1, "invalid file type");
MappedFile* file = block_files_[block_type - 1];
BlockHeader file_header(file);
TimeTicks start = TimeTicks::Now();
while (file_header.NeedToGrowBlockFile(block_count)) {
if (kMaxBlocks == file_header.Header()->max_entries) {
file = NextFile(file);
if (!file)
return NULL;
file_header = BlockHeader(file);
continue;
}
if (!GrowBlockFile(file, file_header.Header()))
return NULL;
break;
}
LOCAL_HISTOGRAM_TIMES("DiskCache.GetFileForNewBlock",
TimeTicks::Now() - start);
return file;
}
MappedFile* BlockFiles::NextFile(MappedFile* file) {
ScopedFlush flush(file);
BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
int16_t new_file = header->next_file;
if (!new_file) {
// RANKINGS is not reported as a type for small entries, but we may be
// extending the rankings block file.
FileType type = Addr::RequiredFileType(header->entry_size);
if (header->entry_size == Addr::BlockSizeForFileType(RANKINGS))
type = RANKINGS;
new_file = CreateNextBlockFile(type);
if (!new_file)
return NULL;
FileLock lock(header);
header->next_file = new_file;
}
// Only the block_file argument is relevant for what we want.
Addr address(BLOCK_256, 1, new_file, 0);
return GetFile(address);
}
int16_t BlockFiles::CreateNextBlockFile(FileType block_type) {
for (int16_t i = kFirstAdditionalBlockFile; i <= kMaxBlockFile; i++) {
if (CreateBlockFile(i, block_type, false))
return i;
}
return 0;
}
// We walk the list of files for this particular block type, deleting the ones
// that are empty.
bool BlockFiles::RemoveEmptyFile(FileType block_type) {
MappedFile* file = block_files_[block_type - 1];
BlockFileHeader* header = reinterpret_cast<BlockFileHeader*>(file->buffer());
while (header->next_file) {
// Only the block_file argument is relevant for what we want.
Addr address(BLOCK_256, 1, header->next_file, 0);
MappedFile* next_file = GetFile(address);
if (!next_file)
return false;
BlockFileHeader* next_header =
reinterpret_cast<BlockFileHeader*>(next_file->buffer());
if (!next_header->num_entries) {
DCHECK_EQ(next_header->entry_size, header->entry_size);
// Delete next_file and remove it from the chain.
int file_index = header->next_file;
header->next_file = next_header->next_file;
DCHECK(block_files_.size() >= static_cast<unsigned int>(file_index));
file->Flush();
// We get a new handle to the file and release the old one so that the
// file gets unmmaped... so we can delete it.
base::FilePath name = Name(file_index);
scoped_refptr<File> this_file(new File(false));
this_file->Init(name);
block_files_[file_index]->Release();
block_files_[file_index] = NULL;
int failure = DeleteCacheFile(name) ? 0 : 1;
UMA_HISTOGRAM_COUNTS("DiskCache.DeleteFailed2", failure);
if (failure)
LOG(ERROR) << "Failed to delete " << name.value() << " from the cache.";
continue;
}
header = next_header;
file = next_file;
}
return true;
}
// Note that we expect to be called outside of a FileLock... however, we cannot
// DCHECK on header->updating because we may be fixing a crash.
bool BlockFiles::FixBlockFileHeader(MappedFile* file) {
ScopedFlush flush(file);
BlockHeader file_header(file);
int file_size = static_cast<int>(file->GetLength());
if (file_size < file_header.Size())
return false; // file_size > 2GB is also an error.
const int kMinHeaderBlockSize = 36;
const int kMaxHeaderBlockSize = 4096;
BlockFileHeader* header = file_header.Header();
if (header->entry_size < kMinHeaderBlockSize ||
header->entry_size > kMaxHeaderBlockSize || header->num_entries < 0)
return false;
// Make sure that we survive crashes.
header->updating = 1;
int expected = header->entry_size * header->max_entries + file_header.Size();
if (file_size != expected) {
int max_expected = header->entry_size * kMaxBlocks + file_header.Size();
if (file_size < expected || header->empty[3] || file_size > max_expected) {
NOTREACHED();
LOG(ERROR) << "Unexpected file size";
return false;
}
// We were in the middle of growing the file.
int num_entries = (file_size - file_header.Size()) / header->entry_size;
header->max_entries = num_entries;
}
file_header.FixAllocationCounters();
int empty_blocks = file_header.EmptyBlocks();
if (empty_blocks + header->num_entries > header->max_entries)
header->num_entries = header->max_entries - empty_blocks;
if (!file_header.ValidateCounters())
return false;
header->updating = 0;
return true;
}
// We are interested in the total number of blocks used by this file type, and
// the max number of blocks that we can store (reported as the percentage of
// used blocks). In order to find out the number of used blocks, we have to
// substract the empty blocks from the total blocks for each file in the chain.
void BlockFiles::GetFileStats(int index, int* used_count, int* load) {
int max_blocks = 0;
*used_count = 0;
*load = 0;
for (;;) {
if (!block_files_[index] && !OpenBlockFile(index))
return;
BlockFileHeader* header =
reinterpret_cast<BlockFileHeader*>(block_files_[index]->buffer());
max_blocks += header->max_entries;
int used = header->max_entries;
for (int i = 0; i < kMaxNumBlocks; i++) {
used -= header->empty[i] * (i + 1);
DCHECK_GE(used, 0);
}
*used_count += used;
if (!header->next_file)
break;
index = header->next_file;
}
if (max_blocks)
*load = *used_count * 100 / max_blocks;
}
base::FilePath BlockFiles::Name(int index) {
// The file format allows for 256 files.
DCHECK(index < 256 && index >= 0);
std::string tmp = base::StringPrintf("%s%d", kBlockName, index);
return path_.AppendASCII(tmp);
}
} // namespace disk_cache