Disk cache: Reference CL for the implementation of file format version 3.

net/disk_cache/v3/backend_worker.cc

+// 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/v3/backend_worker.h"
+
+#include "base/bind.h"
+#include "base/file_util.h"
+#include "base/message_loop.h"
+#include "base/stringprintf.h"
+#include "net/base/net_errors.h"
+#include "net/disk_cache/cache_util.h"
+#include "net/disk_cache/errors.h"
+#include "net/disk_cache/experiments.h"
+#include "net/disk_cache/mapped_file.h"
+#include "net/disk_cache/v3/backend_work_item.h"
+#include "net/disk_cache/v3/disk_format_v3.h"
+
+using base::Time;
+using base::TimeDelta;
+using base::TimeTicks;
+
+namespace {
+
+const char kIndexName[] = "index";
+const char kIndexBackupName[] = "index_bak";
+const char kTable1Name[] = "index_tb1";
+const char kTable2Name[] = "index_tb2";
+const char kTable2TempName[] = "index_tb2_tmp";
+const int kMaxOldFolders = 100;
+
+// Seems like ~240 MB correspond to less than 50k entries for 99% of the people.
+// Note that the actual target is to keep the index table load factor under 55%
+// for most users.
+const int k64kEntriesStore = 240 * 1000 * 1000;
+const int kBaseTableLen = 64 * 1024;
+const int kDefaultCacheSize = 80 * 1024 * 1024;
+
+// Avoid trimming the cache for the first 5 minutes (10 timer ticks).
+const int kTrimDelay = 10;
+
+int DesiredIndexTableLen(int32 storage_size) {
+  if (storage_size <= k64kEntriesStore)
+    return kBaseTableLen;
+  if (storage_size <= k64kEntriesStore * 2)
+    return kBaseTableLen * 2;
+  if (storage_size <= k64kEntriesStore * 4)
+    return kBaseTableLen * 4;
+  if (storage_size <= k64kEntriesStore * 8)
+    return kBaseTableLen * 8;
+
+  // The biggest storage_size for int32 requires a 4 MB table.
+  return kBaseTableLen * 16;
+}
+
+int MaxStorageSizeForTable(int table_len) {
+  return table_len * (k64kEntriesStore / kBaseTableLen);
+}
+
+size_t GetIndexSize(int table_len) {
+  //  
+  //size_t table_size = sizeof(disk_cache::CacheAddr) * table_len;
+  //return sizeof(disk_cache::IndexHeaderV3) + table_size;
+  return 0;
+}
+
+size_t GetIndexBitmapSize(int table_len) {
+  DCHECK_LT(table_len, 1 << 22);
+  size_t base_bits = disk_cache::kBaseBitmapBytes * 8;
+  if (table_len < static_cast<int>(base_bits))
+    return sizeof(disk_cache::IndexBitmap);
+
+  size_t extra_pages = (table_len / 8) - disk_cache::kBaseBitmapBytes;
+  extra_pages = (extra_pages + 4095) / 4096;
+  return sizeof(disk_cache::IndexBitmap) + extra_pages * 4096;
+}
+
+// ------------------------------------------------------------------------
+
+// Sets group for the current experiment. Returns false if the files should be
+// discarded.
+bool InitExperiment(disk_cache::IndexHeaderV3* header) {
+  header->experiment = disk_cache::NO_EXPERIMENT;
+  return true;
+}
+
+}  // namespace
+
+// ------------------------------------------------------------------------
+
+namespace disk_cache {
+
+BackendImplV3::Worker::Worker(const base::FilePath& path,
+                              base::MessageLoopProxy* main_thread)
+      : path_(path),
+        main_thread_(main_thread),
+        cleanup_work_item_(NULL),
+        init_(false),
+        doubling_index_(false),
+        user_flags_(0) {
+}
+
+int BackendImplV3::Worker::Init(uint32 flags, scoped_ptr<InitResult>* result) {
+  DCHECK(!init_);
+  if (init_)
+    return ERR_INIT_FAILED;
+
+  user_flags_ = flags;
+  result->reset(new InitResult);
+
+  bool create_files = false;
+  if (!InitBackingStore(&create_files))
+    return ERR_STORAGE_ERROR;
+
+  init_ = true;
+  if (!LoadIndex(result->get()))
+    return ERR_INIT_FAILED;
+
+  int rv = ERR_NO_ERROR;
+  IndexHeaderV3* index =
+      reinterpret_cast<IndexHeaderV3*>(index_header_->buffer());
+  if (create_files || !index->num_entries)
+    rv = ERR_CACHE_CREATED;
+
+  if (create_files && (flags & EVICTION_V2)) {
+    index->flags |= CACHE_EVICTION_2;
+  }
+
+  if (!(flags & BASIC_UNIT_TEST) && !InitExperiment(index))
+    return ERR_INIT_FAILED;
+
+  if (index->crash != 0)
+    rv = ERR_PREVIOUS_CRASH;
+  index->crash = 1;
+
+  block_files_.reset(new BlockFiles(path_));
+  if (flags & BASIC_UNIT_TEST)
+    block_files_->UseSmallSizeIncrementsForTest();
+
+  if (!block_files_->Init(create_files, kFirstAdditionalBlockFileV3))
+    return ERR_INIT_FAILED;
+
+  block_files_->GetBitmaps(index->max_block_file,
+                           &result->get()->block_bitmaps);
+  index->max_block_file = static_cast<int>(result->get()->block_bitmaps.size());
+
+  if (!InitStats(index, result->get()))
+    return ERR_INIT_FAILED;
+
+#if defined(STRESS_CACHE_EXTENDED_VALIDATION)
+  trace_object_->EnableTracing(false);
+  int sc = SelfCheck();
+  if (sc < 0 && sc != ERR_NUM_ENTRIES_MISMATCH)
+    NOTREACHED();
+  trace_object_->EnableTracing(true);
+#endif
+
+  return rv;
+}
+
+int BackendImplV3::Worker::Restart(uint32 flags,
+                                   scoped_ptr<InitResult>* result) {
+  Trace("Worker::Restart");
+  if (init_) {
+    init_ = false;
+  }
+
+  CloseFiles();
+  DeleteCache(path_, false);
+
+  return Init(flags, result);
+}
+
+int BackendImplV3::Worker::GrowIndex(uint32 flags,
+                                     scoped_ptr<InitResult>* result) {
+  Trace("Worker::GrowIndex, flags 0x%x", flags);
+  if (!init_)
+    return ERR_OPERATION_FAILED;
+
+  if (flags & WorkItem::WORK_COMPLETE) {
+    index_header_ = big_index_header_;
+    big_index_header_ = NULL;
+    if (big_main_table_) {
+      main_table_ = big_main_table_;
+      big_main_table_ = NULL;
+    }
+    if (!big_extra_temp_table_)
+      extra_table_ = big_extra_table_;
+    big_extra_table_ = NULL;
+
+    // If the index takes time to move the cells, it creates a new work item to
+    // notify completion, which executes this code.
+    if (big_extra_temp_table_)
+      return GrowDone();
+
+    return ERR_NO_ERROR;
+  }
+
+  IndexHeaderV3* header =
+      reinterpret_cast<IndexHeaderV3*>(index_header_->buffer());
+
+  int current_main_len = header->table_len / kIndexTablesize * kIndexTablesize;
+  int step_size = std::min(8192, current_main_len / 8);
+  if (user_flags_ & BASIC_UNIT_TEST)
+    step_size = 8;
+  if ((user_flags_ & UNIT_TEST_MODE) && !doubling_index_)
+    step_size = (header->table_len * 3 / 2) & 0x7ffffff0;
+  int new_len = header->table_len + step_size;
+
+  bool double_index = false;
+  if (!doubling_index_) {
+    DCHECK(!big_extra_table_);
+    DCHECK(!big_main_table_);
+    double_index = (new_len / kIndexTablesize !=
+                    header->table_len / kIndexTablesize);
+  }
+
+  int extra_len = new_len - kIndexTablesize;
+  if (double_index) {
+    // We double the table when the extra table is about to reach the size of
+    // the main table. That means that right after this, the new extra table
+    // should be between 19% and 23% of the main table so we start with 25%.
+    extra_len = std::min(8192, current_main_len / 4);
+    extra_len = (user_flags_ & BASIC_UNIT_TEST) ? 128 : extra_len;
+    int main_len = (header->table_len / kIndexTablesize + 1) * kIndexTablesize;
+    new_len = main_len + extra_len;
+
+    if (!CreateExtraTable(extra_len * kBytesPerCell))
+      return ERR_OPERATION_FAILED;
+
+    if (!main_table_->SetLength(main_len * kBytesPerCell))
+      return ERR_OPERATION_FAILED;
+  } else if (doubling_index_) {
+    if (!big_extra_temp_table_->SetLength(extra_len * kBytesPerCell))
+      return ERR_OPERATION_FAILED;
+  } else {
+    if (!extra_table_->SetLength(extra_len * kBytesPerCell))
+      return ERR_OPERATION_FAILED;
+  }
+
+  if (!index_header_->SetLength(GetIndexBitmapSize(new_len)))
+    return ERR_OPERATION_FAILED;
+
+  scoped_refptr<MappedFile> big_index_header = new MappedFile();
+  if (!big_index_header->Init(path_.AppendASCII(kIndexName), 0)) {
+    LOG(ERROR) << "Unable to remap index";
+    return ERR_OPERATION_FAILED;
+  }
+
+  scoped_refptr<MappedFile> big_extra_table = new MappedFile();
+  const char* extra_name = (double_index || doubling_index_) ? kTable2TempName :
+                                                               kTable2Name;
+  if (!big_extra_table->Init(path_.AppendASCII(extra_name), 0)) {
+    LOG(ERROR) << "Unable to remap index_tb2";
+    return ERR_OPERATION_FAILED;
+  }
+
+  if (double_index) {
+    scoped_refptr<MappedFile> big_main_table = new MappedFile();
+    if (!big_main_table->Init(path_.AppendASCII(kTable1Name), 0)) {
+      LOG(ERROR) << "Unable to remap index_tb1";
+      return ERR_OPERATION_FAILED;
+    }
+    big_main_table_.swap(big_main_table);
+
+    // Grab an extra reference to the new extra table that can be used for an
+    // extended period, while the index is being rebuilt. The normal reference
+    // (big_extra_table_) will be released when the work item is completed, but
+    // that doesn't mean the index is done with it.
+    // Note that we are able to process slow grow requests even when the index
+    // is being doubled.
+    big_extra_temp_table_ = big_extra_table;
+  }
+  big_index_header_.swap(big_index_header);
+  big_extra_table_.swap(big_extra_table);
+
+  header = reinterpret_cast<IndexHeaderV3*>(big_index_header_->buffer());
+  header->table_len = new_len;
+
+  result->reset(new InitResult);
+  result->get()->main_table = NULL;
+
+  result->get()->index_bitmap =
+      reinterpret_cast<IndexBitmap*>(big_index_header_->buffer());
+  result->get()->extra_table =
+      reinterpret_cast<IndexBucket*>(big_extra_table_->buffer());
+
+  if (double_index) {
+    result->get()->main_table =
+      reinterpret_cast<IndexBucket*>(big_main_table_->buffer());
+    doubling_index_ = true;
+  }
+
+  return ERR_NO_ERROR;
+}
+
+int BackendImplV3::Worker::GrowFiles(uint32 flags,
+                                     scoped_ptr<InitResult>* result) {
+  Trace("Worker::GrowFiles, flags 0x%x", flags);
+  if (!init_)
+    return ERR_OPERATION_FAILED;
+
+  if (flags & WorkItem::WORK_COMPLETE) {
+    block_files_.reset();
+    block_files_.swap(big_block_files_);
+    return ERR_NO_ERROR;
+  }
+
+  big_block_files_.reset(new BlockFiles(path_));
+  if (user_flags_ & BASIC_UNIT_TEST)
+    big_block_files_->UseSmallSizeIncrementsForTest();
+
+  if (!big_block_files_->Init(false, kFirstAdditionalBlockFileV3))
+    return ERR_INIT_FAILED;
+
+  IndexHeaderV3* index =
+      reinterpret_cast<IndexHeaderV3*>(index_header_->buffer());
+
+  result->reset(new InitResult);
+  big_block_files_->GetBitmaps(index->max_block_file,
+                               &result->get()->block_bitmaps);
+  index->max_block_file = static_cast<int>(result->get()->block_bitmaps.size());
+  return ERR_NO_ERROR;
+}
+
+int BackendImplV3::Worker::Delete(Addr address) {
+  if (address.is_block_file())
+    return ERR_OPERATION_FAILED;
+
+  if (DeleteCacheFile(GetFileName(address))) 
+    return ERR_NO_ERROR;
+
+  return ERR_OPERATION_FAILED;
+}
+
+int BackendImplV3::Worker::Close(Addr address) {
+  if (address.is_block_file())
+    return ERR_OPERATION_FAILED;
+
+  FilesMap::iterator it = files_.find(address.value());
+  if (it != files_.end())
+    files_.erase(it);
+
+  return ERR_NO_ERROR;
+}
+
+void BackendImplV3::Worker::OnDoWork(WorkItem* work_item) {
+  if (work_item->type() == WorkItem::WORK_CLEANUP)
+    return Cleanup(work_item);
+
+  work_item->Start(this);
+}
+
+void BackendImplV3::Worker::DoneWithItem(WorkItem* work_item) {
+  bool rv = main_thread_->PostTask(FROM_HERE,
+                                   base::Bind(&WorkItem::OnDone, work_item));
+  DCHECK(rv);
+}
+
+File* BackendImplV3::Worker::GetBackingFile(Addr address, bool for_write) {
+  disk_cache::File* file;
+  if (address.is_separate_file())
+    file = GetExternalFile(address, for_write);
+  else
+    file = block_files_->GetFile(address);
+  return file;
+}
+
+bool BackendImplV3::Worker::IsValid() {
+  return init_;
+}
+
+// ------------------------------------------------------------------------
+
+BackendImplV3::Worker::~Worker() {
+  if (cleanup_work_item_)
+    main_thread_->PostTask(FROM_HERE,
+                           base::Bind(&WorkItem::OnDone, cleanup_work_item_));
+}
+
+void BackendImplV3::Worker::Cleanup(WorkItem* work_item) {
+  Trace("Worker::Cleanup");
+  if (!work_item->user_callback().is_null())
+    cleanup_work_item_ = work_item;
+
+  if (init_) {
+    IndexHeaderV3* index =
+      reinterpret_cast<IndexHeaderV3*>(index_header_->buffer());
+    index->crash = 0;
+  }
+
+  CloseFiles();
+  init_ = false;
+
+  if (work_item->user_callback().is_null()) {
+    // This is the only message we don't return to the main thread, we are done
+    // with the work item for good.
+    work_item->Release();
+  }
+}
+
+void BackendImplV3::Worker::CloseFiles() {
+  index_header_ = NULL;
+  main_table_ = NULL;
+  extra_table_ = NULL;
+  index_backup_ = NULL;
+  block_files_->CloseFiles();
+  files_.clear();
+
+  big_index_header_ = NULL;
+  big_main_table_ = NULL;
+  big_extra_table_ = NULL;
+  big_extra_temp_table_ = NULL;
+  if (big_block_files_.get())
+    big_block_files_->CloseFiles();
+}
+
+File* BackendImplV3::Worker::GetExternalFile(Addr address, bool for_write) {
+  FilesMap::iterator it = files_.find(address.value());
+  if (it != files_.end())
+    return it->second;
+
+  scoped_refptr<disk_cache::File> file(new disk_cache::File(false));
+  if (for_write)
+    file->set_force_creation();
+  if (file->Init(GetFileName(address)))
+    files_[address.value()] = file.get();
+  else
+    file = NULL;
+
+  return file;
+}
+
+base::FilePath BackendImplV3::Worker::GetFileName(Addr address) const {
+  if (!address.is_separate_file() || !address.is_initialized()) {
+    NOTREACHED();
+    return base::FilePath();
+  }
+
+  std::string tmp = base::StringPrintf("f_%06x", address.FileNumber());
+  return path_.AppendASCII(tmp);
+}
+
+// We just created a new file so we're going to write the header and set the
+// file length to include the hash table (zero filled).
+bool BackendImplV3::Worker::CreateBackingStore(disk_cache::File* file) {
+  IndexHeaderV3 header;
+  
+  // Start with 12.5% of the size of the main table.
+  int extra_len = (user_flags_ & BASIC_UNIT_TEST) ? 8 : kIndexTablesize / 8;
+  header.table_len = kIndexTablesize + extra_len;
+  header.max_bucket = kIndexTablesize / 4 - 1;
+
+  header.create_time = Time::Now().ToInternalValue();
+  header.base_time = (Time::Now() - TimeDelta::FromDays(20)).ToInternalValue();
+
+  if (!file->Write(&header, sizeof(header), 0))
+    return false;
+
+  if (!file->SetLength(GetIndexBitmapSize(header.table_len)))
+    return false;
+
+  int flags = base::PLATFORM_FILE_READ |
+              base::PLATFORM_FILE_WRITE |
+              base::PLATFORM_FILE_CREATE |
+              base::PLATFORM_FILE_EXCLUSIVE_WRITE;
+
+  base::FilePath name = path_.AppendASCII(kIndexBackupName);
+  scoped_refptr<disk_cache::File> file2(new disk_cache::File(
+      base::CreatePlatformFile(name, flags, NULL, NULL)));
+
+  if (!file2->IsValid())
+    return false;
+
+  if (!file2->Write(&header, sizeof(header), 0))
+    return false;
+
+  if (!file2->SetLength(GetIndexBitmapSize(header.table_len)))
+    return false;
+
+  name = path_.AppendASCII(kTable1Name);
+  file2 = new disk_cache::File(base::CreatePlatformFile(name, flags, NULL,
+                                                        NULL));
+  if (!file2->IsValid())
+    return false;
+
+  if (!file2->SetLength(kIndexTablesize * kBytesPerCell))
+    return false;
+
+  name = path_.AppendASCII(kTable2Name);
+  file2 = new disk_cache::File(base::CreatePlatformFile(name, flags, NULL,
+                                                        NULL));
+  if (!file2->IsValid())
+    return false;
+
+  if (!file2->SetLength(extra_len * kBytesPerCell))
+    return false;
+
+  return true;
+}
+
+bool BackendImplV3::Worker::CreateExtraTable(int extra_len) {
+  int flags = base::PLATFORM_FILE_READ |
+              base::PLATFORM_FILE_WRITE |
+              base::PLATFORM_FILE_CREATE |
+              base::PLATFORM_FILE_EXCLUSIVE_WRITE;
+
+  base::FilePath name = path_.AppendASCII(kTable2TempName);
+  scoped_refptr<disk_cache::File> file(new disk_cache::File(
+      base::CreatePlatformFile(name, flags, NULL, NULL)));
+  if (!file->IsValid())
+    return false;
+
+  if (!file->SetLength(extra_len * kBytesPerCell))
+    return false;
+
+  return true;
+}
+
+bool BackendImplV3::Worker::InitBackingStore(bool* file_created) {
+  if (!file_util::CreateDirectory(path_))
+    return false;
+
+  base::FilePath index_name = path_.AppendASCII(kIndexName);
+
+  int flags = base::PLATFORM_FILE_READ |
+              base::PLATFORM_FILE_WRITE |
+              base::PLATFORM_FILE_OPEN_ALWAYS |
+              base::PLATFORM_FILE_EXCLUSIVE_WRITE;
+  scoped_refptr<disk_cache::File> file(new disk_cache::File(
+      base::CreatePlatformFile(index_name, flags, file_created, NULL)));
+
+  if (!file->IsValid())
+    return false;
+
+  bool ret = true;
+  if (*file_created)
+    ret = CreateBackingStore(file);
+
+  file = NULL;
+  if (!ret)
+    return false;
+
+  index_header_ = new MappedFile();
+  if (!index_header_->Init(index_name, 0)) {
+    LOG(ERROR) << "Unable to map index";
+    return false;
+  }
+
+  if (index_header_->GetLength() < sizeof(IndexBitmap)) {
+    // We verify this again on CheckIndex() but it's easier to make sure now
+    // that the header is there.
+    LOG(ERROR) << "Corrupt index file";
+    return false;
+  }
+
+  main_table_ = new MappedFile();
+  if (!main_table_->Init(path_.AppendASCII(kTable1Name), 0)) {
+    LOG(ERROR) << "Unable to map index_tb1";
+    return false;
+  }
+
+  extra_table_ = new MappedFile();
+  if (!extra_table_->Init(path_.AppendASCII(kTable2Name), 0)) {
+    LOG(ERROR) << "Unable to map index_tb2";
+    return false;
+  }
+
+  index_backup_ = new MappedFile();
+  if (!index_backup_->Init(path_.AppendASCII(kIndexBackupName), 0)) {
+    LOG(ERROR) << "Unable to map index_bak";
+    return false;
+  }
+
+  return true;
+}
+
+bool BackendImplV3::Worker::LoadIndex(InitResult* init_result) {
+  init_result->index_bitmap =
+      reinterpret_cast<IndexBitmap*>(index_header_->buffer());
+  init_result->main_table =
+      reinterpret_cast<IndexBucket*>(main_table_->buffer());
+  init_result->extra_table =
+      reinterpret_cast<IndexBucket*>(extra_table_->buffer());
+
+  if (!CheckIndexFile(index_header_))
+    return false;
+
+  if (!CheckIndexFile(index_backup_))
+    return false;
+
+  IndexHeaderV3& header = init_result->index_bitmap->header;
+
+  size_t extra_table_len = header.table_len % kIndexTablesize;
+  size_t main_table_len = (kIndexTablesize - extra_table_len) * kBytesPerCell;
+  extra_table_len *= kBytesPerCell;
+
+  if (main_table_->GetLength() < main_table_len ||
+      extra_table_->GetLength() < extra_table_len) {
+    LOG(ERROR) << "Truncated table";
+    return false;
+  }
+
+  IndexBitmap* index = reinterpret_cast<IndexBitmap*>(index_backup_->buffer());
+
+  init_result->backup_header.reset(new IndexHeaderV3);
+  memcpy(init_result->backup_header.get(), &index->header,
+         sizeof(index->header));
+
+  size_t bitmap_len = GetIndexBitmapSize(index->header.table_len) -
+                      sizeof(index->header);
+  init_result->backup_bitmap.reset(new uint32[bitmap_len / 4]);
+  memcpy(init_result->backup_bitmap.get(), &index->bitmap, bitmap_len);
+
+  // Close the backup.
+  index_backup_ = NULL;
+  return true;
+}
+
+bool BackendImplV3::Worker::CheckIndexFile(MappedFile* file) {
+  size_t current_size = file->GetLength();
+  if (current_size < sizeof(IndexBitmap)) {
+    LOG(ERROR) << "Corrupt Index file";
+    return false;
+  }
+
+  IndexHeaderV3* header = reinterpret_cast<IndexHeaderV3*>(file->buffer());
+
+  if (kIndexMagic != header->magic ||
+      kCurrentVersion != header->version) {
+    LOG(ERROR) << "Invalid file version or magic";
+    return false;
+  }
+
+  if (header->table_len <= 0 || header->table_len > 1 << 22) {
+    LOG(ERROR) << "Invalid table size";
+    return false;
+  }
+
+  int min_mask = (user_flags_ & BASIC_UNIT_TEST) ? 0x3 : 0xff;
+  if (current_size < GetIndexBitmapSize(header->table_len) ||
+      header->table_len & (min_mask)) {
+    LOG(ERROR) << "Corrupt Index file";
+    return false;
+  }
+
+  //AdjustMaxCacheSize(header->table_len);
+
+#if !defined(NET_BUILD_STRESS_CACHE)
+  if (header->num_bytes < 0 || header->max_bytes < 0 ||
+      header->num_bytes > header->max_bytes + kDefaultCacheSize) {
+    LOG(ERROR) << "Invalid cache size";
+    return false;
+  }
+#endif
+
+  if (header->num_entries < 0) {
+    LOG(ERROR) << "Invalid number of entries";
+    return false;
+  }
+
+  // Load the table into memory with a single read.
+  //scoped_array<char> buf(new char[current_size]);
+  //return index_->Read(buf.get(), current_size, 0);
+  
+  return true;
+}
+
+bool BackendImplV3::Worker::InitStats(IndexHeaderV3* index,
+                                      InitResult* result) {
+  Addr address(index->stats);
+  if (!address.is_initialized())
+    return true;
+
+  if (!address.is_block_file()) {
+    NOTREACHED();
+    return false;
+  }
+
+  int size = address.num_blocks() * address.BlockSize();
+
+  // Load the required data.
+  MappedFile* file = GetMappedFile(address);
+  if (!file)
+    return false;
+
+  scoped_ptr<char[]> data(new char[size]);
+  size_t offset = address.start_block() * address.BlockSize() +
+                  kBlockHeaderSize;
+  if (!file->Read(data.get(), size, offset))
+    return false;
+
+  result->stats_data = data.Pass();
+  return true;
+}
+
+int BackendImplV3::Worker::GrowDone() {
+  Trace("Worker::GrowDone");
+  if (!init_)
+    return ERR_OPERATION_FAILED;
+
+  DCHECK(doubling_index_);
+  doubling_index_ = false;
+
+  extra_table_ = big_extra_temp_table_;
+  big_extra_temp_table_ = NULL;
+
+  return ERR_NO_ERROR;
+}
+
+}  // namespace disk_cache