Persist sessionStorage on disk.

webkit/dom_storage/dom_storage_namespace.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_namespace.h"
 
 #include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/location.h"
 #include "base/logging.h"
 #include "webkit/dom_storage/dom_storage_area.h"
 #include "webkit/dom_storage/dom_storage_task_runner.h"
 #include "webkit/dom_storage/dom_storage_types.h"
+#include "webkit/dom_storage/session_storage_database.h"
 
 namespace dom_storage {
 
 DomStorageNamespace::DomStorageNamespace(
     const FilePath& directory,
     DomStorageTaskRunner* task_runner)
     : namespace_id_(kLocalStorageNamespaceId),
       directory_(directory),
       task_runner_(task_runner) {
 }
 
 DomStorageNamespace::DomStorageNamespace(
     int64 namespace_id,
+    SessionStorageDatabase* session_storage_database,
     DomStorageTaskRunner* task_runner)
     : namespace_id_(namespace_id),
-      task_runner_(task_runner) {
+      task_runner_(task_runner),
+      session_storage_database_(session_storage_database) {
   DCHECK_NE(kLocalStorageNamespaceId, namespace_id);
 }
 
 DomStorageNamespace::~DomStorageNamespace() {
 }
 
 DomStorageArea* DomStorageNamespace::OpenStorageArea(const GURL& origin) {
   if (AreaHolder* holder = GetAreaHolder(origin)) {
     ++(holder->open_count_);
     return holder->area_;
   }
-  DomStorageArea* area = new DomStorageArea(namespace_id_, origin,
-                                            directory_, task_runner_);
+  DomStorageArea* area;
+  if (namespace_id_ == kLocalStorageNamespaceId) {
+    area = new DomStorageArea(namespace_id_, origin, directory_, task_runner_);
+  } else {
+    area = new DomStorageArea(namespace_id_, origin, session_storage_database_,
+                              task_runner_);
+  }
   areas_[origin] = AreaHolder(area, 1);
   return area;
 }
 
 void DomStorageNamespace::CloseStorageArea(DomStorageArea* area) {
   AreaHolder* holder = GetAreaHolder(area->origin());
   DCHECK(holder);
   DCHECK_EQ(holder->area_.get(), area);
   --(holder->open_count_);
   // TODO(michaeln): Clean up areas that aren't needed in memory anymore.
   // The in-process-webkit based impl didn't do this either, but would be nice.
 }
 
 DomStorageNamespace* DomStorageNamespace::Clone(int64 clone_namespace_id) {
   DCHECK_NE(kLocalStorageNamespaceId, namespace_id_);
   DCHECK_NE(kLocalStorageNamespaceId, clone_namespace_id);
-  DomStorageNamespace* clone =
-      new DomStorageNamespace(clone_namespace_id, task_runner_);
+  DomStorageNamespace* clone = new DomStorageNamespace(
+      clone_namespace_id, session_storage_database_, task_runner_);
   AreaMap::const_iterator it = areas_.begin();
+  // Clone the in-memory structures.
   for (; it != areas_.end(); ++it) {
     DomStorageArea* area = it->second.area_->ShallowCopy(clone_namespace_id);
     clone->areas_[it->first] = AreaHolder(area, 0);
   }
+  // And clone the on-disk structures, too.
+  if (session_storage_database_.get()) {
+    bool success = task_runner_->PostShutdownBlockingTask(
+        FROM_HERE,
+        DomStorageTaskRunner::COMMIT_SEQUENCE,
+        base::Bind(&SessionStorageDatabase::CloneNamespace,
+                   session_storage_database_.get(), namespace_id_,
+                   clone_namespace_id));
+    DCHECK(success);
+  }
   return clone;
 }
 
 void DomStorageNamespace::DeleteOrigin(const GURL& origin) {
   AreaHolder* holder = GetAreaHolder(origin);
   if (holder) {
     holder->area_->DeleteOrigin();
     return;
   }
   if (!directory_.empty()) {
     scoped_refptr<DomStorageArea> area =
         new DomStorageArea(namespace_id_, origin, directory_, task_runner_);
     area->DeleteOrigin();
+  } else if (session_storage_database_.get()) {

[michaeln, 2012/05/16 08:10:55]

i think the DomStorageNamespace::DeleteOrigin method is unreachable for session
storage namespaces right now. also i think there's a race condition with this
handling of that function for session storage.

suppose immediately after this block executes, there's a call to
DomStorageNamespace::OpenStorageArea for this 'origin' followed by something
that causes the area to be read from the database. those calls to open+read on
the primary sequence will be racing with deletion scheduled on the commit
sequence by the area->DeleteOrigin() method call below.

since this is currently unreachable (its only reached via the
DomStorageContext::DeleteOrigin method which only calls thru for the local
storage namespace)... consider putting a
DCHECK(!session_storage_database_.get()) here for now

[marja, 2012/05/30 11:46:19]

Done.

Ah, yes, there was a race. What if I set is_initial_import_done to true in
DomStorageArea::DeleteOrigin, when it posts the actual deletion task... That
should remove the race, no?

But, anyhow, I don't have a clear idea on how this origin-based deletion should
work.. Should SessionStorageDatabase have a function to delete an origin from
all namespaces?

(I guess it's plugged into this "modification times for origins" logic, so
should it instead have a function to delete all origins which have been modified
after a certain time?)

+    scoped_refptr<DomStorageArea> area =
+        new DomStorageArea(namespace_id_, origin,
+                           session_storage_database_.get(), task_runner_);
+    area->DeleteOrigin();
   }
 }
 
 void DomStorageNamespace::PurgeMemory() {
   if (directory_.empty())
     return;  // We can't purge w/o backing on disk.
   AreaMap::iterator it = areas_.begin();
   while (it != areas_.end()) {
     // Leave it alone if changes are pending
     if (it->second.area_->HasUncommittedChanges()) {
@@ skipping 38 matching lines @@
 
 DomStorageNamespace::AreaHolder::AreaHolder(
     DomStorageArea* area, int count)
     : area_(area), open_count_(count) {
 }
 
 DomStorageNamespace::AreaHolder::~AreaHolder() {
 }
 
 }  // namespace dom_storage