[BlobStorage] BlobMemoryController & tests

storage/browser/blob/blob_memory_controller.cc

Index: storage/browser/blob/blob_memory_controller.cc
diff --git a/storage/browser/blob/blob_memory_controller.cc b/storage/browser/blob/blob_memory_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..422cddf748963812aef5869e5d7e35cb3c10fd28
--- /dev/null
+++ b/storage/browser/blob/blob_memory_controller.cc
@@ -0,0 +1,730 @@
+// Copyright 2016 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 "storage/browser/blob/blob_memory_controller.h"
+
+#include <algorithm>
+
+#include "base/callback.h"
+#include "base/callback_helpers.h"
+#include "base/containers/small_map.h"
+#include "base/files/file_util.h"
+#include "base/guid.h"
+#include "base/location.h"
+#include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/numerics/safe_math.h"
+#include "base/single_thread_task_runner.h"
+#include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/task_runner.h"
+#include "base/task_runner_util.h"
+#include "base/threading/thread_restrictions.h"
+#include "base/time/time.h"
+#include "base/trace_event/trace_event.h"
+#include "base/tuple.h"
+#include "storage/browser/blob/blob_data_builder.h"
+#include "storage/browser/blob/blob_data_item.h"
+#include "storage/browser/blob/shareable_blob_data_item.h"
+#include "storage/browser/blob/shareable_file_reference.h"
+#include "storage/common/data_element.h"
+
+using base::File;
+using base::FilePath;
+
+namespace storage {
+namespace {
+using FileCreationInfo = BlobMemoryController::FileCreationInfo;
+using MemoryAllocation = BlobMemoryController::MemoryAllocation;
+using QuotaAllocationTask = BlobMemoryController::QuotaAllocationTask;
+
+File::Error CreateBlobDirectory(const FilePath& blob_storage_dir) {
+  File::Error error = File::FILE_OK;
+  base::CreateDirectoryAndGetError(blob_storage_dir, &error);
+  UMA_HISTOGRAM_ENUMERATION("Storage.Blob.CreateDirectoryResult", -error,
+                            -File::FILE_ERROR_MAX);
+  return error;
+}
+
+void DestructFile(File infos_without_references) {}
+
+// Used for new unpopulated file items. Caller must populate file reference in
+// returned FileCreationInfos.
+std::pair<std::vector<FileCreationInfo>, File::Error> CreateEmptyFiles(
+    const FilePath& blob_storage_dir,
+    scoped_refptr<base::TaskRunner> file_task_runner,
+    std::vector<base::FilePath> file_paths) {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  File::Error dir_create_status = CreateBlobDirectory(blob_storage_dir);
+  if (dir_create_status != File::FILE_OK)
+    return std::make_pair(std::vector<FileCreationInfo>(), dir_create_status);
+
+  std::vector<FileCreationInfo> result;
+  for (const base::FilePath& file_path : file_paths) {
+    FileCreationInfo creation_info;
+    // Try to open our file.
+    File file(file_path, File::FLAG_CREATE_ALWAYS | File::FLAG_WRITE);
+    creation_info.path = std::move(file_path);
+    creation_info.file_deletion_runner = file_task_runner;
+    creation_info.error = file.error_details();
+    if (creation_info.error != File::FILE_OK) {
+      return std::make_pair(std::vector<FileCreationInfo>(),
+                            creation_info.error);
+    }
+
+    // Grab the file info to get the "last modified" time and store the file.
+    File::Info file_info;
+    bool success = file.GetInfo(&file_info);
+    creation_info.error = success ? File::FILE_OK : File::FILE_ERROR_FAILED;
+    if (!success) {
+      return std::make_pair(std::vector<FileCreationInfo>(),
+                            creation_info.error);
+    }
+    creation_info.file = std::move(file);
+
+    result.push_back(std::move(creation_info));
+  }
+  return std::make_pair(std::move(result), File::FILE_OK);
+}
+
+// Used to evict multiple memory items out to a single file. Caller must
+// populate file reference in returned FileCreationInfo.
+FileCreationInfo CreateFileAndWriteItems(
+    const FilePath& blob_storage_dir,
+    const FilePath& file_path,
+    scoped_refptr<base::TaskRunner> file_task_runner,
+    std::vector<DataElement*> items,
+    size_t total_size_bytes) {
+  DCHECK_NE(0u, total_size_bytes);
+  UMA_HISTOGRAM_MEMORY_KB("Storage.Blob.PageFileSize", total_size_bytes / 1024);
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  FileCreationInfo creation_info;
+  creation_info.file_deletion_runner = std::move(file_task_runner);
+  creation_info.error = CreateBlobDirectory(blob_storage_dir);
+  if (creation_info.error != File::FILE_OK)
+    return creation_info;
+
+  // Create the page file.
+  File file(file_path, File::FLAG_CREATE_ALWAYS | File::FLAG_WRITE);
+  creation_info.path = file_path;
+  creation_info.error = file.error_details();
+  if (creation_info.error != File::FILE_OK)
+    return creation_info;
+
+  // Write data.
+  file.SetLength(total_size_bytes);
+  int bytes_written = 0;
+  for (DataElement* element : items) {
+    DCHECK_EQ(DataElement::TYPE_BYTES, element->type());
+    size_t length = base::checked_cast<size_t>(element->length());
+    size_t bytes_left = length;
+    while (bytes_left > 0) {
+      bytes_written =
+          file.WriteAtCurrentPos(element->bytes() + (length - bytes_left),
+                                 base::saturated_cast<int>(bytes_left));
+      if (bytes_written < 0)
+        break;
+      DCHECK_LE(static_cast<size_t>(bytes_written), bytes_left);
+      bytes_left -= bytes_written;
+    }
+    if (bytes_written < 0)
+      break;
+  }
+
+  File::Info info;
+  bool success = file.GetInfo(&info);
+  creation_info.error =
+      bytes_written < 0 || !success ? File::FILE_ERROR_FAILED : File::FILE_OK;
+  creation_info.last_modified = info.last_modified;
+  return creation_info;
+}
+
+uint64_t GetTotalSizeAndFileSizes(
+    const std::vector<scoped_refptr<ShareableBlobDataItem>>&
+        unreserved_file_items,
+    std::vector<uint64_t>* file_sizes_output) {
+  uint64_t total_size_output = 0;
+  base::SmallMap<std::map<uint64_t, uint64_t>> file_id_to_sizes;
+  for (const auto& item : unreserved_file_items) {
+    const DataElement& element = item->item()->data_element();
+    uint64_t file_id = BlobDataBuilder::GetFutureFileID(element);
+    auto it = file_id_to_sizes.find(file_id);
+    if (it != file_id_to_sizes.end())
+      it->second = std::max(it->second, element.offset() + element.length());
+    else
+      file_id_to_sizes[file_id] = element.offset() + element.length();
+    total_size_output += element.length();
+  }
+  for (const auto& size_pair : file_id_to_sizes) {
+    file_sizes_output->push_back(size_pair.second);
+  }
+  return total_size_output;
+}
+
+}  // namespace
+
+FileCreationInfo::FileCreationInfo() {}
+FileCreationInfo::~FileCreationInfo() {
+  if (file.IsValid()) {
+    DCHECK(file_deletion_runner);
+    file_deletion_runner->PostTask(
+        FROM_HERE, base::Bind(&DestructFile, base::Passed(&file)));
+  }
+}
+FileCreationInfo::FileCreationInfo(FileCreationInfo&&) = default;
+FileCreationInfo& FileCreationInfo::operator=(FileCreationInfo&&) = default;
+
+MemoryAllocation::MemoryAllocation(
+    base::WeakPtr<BlobMemoryController> controller,
+    uint64_t item_id,
+    size_t length)
+    : controller(controller), item_id(item_id), length(length) {}
+
+MemoryAllocation::~MemoryAllocation() {
+  if (controller)
+    controller->RevokeMemoryAllocation(item_id, length);
+}
+
+BlobMemoryController::QuotaAllocationTask::~QuotaAllocationTask() {}
+
+class BlobMemoryController::MemoryQuotaAllocationTask
+    : public BlobMemoryController::QuotaAllocationTask {
+ public:
+  MemoryQuotaAllocationTask(
+      BlobMemoryController* controller,
+      size_t quota_request_size,
+      std::vector<scoped_refptr<ShareableBlobDataItem>> pending_items,
+      MemoryQuotaRequestCallback done_callback)
+      : controller_(controller),
+        pending_items_(std::move(pending_items)),
+        done_callback_(std::move(done_callback)),
+        allocation_size_(quota_request_size),
+        weak_factory_(this) {}
+
+  ~MemoryQuotaAllocationTask() override = default;
+
+  void RunDoneCallback(bool success) {
+    // Make sure we clear the weak pointers we gave to the caller beforehand.
+    weak_factory_.InvalidateWeakPtrs();
+    if (success)
+      controller_->GrantMemoryAllocations(&pending_items_, allocation_size_);
+    done_callback_.Run(success);
+  }
+
+  base::WeakPtr<QuotaAllocationTask> GetWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
+
+  void Cancel() override {
+    DCHECK_GE(controller_->pending_memory_quota_total_size_, allocation_size_);
+    controller_->pending_memory_quota_total_size_ -= allocation_size_;
+    // This call destroys this object.
+    controller_->pending_memory_quota_tasks_.erase(my_list_position_);
+  }
+
+  // The my_list_position_ iterator is stored so that we can remove ourself
+  // from the task list when we are cancelled.
+  void set_my_list_position(
+      PendingMemoryQuotaTaskList::iterator my_list_position) {
+    my_list_position_ = my_list_position;
+  }
+
+  size_t allocation_size() const { return allocation_size_; }
+
+ private:
+  BlobMemoryController* controller_;
+  std::vector<scoped_refptr<ShareableBlobDataItem>> pending_items_;
+  MemoryQuotaRequestCallback done_callback_;
+
+  size_t allocation_size_;
+  PendingMemoryQuotaTaskList::iterator my_list_position_;
+
+  base::WeakPtrFactory<MemoryQuotaAllocationTask> weak_factory_;
+  DISALLOW_COPY_AND_ASSIGN(MemoryQuotaAllocationTask);
+};
+
+class BlobMemoryController::FileQuotaAllocationTask
+    : public BlobMemoryController::QuotaAllocationTask {
+ public:
+  // We post a task to create the file for the items right away.
+  FileQuotaAllocationTask(
+      BlobMemoryController* memory_controller,
+      std::vector<scoped_refptr<ShareableBlobDataItem>> unreserved_file_items,
+      const FileQuotaRequestCallback& done_callback)
+      : controller_(memory_controller),
+        done_callback_(done_callback),
+        weak_factory_(this) {
+    // Get the file sizes and total size.
+    std::vector<uint64_t> file_sizes;
+    uint64_t total_size =
+        GetTotalSizeAndFileSizes(unreserved_file_items, &file_sizes);
+    DCHECK_LE(total_size, controller_->GetAvailableFileSpaceForBlobs());
+    allocation_size_ = total_size;
+
+    // Check & set our item states.
+    for (auto& shareable_item : unreserved_file_items) {
+      DCHECK_EQ(ShareableBlobDataItem::QUOTA_NEEDED, shareable_item->state());
+      DCHECK_EQ(DataElement::TYPE_FILE, shareable_item->item()->type());
+      shareable_item->set_state(ShareableBlobDataItem::QUOTA_REQUESTED);
+    }
+    pending_items_ = std::move(unreserved_file_items);
+
+    // Increment disk usage and create our file references.
+    controller_->disk_used_ += allocation_size_;
+    std::vector<base::FilePath> file_paths;
+    std::vector<scoped_refptr<ShareableFileReference>> references;
+    for (size_t i = 0; i < file_sizes.size(); i++) {
+      file_paths.push_back(controller_->GenerateNextPageFileName());
+      references.push_back(ShareableFileReference::GetOrCreate(
+          file_paths.back(), ShareableFileReference::DELETE_ON_FINAL_RELEASE,
+          controller_->file_runner_.get()));
+      references.back()->AddFinalReleaseCallback(
+          base::Bind(&BlobMemoryController::OnBlobFileDelete,
+                     controller_->weak_factory_.GetWeakPtr(), file_sizes[i]));
+    }
+
+    // Send file creation task to file thread.
+    base::PostTaskAndReplyWithResult(
+        controller_->file_runner_.get(), FROM_HERE,
+        base::Bind(&CreateEmptyFiles, controller_->blob_storage_dir_,
+                   controller_->file_runner_, base::Passed(&file_paths)),
+        base::Bind(&FileQuotaAllocationTask::OnCreateEmptyFiles,
+                   weak_factory_.GetWeakPtr(), base::Passed(&references)));
+    controller_->RecordTracingCounters();
+  }
+  ~FileQuotaAllocationTask() override {}
+
+  void RunDoneCallback(bool success, std::vector<FileCreationInfo> file_info) {
+    // Make sure we clear the weak pointers we gave to the caller beforehand.
+    weak_factory_.InvalidateWeakPtrs();
+
+    // We want to destroy this object on the exit of this method if we were
+    // successful.
+    std::unique_ptr<FileQuotaAllocationTask> this_object;
+    if (success) {
+      for (auto& item : pending_items_) {
+        item->set_state(ShareableBlobDataItem::QUOTA_GRANTED);
+      }
+      this_object = std::move(*my_list_position_);
+      controller_->pending_file_quota_tasks_.erase(my_list_position_);
+    }
+
+    done_callback_.Run(success, std::move(file_info));
+  }
+
+  base::WeakPtr<QuotaAllocationTask> GetWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
+
+  void Cancel() override {
+    // This call destroys this object. We rely on ShareableFileReference's
+    // final release callback for disk_usage_ accounting.
+    controller_->pending_file_quota_tasks_.erase(my_list_position_);
+  }
+
+  void OnCreateEmptyFiles(
+      std::vector<scoped_refptr<ShareableFileReference>> references,
+      std::pair<std::vector<FileCreationInfo>, File::Error> files_and_error) {
+    auto& files = files_and_error.first;
+    if (files.empty()) {
+      DCHECK_GE(controller_->disk_used_, allocation_size_);
+      controller_->disk_used_ -= allocation_size_;
+      // This will call our callback and delete the object correctly.
+      controller_->DisableFilePaging(files_and_error.second);
+      return;
+    }
+    DCHECK_EQ(files.size(), references.size());
+    for (size_t i = 0; i < files.size(); i++) {
+      files[i].file_reference = std::move(references[i]);
+    }
+    RunDoneCallback(true, std::move(files));
+  }
+
+  // The my_list_position_ iterator is stored so that we can remove ourself
+  // from the task list when we are cancelled.
+  void set_my_list_position(
+      PendingFileQuotaTaskList::iterator my_list_position) {
+    my_list_position_ = my_list_position;
+  }
+
+ private:
+  BlobMemoryController* controller_;
+  std::vector<scoped_refptr<ShareableBlobDataItem>> pending_items_;
+  scoped_refptr<base::TaskRunner> file_runner_;
+  FileQuotaRequestCallback done_callback_;
+
+  uint64_t allocation_size_;
+  PendingFileQuotaTaskList::iterator my_list_position_;
+
+  base::WeakPtrFactory<FileQuotaAllocationTask> weak_factory_;
+  DISALLOW_COPY_AND_ASSIGN(FileQuotaAllocationTask);
+};
+
+BlobMemoryController::BlobMemoryController(
+    const base::FilePath& storage_directory,
+    scoped_refptr<base::TaskRunner> file_runner)
+    : file_paging_enabled_(file_runner.get() != nullptr),
+      blob_storage_dir_(storage_directory),
+      file_runner_(std::move(file_runner)),
+      populated_memory_items_(
+          base::MRUCache<uint64_t, ShareableBlobDataItem*>::NO_AUTO_EVICT),
+      weak_factory_(this) {}
+
+BlobMemoryController::~BlobMemoryController() {}
+
+void BlobMemoryController::DisableFilePaging(base::File::Error reason) {
+  UMA_HISTOGRAM_ENUMERATION("Storage.Blob.PagingDisabled", -reason,
+                            -File::FILE_ERROR_MAX);
+  file_paging_enabled_ = false;
+  in_flight_memory_used_ = 0;
+  items_paging_to_file_.clear();
+  pending_evictions_ = 0;
+  pending_memory_quota_total_size_ = 0;
+  populated_memory_items_.Clear();
+  populated_memory_items_bytes_ = 0;
+  file_runner_ = nullptr;
+
+  PendingMemoryQuotaTaskList old_memory_tasks;
+  PendingFileQuotaTaskList old_file_tasks;
+  std::swap(old_memory_tasks, pending_memory_quota_tasks_);
+  std::swap(old_file_tasks, pending_file_quota_tasks_);
+
+  // Don't call the callbacks until we have a consistent state.
+  for (auto& memory_request : old_memory_tasks) {
+    memory_request->RunDoneCallback(false);
+  }
+  for (auto& file_request : old_file_tasks) {
+    file_request->RunDoneCallback(false, std::vector<FileCreationInfo>());
+  }
+}
+
+BlobMemoryController::Strategy BlobMemoryController::DetermineStrategy(
+    size_t preemptive_transported_bytes,
+    uint64_t total_transportation_bytes) const {
+  if (total_transportation_bytes == 0)
+    return Strategy::NONE_NEEDED;
+  if (!CanReserveQuota(total_transportation_bytes))
+    return Strategy::TOO_LARGE;
+
+  // Handle the case where we have all the bytes preemptively transported, and
+  // we can also fit them.
+  if (preemptive_transported_bytes == total_transportation_bytes &&
+      pending_memory_quota_tasks_.empty() &&
+      preemptive_transported_bytes < GetAvailableMemoryForBlobs()) {
+    return Strategy::NONE_NEEDED;
+  }
+  if (file_paging_enabled_ &&
+      (total_transportation_bytes > limits_.memory_limit_before_paging())) {
+    return Strategy::FILE;
+  }
+  if (total_transportation_bytes > limits_.max_ipc_memory_size)
+    return Strategy::SHARED_MEMORY;
+  return Strategy::IPC;
+}
+
+bool BlobMemoryController::CanReserveQuota(uint64_t size) const {
+  // We check each size independently as a blob can't be constructed in both
+  // disk and memory.
+  return size <= GetAvailableMemoryForBlobs() ||
+         size <= GetAvailableFileSpaceForBlobs();
+}
+
+base::WeakPtr<QuotaAllocationTask> BlobMemoryController::ReserveMemoryQuota(
+    std::vector<scoped_refptr<ShareableBlobDataItem>> unreserved_memory_items,
+    const MemoryQuotaRequestCallback& done_callback) {
+  if (unreserved_memory_items.empty()) {
+    done_callback.Run(true);
+    return base::WeakPtr<QuotaAllocationTask>();
+  }
+
+  base::CheckedNumeric<uint64_t> unsafe_total_bytes_needed = 0;
+  for (auto& item : unreserved_memory_items) {
+    DCHECK_EQ(ShareableBlobDataItem::QUOTA_NEEDED, item->state());
+    DCHECK(item->item()->type() == DataElement::TYPE_BYTES_DESCRIPTION ||
+           item->item()->type() == DataElement::TYPE_BYTES);
+    DCHECK(item->item()->length() > 0);
+    unsafe_total_bytes_needed += item->item()->length();
+    item->set_state(ShareableBlobDataItem::QUOTA_REQUESTED);
+  }
+
+  uint64_t total_bytes_needed = unsafe_total_bytes_needed.ValueOrDie();
+  DCHECK_GT(total_bytes_needed, 0ull);
+
+  // If we're currently waiting for blobs to page already, then we add
+  // ourselves to the end of the queue. Once paging is complete, we'll schedule
+  // more paging for any more pending blobs.
+  if (!pending_memory_quota_tasks_.empty()) {
+    return AppendMemoryTask(total_bytes_needed,
+                            std::move(unreserved_memory_items), done_callback);
+  }
+
+  // Store right away if we can.
+  if (total_bytes_needed <= GetAvailableMemoryForBlobs()) {
+    GrantMemoryAllocations(&unreserved_memory_items,
+                           static_cast<size_t>(total_bytes_needed));
+    MaybeScheduleEvictionUntilSystemHealthy();
+    done_callback.Run(true);
+    return base::WeakPtr<QuotaAllocationTask>();
+  }
+
+  // Size is larger than available memory.
+  DCHECK(pending_memory_quota_tasks_.empty());
+  DCHECK_EQ(0u, pending_memory_quota_total_size_);
+
+  auto weak_ptr = AppendMemoryTask(
+      total_bytes_needed, std::move(unreserved_memory_items), done_callback);
+  MaybeScheduleEvictionUntilSystemHealthy();
+  return weak_ptr;
+}
+
+base::WeakPtr<QuotaAllocationTask> BlobMemoryController::ReserveFileQuota(
+    std::vector<scoped_refptr<ShareableBlobDataItem>> unreserved_file_items,
+    const FileQuotaRequestCallback& done_callback) {
+  pending_file_quota_tasks_.push_back(base::MakeUnique<FileQuotaAllocationTask>(
+      this, std::move(unreserved_file_items), done_callback));
+  pending_file_quota_tasks_.back()->set_my_list_position(
+      --pending_file_quota_tasks_.end());
+  return pending_file_quota_tasks_.back()->GetWeakPtr();
+}
+
+void BlobMemoryController::NotifyMemoryItemsUsed(
+    std::vector<scoped_refptr<ShareableBlobDataItem>>& items) {
+  for (const auto& item : items) {
+    DCHECK_EQ(DataElement::TYPE_BYTES, item->item()->type());
+    DCHECK_EQ(ShareableBlobDataItem::POPULATED_WITH_QUOTA, item->state());
+    // We don't want to re-add the item if we're currently paging it to disk.
+    if (items_paging_to_file_.find(item->item_id()) !=
+        items_paging_to_file_.end()) {
+      return;
+    }
+    auto iterator = populated_memory_items_.Get(item->item_id());
+    if (iterator == populated_memory_items_.end()) {
+      populated_memory_items_bytes_ +=
+          static_cast<size_t>(item->item()->length());
+      populated_memory_items_.Put(item->item_id(), item.get());
+    }
+  }
+  MaybeScheduleEvictionUntilSystemHealthy();
+}
+
+base::WeakPtr<QuotaAllocationTask> BlobMemoryController::AppendMemoryTask(
+    uint64_t total_bytes_needed,
+    std::vector<scoped_refptr<ShareableBlobDataItem>> unreserved_memory_items,
+    const MemoryQuotaRequestCallback& done_callback) {
+  DCHECK(file_paging_enabled_)
+      << "Caller tried to reserve memory when CanReserveQuota("
+      << total_bytes_needed << ") would have returned false.";
+
+  pending_memory_quota_total_size_ += total_bytes_needed;
+  pending_memory_quota_tasks_.push_back(
+      base::MakeUnique<MemoryQuotaAllocationTask>(
+          this, total_bytes_needed, std::move(unreserved_memory_items),
+          std::move(done_callback)));
+  pending_memory_quota_tasks_.back()->set_my_list_position(
+      --pending_memory_quota_tasks_.end());
+
+  return pending_memory_quota_tasks_.back()->GetWeakPtr();
+}
+
+void BlobMemoryController::MaybeGrantPendingMemoryRequests() {
+  while (!pending_memory_quota_tasks_.empty() &&
+         limits_.max_blob_in_memory_space - blob_memory_used_ >=
+             pending_memory_quota_tasks_.front()->allocation_size()) {
+    std::unique_ptr<MemoryQuotaAllocationTask> memory_task =
+        std::move(pending_memory_quota_tasks_.front());
+    pending_memory_quota_tasks_.pop_front();
+    pending_memory_quota_total_size_ -= memory_task->allocation_size();
+    memory_task->RunDoneCallback(true);
+  }
+  RecordTracingCounters();
+}
+
+size_t BlobMemoryController::CollectItemsForEviction(
+    std::vector<scoped_refptr<ShareableBlobDataItem>>* output) {
+  base::CheckedNumeric<size_t> total_items_size = 0;
+  // Process the recent item list and remove items until we have at least a
+  // minimum file size or we're at the end of our items to page to disk.
+  while (total_items_size.ValueOrDie() < limits_.min_page_file_size &&
+         !populated_memory_items_.empty()) {
+    auto iterator = --populated_memory_items_.end();
+    ShareableBlobDataItem* item = iterator->second;
+    DCHECK_EQ(item->item()->type(), DataElement::TYPE_BYTES);
+    populated_memory_items_.Erase(iterator);
+    size_t size = base::checked_cast<size_t>(item->item()->length());
+    populated_memory_items_bytes_ -= size;
+    total_items_size += size;
+    output->push_back(make_scoped_refptr(item));
+  }
+  return total_items_size.ValueOrDie();
+}
+
+void BlobMemoryController::MaybeScheduleEvictionUntilSystemHealthy() {
+  // Don't do eviction when others are happening, as we don't change our
+  // pending_memory_quota_total_size_ value until after the paging files have
+  // been written.
+  if (pending_evictions_ != 0 || !file_paging_enabled_)
+    return;
+
+  // We try to page items to disk until our current system size + requested
+  // memory is below our size limit.
+  while (pending_memory_quota_total_size_ + blob_memory_used_ >
+         limits_.memory_limit_before_paging()) {
+    // We only page when we have enough items to fill a whole page file.
+    if (populated_memory_items_bytes_ < limits_.min_page_file_size)
+      break;
+    DCHECK_LE(limits_.min_page_file_size,
+              static_cast<uint64_t>(blob_memory_used_));
+
+    std::vector<scoped_refptr<ShareableBlobDataItem>> items_to_swap;
+    size_t total_items_size = CollectItemsForEviction(&items_to_swap);
+    if (total_items_size == 0)
+      break;
+
+    std::vector<DataElement*> items_for_paging;
+    for (auto& shared_blob_item : items_to_swap) {
+      items_paging_to_file_.insert(shared_blob_item->item_id());
+      items_for_paging.push_back(shared_blob_item->item()->data_element_ptr());
+    }
+
+    // Update our bookkeeping.
+    pending_evictions_++;
+    disk_used_ += total_items_size;
+    in_flight_memory_used_ += total_items_size;
+
+    // Create our file reference.
+    FilePath page_file_path = GenerateNextPageFileName();
+    scoped_refptr<ShareableFileReference> file_reference =
+        ShareableFileReference::GetOrCreate(
+            page_file_path,
+            ShareableFileReference::DELETE_ON_FINAL_RELEASE,
+            file_runner_.get());
+    // Add the release callback so we decrement our disk usage on file deletion.
+    file_reference->AddFinalReleaseCallback(
+        base::Bind(&BlobMemoryController::OnBlobFileDelete,
+                   weak_factory_.GetWeakPtr(), total_items_size));
+
+    // Post the file writing task.
+    base::PostTaskAndReplyWithResult(
+        file_runner_.get(), FROM_HERE,
+        base::Bind(&CreateFileAndWriteItems, blob_storage_dir_,
+                   base::Passed(&page_file_path), file_runner_,
+                   base::Passed(&items_for_paging), total_items_size),
+        base::Bind(&BlobMemoryController::OnEvictionComplete,
+                   weak_factory_.GetWeakPtr(), base::Passed(&file_reference),
+                   base::Passed(&items_to_swap), total_items_size));
+  }
+  RecordTracingCounters();
+}
+
+void BlobMemoryController::OnEvictionComplete(
+    scoped_refptr<ShareableFileReference> file_reference,
+    std::vector<scoped_refptr<ShareableBlobDataItem>> items,
+    size_t total_items_size,
+    FileCreationInfo result) {
+  if (!file_paging_enabled_)
+    return;
+
+  if (result.error != File::FILE_OK) {
+    DisableFilePaging(result.error);
+    return;
+  }
+
+  DCHECK_LT(0, pending_evictions_);
+  pending_evictions_--;
+
+  // Switch item from memory to the new file.
+  uint64_t offset = 0;
+  for (const scoped_refptr<ShareableBlobDataItem>& shareable_item : items) {
+    scoped_refptr<BlobDataItem> new_item(
+        new BlobDataItem(base::WrapUnique(new DataElement()), file_reference));
+    new_item->data_element_ptr()->SetToFilePathRange(
+        file_reference->path(), offset, shareable_item->item()->length(),
+        result.last_modified);
+    DCHECK(shareable_item->memory_allocation_);
+    shareable_item->set_memory_allocation(nullptr);
+    shareable_item->set_item(new_item);
+    items_paging_to_file_.erase(shareable_item->item_id());
+    offset += shareable_item->item()->length();
+  }
+  in_flight_memory_used_ -= total_items_size;
+
+  // We want callback on blobs up to the amount we've freed.
+  MaybeGrantPendingMemoryRequests();
+
+  // If we still have more blobs waiting and we're not waiting on more paging
+  // operations, schedule more.
+  MaybeScheduleEvictionUntilSystemHealthy();
+}
+
+FilePath BlobMemoryController::GenerateNextPageFileName() {
+  std::string file_name = base::Uint64ToString(current_file_num_++);
+  return blob_storage_dir_.Append(FilePath::FromUTF8Unsafe(file_name));
+}
+
+void BlobMemoryController::RecordTracingCounters() const {
+  TRACE_COUNTER2("Blob", "MemoryUsage", "TotalStorage", blob_memory_used_,
+                 "InFlightToDisk", in_flight_memory_used_);
+  TRACE_COUNTER1("Blob", "DiskUsage", disk_used_);
+  TRACE_COUNTER1("Blob", "TranfersPendingOnDisk",
+                 pending_memory_quota_tasks_.size());
+  TRACE_COUNTER1("Blob", "TranfersBytesPendingOnDisk",
+                 pending_memory_quota_total_size_);
+}
+
+size_t BlobMemoryController::GetAvailableMemoryForBlobs() const {
+  if (limits_.max_blob_in_memory_space < memory_usage())
+    return 0;
+  return limits_.max_blob_in_memory_space - memory_usage();
+}
+
+uint64_t BlobMemoryController::GetAvailableFileSpaceForBlobs() const {
+  if (!file_paging_enabled_)
+    return 0;
+  // Sometimes we're only paging part of what we need for the new blob, so add
+  // the rest of the size we need into our disk usage if this is the case.
+  uint64_t total_disk_used = disk_used_;
+  if (in_flight_memory_used_ < pending_memory_quota_total_size_) {
+    total_disk_used +=
+        pending_memory_quota_total_size_ - in_flight_memory_used_;
+  }
+  if (limits_.max_blob_disk_space < total_disk_used)
+    return 0;
+  return limits_.max_blob_disk_space - total_disk_used;
+}
+
+void BlobMemoryController::GrantMemoryAllocations(
+    std::vector<scoped_refptr<ShareableBlobDataItem>>* items,
+    size_t total_bytes) {
+  blob_memory_used_ += total_bytes;
+  for (auto& item : *items) {
+    item->set_state(ShareableBlobDataItem::QUOTA_GRANTED);
+    item->set_memory_allocation(base::MakeUnique<MemoryAllocation>(
+        weak_factory_.GetWeakPtr(), item->item_id(),
+        base::checked_cast<size_t>(item->item()->length())));
+  }
+}
+
+void BlobMemoryController::RevokeMemoryAllocation(uint64_t item_id,
+                                                  size_t length) {
+  DCHECK_LE(length, blob_memory_used_);
+  blob_memory_used_ -= length;
+  auto iterator = populated_memory_items_.Get(item_id);
+  if (iterator != populated_memory_items_.end()) {
+    DCHECK_GE(populated_memory_items_bytes_, length);
+    populated_memory_items_bytes_ -= length;
+    populated_memory_items_.Erase(iterator);
+  }
+  MaybeGrantPendingMemoryRequests();
+}
+
+void BlobMemoryController::OnBlobFileDelete(uint64_t size,
+                                            const FilePath& path) {
+  DCHECK_LE(size, disk_used_);
+  disk_used_ -= size;
+}
+
+}  // namespace storage