Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

19 files changed, 1957 insertions, 0 deletions

diff --git a/dom/fs/child/FileSystemAccessHandleChild.cpp b/dom/fs/child/FileSystemAccessHandleChild.cpp
new file mode 100644
index 0000000000..b32d9b2dc6
--- /dev/null
+++ b/dom/fs/child/FileSystemAccessHandleChild.cpp
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemAccessHandleChild.h"
+
+#include "mozilla/dom/FileSystemSyncAccessHandle.h"
+#include "private/pprio.h"
+
+namespace mozilla::dom {
+
+FileSystemAccessHandleChild::FileSystemAccessHandleChild()
+    : mAccessHandle(nullptr) {}
+
+FileSystemAccessHandleChild::~FileSystemAccessHandleChild() = default;
+
+void FileSystemAccessHandleChild::SetAccessHandle(
+    FileSystemSyncAccessHandle* aAccessHandle) {
+  MOZ_ASSERT(aAccessHandle);
+  MOZ_ASSERT(!mAccessHandle);
+
+  mAccessHandle = aAccessHandle;
+}
+
+void FileSystemAccessHandleChild::ActorDestroy(ActorDestroyReason aWhy) {
+  if (mAccessHandle) {
+    mAccessHandle->ClearActor();
+    mAccessHandle = nullptr;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/fs/child/FileSystemAccessHandleChild.h b/dom/fs/child/FileSystemAccessHandleChild.h
new file mode 100644
index 0000000000..d616178646
--- /dev/null
+++ b/dom/fs/child/FileSystemAccessHandleChild.h
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMACCESSHANDLECHILD_H_
+#define DOM_FS_CHILD_FILESYSTEMACCESSHANDLECHILD_H_
+
+#include "mozilla/dom/PFileSystemAccessHandleChild.h"
+
+namespace mozilla::dom {
+
+class FileSystemSyncAccessHandle;
+
+class FileSystemAccessHandleChild : public PFileSystemAccessHandleChild {
+ public:
+  FileSystemAccessHandleChild();
+
+  NS_INLINE_DECL_REFCOUNTING(FileSystemAccessHandleChild, override)
+
+  FileSystemSyncAccessHandle* MutableAccessHandlePtr() const {
+    MOZ_ASSERT(mAccessHandle);
+    return mAccessHandle;
+  }
+
+  void SetAccessHandle(FileSystemSyncAccessHandle* aAccessHandle);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+ private:
+  virtual ~FileSystemAccessHandleChild();
+
+  // Use a weak ref so actor does not hold DOM object alive past content use.
+  // The weak reference is cleared in FileSystemSyncAccessHandle::LastRelease.
+  FileSystemSyncAccessHandle* MOZ_NON_OWNING_REF mAccessHandle;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // DOM_FS_CHILD_FILESYSTEMACCESSHANDLECHILD_H_
diff --git a/dom/fs/child/FileSystemAccessHandleControlChild.cpp b/dom/fs/child/FileSystemAccessHandleControlChild.cpp
new file mode 100644
index 0000000000..60cb4e621b
--- /dev/null
+++ b/dom/fs/child/FileSystemAccessHandleControlChild.cpp
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemAccessHandleControlChild.h"
+
+#include "mozilla/dom/FileSystemSyncAccessHandle.h"
+
+namespace mozilla::dom {
+
+void FileSystemAccessHandleControlChild::SetAccessHandle(
+    FileSystemSyncAccessHandle* aAccessHandle) {
+  MOZ_ASSERT(aAccessHandle);
+  MOZ_ASSERT(!mAccessHandle);
+
+  mAccessHandle = aAccessHandle;
+}
+
+void FileSystemAccessHandleControlChild::Shutdown() {
+  if (!CanSend()) {
+    return;
+  }
+
+  Close();
+}
+
+void FileSystemAccessHandleControlChild::ActorDestroy(
+    ActorDestroyReason /* aWhy */) {
+  if (mAccessHandle) {
+    mAccessHandle->ClearControlActor();
+    mAccessHandle = nullptr;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/fs/child/FileSystemAccessHandleControlChild.h b/dom/fs/child/FileSystemAccessHandleControlChild.h
new file mode 100644
index 0000000000..93ddb36e55
--- /dev/null
+++ b/dom/fs/child/FileSystemAccessHandleControlChild.h
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMACCESSHANDLECONTROLCHILD_H_
+#define DOM_FS_CHILD_FILESYSTEMACCESSHANDLECONTROLCHILD_H_
+
+#include "mozilla/dom/PFileSystemAccessHandleControlChild.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla::dom {
+
+class FileSystemSyncAccessHandle;
+
+class FileSystemAccessHandleControlChild
+    : public PFileSystemAccessHandleControlChild {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_WITH_DESTROY(FileSystemAccessHandleControlChild,
+                                          Destroy(), override)
+
+  void SetAccessHandle(FileSystemSyncAccessHandle* aAccessHandle);
+
+  void Shutdown();
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+ protected:
+  virtual ~FileSystemAccessHandleControlChild() = default;
+
+  // This is called when the object's refcount drops to zero. We use this custom
+  // callback to close the top level actor if it hasn't been explicitly closed
+  // yet. For example when `FileSystemSyncAccessHandle::Create` fails after
+  // creating and binding the top level actor.
+  virtual void Destroy() {
+    Shutdown();
+    delete this;
+  }
+
+  // The weak reference is cleared in ActorDestroy.
+  FileSystemSyncAccessHandle* MOZ_NON_OWNING_REF mAccessHandle;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // DOM_FS_CHILD_FILESYSTEMACCESSHANDLECONTROLCHILD_H_
diff --git a/dom/fs/child/FileSystemAsyncCopy.cpp b/dom/fs/child/FileSystemAsyncCopy.cpp
new file mode 100644
index 0000000000..782d67b5cd
--- /dev/null
+++ b/dom/fs/child/FileSystemAsyncCopy.cpp
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "fs/FileSystemAsyncCopy.h"
+
+#include "fs/FileSystemConstants.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+
+namespace mozilla::dom::fs {
+
+nsresult AsyncCopy(nsIInputStream* aSource, nsIOutputStream* aSink,
+                   nsISerialEventTarget* aIOTarget, const nsAsyncCopyMode aMode,
+                   const bool aCloseSource, const bool aCloseSink,
+                   std::function<void(uint32_t)>&& aProgressCallback,
+                   MoveOnlyFunction<void(nsresult)>&& aCompleteCallback) {
+  struct CallbackClosure {
+    CallbackClosure(std::function<void(uint32_t)>&& aProgressCallback,
+                    MoveOnlyFunction<void(nsresult)>&& aCompleteCallback) {
+      mProgressCallbackWrapper = MakeUnique<std::function<void(uint32_t)>>(
+          [progressCallback = std::move(aProgressCallback)](uint32_t count) {
+            progressCallback(count);
+          });
+
+      mCompleteCallbackWrapper = MakeUnique<MoveOnlyFunction<void(nsresult)>>(
+          [completeCallback =
+               std::move(aCompleteCallback)](nsresult rv) mutable {
+            auto callback = std::move(completeCallback);
+            callback(rv);
+          });
+    }
+
+    UniquePtr<std::function<void(uint32_t)>> mProgressCallbackWrapper;
+    UniquePtr<MoveOnlyFunction<void(nsresult)>> mCompleteCallbackWrapper;
+  };
+
+  auto* callbackClosure = new CallbackClosure(std::move(aProgressCallback),
+                                              std::move(aCompleteCallback));
+
+  QM_TRY(
+      MOZ_TO_RESULT(NS_AsyncCopy(
+          aSource, aSink, aIOTarget, aMode, kStreamCopyBlockSize,
+          [](void* aClosure, nsresult aRv) {
+            auto* callbackClosure = static_cast<CallbackClosure*>(aClosure);
+            (*callbackClosure->mCompleteCallbackWrapper)(aRv);
+            delete callbackClosure;
+          },
+          callbackClosure, aCloseSource, aCloseSink, /* aCopierCtx */ nullptr,
+          [](void* aClosure, uint32_t aCount) {
+            auto* callbackClosure = static_cast<CallbackClosure*>(aClosure);
+            (*callbackClosure->mProgressCallbackWrapper)(aCount);
+          })),
+      [callbackClosure](nsresult rv) {
+        delete callbackClosure;
+        return rv;
+      });
+
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemBackgroundRequestHandler.cpp b/dom/fs/child/FileSystemBackgroundRequestHandler.cpp
new file mode 100644
index 0000000000..d88ec05a8c
--- /dev/null
+++ b/dom/fs/child/FileSystemBackgroundRequestHandler.cpp
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemBackgroundRequestHandler.h"
+
+#include "fs/FileSystemChildFactory.h"
+#include "mozilla/dom/FileSystemManagerChild.h"
+#include "mozilla/dom/PFileSystemManager.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+
+namespace mozilla::dom {
+
+FileSystemBackgroundRequestHandler::FileSystemBackgroundRequestHandler(
+    fs::FileSystemChildFactory* aChildFactory)
+    : mChildFactory(aChildFactory), mCreatingFileSystemManagerChild(false) {}
+
+FileSystemBackgroundRequestHandler::FileSystemBackgroundRequestHandler(
+    RefPtr<FileSystemManagerChild> aFileSystemManagerChild)
+    : mFileSystemManagerChild(std::move(aFileSystemManagerChild)),
+      mCreatingFileSystemManagerChild(false) {}
+
+FileSystemBackgroundRequestHandler::FileSystemBackgroundRequestHandler()
+    : FileSystemBackgroundRequestHandler(new fs::FileSystemChildFactory()) {}
+
+FileSystemBackgroundRequestHandler::~FileSystemBackgroundRequestHandler() =
+    default;
+
+void FileSystemBackgroundRequestHandler::ClearActor() {
+  MOZ_ASSERT(mFileSystemManagerChild);
+
+  mFileSystemManagerChild = nullptr;
+}
+
+void FileSystemBackgroundRequestHandler::Shutdown() {
+  mShutdown.Flip();
+
+  if (mFileSystemManagerChild) {
+    MOZ_ASSERT(!mCreatingFileSystemManagerChild);
+
+    mFileSystemManagerChild->Shutdown();
+
+    mFileSystemManagerChild = nullptr;
+
+    return;
+  }
+
+  if (mCreatingFileSystemManagerChild) {
+    MOZ_ASSERT(!mFileSystemManagerChild);
+
+    mCreateFileSystemManagerParentPromiseRequestHolder.Disconnect();
+
+    mCreatingFileSystemManagerChild = false;
+
+    // We must either resolve/reject the promise or steal the internal promise
+    // before the holder is destroyed. The former isn't possible during
+    // shutdown.
+    Unused << mCreateFileSystemManagerChildPromiseHolder.Steal();
+  }
+}
+
+const RefPtr<FileSystemManagerChild>&
+FileSystemBackgroundRequestHandler::FileSystemManagerChildStrongRef() const {
+  return mFileSystemManagerChild;
+}
+
+RefPtr<BoolPromise>
+FileSystemBackgroundRequestHandler::CreateFileSystemManagerChild(
+    const mozilla::ipc::PrincipalInfo& aPrincipalInfo) {
+  MOZ_ASSERT(!mFileSystemManagerChild);
+  MOZ_ASSERT(!mShutdown);
+
+  using mozilla::ipc::BackgroundChild;
+  using mozilla::ipc::Endpoint;
+  using mozilla::ipc::PBackgroundChild;
+
+  if (!mCreatingFileSystemManagerChild) {
+    PBackgroundChild* backgroundChild =
+        BackgroundChild::GetOrCreateForCurrentThread();
+    if (NS_WARN_IF(!backgroundChild)) {
+      return BoolPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
+    }
+
+    // Create a new IPC connection
+    Endpoint<PFileSystemManagerParent> parentEndpoint;
+    Endpoint<PFileSystemManagerChild> childEndpoint;
+    MOZ_ALWAYS_SUCCEEDS(
+        PFileSystemManager::CreateEndpoints(&parentEndpoint, &childEndpoint));
+
+    RefPtr<FileSystemManagerChild> child = mChildFactory->Create();
+    if (!childEndpoint.Bind(child)) {
+      return BoolPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
+    }
+
+    mCreatingFileSystemManagerChild = true;
+
+    backgroundChild
+        ->SendCreateFileSystemManagerParent(aPrincipalInfo,
+                                            std::move(parentEndpoint))
+        ->Then(
+            GetCurrentSerialEventTarget(), __func__,
+            [self = RefPtr<FileSystemBackgroundRequestHandler>(this),
+             child](nsresult rv) {
+              self->mCreateFileSystemManagerParentPromiseRequestHolder
+                  .Complete();
+
+              self->mCreatingFileSystemManagerChild = false;
+
+              if (NS_FAILED(rv)) {
+                self->mCreateFileSystemManagerChildPromiseHolder.RejectIfExists(
+                    rv, __func__);
+              } else {
+                self->mFileSystemManagerChild = child;
+
+                self->mFileSystemManagerChild->SetBackgroundRequestHandler(
+                    self);
+
+                self->mCreateFileSystemManagerChildPromiseHolder
+                    .ResolveIfExists(true, __func__);
+              }
+            },
+            [self = RefPtr<FileSystemBackgroundRequestHandler>(this)](
+                const mozilla::ipc::ResponseRejectReason&) {
+              self->mCreateFileSystemManagerParentPromiseRequestHolder
+                  .Complete();
+
+              self->mCreatingFileSystemManagerChild = false;
+
+              self->mCreateFileSystemManagerChildPromiseHolder.RejectIfExists(
+                  NS_ERROR_FAILURE, __func__);
+            })
+        ->Track(mCreateFileSystemManagerParentPromiseRequestHolder);
+  }
+
+  return mCreateFileSystemManagerChildPromiseHolder.Ensure(__func__);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/fs/child/FileSystemBackgroundRequestHandler.h b/dom/fs/child/FileSystemBackgroundRequestHandler.h
new file mode 100644
index 0000000000..a206375384
--- /dev/null
+++ b/dom/fs/child/FileSystemBackgroundRequestHandler.h
@@ -0,0 +1,73 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMBACKGROUNDREQUESTHANDLER_H_
+#define DOM_FS_CHILD_FILESYSTEMBACKGROUNDREQUESTHANDLER_H_
+
+#include "mozilla/MozPromise.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/dom/quota/ForwardDecls.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+
+template <class T>
+class RefPtr;
+
+namespace mozilla {
+
+namespace ipc {
+class PrincipalInfo;
+}  // namespace ipc
+
+namespace dom {
+
+class FileSystemManagerChild;
+
+namespace fs {
+class FileSystemChildFactory;
+}
+
+class FileSystemBackgroundRequestHandler {
+ public:
+  explicit FileSystemBackgroundRequestHandler(
+      fs::FileSystemChildFactory* aChildFactory);
+
+  explicit FileSystemBackgroundRequestHandler(
+      RefPtr<FileSystemManagerChild> aFileSystemManagerChild);
+
+  FileSystemBackgroundRequestHandler();
+
+  NS_INLINE_DECL_REFCOUNTING(FileSystemBackgroundRequestHandler)
+
+  void ClearActor();
+
+  void Shutdown();
+
+  const RefPtr<FileSystemManagerChild>& FileSystemManagerChildStrongRef() const;
+
+  virtual RefPtr<mozilla::BoolPromise> CreateFileSystemManagerChild(
+      const mozilla::ipc::PrincipalInfo& aPrincipalInfo);
+
+ protected:
+  virtual ~FileSystemBackgroundRequestHandler();
+
+  const UniquePtr<fs::FileSystemChildFactory> mChildFactory;
+
+  MozPromiseRequestHolder<
+      mozilla::ipc::PBackgroundChild::CreateFileSystemManagerParentPromise>
+      mCreateFileSystemManagerParentPromiseRequestHolder;
+  MozPromiseHolder<BoolPromise> mCreateFileSystemManagerChildPromiseHolder;
+
+  RefPtr<FileSystemManagerChild> mFileSystemManagerChild;
+
+  FlippedOnce<false> mShutdown;
+
+  bool mCreatingFileSystemManagerChild;
+};  // class FileSystemBackgroundRequestHandler
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // DOM_FS_CHILD_FILESYSTEMBACKGROUNDREQUESTHANDLER_H_
diff --git a/dom/fs/child/FileSystemChildFactory.cpp b/dom/fs/child/FileSystemChildFactory.cpp
new file mode 100644
index 0000000000..bf4c493dd8
--- /dev/null
+++ b/dom/fs/child/FileSystemChildFactory.cpp
@@ -0,0 +1,19 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "fs/FileSystemChildFactory.h"
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/FileSystemManagerChild.h"
+
+namespace mozilla::dom::fs {
+
+already_AddRefed<FileSystemManagerChild> FileSystemChildFactory::Create()
+    const {
+  return MakeAndAddRef<FileSystemManagerChild>();
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemDirectoryIteratorFactory.cpp b/dom/fs/child/FileSystemDirectoryIteratorFactory.cpp
new file mode 100644
index 0000000000..26b605f5b6
--- /dev/null
+++ b/dom/fs/child/FileSystemDirectoryIteratorFactory.cpp
@@ -0,0 +1,237 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemDirectoryIteratorFactory.h"
+
+#include "FileSystemEntryMetadataArray.h"
+#include "fs/FileSystemRequestHandler.h"
+#include "jsapi.h"
+#include "mozilla/dom/FileSystemDirectoryHandle.h"
+#include "mozilla/dom/FileSystemDirectoryIterator.h"
+#include "mozilla/dom/FileSystemFileHandle.h"
+#include "mozilla/dom/FileSystemHandle.h"
+#include "mozilla/dom/FileSystemLog.h"
+#include "mozilla/dom/FileSystemManager.h"
+#include "mozilla/dom/IterableIterator.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+
+namespace mozilla::dom::fs {
+
+namespace {
+
+template <IterableIteratorBase::IteratorType Type>
+struct ValueResolver;
+
+template <>
+struct ValueResolver<IterableIteratorBase::Keys> {
+  void operator()(nsIGlobalObject* aGlobal, RefPtr<FileSystemManager>& aManager,
+                  const FileSystemEntryMetadata& aValue,
+                  const RefPtr<Promise>& aPromise) {
+    aPromise->MaybeResolve(aValue.entryName());
+  }
+};
+
+template <>
+struct ValueResolver<IterableIteratorBase::Values> {
+  void operator()(nsIGlobalObject* aGlobal, RefPtr<FileSystemManager>& aManager,
+                  const FileSystemEntryMetadata& aValue,
+                  const RefPtr<Promise>& aPromise) {
+    RefPtr<FileSystemHandle> handle;
+
+    if (aValue.directory()) {
+      handle = new FileSystemDirectoryHandle(aGlobal, aManager, aValue);
+    } else {
+      handle = new FileSystemFileHandle(aGlobal, aManager, aValue);
+    }
+
+    aPromise->MaybeResolve(std::move(handle));
+  }
+};
+
+template <>
+struct ValueResolver<IterableIteratorBase::Entries> {
+  void operator()(nsIGlobalObject* aGlobal, RefPtr<FileSystemManager>& aManager,
+                  const FileSystemEntryMetadata& aValue,
+                  const RefPtr<Promise>& aPromise) {
+    RefPtr<FileSystemHandle> handle;
+
+    if (aValue.directory()) {
+      handle = new FileSystemDirectoryHandle(aGlobal, aManager, aValue);
+    } else {
+      handle = new FileSystemFileHandle(aGlobal, aManager, aValue);
+    }
+
+    iterator_utils::ResolvePromiseWithKeyAndValue(aPromise, aValue.entryName(),
+                                                  handle);
+  }
+};
+
+// TODO: PageSize could be compile-time shared between content and parent
+template <class ValueResolver, size_t PageSize = 1024u>
+class DoubleBufferQueueImpl
+    : public mozilla::dom::FileSystemDirectoryIterator::Impl {
+  static_assert(PageSize > 0u);
+
+ public:
+  using DataType = FileSystemEntryMetadata;
+  explicit DoubleBufferQueueImpl(const FileSystemEntryMetadata& aMetadata)
+      : mEntryId(aMetadata.entryId()),
+        mData(),
+        mWithinPageEnd(0u),
+        mWithinPageIndex(0u),
+        mCurrentPageIsLastPage(true),
+        mPageNumber(0u) {}
+
+  // XXX This doesn't have to be public
+  void ResolveValue(nsIGlobalObject* aGlobal,
+                    RefPtr<FileSystemManager>& aManager,
+                    const Maybe<DataType>& aValue, RefPtr<Promise> aPromise) {
+    MOZ_ASSERT(aPromise);
+    MOZ_ASSERT(aPromise.get());
+
+    if (!aValue) {
+      iterator_utils::ResolvePromiseForFinished(aPromise);
+      return;
+    }
+
+    ValueResolver{}(aGlobal, aManager, *aValue, aPromise);
+  }
+
+  already_AddRefed<Promise> Next(nsIGlobalObject* aGlobal,
+                                 RefPtr<FileSystemManager>& aManager,
+                                 ErrorResult& aError) override {
+    RefPtr<Promise> promise = Promise::Create(aGlobal, aError);
+    if (aError.Failed()) {
+      return nullptr;
+    }
+
+    next(aGlobal, aManager, promise, aError);
+    if (aError.Failed()) {
+      return nullptr;
+    }
+
+    return promise.forget();
+  }
+
+  ~DoubleBufferQueueImpl() = default;
+
+ protected:
+  void next(nsIGlobalObject* aGlobal, RefPtr<FileSystemManager>& aManager,
+            RefPtr<Promise> aResult, ErrorResult& aError) {
+    LOG_VERBOSE(("next"));
+    MOZ_ASSERT(aResult);
+
+    Maybe<DataType> rawValue;
+
+    // TODO: Would it be better to prefetch the items before
+    // we hit the end of a page?
+    // How likely it is that it would that lead to wasted fetch operations?
+    if (0u == mWithinPageIndex) {
+      RefPtr<Promise> promise = Promise::Create(aGlobal, aError);
+      if (aError.Failed()) {
+        return;
+      }
+
+      auto newPage = MakeRefPtr<FileSystemEntryMetadataArray>();
+
+      RefPtr<DomPromiseListener> listener = new DomPromiseListener(
+          [global = nsCOMPtr<nsIGlobalObject>(aGlobal),
+           manager = RefPtr<FileSystemManager>(aManager), newPage, aResult,
+           this](JSContext* aCx, JS::Handle<JS::Value> aValue) mutable {
+            MOZ_ASSERT(0u == mWithinPageIndex);
+            MOZ_ASSERT(newPage->Length() <= PageSize);
+
+            const size_t startPos = mCurrentPageIsLastPage ? 0u : PageSize;
+            if (mData.Length() < 2 * PageSize) {
+              mData.InsertElementsAt(startPos, newPage->Elements(),
+                                     newPage->Length());
+            } else {
+              mData.ReplaceElementsAt(startPos, newPage->Length(),
+                                      newPage->Elements(), newPage->Length());
+            }
+            MOZ_ASSERT(mData.Length() <= 2 * PageSize);
+            mWithinPageEnd = newPage->Length();
+
+            Maybe<DataType> value;
+            if (0 != newPage->Length()) {
+              nextInternal(value);
+            }
+
+            ResolveValue(global, manager, value, aResult);
+          },
+          [aResult](nsresult aRv) { aResult->MaybeReject(aRv); });
+      promise->AppendNativeHandler(listener);
+
+      FileSystemRequestHandler{}.GetEntries(aManager, mEntryId, mPageNumber,
+                                            promise, newPage, aError);
+      if (aError.Failed()) {
+        return;
+      }
+
+      ++mPageNumber;
+      return;
+    }
+
+    nextInternal(rawValue);
+
+    ResolveValue(aGlobal, aManager, rawValue, aResult);
+  }
+
+  bool nextInternal(Maybe<DataType>& aNext) {
+    if (mWithinPageIndex >= mWithinPageEnd) {
+      return false;
+    }
+
+    const size_t previous =
+        mWithinPageIndex + (mCurrentPageIsLastPage ? 0 : PageSize);
+    MOZ_ASSERT(2u * PageSize > previous);
+    MOZ_ASSERT(previous < mData.Length());
+
+    ++mWithinPageIndex;
+
+    if (mWithinPageIndex == PageSize) {
+      // Page end reached
+      mWithinPageIndex = 0u;
+      mCurrentPageIsLastPage = !mCurrentPageIsLastPage;
+    }
+
+    aNext = Some(mData[previous]);
+    return true;
+  }
+
+  const EntryId mEntryId;
+
+  nsTArray<DataType> mData;  // TODO: Fixed size above one page?
+
+  size_t mWithinPageEnd = 0u;
+  size_t mWithinPageIndex = 0u;
+  bool mCurrentPageIsLastPage = true;  // In the beginning, first page is free
+  PageNumber mPageNumber = 0u;
+};
+
+template <IterableIteratorBase::IteratorType Type>
+using UnderlyingQueue = DoubleBufferQueueImpl<ValueResolver<Type>>;
+
+}  // namespace
+
+UniquePtr<mozilla::dom::FileSystemDirectoryIterator::Impl>
+FileSystemDirectoryIteratorFactory::Create(
+    const FileSystemEntryMetadata& aMetadata,
+    IterableIteratorBase::IteratorType aType) {
+  if (IterableIteratorBase::Entries == aType) {
+    return MakeUnique<UnderlyingQueue<IterableIteratorBase::Entries>>(
+        aMetadata);
+  }
+
+  if (IterableIteratorBase::Values == aType) {
+    return MakeUnique<UnderlyingQueue<IterableIteratorBase::Values>>(aMetadata);
+  }
+
+  return MakeUnique<UnderlyingQueue<IterableIteratorBase::Keys>>(aMetadata);
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemDirectoryIteratorFactory.h b/dom/fs/child/FileSystemDirectoryIteratorFactory.h
new file mode 100644
index 0000000000..278f0a9ef0
--- /dev/null
+++ b/dom/fs/child/FileSystemDirectoryIteratorFactory.h
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMDIRECTORYITERATORFACTORY_H_
+#define DOM_FS_CHILD_FILESYSTEMDIRECTORYITERATORFACTORY_H_
+
+#include "mozilla/dom/FileSystemDirectoryIterator.h"
+
+namespace mozilla::dom::fs {
+
+class FileSystemEntryMetadata;
+
+struct FileSystemDirectoryIteratorFactory {
+  static UniquePtr<mozilla::dom::FileSystemDirectoryIterator::Impl> Create(
+      const FileSystemEntryMetadata& aMetadata,
+      IterableIteratorBase::IteratorType aType);
+};
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_CHILD_FILESYSTEMDIRECTORYITERATORFACTORY_H_
diff --git a/dom/fs/child/FileSystemEntryMetadataArray.h b/dom/fs/child/FileSystemEntryMetadataArray.h
new file mode 100644
index 0000000000..cd5370846a
--- /dev/null
+++ b/dom/fs/child/FileSystemEntryMetadataArray.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMENTRYMETADATAARRAY_H_
+#define DOM_FS_CHILD_FILESYSTEMENTRYMETADATAARRAY_H_
+
+#include "nsTArray.h"
+
+namespace mozilla::dom::fs {
+
+class FileSystemEntryMetadata;
+
+class FileSystemEntryMetadataArray : public nsTArray<FileSystemEntryMetadata> {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(FileSystemEntryMetadataArray);
+
+ private:
+  ~FileSystemEntryMetadataArray() = default;
+};
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_CHILD_FILESYSTEMENTRYMETADATAARRAY_H_
diff --git a/dom/fs/child/FileSystemManagerChild.cpp b/dom/fs/child/FileSystemManagerChild.cpp
new file mode 100644
index 0000000000..7a86ac6628
--- /dev/null
+++ b/dom/fs/child/FileSystemManagerChild.cpp
@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemManagerChild.h"
+
+#include "FileSystemAccessHandleChild.h"
+#include "FileSystemBackgroundRequestHandler.h"
+#include "FileSystemWritableFileStreamChild.h"
+#include "mozilla/dom/FileSystemSyncAccessHandle.h"
+#include "mozilla/dom/FileSystemWritableFileStream.h"
+
+namespace mozilla::dom {
+
+void FileSystemManagerChild::SetBackgroundRequestHandler(
+    FileSystemBackgroundRequestHandler* aBackgroundRequestHandler) {
+  MOZ_ASSERT(aBackgroundRequestHandler);
+  MOZ_ASSERT(!mBackgroundRequestHandler);
+
+  mBackgroundRequestHandler = aBackgroundRequestHandler;
+}
+
+void FileSystemManagerChild::CloseAllWritables(
+    std::function<void()>&& aCallback) {
+  nsTArray<RefPtr<BoolPromise>> promises;
+  CloseAllWritablesImpl(promises);
+
+  BoolPromise::AllSettled(GetCurrentSerialEventTarget(), promises)
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [callback = std::move(aCallback)](
+                 const BoolPromise::AllSettledPromiseType::ResolveOrRejectValue&
+                 /* aValues */) { callback(); });
+}
+
+#ifdef DEBUG
+bool FileSystemManagerChild::AllSyncAccessHandlesClosed() const {
+  for (const auto& item : ManagedPFileSystemAccessHandleChild()) {
+    auto* child = static_cast<FileSystemAccessHandleChild*>(item);
+    auto* handle = child->MutableAccessHandlePtr();
+
+    if (!handle->IsClosed()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool FileSystemManagerChild::AllWritableFileStreamsClosed() const {
+  for (const auto& item : ManagedPFileSystemWritableFileStreamChild()) {
+    auto* const child = static_cast<FileSystemWritableFileStreamChild*>(item);
+    auto* const handle = child->MutableWritableFileStreamPtr();
+    if (!handle) {
+      continue;
+    }
+
+    if (!handle->IsClosed()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+#endif
+
+void FileSystemManagerChild::Shutdown() {
+  if (!CanSend()) {
+    return;
+  }
+
+  Close();
+}
+
+already_AddRefed<PFileSystemWritableFileStreamChild>
+FileSystemManagerChild::AllocPFileSystemWritableFileStreamChild() {
+  return MakeAndAddRef<FileSystemWritableFileStreamChild>();
+}
+
+::mozilla::ipc::IPCResult FileSystemManagerChild::RecvCloseAll(
+    CloseAllResolver&& aResolver) {
+  nsTArray<RefPtr<BoolPromise>> promises;
+
+  // NOTE: getFile() creates blobs that read the data from the child;
+  // we'll need to abort any reads and resolve this call only when all
+  // blobs are closed.
+
+  for (const auto& item : ManagedPFileSystemAccessHandleChild()) {
+    auto* child = static_cast<FileSystemAccessHandleChild*>(item);
+    auto* handle = child->MutableAccessHandlePtr();
+
+    if (handle->IsOpen()) {
+      promises.AppendElement(handle->BeginClose());
+    } else if (handle->IsClosing()) {
+      promises.AppendElement(handle->OnClose());
+    }
+  }
+
+  CloseAllWritablesImpl(promises);
+
+  BoolPromise::AllSettled(GetCurrentSerialEventTarget(), promises)
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [resolver = std::move(aResolver)](
+                 const BoolPromise::AllSettledPromiseType::ResolveOrRejectValue&
+                 /* aValues */) { resolver(NS_OK); });
+
+  return IPC_OK();
+}
+
+void FileSystemManagerChild::ActorDestroy(ActorDestroyReason aWhy) {
+  if (mBackgroundRequestHandler) {
+    mBackgroundRequestHandler->ClearActor();
+    mBackgroundRequestHandler = nullptr;
+  }
+}
+
+template <class T>
+void FileSystemManagerChild::CloseAllWritablesImpl(T& aPromises) {
+  for (const auto& item : ManagedPFileSystemWritableFileStreamChild()) {
+    auto* const child = static_cast<FileSystemWritableFileStreamChild*>(item);
+    auto* const handle = child->MutableWritableFileStreamPtr();
+
+    if (handle && !handle->IsClosed()) {
+      aPromises.AppendElement(handle->BeginClose());
+    }
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/fs/child/FileSystemManagerChild.h b/dom/fs/child/FileSystemManagerChild.h
new file mode 100644
index 0000000000..bd5520a982
--- /dev/null
+++ b/dom/fs/child/FileSystemManagerChild.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMMANAGERCHILD_H_
+#define DOM_FS_CHILD_FILESYSTEMMANAGERCHILD_H_
+
+#include "mozilla/dom/FileSystemWritableFileStreamChild.h"
+#include "mozilla/dom/PFileSystemManagerChild.h"
+#include "mozilla/dom/quota/ForwardDecls.h"
+
+namespace mozilla::dom {
+
+class FileSystemBackgroundRequestHandler;
+
+class FileSystemManagerChild : public PFileSystemManagerChild {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_WITH_DESTROY(FileSystemManagerChild, Destroy(),
+                                          override)
+
+  void SetBackgroundRequestHandler(
+      FileSystemBackgroundRequestHandler* aBackgroundRequestHandler);
+
+  void CloseAllWritables(std::function<void()>&& aCallback);
+
+#ifdef DEBUG
+  virtual bool AllSyncAccessHandlesClosed() const;
+
+  virtual bool AllWritableFileStreamsClosed() const;
+#endif
+
+  virtual void Shutdown();
+
+  already_AddRefed<PFileSystemWritableFileStreamChild>
+  AllocPFileSystemWritableFileStreamChild();
+
+  ::mozilla::ipc::IPCResult RecvCloseAll(CloseAllResolver&& aResolver);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+ protected:
+  virtual ~FileSystemManagerChild() = default;
+
+  virtual void Destroy() {
+    Shutdown();
+    delete this;
+  }
+
+  // The weak reference is cleared in ActorDestroy.
+  FileSystemBackgroundRequestHandler* MOZ_NON_OWNING_REF
+      mBackgroundRequestHandler;
+
+ private:
+  template <class T>
+  void CloseAllWritablesImpl(T& aPromises);
+};
+
+}  // namespace mozilla::dom
+
+#endif  // DOM_FS_CHILD_FILESYSTEMMANAGERCHILD_H_
diff --git a/dom/fs/child/FileSystemRequestHandler.cpp b/dom/fs/child/FileSystemRequestHandler.cpp
new file mode 100644
index 0000000000..ffb444b979
--- /dev/null
+++ b/dom/fs/child/FileSystemRequestHandler.cpp
@@ -0,0 +1,631 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "fs/FileSystemRequestHandler.h"
+
+#include "FileSystemEntryMetadataArray.h"
+#include "fs/FileSystemConstants.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileSystemAccessHandleChild.h"
+#include "mozilla/dom/FileSystemDirectoryHandle.h"
+#include "mozilla/dom/FileSystemFileHandle.h"
+#include "mozilla/dom/FileSystemHandle.h"
+#include "mozilla/dom/FileSystemHelpers.h"
+#include "mozilla/dom/FileSystemLog.h"
+#include "mozilla/dom/FileSystemManager.h"
+#include "mozilla/dom/FileSystemManagerChild.h"
+#include "mozilla/dom/FileSystemSyncAccessHandle.h"
+#include "mozilla/dom/FileSystemWritableFileStream.h"
+#include "mozilla/dom/FileSystemWritableFileStreamChild.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/WorkerRef.h"
+#include "mozilla/dom/fs/IPCRejectReporter.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "mozilla/ipc/RandomAccessStreamUtils.h"
+
+namespace mozilla::dom::fs {
+
+using mozilla::ipc::RejectCallback;
+
+namespace {
+
+void HandleFailedStatus(nsresult aError, const RefPtr<Promise>& aPromise) {
+  switch (aError) {
+    case NS_ERROR_FILE_ACCESS_DENIED:
+      aPromise->MaybeRejectWithNotAllowedError("Permission denied");
+      break;
+    case NS_ERROR_FILE_NOT_FOUND:
+      [[fallthrough]];
+    case NS_ERROR_DOM_NOT_FOUND_ERR:
+      aPromise->MaybeRejectWithNotFoundError("Entry not found");
+      break;
+    case NS_ERROR_DOM_FILESYSTEM_NO_MODIFICATION_ALLOWED_ERR:
+      aPromise->MaybeRejectWithInvalidModificationError("Disallowed by system");
+      break;
+    case NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR:
+      aPromise->MaybeRejectWithNoModificationAllowedError(
+          "No modification allowed");
+      break;
+    case NS_ERROR_DOM_TYPE_MISMATCH_ERR:
+      aPromise->MaybeRejectWithTypeMismatchError("Wrong type");
+      break;
+    case NS_ERROR_DOM_INVALID_MODIFICATION_ERR:
+      aPromise->MaybeRejectWithInvalidModificationError("Invalid modification");
+      break;
+    default:
+      if (NS_FAILED(aError)) {
+        aPromise->MaybeRejectWithUnknownError("Unknown failure");
+      } else {
+        aPromise->MaybeResolveWithUndefined();
+      }
+      break;
+  }
+}
+
+bool MakeResolution(nsIGlobalObject* aGlobal,
+                    FileSystemGetEntriesResponse&& aResponse,
+                    const bool& /* aResult */,
+                    RefPtr<FileSystemEntryMetadataArray>& aSink) {
+  // TODO: Add page size to FileSystemConstants, preallocate and handle overflow
+  const auto& listing = aResponse.get_FileSystemDirectoryListing();
+
+  for (const auto& it : listing.files()) {
+    aSink->AppendElement(it);
+  }
+
+  for (const auto& it : listing.directories()) {
+    aSink->AppendElement(it);
+  }
+
+  return true;
+}
+
+RefPtr<FileSystemDirectoryHandle> MakeResolution(
+    nsIGlobalObject* aGlobal, FileSystemGetHandleResponse&& aResponse,
+    const RefPtr<FileSystemDirectoryHandle>& /* aResult */,
+    RefPtr<FileSystemManager>& aManager) {
+  RefPtr<FileSystemDirectoryHandle> result = new FileSystemDirectoryHandle(
+      aGlobal, aManager,
+      FileSystemEntryMetadata(aResponse.get_EntryId(), kRootName,
+                              /* directory */ true));
+  return result;
+}
+
+RefPtr<FileSystemDirectoryHandle> MakeResolution(
+    nsIGlobalObject* aGlobal, FileSystemGetHandleResponse&& aResponse,
+    const RefPtr<FileSystemDirectoryHandle>& /* aResult */, const Name& aName,
+    RefPtr<FileSystemManager>& aManager) {
+  RefPtr<FileSystemDirectoryHandle> result = new FileSystemDirectoryHandle(
+      aGlobal, aManager,
+      FileSystemEntryMetadata(aResponse.get_EntryId(), aName,
+                              /* directory */ true));
+
+  return result;
+}
+
+RefPtr<FileSystemFileHandle> MakeResolution(
+    nsIGlobalObject* aGlobal, FileSystemGetHandleResponse&& aResponse,
+    const RefPtr<FileSystemFileHandle>& /* aResult */, const Name& aName,
+    RefPtr<FileSystemManager>& aManager) {
+  RefPtr<FileSystemFileHandle> result = new FileSystemFileHandle(
+      aGlobal, aManager,
+      FileSystemEntryMetadata(aResponse.get_EntryId(), aName,
+                              /* directory */ false));
+  return result;
+}
+
+RefPtr<FileSystemSyncAccessHandle> MakeResolution(
+    nsIGlobalObject* aGlobal, FileSystemGetAccessHandleResponse&& aResponse,
+    const RefPtr<FileSystemSyncAccessHandle>& /* aReturns */,
+    const FileSystemEntryMetadata& aMetadata,
+    RefPtr<FileSystemManager>& aManager) {
+  auto& properties = aResponse.get_FileSystemAccessHandleProperties();
+
+  QM_TRY_UNWRAP(
+      RefPtr<FileSystemSyncAccessHandle> result,
+      FileSystemSyncAccessHandle::Create(
+          aGlobal, aManager, std::move(properties.streamParams()),
+          std::move(properties.accessHandleChildEndpoint()),
+          std::move(properties.accessHandleControlChildEndpoint()), aMetadata),
+      nullptr);
+
+  return result;
+}
+
+RefPtr<FileSystemWritableFileStream> MakeResolution(
+    nsIGlobalObject* aGlobal,
+    FileSystemGetWritableFileStreamResponse&& aResponse,
+    const RefPtr<FileSystemWritableFileStream>& /* aReturns */,
+    const FileSystemEntryMetadata& aMetadata,
+    RefPtr<FileSystemManager>& aManager) {
+  auto& properties = aResponse.get_FileSystemWritableFileStreamProperties();
+
+  auto* const actor = static_cast<FileSystemWritableFileStreamChild*>(
+      properties.writableFileStream().AsChild().get());
+
+  QM_TRY_UNWRAP(RefPtr<FileSystemWritableFileStream> result,
+                FileSystemWritableFileStream::Create(
+                    aGlobal, aManager, std::move(properties.streamParams()),
+                    actor, aMetadata),
+                nullptr);
+
+  return result;
+}
+
+RefPtr<File> MakeResolution(nsIGlobalObject* aGlobal,
+                            FileSystemGetFileResponse&& aResponse,
+                            const RefPtr<File>& /* aResult */,
+                            const Name& aName,
+                            RefPtr<FileSystemManager>& aManager) {
+  auto& fileProperties = aResponse.get_FileSystemFileProperties();
+
+  RefPtr<BlobImpl> blobImpl = IPCBlobUtils::Deserialize(fileProperties.file());
+  MOZ_ASSERT(blobImpl);
+  RefPtr<File> result = File::Create(aGlobal, blobImpl);
+  return result;
+}
+
+template <class TResponse, class... Args>
+void ResolveCallback(
+    TResponse&& aResponse,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    Args&&... args) {
+  MOZ_ASSERT(aPromise);
+  QM_TRY(OkIf(Promise::PromiseState::Pending == aPromise->State()), QM_VOID);
+
+  if (TResponse::Tnsresult == aResponse.type()) {
+    HandleFailedStatus(aResponse.get_nsresult(), aPromise);
+    return;
+  }
+
+  auto resolution = MakeResolution(aPromise->GetParentObject(),
+                                   std::forward<TResponse>(aResponse),
+                                   std::forward<Args>(args)...);
+  if (!resolution) {
+    aPromise->MaybeRejectWithUnknownError("Could not complete request");
+    return;
+  }
+
+  aPromise->MaybeResolve(resolution);
+}
+
+template <>
+void ResolveCallback(
+    FileSystemRemoveEntryResponse&& aResponse,
+    RefPtr<Promise> aPromise) {  // NOLINT(performance-unnecessary-value-param)
+  MOZ_ASSERT(aPromise);
+  QM_TRY(OkIf(Promise::PromiseState::Pending == aPromise->State()), QM_VOID);
+
+  if (FileSystemRemoveEntryResponse::Tvoid_t == aResponse.type()) {
+    aPromise->MaybeResolveWithUndefined();
+    return;
+  }
+
+  MOZ_ASSERT(FileSystemRemoveEntryResponse::Tnsresult == aResponse.type());
+  HandleFailedStatus(aResponse.get_nsresult(), aPromise);
+}
+
+template <>
+void ResolveCallback(
+    FileSystemMoveEntryResponse&& aResponse,
+    RefPtr<Promise> aPromise) {  // NOLINT(performance-unnecessary-value-param)
+  MOZ_ASSERT(aPromise);
+  QM_TRY(OkIf(Promise::PromiseState::Pending == aPromise->State()), QM_VOID);
+
+  MOZ_ASSERT(FileSystemMoveEntryResponse::Tnsresult == aResponse.type());
+  const auto& status = aResponse.get_nsresult();
+  if (NS_OK == status) {
+    aPromise->MaybeResolveWithUndefined();
+    return;
+  }
+  HandleFailedStatus(status, aPromise);
+}
+
+template <>
+void ResolveCallback(FileSystemResolveResponse&& aResponse,
+                     // NOLINTNEXTLINE(performance-unnecessary-value-param)
+                     RefPtr<Promise> aPromise) {
+  MOZ_ASSERT(aPromise);
+  QM_TRY(OkIf(Promise::PromiseState::Pending == aPromise->State()), QM_VOID);
+
+  if (FileSystemResolveResponse::Tnsresult == aResponse.type()) {
+    HandleFailedStatus(aResponse.get_nsresult(), aPromise);
+    return;
+  }
+
+  auto& maybePath = aResponse.get_MaybeFileSystemPath();
+  if (maybePath.isSome()) {
+    aPromise->MaybeResolve(maybePath.value().path());
+    return;
+  }
+
+  // Spec says if there is no parent/child relationship, return null
+  aPromise->MaybeResolve(JS::NullHandleValue);
+}
+
+template <class TResponse, class TReturns, class... Args,
+          std::enable_if_t<std::is_same<TReturns, void>::value, bool> = true>
+mozilla::ipc::ResolveCallback<TResponse> SelectResolveCallback(
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    Args&&... args) {
+  using TOverload = void (*)(TResponse&&, RefPtr<Promise>, Args...);
+  return static_cast<std::function<void(TResponse&&)>>(
+      // NOLINTNEXTLINE(modernize-avoid-bind)
+      std::bind(static_cast<TOverload>(ResolveCallback), std::placeholders::_1,
+                aPromise, std::forward<Args>(args)...));
+}
+
+template <class TResponse, class TReturns, class... Args,
+          std::enable_if_t<!std::is_same<TReturns, void>::value, bool> = true>
+mozilla::ipc::ResolveCallback<TResponse> SelectResolveCallback(
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    Args&&... args) {
+  using TOverload =
+      void (*)(TResponse&&, RefPtr<Promise>, const TReturns&, Args...);
+  return static_cast<std::function<void(TResponse&&)>>(
+      // NOLINTNEXTLINE(modernize-avoid-bind)
+      std::bind(static_cast<TOverload>(ResolveCallback), std::placeholders::_1,
+                aPromise, TReturns(), std::forward<Args>(args)...));
+}
+
+void RejectCallback(
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    mozilla::ipc::ResponseRejectReason aReason) {
+  IPCRejectReporter(aReason);
+  QM_TRY(OkIf(Promise::PromiseState::Pending == aPromise->State()), QM_VOID);
+  aPromise->MaybeRejectWithUndefined();
+}
+
+mozilla::ipc::RejectCallback GetRejectCallback(
+    RefPtr<Promise> aPromise) {  // NOLINT(performance-unnecessary-value-param)
+  return static_cast<mozilla::ipc::RejectCallback>(
+      // NOLINTNEXTLINE(modernize-avoid-bind)
+      std::bind(RejectCallback, aPromise, std::placeholders::_1));
+}
+
+struct BeginRequestFailureCallback {
+  explicit BeginRequestFailureCallback(RefPtr<Promise> aPromise)
+      : mPromise(std::move(aPromise)) {}
+
+  void operator()(nsresult aRv) const {
+    if (aRv == NS_ERROR_DOM_SECURITY_ERR) {
+      mPromise->MaybeRejectWithSecurityError(
+          "Security error when calling GetDirectory");
+      return;
+    }
+    mPromise->MaybeRejectWithUnknownError("Could not create actor");
+  }
+
+  RefPtr<Promise> mPromise;
+};
+
+}  // namespace
+
+void FileSystemRequestHandler::GetRootHandle(
+    RefPtr<FileSystemManager>
+        aManager,              // NOLINT(performance-unnecessary-value-param)
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(aPromise);
+  LOG(("GetRootHandle"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [onResolve = SelectResolveCallback<FileSystemGetHandleResponse,
+                                         RefPtr<FileSystemDirectoryHandle>>(
+           aPromise, aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetRootHandle(std::move(onResolve), std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::GetDirectoryHandle(
+    RefPtr<FileSystemManager>& aManager,
+    const FileSystemChildMetadata& aDirectory, bool aCreate,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aDirectory.parentId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("GetDirectoryHandle"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  if (!IsValidName(aDirectory.childName())) {
+    aPromise->MaybeRejectWithTypeError("Invalid directory name");
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetHandleRequest(aDirectory, aCreate),
+       onResolve = SelectResolveCallback<FileSystemGetHandleResponse,
+                                         RefPtr<FileSystemDirectoryHandle>>(
+           aPromise, aDirectory.childName(), aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetDirectoryHandle(request, std::move(onResolve),
+                                      std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::GetFileHandle(
+    RefPtr<FileSystemManager>& aManager, const FileSystemChildMetadata& aFile,
+    bool aCreate,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aFile.parentId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("GetFileHandle"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  if (!IsValidName(aFile.childName())) {
+    aPromise->MaybeRejectWithTypeError("Invalid filename");
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetHandleRequest(aFile, aCreate),
+       onResolve = SelectResolveCallback<FileSystemGetHandleResponse,
+                                         RefPtr<FileSystemFileHandle>>(
+           aPromise, aFile.childName(), aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetFileHandle(request, std::move(onResolve),
+                                 std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::GetAccessHandle(
+    RefPtr<FileSystemManager>& aManager, const FileSystemEntryMetadata& aFile,
+    const RefPtr<Promise>& aPromise, ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(aPromise);
+  LOG(("GetAccessHandle %s", NS_ConvertUTF16toUTF8(aFile.entryName()).get()));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetAccessHandleRequest(aFile.entryId()),
+       onResolve = SelectResolveCallback<FileSystemGetAccessHandleResponse,
+                                         RefPtr<FileSystemSyncAccessHandle>>(
+           aPromise, aFile, aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetAccessHandle(request, std::move(onResolve),
+                                   std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::GetWritable(RefPtr<FileSystemManager>& aManager,
+                                           const FileSystemEntryMetadata& aFile,
+                                           bool aKeepData,
+                                           const RefPtr<Promise>& aPromise,
+                                           ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(aPromise);
+  LOG(("GetWritable %s keep %d", NS_ConvertUTF16toUTF8(aFile.entryName()).get(),
+       aKeepData));
+
+  // XXX This should be removed once bug 1798513 is fixed.
+  if (!StaticPrefs::dom_fs_writable_file_stream_enabled()) {
+    aError.Throw(NS_ERROR_NOT_IMPLEMENTED);
+    return;
+  }
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetWritableRequest(aFile.entryId(), aKeepData),
+       onResolve =
+           SelectResolveCallback<FileSystemGetWritableFileStreamResponse,
+                                 RefPtr<FileSystemWritableFileStream>>(
+               aPromise, aFile, aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetWritable(request, std::move(onResolve),
+                               std::move(onReject));
+      },
+      [promise = aPromise](const auto&) {
+        promise->MaybeRejectWithUnknownError("Could not create actor");
+      });
+}
+
+void FileSystemRequestHandler::GetFile(
+    RefPtr<FileSystemManager>& aManager, const FileSystemEntryMetadata& aFile,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aFile.entryId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("GetFile %s", NS_ConvertUTF16toUTF8(aFile.entryName()).get()));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetFileRequest(aFile.entryId()),
+       onResolve =
+           SelectResolveCallback<FileSystemGetFileResponse, RefPtr<File>>(
+               aPromise, aFile.entryName(), aManager),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetFile(request, std::move(onResolve), std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::GetEntries(
+    RefPtr<FileSystemManager>& aManager, const EntryId& aDirectory,
+    PageNumber aPage,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    RefPtr<FileSystemEntryMetadataArray>& aSink, ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aDirectory.IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("GetEntries, page %u", aPage));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemGetEntriesRequest(aDirectory, aPage),
+       onResolve = SelectResolveCallback<FileSystemGetEntriesResponse, bool>(
+           aPromise, aSink),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendGetEntries(request, std::move(onResolve),
+                              std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::RemoveEntry(
+    RefPtr<FileSystemManager>& aManager, const FileSystemChildMetadata& aEntry,
+    bool aRecursive,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aEntry.parentId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("RemoveEntry"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  if (!IsValidName(aEntry.childName())) {
+    aPromise->MaybeRejectWithTypeError("Invalid name");
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemRemoveEntryRequest(aEntry, aRecursive),
+       onResolve =
+           SelectResolveCallback<FileSystemRemoveEntryResponse, void>(aPromise),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendRemoveEntry(request, std::move(onResolve),
+                               std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::MoveEntry(
+    RefPtr<FileSystemManager>& aManager, FileSystemHandle* aHandle,
+    const FileSystemEntryMetadata& aEntry,
+    const FileSystemChildMetadata& aNewEntry,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(aPromise);
+  LOG(("MoveEntry"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  // reject invalid names: empty, path separators, current & parent directories
+  if (!IsValidName(aNewEntry.childName())) {
+    aPromise->MaybeRejectWithTypeError("Invalid name");
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemMoveEntryRequest(aEntry, aNewEntry),
+       onResolve =
+           SelectResolveCallback<FileSystemMoveEntryResponse, void>(aPromise),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendMoveEntry(request, std::move(onResolve),
+                             std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::RenameEntry(
+    RefPtr<FileSystemManager>& aManager, FileSystemHandle* aHandle,
+    const FileSystemEntryMetadata& aEntry, const Name& aName,
+    RefPtr<Promise> aPromise,  // NOLINT(performance-unnecessary-value-param)
+    ErrorResult& aError) {
+  MOZ_ASSERT(!aEntry.entryId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("RenameEntry"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  // reject invalid names: empty, path separators, current & parent directories
+  if (!IsValidName(aName)) {
+    aPromise->MaybeRejectWithTypeError("Invalid name");
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemRenameEntryRequest(aEntry, aName),
+       onResolve =
+           SelectResolveCallback<FileSystemMoveEntryResponse, void>(aPromise),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendRenameEntry(request, std::move(onResolve),
+                               std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+void FileSystemRequestHandler::Resolve(
+    RefPtr<FileSystemManager>& aManager,
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
+    const FileSystemEntryPair& aEndpoints, RefPtr<Promise> aPromise,
+    ErrorResult& aError) {
+  MOZ_ASSERT(aManager);
+  MOZ_ASSERT(!aEndpoints.parentId().IsEmpty());
+  MOZ_ASSERT(!aEndpoints.childId().IsEmpty());
+  MOZ_ASSERT(aPromise);
+  LOG(("Resolve"));
+
+  if (aManager->IsShutdown()) {
+    aError.Throw(NS_ERROR_ILLEGAL_DURING_SHUTDOWN);
+    return;
+  }
+
+  aManager->BeginRequest(
+      [request = FileSystemResolveRequest(aEndpoints),
+       onResolve =
+           SelectResolveCallback<FileSystemResolveResponse, void>(aPromise),
+       onReject = GetRejectCallback(aPromise)](const auto& actor) mutable {
+        actor->SendResolve(request, std::move(onResolve), std::move(onReject));
+      },
+      BeginRequestFailureCallback(aPromise));
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemShutdownBlocker.cpp b/dom/fs/child/FileSystemShutdownBlocker.cpp
new file mode 100644
index 0000000000..bddbf18c6b
--- /dev/null
+++ b/dom/fs/child/FileSystemShutdownBlocker.cpp
@@ -0,0 +1,167 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "fs/FileSystemShutdownBlocker.h"
+
+#include "MainThreadUtils.h"
+#include "mozilla/Services.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIAsyncShutdown.h"
+#include "nsISupportsImpl.h"
+#include "nsIWritablePropertyBag2.h"
+#include "nsStringFwd.h"
+
+namespace mozilla::dom::fs {
+
+namespace {
+
+nsString CreateBlockerName() {
+  const int32_t blockerIdLength = 32;
+  nsAutoCString blockerId;
+  blockerId.SetLength(blockerIdLength);
+  NS_MakeRandomString(blockerId.BeginWriting(), blockerIdLength);
+
+  nsString blockerName = u"OPFS_"_ns;
+  blockerName.Append(NS_ConvertUTF8toUTF16(blockerId));
+
+  return blockerName;
+}
+
+class FileSystemWritableBlocker : public FileSystemShutdownBlocker {
+ public:
+  FileSystemWritableBlocker() : mName(CreateBlockerName()) {}
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIASYNCSHUTDOWNBLOCKER
+
+  NS_IMETHODIMP Block() override;
+
+  NS_IMETHODIMP Unblock() override;
+
+ protected:
+  virtual ~FileSystemWritableBlocker() = default;
+
+  Result<already_AddRefed<nsIAsyncShutdownClient>, nsresult> GetBarrier() const;
+
+ private:
+  const nsString mName;
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(FileSystemWritableBlocker,
+                            FileSystemShutdownBlocker, nsIAsyncShutdownBlocker)
+
+NS_IMETHODIMP FileSystemWritableBlocker::Block() {
+  MOZ_ASSERT(NS_IsMainThread());
+  QM_TRY_UNWRAP(nsCOMPtr<nsIAsyncShutdownClient> barrier, GetBarrier());
+
+  QM_TRY(MOZ_TO_RESULT(barrier->AddBlocker(
+      this, NS_ConvertUTF8toUTF16(nsCString(__FILE__)), __LINE__,
+      NS_ConvertUTF8toUTF16(nsCString(__func__)))));
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP FileSystemWritableBlocker::Unblock() {
+  MOZ_ASSERT(NS_IsMainThread());
+  QM_TRY_UNWRAP(nsCOMPtr<nsIAsyncShutdownClient> barrier, GetBarrier());
+
+  MOZ_ASSERT(NS_SUCCEEDED(barrier->RemoveBlocker(this)));
+
+  return NS_OK;
+}
+
+Result<already_AddRefed<nsIAsyncShutdownClient>, nsresult>
+FileSystemWritableBlocker::GetBarrier() const {
+  nsCOMPtr<nsIAsyncShutdownService> svc = services::GetAsyncShutdownService();
+  QM_TRY(OkIf(svc), Err(NS_ERROR_FAILURE));
+
+  nsCOMPtr<nsIAsyncShutdownClient> barrier;
+  QM_TRY(MOZ_TO_RESULT(svc->GetXpcomWillShutdown(getter_AddRefs(barrier))));
+
+  return barrier.forget();
+}
+
+NS_IMETHODIMP
+FileSystemWritableBlocker::GetName(nsAString& aName) {
+  aName = mName;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FileSystemWritableBlocker::GetState(nsIPropertyBag** aBagOut) {
+  MOZ_ASSERT(aBagOut);
+
+  nsCOMPtr<nsIWritablePropertyBag2> propertyBag =
+      do_CreateInstance("@mozilla.org/hash-property-bag;1");
+
+  QM_TRY(OkIf(propertyBag), NS_ERROR_OUT_OF_MEMORY)
+
+  propertyBag.forget(aBagOut);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FileSystemWritableBlocker::BlockShutdown(
+    nsIAsyncShutdownClient* /* aBarrier */) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  return NS_OK;
+}
+
+class FileSystemNullBlocker : public FileSystemShutdownBlocker {
+ public:
+  NS_IMETHODIMP Block() override { return NS_OK; }
+
+  NS_IMETHODIMP Unblock() override { return NS_OK; }
+
+ protected:
+  virtual ~FileSystemNullBlocker() = default;
+};
+
+}  // namespace
+
+/* static */
+already_AddRefed<FileSystemShutdownBlocker>
+FileSystemShutdownBlocker::CreateForWritable() {
+// The shutdown blocker watches for xpcom-will-shutdown which is not fired
+// during content process shutdown in release builds.
+#ifdef DEBUG
+  if (NS_IsMainThread()) {
+    RefPtr<FileSystemShutdownBlocker> shutdownBlocker =
+        new FileSystemWritableBlocker();
+
+    return shutdownBlocker.forget();
+  }
+#endif
+
+  RefPtr<FileSystemShutdownBlocker> shutdownBlocker =
+      new FileSystemNullBlocker();
+
+  return shutdownBlocker.forget();
+}
+
+NS_IMPL_ISUPPORTS(FileSystemShutdownBlocker, nsIAsyncShutdownBlocker)
+
+/* nsIAsyncShutdownBlocker methods */
+NS_IMETHODIMP
+FileSystemShutdownBlocker::GetName(nsAString& /* aName */) { return NS_OK; }
+
+NS_IMETHODIMP
+FileSystemShutdownBlocker::GetState(nsIPropertyBag** /* aBagOut */) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FileSystemShutdownBlocker::BlockShutdown(
+    nsIAsyncShutdownClient* /* aBarrier */) {
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemThreadSafeStreamOwner.cpp b/dom/fs/child/FileSystemThreadSafeStreamOwner.cpp
new file mode 100644
index 0000000000..2b2d2913d9
--- /dev/null
+++ b/dom/fs/child/FileSystemThreadSafeStreamOwner.cpp
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "fs/FileSystemThreadSafeStreamOwner.h"
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/FileSystemLog.h"
+#include "mozilla/dom/FileSystemWritableFileStream.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "nsIOutputStream.h"
+#include "nsIRandomAccessStream.h"
+
+namespace mozilla::dom::fs {
+
+namespace {
+
+nsresult TruncFile(nsCOMPtr<nsIRandomAccessStream>& aStream, int64_t aEOF) {
+  int64_t offset = 0;
+  QM_TRY(MOZ_TO_RESULT(aStream->Tell(&offset)));
+
+  QM_TRY(MOZ_TO_RESULT(aStream->Seek(nsISeekableStream::NS_SEEK_SET, aEOF)));
+
+  QM_TRY(MOZ_TO_RESULT(aStream->SetEOF()));
+
+  QM_TRY(MOZ_TO_RESULT(aStream->Seek(nsISeekableStream::NS_SEEK_END, 0)));
+
+  // Restore original offset
+  QM_TRY(MOZ_TO_RESULT(aStream->Seek(nsISeekableStream::NS_SEEK_SET, offset)));
+
+  return NS_OK;
+}
+
+}  // namespace
+
+FileSystemThreadSafeStreamOwner::FileSystemThreadSafeStreamOwner(
+    FileSystemWritableFileStream* aWritableFileStream,
+    nsCOMPtr<nsIRandomAccessStream>&& aStream)
+    :
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+      mWritableFileStream(aWritableFileStream),
+#endif
+      mStream(std::forward<nsCOMPtr<nsIRandomAccessStream>>(aStream)),
+      mClosed(false) {
+  MOZ_ASSERT(mWritableFileStream);
+}
+
+nsresult FileSystemThreadSafeStreamOwner::Truncate(uint64_t aSize) {
+  MOZ_DIAGNOSTIC_ASSERT(mWritableFileStream->IsCommandActive());
+
+  if (mClosed) {  // Multiple closes can end up in a queue
+    return NS_ERROR_DOM_INVALID_STATE_ERR;
+  }
+
+  int64_t where = 0;
+  QM_TRY(MOZ_TO_RESULT(mStream->Tell(&where)));
+
+  // Truncate filehandle (can extend with 0's)
+  LOG(("%p: Truncate to %" PRIu64, this, aSize));
+  QM_TRY(MOZ_TO_RESULT(TruncFile(mStream, aSize)));
+
+  // Per non-normative text in the spec (2.5.3) we should adjust
+  // the cursor position to be within the new file size
+  if (static_cast<uint64_t>(where) > aSize) {
+    QM_TRY(MOZ_TO_RESULT(mStream->Seek(nsISeekableStream::NS_SEEK_END, 0)));
+  }
+
+  return NS_OK;
+}
+
+nsresult FileSystemThreadSafeStreamOwner::Seek(uint64_t aPosition) {
+  MOZ_DIAGNOSTIC_ASSERT(mWritableFileStream->IsCommandActive());
+
+  if (mClosed) {  // Multiple closes can end up in a queue
+    return NS_ERROR_DOM_INVALID_STATE_ERR;
+  }
+
+  const auto checkedPosition = CheckedInt<int64_t>(aPosition);
+  if (!checkedPosition.isValid()) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return mStream->Seek(nsISeekableStream::NS_SEEK_SET, checkedPosition.value());
+}
+
+void FileSystemThreadSafeStreamOwner::Close() {
+  if (mClosed) {  // Multiple closes can end up in a queue
+    return;
+  }
+
+  mClosed = true;
+  mStream->OutputStream()->Close();
+}
+
+nsCOMPtr<nsIOutputStream> FileSystemThreadSafeStreamOwner::OutputStream() {
+  MOZ_DIAGNOSTIC_ASSERT(mWritableFileStream->IsCommandActive());
+
+  return mStream->OutputStream();
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/child/FileSystemWritableFileStreamChild.cpp b/dom/fs/child/FileSystemWritableFileStreamChild.cpp
new file mode 100644
index 0000000000..862e8f345e
--- /dev/null
+++ b/dom/fs/child/FileSystemWritableFileStreamChild.cpp
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileSystemWritableFileStreamChild.h"
+
+#include "mozilla/dom/FileSystemLog.h"
+#include "mozilla/dom/FileSystemWritableFileStream.h"
+
+namespace mozilla::dom {
+
+FileSystemWritableFileStreamChild::FileSystemWritableFileStreamChild()
+    : mStream(nullptr) {
+  LOG(("Created new WritableFileStreamChild %p", this));
+}
+
+FileSystemWritableFileStreamChild::~FileSystemWritableFileStreamChild() =
+    default;
+
+void FileSystemWritableFileStreamChild::SetStream(
+    FileSystemWritableFileStream* aStream) {
+  MOZ_ASSERT(aStream);
+  MOZ_ASSERT(!mStream);
+
+  mStream = aStream;
+}
+
+void FileSystemWritableFileStreamChild::ActorDestroy(ActorDestroyReason aWhy) {
+  LOG(("Destroy WritableFileStreamChild %p", this));
+
+  if (mStream) {
+    mStream->ClearActor();
+    mStream = nullptr;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/fs/child/FileSystemWritableFileStreamChild.h b/dom/fs/child/FileSystemWritableFileStreamChild.h
new file mode 100644
index 0000000000..9728fc4c78
--- /dev/null
+++ b/dom/fs/child/FileSystemWritableFileStreamChild.h
@@ -0,0 +1,42 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_CHILD_FILESYSTEMWRITABLEFILESTREAM_H_
+#define DOM_FS_CHILD_FILESYSTEMWRITABLEFILESTREAM_H_
+
+#include "mozilla/dom/PFileSystemWritableFileStreamChild.h"
+
+namespace mozilla::dom {
+
+class FileSystemWritableFileStream;
+
+class FileSystemWritableFileStreamChild
+    : public PFileSystemWritableFileStreamChild {
+ public:
+  FileSystemWritableFileStreamChild();
+
+  NS_INLINE_DECL_REFCOUNTING(FileSystemWritableFileStreamChild, override)
+
+  FileSystemWritableFileStream* MutableWritableFileStreamPtr() const {
+    MOZ_ASSERT(mStream);
+    return mStream;
+  }
+
+  void SetStream(FileSystemWritableFileStream* aStream);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+ private:
+  virtual ~FileSystemWritableFileStreamChild();
+
+  // Use a weak ref so actor does not hold DOM object alive past content use.
+  // The weak reference is cleared in FileSystemWritableFileStream::LastRelease.
+  FileSystemWritableFileStream* MOZ_NON_OWNING_REF mStream;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // DOM_FS_CHILD_FILESYSTEMWRITABLEFILESTREAM_H_
diff --git a/dom/fs/child/moz.build b/dom/fs/child/moz.build
new file mode 100644
index 0000000000..e52cb6b206
--- /dev/null
+++ b/dom/fs/child/moz.build
@@ -0,0 +1,35 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+EXPORTS.mozilla.dom += [
+    "FileSystemAccessHandleChild.h",
+    "FileSystemAccessHandleControlChild.h",
+    "FileSystemManagerChild.h",
+    "FileSystemWritableFileStreamChild.h",
+]
+
+UNIFIED_SOURCES += [
+    "FileSystemAccessHandleChild.cpp",
+    "FileSystemAccessHandleControlChild.cpp",
+    "FileSystemAsyncCopy.cpp",
+    "FileSystemBackgroundRequestHandler.cpp",
+    "FileSystemChildFactory.cpp",
+    "FileSystemDirectoryIteratorFactory.cpp",
+    "FileSystemManagerChild.cpp",
+    "FileSystemRequestHandler.cpp",
+    "FileSystemShutdownBlocker.cpp",
+    "FileSystemThreadSafeStreamOwner.cpp",
+    "FileSystemWritableFileStreamChild.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/fs/include",
+    "/netwerk/base",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")