Persist sessionStorage on disk.

webkit/dom_storage/dom_storage_area.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 "webkit/dom_storage/dom_storage_area.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/time.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebString.h"
 #include "webkit/database/database_util.h"
 #include "webkit/dom_storage/dom_storage_map.h"
 #include "webkit/dom_storage/dom_storage_namespace.h"
 #include "webkit/dom_storage/dom_storage_task_runner.h"
 #include "webkit/dom_storage/dom_storage_types.h"
 #include "webkit/dom_storage/local_storage_database_adapter.h"
+#include "webkit/dom_storage/session_storage_database.h"
+#include "webkit/dom_storage/session_storage_database_adapter.h"
 #include "webkit/fileapi/file_system_util.h"
 #include "webkit/glue/webkit_glue.h"
 
 using webkit_database::DatabaseUtil;
 
 namespace dom_storage {
 
 static const int kCommitTimerSeconds = 1;
 
 DomStorageArea::CommitBatch::CommitBatch()
@@ skipping 25 matching lines @@
 }
 
 DomStorageArea::DomStorageArea(const GURL& origin, const FilePath& directory,
                                DomStorageTaskRunner* task_runner)
     : namespace_id_(kLocalStorageNamespaceId), origin_(origin),
       directory_(directory),
       task_runner_(task_runner),
       map_(new DomStorageMap(kPerAreaQuota + kPerAreaOverQuotaAllowance)),
       is_initial_import_done_(true),
       is_shutdown_(false),
-      commit_batches_in_flight_(0) {
+      commit_batches_in_flight_(0),
+      deletion_in_progress_(false) {
   if (!directory.empty()) {
     FilePath path = directory.Append(DatabaseFileNameFromOrigin(origin_));
     backing_.reset(new LocalStorageDatabaseAdapter(path));
     is_initial_import_done_ = false;
   }
 }
 
 DomStorageArea::DomStorageArea(
     int64 namespace_id,
     const std::string& persistent_namespace_id,
     const GURL& origin,
+    SessionStorageDatabase* session_storage_backing,
     DomStorageTaskRunner* task_runner)
     : namespace_id_(namespace_id),
       persistent_namespace_id_(persistent_namespace_id),
       origin_(origin),
       task_runner_(task_runner),
       map_(new DomStorageMap(kPerAreaQuota + kPerAreaOverQuotaAllowance)),
+      session_storage_backing_(session_storage_backing),
       is_initial_import_done_(true),
       is_shutdown_(false),
-      commit_batches_in_flight_(0) {
+      commit_batches_in_flight_(0),
+      deletion_in_progress_(false) {
   DCHECK(namespace_id != kLocalStorageNamespaceId);
+  if (session_storage_backing) {
+    backing_.reset(new SessionStorageDatabaseAdapter(
+        session_storage_backing, persistent_namespace_id, origin));
+    is_initial_import_done_ = false;
+  }
 }
 
 DomStorageArea::~DomStorageArea() {
 }
 
 void DomStorageArea::ExtractValues(ValuesMap* map) {
   if (is_shutdown_)
     return;
   InitialImportIfNeeded();
   map_->ExtractValues(map);
@@ skipping 66 matching lines @@
   }
 
   return true;
 }
 
 DomStorageArea* DomStorageArea::ShallowCopy(
     int64 destination_namespace_id,
     const std::string& destination_persistent_namespace_id) {
   DCHECK_NE(kLocalStorageNamespaceId, namespace_id_);
   DCHECK_NE(kLocalStorageNamespaceId, destination_namespace_id);
-  DCHECK(!backing_.get());  // SessionNamespaces aren't stored on disk.
 
   DomStorageArea* copy = new DomStorageArea(
       destination_namespace_id, destination_persistent_namespace_id, origin_,
-      task_runner_);
+      session_storage_backing_, task_runner_);
   copy->map_ = map_;
   copy->is_shutdown_ = is_shutdown_;
+  copy->is_initial_import_done_ = true;
+
+  // All the uncommitted changes to this area need to happen before the actual
+  // shallow copy is made (scheduled by the upper layer). Another OnCommitTimer
+  // call might be in the event queue at this point, but it's handled gracefully
+  // when it fires.
+  if (commit_batch_.get())
+    OnCommitTimer();
   return copy;
 }
 
 bool DomStorageArea::HasUncommittedChanges() const {
   DCHECK(!is_shutdown_);
   return commit_batch_.get() || commit_batches_in_flight_;
 }
 
 void DomStorageArea::DeleteOrigin() {
   DCHECK(!is_shutdown_);
   if (HasUncommittedChanges()) {
     // TODO(michaeln): This logically deletes the data immediately,
     // and in a matter of a second, deletes the rows from the backing
     // database file, but the file itself will linger until shutdown
     // or purge time. Ideally, this should delete the file more
     // quickly.
     Clear();
     return;
   }
   map_ = new DomStorageMap(kPerAreaQuota + kPerAreaOverQuotaAllowance);
-  if (backing_.get()) {
+  if (backing_.get() && !session_storage_backing_.get()) {
+    // This is localStorage.
     is_initial_import_done_ = false;
     backing_->Reset();
     backing_->DeleteFiles();
+  } else if (session_storage_backing_.get()) {
+    // No need to read the data (there will be no data), also, the
+    // PRIMARY_SEQUENCE thread shouldn't try to read the data while
+    // SessionStorageDatabase::DeleteArea is in progress.
+    is_initial_import_done_ = true;
+    {
+      base::AutoLock lock(deletion_in_progress_lock_);

[michaeln, 2012/07/10 01:16:58]

What does the flag+lock accomplish given that is_initial_import_done_ is true?
Looks like it's to avoid importing while deleting, but i think the
is_import_done flag guards against that already.

Also, i think this method may actually be unreachable in the case of session
storage atm? Namespaces get deleted wholesale, but there's no codepath or
usecase for deleting an individual origin out of a session namespace just yet
(see DomStorageNamespace for the DeleteOrigin callsite). If that's right, you
may want to just DCHECK that assumption here instead.

[marja, 2012/07/10 13:40:52]

The lock was guarding the bool (I didn't want to assume that assigning a bool is
atomic).

This is indeed not wired in -> removed this code (and the deletion_in_progress_,
deletion_in_progress_lock_) and added a DCHECK here.

+      deletion_in_progress_ = true;
+    }
+    task_runner_->PostShutdownBlockingTask(
+        FROM_HERE,
+        DomStorageTaskRunner::COMMIT_SEQUENCE,
+        base::Bind(&DomStorageArea::DeleteOriginInCommitSequence, this));
   }
 }
 
 void DomStorageArea::PurgeMemory() {
   DCHECK(!is_shutdown_);
   if (!is_initial_import_done_ ||  // We're not using any memory.
       !backing_.get() ||  // We can't purge anything.
       HasUncommittedChanges())  // We leave things alone with changes pending.
     return;
 
@@ skipping 17 matching lines @@
       FROM_HERE,
       DomStorageTaskRunner::COMMIT_SEQUENCE,
       base::Bind(&DomStorageArea::ShutdownInCommitSequence, this));
   DCHECK(success);
 }
 
 void DomStorageArea::InitialImportIfNeeded() {
   if (is_initial_import_done_)
     return;
 
-  DCHECK_EQ(kLocalStorageNamespaceId, namespace_id_);
+  is_initial_import_done_ = true;
+  {
+    base::AutoLock lock(deletion_in_progress_lock_);
+    if (deletion_in_progress_) {
+      // The data is getting deleted in the commit sequence; we shouldn't read
+      // it just before deletion. The data will be empty, so it's ok to not read
+      // anything.
+      return;
+    }
+  }
+
   DCHECK(backing_.get());
 
   ValuesMap initial_values;
   backing_->ReadAllValues(&initial_values);
   map_->SwapValues(&initial_values);
-  is_initial_import_done_ = true;
 }
 
 DomStorageArea::CommitBatch* DomStorageArea::CreateCommitBatchIfNeeded() {
   DCHECK(!is_shutdown_);
   if (!commit_batch_.get()) {
     commit_batch_.reset(new CommitBatch());
 
     // Start a timer to commit any changes that accrue in the batch, but only if
     // no commits are currently in flight. In that case the timer will be
     // started after the commits have happened.
     if (!commit_batches_in_flight_) {
       task_runner_->PostDelayedTask(
           FROM_HERE,
           base::Bind(&DomStorageArea::OnCommitTimer, this),
           base::TimeDelta::FromSeconds(kCommitTimerSeconds));
     }
   }
   return commit_batch_.get();
 }
 
 void DomStorageArea::OnCommitTimer() {
-  DCHECK_EQ(kLocalStorageNamespaceId, namespace_id_);
   if (is_shutdown_)
     return;
 
   DCHECK(backing_.get());
-  DCHECK(commit_batch_.get());
-  DCHECK(!commit_batches_in_flight_);
+
+  // It's possible that there is nothing to commit, since a shallow copy occured
+  // before the timer fired.
+  if (!commit_batch_.get())
+    return;
 
   // This method executes on the primary sequence, we schedule
   // a task for immediate execution on the commit sequence.
   DCHECK(task_runner_->IsRunningOnPrimarySequence());
   bool success = task_runner_->PostShutdownBlockingTask(
       FROM_HERE,
       DomStorageTaskRunner::COMMIT_SEQUENCE,
       base::Bind(&DomStorageArea::CommitChanges, this,
                  base::Owned(commit_batch_.release())));
   ++commit_batches_in_flight_;
   DCHECK(success);
 }
 
 void DomStorageArea::CommitChanges(const CommitBatch* commit_batch) {
   // This method executes on the commit sequence.
   DCHECK(task_runner_->IsRunningOnCommitSequence());
   bool success = backing_->CommitChanges(commit_batch->clear_all_first,
                                          commit_batch->changed_values);
   DCHECK(success);  // TODO(michaeln): what if it fails?
   task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&DomStorageArea::OnCommitComplete, this));
 }
 
 void DomStorageArea::OnCommitComplete() {
   // We're back on the primary sequence in this method.
   DCHECK(task_runner_->IsRunningOnPrimarySequence());
+  --commit_batches_in_flight_;
   if (is_shutdown_)
     return;
-  --commit_batches_in_flight_;
   if (commit_batch_.get() && !commit_batches_in_flight_) {
     // More changes have accrued, restart the timer.
     task_runner_->PostDelayedTask(
         FROM_HERE,
         base::Bind(&DomStorageArea::OnCommitTimer, this),
         base::TimeDelta::FromSeconds(kCommitTimerSeconds));
   }
 }
 
+void DomStorageArea::DeleteOriginInCommitSequence() {
+  session_storage_backing_->DeleteArea(persistent_namespace_id_, origin_);
+  base::AutoLock lock(deletion_in_progress_lock_);
+  deletion_in_progress_ = false;
+}
+
 void DomStorageArea::ShutdownInCommitSequence() {
   // This method executes on the commit sequence.
   DCHECK(task_runner_->IsRunningOnCommitSequence());
   DCHECK(backing_.get());
   if (commit_batch_.get()) {
     // Commit any changes that accrued prior to the timer firing.
     bool success = backing_->CommitChanges(
         commit_batch_->clear_all_first,
         commit_batch_->changed_values);
     DCHECK(success);
   }
   commit_batch_.reset();
   backing_.reset();
+  session_storage_backing_ = NULL;
 }
 
 }  // namespace dom_storage