net: Implement canceling of all async operations in FileStream.

net/base/file_stream_posix.cc

Index: net/base/file_stream_posix.cc
===================================================================
--- net/base/file_stream_posix.cc	(revision 145483)
+++ net/base/file_stream_posix.cc	(working copy)
@@ -20,12 +20,12 @@
 #include "base/eintr_wrapper.h"
 #include "base/file_path.h"
 #include "base/logging.h"
+#include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/string_util.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/worker_pool.h"
-#include "base/synchronization/waitable_event.h"
 #include "net/base/file_stream_metrics.h"
 #include "net/base/file_stream_net_log_parameters.h"
 #include "net/base/io_buffer.h"
@@ -49,320 +49,486 @@
                FROM_CURRENT == SEEK_CUR &&
                FROM_END     == SEEK_END, whence_matches_system);
 
-namespace {
+class FileStreamPosix::AsyncContext {
+ public:
+  explicit AsyncContext(const BoundNetLog& bound_net_log);
+  AsyncContext(base::PlatformFile file, const BoundNetLog& bound_net_log);
 
-int RecordAndMapError(int error,
-                      FileErrorSource source,
-                      bool record_uma,
-                      const net::BoundNetLog& bound_net_log) {
-  net::Error net_error = MapSystemError(error);
+  // Destroys the context. It can be deleted in the method or deletion can be
+  // deferred to WorkerPool if some asynchronous operation is now in progress
+  // or if auto-closing is needed.
+  void Destroy();
 
-  bound_net_log.AddEvent(
-      net::NetLog::TYPE_FILE_STREAM_ERROR,
-      base::Bind(&NetLogFileStreamErrorCallback,
-                 source, error, net_error));
+  bool record_uma() { return record_uma_; }
+  void set_record_uma(bool value) { record_uma_ = value; }
+  base::PlatformFile file() { return file_; }
+  bool auto_closed() { return auto_closed_; }
+  void set_auto_closed(bool value) { auto_closed_ = value; }
+  bool async_in_progress() { return async_in_progress_; }
 
-  RecordFileError(error, source, record_uma);
+  int RecordAndMapError(int error, FileErrorSource source);
 
-  return net_error;
+  // Sync and async versions of all operations
+  void OpenAsync(const FilePath& path,
+                 int open_flags,
+                 const CompletionCallback& callback);
+  int OpenSync(const FilePath& path, int open_flags);
+
+  void CloseAsync(const CompletionCallback& callback);
+  void CloseSync();
+
+  void SeekAsync(Whence whence,
+                 int64 offset,
+                 const Int64CompletionCallback& callback);
+  int64 SeekSync(Whence whence, int64 offset);
+
+  void ReadAsync(IOBuffer* buf,
+                 int buf_len,
+                 const CompletionCallback& callback);
+  int ReadSync(char* buf, int buf_len);
+
+  void WriteAsync(IOBuffer* in_buf,
+                  int buf_len,
+                  const CompletionCallback& callback);
+  int WriteSync(const char* in_buf, int buf_len);
+
+ private:
+  // Map system error into network error code and log it with |bound_net_log_|.
+  // Method should be called with |net_log_lock_| locked.
+  int MapAndLogError(int error, FileErrorSource source);
+
+  // Opens a file with some network logging.
+  // The result code is written to |result|.
+  void OpenFileImpl(const FilePath& path, int open_flags, int* result);
+
+  // Closes a file with some network logging.
+  void CloseFileImpl();
+
+  // Adjusts the position from where the data is read.
+  void SeekFileImpl(Whence whence, int64 offset, int64* result);
+
+  // ReadFile() is a simple wrapper around read() that handles EINTR signals
+  // and calls RecordAndMapError() to map errno to net error codes.
+  void ReadFileImpl(scoped_refptr<IOBuffer> buf, int buf_len, int* result);
+
+  // WriteFile() is a simple wrapper around write() that handles EINTR signals
+  // and calls MapSystemError() to map errno to net error codes. It tries
+  // to write to completion.
+  void WriteFileImpl(scoped_refptr<IOBuffer> buf, int buf_len, int* result);
+
+  // Called when asynchronous Close(), Open(), Read(), Write() or Seek()
+  // is completed. |result| contains the result or a network error code.
+  template <typename R>
+  void OnAsyncCompleted(const base::Callback<void(R)>& callback, R* result);
+
+  // Delete the context with asynchronous closing if necessary.
+  void DeleteAbandoned();
+
+  base::PlatformFile file_;
+  bool auto_closed_;
+  bool record_uma_;
+  bool async_in_progress_;
+  bool destroyed_;
+  base::Lock net_log_lock_;
+  BoundNetLog bound_net_log_;
+};
+
+
+FileStreamPosix::AsyncContext::AsyncContext(const BoundNetLog& bound_net_log)
+  : file_(base::kInvalidPlatformFileValue),
+    auto_closed_(true),
+    record_uma_(false),
+    async_in_progress_(false),
+    destroyed_(false),
+    bound_net_log_(bound_net_log) {
 }
 
-// Opens a file with some network logging.
-// The opened file and the result code are written to |file| and |result|.
-void OpenFile(const FilePath& path,
-              int open_flags,
-              bool record_uma,
-              base::PlatformFile* file,
-              int* result,
-              const net::BoundNetLog& bound_net_log) {
-  std::string file_name = path.AsUTF8Unsafe();
-  bound_net_log.BeginEvent(
-      net::NetLog::TYPE_FILE_STREAM_OPEN,
-      NetLog::StringCallback("file_name", &file_name));
+FileStreamPosix::AsyncContext::AsyncContext(base::PlatformFile file,
+                                            const BoundNetLog& bound_net_log)
+  : file_(file),
+    auto_closed_(false),
+    record_uma_(false),
+    async_in_progress_(false),
+    destroyed_(false),
+    bound_net_log_(bound_net_log) {
+}
 
-  *result = OK;
-  *file = base::CreatePlatformFile(path, open_flags, NULL, NULL);
-  if (*file == base::kInvalidPlatformFileValue) {
-    bound_net_log.EndEvent(net::NetLog::TYPE_FILE_STREAM_OPEN);
-    *result = RecordAndMapError(errno, FILE_ERROR_SOURCE_OPEN, record_uma,
-                                bound_net_log);
+void FileStreamPosix::AsyncContext::Destroy() {
+  {
+    // By locking we don't allow any operation with |bound_net_log_| to be
+    // in progress while this method is executed. Attempt to do something
+    // with |bound_net_log_| will be done either before this method or after
+    // we switch |context_->destroyed_| which will prohibit any operation on
+    // |bound_net_log_|.
+    base::AutoLock locked(net_log_lock_);
+    destroyed_ = true;
   }
+  if (!async_in_progress_)
+    DeleteAbandoned();
 }
 
-// Opens a file using OpenFile() and then signals the completion.
-void OpenFileAndSignal(const FilePath& path,
-                       int open_flags,
-                       bool record_uma,
-                       base::PlatformFile* file,
-                       int* result,
-                       base::WaitableEvent* on_io_complete,
-                       const net::BoundNetLog& bound_net_log) {
-  OpenFile(path, open_flags, record_uma, file, result, bound_net_log);
-  on_io_complete->Signal();
+int FileStreamPosix::AsyncContext::RecordAndMapError(int error,
+                                                     FileErrorSource source) {
+  int net_error;
+  {
+    base::AutoLock locked(net_log_lock_);
+    net_error = MapAndLogError(error, source);
+  }
+  RecordFileError(error, source, record_uma_);
+  return net_error;
 }
 
-// Closes a file with some network logging.
-void CloseFile(base::PlatformFile file,
-               const net::BoundNetLog& bound_net_log) {
-  bound_net_log.AddEvent(net::NetLog::TYPE_FILE_STREAM_CLOSE);
-  if (file == base::kInvalidPlatformFileValue)
-    return;
+void FileStreamPosix::AsyncContext::OpenAsync(
+    const FilePath& path,
+    int open_flags,
+    const CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
 
-  if (!base::ClosePlatformFile(file))
-    NOTREACHED();
-  bound_net_log.EndEvent(net::NetLog::TYPE_FILE_STREAM_OPEN);
+  int* result = new int(OK);
+  const bool posted = base::WorkerPool::PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AsyncContext::OpenFileImpl, base::Unretained(this),
+                 path, open_flags, result),
+      base::Bind(&AsyncContext::OnAsyncCompleted<int>,
+                 base::Unretained(this),
+                 callback, base::Owned(result)),
+      true /* task_is_slow */);
+  DCHECK(posted);
+
+  async_in_progress_ = true;
 }
 
-// Closes a file with CloseFile() and signals the completion.
-void CloseFileAndSignal(base::PlatformFile* file,
-                        base::WaitableEvent* on_io_complete,
-                        const net::BoundNetLog& bound_net_log) {
-  CloseFile(*file, bound_net_log);
-  *file = base::kInvalidPlatformFileValue;
-  on_io_complete->Signal();
+int FileStreamPosix::AsyncContext::OpenSync(const FilePath& path,
+                                            int open_flags) {
+  int result = OK;
+  OpenFileImpl(path, open_flags, &result);
+  return result;
 }
 
-// Adjusts the position from where the data is read.
-void SeekFile(base::PlatformFile file,
-              Whence whence,
-              int64 offset,
-              int64* result,
-              bool record_uma,
-              const net::BoundNetLog& bound_net_log) {
-  off_t res = lseek(file, static_cast<off_t>(offset),
-                    static_cast<int>(whence));
-  if (res == static_cast<off_t>(-1)) {
-    *result = RecordAndMapError(errno,
-                                FILE_ERROR_SOURCE_SEEK,
-                                record_uma,
-                                bound_net_log);
-    return;
-  }
-  *result = res;
+void FileStreamPosix::AsyncContext::CloseAsync(
+    const CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
+
+  // Value OK will never be changed in AsyncContext::CloseFile() and is needed
+  // here just to use the same AsyncContext::OnAsyncCompleted().
+  int* result = new int(OK);
+  const bool posted = base::WorkerPool::PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AsyncContext::CloseFileImpl, base::Unretained(this)),
+      base::Bind(&AsyncContext::OnAsyncCompleted<int>,
+                 base::Unretained(this),
+                 callback, base::Owned(result)),
+      true /* task_is_slow */);
+  DCHECK(posted);
+
+  async_in_progress_ = true;
 }
 
-// Seeks a file by calling SeekSync() and signals the completion.
-void SeekFileAndSignal(base::PlatformFile file,
-                       Whence whence,
-                       int64 offset,
-                       int64* result,
-                       bool record_uma,
-                       base::WaitableEvent* on_io_complete,
-                       const net::BoundNetLog& bound_net_log) {
-  SeekFile(file, whence, offset, result, record_uma, bound_net_log);
-  on_io_complete->Signal();
+void FileStreamPosix::AsyncContext::CloseSync() {
+  DCHECK(!async_in_progress_);
+  CloseFileImpl();
 }
 
-// ReadFile() is a simple wrapper around read() that handles EINTR signals and
-// calls MapSystemError() to map errno to net error codes.
-void ReadFile(base::PlatformFile file,
-              char* buf,
-              int buf_len,
-              bool record_uma,
-              int* result,
-              const net::BoundNetLog& bound_net_log) {
-  base::ThreadRestrictions::AssertIOAllowed();
-  // read(..., 0) returns 0 to indicate end-of-file.
+void FileStreamPosix::AsyncContext::SeekAsync(
+    Whence whence,
+    int64 offset,
+    const Int64CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
 
-  // Loop in the case of getting interrupted by a signal.
-  ssize_t res = HANDLE_EINTR(read(file, buf, static_cast<size_t>(buf_len)));
-  if (res == -1) {
-    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_READ,
-                            record_uma, bound_net_log);
+  int64* result = new int64(-1);
+  const bool posted = base::WorkerPool::PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AsyncContext::SeekFileImpl, base::Unretained(this),
+                 whence, offset, result),
+      base::Bind(&AsyncContext::OnAsyncCompleted<int64>,
+                 base::Unretained(this),
+                 callback, base::Owned(result)),
+      true /* task is slow */);
+  DCHECK(posted);
+
+  async_in_progress_ = true;
+}
+
+int64 FileStreamPosix::AsyncContext::SeekSync(Whence whence, int64 offset) {
+  off_t result = -1;
+  SeekFileImpl(whence, offset, &result);
+  return result;
+}
+
+void FileStreamPosix::AsyncContext::ReadAsync(
+    IOBuffer* in_buf,
+    int buf_len,
+    const CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
+
+  int* result = new int(OK);
+  scoped_refptr<IOBuffer> buf = in_buf;
+  const bool posted = base::WorkerPool::PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AsyncContext::ReadFileImpl, base::Unretained(this),
+                 buf, buf_len, result),
+      base::Bind(&AsyncContext::OnAsyncCompleted<int>,
+                 base::Unretained(this),
+                 callback, base::Owned(result)),
+      true /* task is slow */);
+  DCHECK(posted);
+
+  async_in_progress_ = true;
+}
+
+int FileStreamPosix::AsyncContext::ReadSync(char* in_buf, int buf_len) {
+  int result = OK;
+  scoped_refptr<IOBuffer> buf = new WrappedIOBuffer(in_buf);
+  ReadFileImpl(buf, buf_len, &result);
+  return result;
+}
+
+void FileStreamPosix::AsyncContext::WriteAsync(
+    IOBuffer* in_buf,
+    int buf_len,
+    const CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
+
+  int* result = new int(OK);
+  scoped_refptr<IOBuffer> buf = in_buf;
+  const bool posted = base::WorkerPool::PostTaskAndReply(
+      FROM_HERE,
+      base::Bind(&AsyncContext::WriteFileImpl, base::Unretained(this),
+                 buf, buf_len, result),
+      base::Bind(&AsyncContext::OnAsyncCompleted<int>,
+                 base::Unretained(this),
+                 callback, base::Owned(result)),
+      true /* task is slow */);
+  DCHECK(posted);
+
+  async_in_progress_ = true;
+}
+
+int FileStreamPosix::AsyncContext::WriteSync(const char* in_buf, int buf_len) {
+  int result = OK;
+  scoped_refptr<IOBuffer> buf = new WrappedIOBuffer(in_buf);
+  WriteFileImpl(buf, buf_len, &result);
+  return result;
+}
+
+int FileStreamPosix::AsyncContext::MapAndLogError(int error,
+                                                  FileErrorSource source) {
+  net_log_lock_.AssertAcquired();
+  // The following check is against incorrect use or bug. File descriptor
+  // shouldn't ever be closed outside of FileStream while it still tries to do
+  // something with it.
+  DCHECK(error != EBADF);
+  net::Error net_error = MapSystemError(error);
+
+  if (!destroyed_) {
+    bound_net_log_.AddEvent(
+        net::NetLog::TYPE_FILE_STREAM_ERROR,
+        base::Bind(&NetLogFileStreamErrorCallback,
+                   source, error, net_error));
   }
-  *result = res;
+
+  return net_error;
 }
 
-// Reads a file using ReadFile() and signals the completion.
-void ReadFileAndSignal(base::PlatformFile file,
-                       scoped_refptr<IOBuffer> buf,
-                       int buf_len,
-                       bool record_uma,
-                       int* result,
-                       base::WaitableEvent* on_io_complete,
-                       const net::BoundNetLog& bound_net_log) {
-  ReadFile(file, buf->data(), buf_len, record_uma, result, bound_net_log);
-  on_io_complete->Signal();
+void FileStreamPosix::AsyncContext::OpenFileImpl(const FilePath& path,
+                                                 int open_flags,
+                                                 int* result) {
+  std::string file_name = path.AsUTF8Unsafe();
+  {
+    base::AutoLock locked(net_log_lock_);
+    // Bail out quickly if operation was already canceled
+    if (destroyed_)
+      return;
+
+    bound_net_log_.BeginEvent(
+        net::NetLog::TYPE_FILE_STREAM_OPEN,
+        NetLog::StringCallback("file_name", &file_name));
+  }
+
+  *result = OK;
+  file_ = base::CreatePlatformFile(path, open_flags, NULL, NULL);
+  if (file_ == base::kInvalidPlatformFileValue) {
+    int error = errno;
+    {
+      base::AutoLock locked(net_log_lock_);
+      if (!destroyed_)
+        bound_net_log_.EndEvent(net::NetLog::TYPE_FILE_STREAM_OPEN);
+      *result = MapAndLogError(error, FILE_ERROR_SOURCE_OPEN);
+    }
+    RecordFileError(error, FILE_ERROR_SOURCE_OPEN, record_uma_);
+  }
 }
 
-// WriteFile() is a simple wrapper around write() that handles EINTR signals and
-// calls MapSystemError() to map errno to net error codes.  It tries to write to
-// completion.
-void WriteFile(base::PlatformFile file,
-               const char* buf,
-               int buf_len,
-               bool record_uma,
-               int* result,
-               const net::BoundNetLog& bound_net_log) {
+void FileStreamPosix::AsyncContext::CloseFileImpl() {
+  {
+    base::AutoLock locked(net_log_lock_);
+    if (!destroyed_)
+      bound_net_log_.AddEvent(net::NetLog::TYPE_FILE_STREAM_CLOSE);
+  }
+
+  if (file_ == base::kInvalidPlatformFileValue)
+    return;
+  if (!base::ClosePlatformFile(file_))
+    NOTREACHED();
+  file_ = base::kInvalidPlatformFileValue;
+
+  {
+    base::AutoLock locked(net_log_lock_);
+    if (!destroyed_)
+      bound_net_log_.EndEvent(net::NetLog::TYPE_FILE_STREAM_OPEN);
+  }
+}
+
+void FileStreamPosix::AsyncContext::SeekFileImpl(Whence whence,
+                                                 int64 offset,
+                                                 int64* result) {
   base::ThreadRestrictions::AssertIOAllowed();
 
-  ssize_t res = HANDLE_EINTR(write(file, buf, buf_len));
-  if (res == -1) {
-    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_WRITE, record_uma,
-                            bound_net_log);
-  }
+  // If context has been already destroyed nobody waits for operation results.
+  if (destroyed_)
+    return;
+
+  off_t res = lseek(file_, static_cast<off_t>(offset),
+                    static_cast<int>(whence));
+  if (res == static_cast<off_t>(-1))
+    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_SEEK);
   *result = res;
 }
 
-// Writes a file using WriteFile() and signals the completion.
-void WriteFileAndSignal(base::PlatformFile file,
-                        scoped_refptr<IOBuffer> buf,
-                        int buf_len,
-                        bool record_uma,
-                        int* result,
-                        base::WaitableEvent* on_io_complete,
-                        const net::BoundNetLog& bound_net_log) {
-  WriteFile(file, buf->data(), buf_len, record_uma, result, bound_net_log);
-  on_io_complete->Signal();
+void FileStreamPosix::AsyncContext::ReadFileImpl(scoped_refptr<IOBuffer> buf,
+                                                 int buf_len,
+                                                 int* result) {
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  // If context has been already destroyed nobody waits for operation results.
+  if (destroyed_)
+    return;
+
+  // Loop in the case of getting interrupted by a signal.
+  ssize_t res = HANDLE_EINTR(read(file_, buf->data(),
+                                  static_cast<size_t>(buf_len)));
+  if (res == -1)
+    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_READ);
+  *result = res;
 }
 
-// FlushFile() is a simple wrapper around fsync() that handles EINTR signals and
-// calls MapSystemError() to map errno to net error codes.  It tries to flush to
-// completion.
-int FlushFile(base::PlatformFile file,
-              bool record_uma,
-              const net::BoundNetLog& bound_net_log) {
+void FileStreamPosix::AsyncContext::WriteFileImpl(scoped_refptr<IOBuffer> buf,
+                                                  int buf_len,
+                                                  int* result) {
   base::ThreadRestrictions::AssertIOAllowed();
-  ssize_t res = HANDLE_EINTR(fsync(file));
-  if (res == -1) {
-    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_FLUSH, record_uma,
-                            bound_net_log);
-  }
-  return res;
+
+  // If context has been already destroyed nobody waits for operation results.
+  if (destroyed_)
+    return;
+
+  ssize_t res = HANDLE_EINTR(write(file_, buf->data(), buf_len));
+  if (res == -1)
+    res = RecordAndMapError(errno, FILE_ERROR_SOURCE_WRITE);
+  *result = res;
 }
 
-// Called when Read(), Write() or Seek() is completed.
-// |result| contains the result or a network error code.
 template <typename R>
-void OnIOComplete(const base::WeakPtr<FileStreamPosix>& stream,
-                  const base::Callback<void(R)>& callback,
-                  R* result) {
-  if (!stream.get())
-    return;
+void FileStreamPosix::AsyncContext::OnAsyncCompleted(
+    const base::Callback<void(R)>& callback,
+    R* result) {
+  if (destroyed_) {
+    DeleteAbandoned();
+  } else {
+    // Reset this before Run() as Run() may issue a new async operation.
+    async_in_progress_ = false;
+    callback.Run(*result);
+  }
+}
 
-  // Reset this before Run() as Run() may issue a new async operation.
-  stream->ResetOnIOComplete();
-  callback.Run(*result);
+void FileStreamPosix::AsyncContext::DeleteAbandoned() {
+  if (auto_closed_ && file_ != base::kInvalidPlatformFileValue) {
+    const bool posted = base::WorkerPool::PostTask(
+        FROM_HERE,
+        // Context should be deleted after closing, thus Owned().
+        base::Bind(&AsyncContext::CloseFileImpl, base::Owned(this)),
+        true /* task_is_slow */);
+    DCHECK(posted);
+  } else {
+    delete this;
+  }
 }
 
-}  // namespace
 
 // FileStreamPosix ------------------------------------------------------------
 
 FileStreamPosix::FileStreamPosix(net::NetLog* net_log)
-    : file_(base::kInvalidPlatformFileValue),
+    : context_(NULL),
       open_flags_(0),
-      auto_closed_(true),
-      record_uma_(false),
       bound_net_log_(net::BoundNetLog::Make(net_log,
-                                            net::NetLog::SOURCE_FILESTREAM)),
-      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+                                            net::NetLog::SOURCE_FILESTREAM)) {
+  context_ = new AsyncContext(bound_net_log_);
+
   bound_net_log_.BeginEvent(net::NetLog::TYPE_FILE_STREAM_ALIVE);
 }
 
-FileStreamPosix::FileStreamPosix(
-    base::PlatformFile file, int flags, net::NetLog* net_log)
-    : file_(file),
+FileStreamPosix::FileStreamPosix(base::PlatformFile file,
+                                 int flags,
+                                 net::NetLog* net_log)
+    : context_(NULL),
       open_flags_(flags),
-      auto_closed_(false),
-      record_uma_(false),
       bound_net_log_(net::BoundNetLog::Make(net_log,
-                                            net::NetLog::SOURCE_FILESTREAM)),
-      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+                                            net::NetLog::SOURCE_FILESTREAM)) {
+  context_ = new AsyncContext(file, bound_net_log_);
+
   bound_net_log_.BeginEvent(net::NetLog::TYPE_FILE_STREAM_ALIVE);
 }
 
 FileStreamPosix::~FileStreamPosix() {
-  if (open_flags_ & base::PLATFORM_FILE_ASYNC) {
-    // Block until the last open/close/read/write operation is complete.
-    // TODO(satorux): Ideally we should not block. crbug.com/115067
-    WaitForIOCompletion();
-  }
+  if (IsOpen() && context_->auto_closed() && !is_async())
+    CloseSync();
+  context_->Destroy();
 
-  if (auto_closed_) {
-    if (open_flags_ & base::PLATFORM_FILE_ASYNC) {
-      // Close the file in the background.
-      if (IsOpen()) {
-        const bool posted = base::WorkerPool::PostTask(
-            FROM_HERE,
-            base::Bind(&CloseFile, file_, bound_net_log_),
-            true /* task_is_slow */);
-        DCHECK(posted);
-      }
-    } else {
-      CloseSync();
-    }
-  }
-
   bound_net_log_.EndEvent(net::NetLog::TYPE_FILE_STREAM_ALIVE);
 }
 
 void FileStreamPosix::Close(const CompletionCallback& callback) {
-  DCHECK(open_flags_ & base::PLATFORM_FILE_ASYNC);
-
-  DCHECK(!weak_ptr_factory_.HasWeakPtrs());
-  DCHECK(!on_io_complete_.get());
-  on_io_complete_.reset(new base::WaitableEvent(
-      false  /* manual_reset */, false  /* initially_signaled */));
-
-  // Passing &file_ to a thread pool looks unsafe but it's safe here as the
-  // destructor ensures that the close operation is complete with
-  // WaitForIOCompletion(). See also the destructor.
-  const bool posted = base::WorkerPool::PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&CloseFileAndSignal, &file_, on_io_complete_.get(),
-                 bound_net_log_),
-      base::Bind(&FileStreamPosix::OnClosed,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 callback),
-      true /* task_is_slow */);
-
-  DCHECK(posted);
+  DCHECK(is_async());
+  context_->CloseAsync(callback);
 }
 
 void FileStreamPosix::CloseSync() {
+  // CloseSync() should be called on the correct thread even if it eventually
+  // ends up inside CloseAndCancelAsync().
+  base::ThreadRestrictions::AssertIOAllowed();
+
   // TODO(satorux): Replace the following async stuff with a
-  // DCHECK(open_flags & ASYNC) once once all async clients are migrated to
+  // DCHECK(open_flags & ASYNC) once all async clients are migrated to
   // use Close(). crbug.com/114783
+  if (context_->async_in_progress())
+    CloseAndCancelAsync();
+  else
+    context_->CloseSync();
+}
 
-  // Abort any existing asynchronous operations.
-  weak_ptr_factory_.InvalidateWeakPtrs();
-  // Block until the last open/read/write operation is complete.
-  // TODO(satorux): Ideally we should not block. crbug.com/115067
-  WaitForIOCompletion();
+void FileStreamPosix::CloseAndCancelAsync() {
+  if (!IsOpen())
+    return;
 
-  CloseFile(file_, bound_net_log_);
-  file_ = base::kInvalidPlatformFileValue;
+  DCHECK(is_async());
+
+  AsyncContext* old_ctx = context_;
+  context_ = new AsyncContext(bound_net_log_);
+  context_->set_record_uma(old_ctx->record_uma());
+  old_ctx->set_auto_closed(true);
+  old_ctx->Destroy();
 }
 
-int FileStreamPosix::Open(const FilePath& path, int open_flags,
-                     const CompletionCallback& callback) {
+int FileStreamPosix::Open(const FilePath& path,
+                          int open_flags,
+                          const CompletionCallback& callback) {
   if (IsOpen()) {
     DLOG(FATAL) << "File is already open!";
     return ERR_UNEXPECTED;
   }
 
   open_flags_ = open_flags;
-  DCHECK(open_flags_ & base::PLATFORM_FILE_ASYNC);
-
-  DCHECK(!weak_ptr_factory_.HasWeakPtrs());
-  DCHECK(!on_io_complete_.get());
-  on_io_complete_.reset(new base::WaitableEvent(
-      false  /* manual_reset */, false  /* initially_signaled */));
-
-  // Passing &file_ to a thread pool looks unsafe but it's safe here as the
-  // destructor ensures that the open operation is complete with
-  // WaitForIOCompletion(). See also the destructor.
-  int* result = new int(OK);
-  const bool posted = base::WorkerPool::PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&OpenFileAndSignal,
-                 path, open_flags, record_uma_, &file_, result,
-                 on_io_complete_.get(), bound_net_log_),
-      base::Bind(&OnIOComplete<int>, weak_ptr_factory_.GetWeakPtr(),
-                 callback, base::Owned(result)),
-      true /* task_is_slow */);
-  DCHECK(posted);
+  DCHECK(is_async());
+  context_->OpenAsync(path, open_flags, callback);
   return ERR_IO_PENDING;
 }
 
@@ -373,59 +539,36 @@
   }
 
   open_flags_ = open_flags;
-  // TODO(satorux): Put a DCHECK once once all async clients are migrated
+  // TODO(satorux): Put a DCHECK once all async clients are migrated
   // to use Open(). crbug.com/114783
   //
-  // DCHECK(!(open_flags_ & base::PLATFORM_FILE_ASYNC));
-
-  int result = OK;
-  OpenFile(path, open_flags_, record_uma_, &file_, &result, bound_net_log_);
-  return result;
+  // DCHECK(!is_async());
+  return context_->OpenSync(path, open_flags_);
 }
 
 bool FileStreamPosix::IsOpen() const {
-  return file_ != base::kInvalidPlatformFileValue;
+  return context_->file() != base::kInvalidPlatformFileValue;
 }
 
-int FileStreamPosix::Seek(Whence whence, int64 offset,
+int FileStreamPosix::Seek(Whence whence,
+                          int64 offset,
                           const Int64CompletionCallback& callback) {
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
-  // Make sure we're async and we have no other in-flight async operations.
-  DCHECK(open_flags_ & base::PLATFORM_FILE_ASYNC);
-  DCHECK(!weak_ptr_factory_.HasWeakPtrs());
-  DCHECK(!on_io_complete_.get());
-
-  on_io_complete_.reset(new base::WaitableEvent(
-      false  /* manual_reset */, false  /* initially_signaled */));
-
-  int64* result = new int64(-1);
-  const bool posted = base::WorkerPool::PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&SeekFileAndSignal, file_, whence, offset, result,
-                 record_uma_, on_io_complete_.get(), bound_net_log_),
-      base::Bind(&OnIOComplete<int64>,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 callback, base::Owned(result)),
-      true /* task is slow */);
-  DCHECK(posted);
+  // Make sure we're async.
+  DCHECK(is_async());
+  context_->SeekAsync(whence, offset, callback);
   return ERR_IO_PENDING;
 }
 
 int64 FileStreamPosix::SeekSync(Whence whence, int64 offset) {
-  base::ThreadRestrictions::AssertIOAllowed();
-
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
   // If we're in async, make sure we don't have a request in flight.
-  DCHECK(!(open_flags_ & base::PLATFORM_FILE_ASYNC) ||
-         !on_io_complete_.get());
-
-  off_t result = -1;
-  SeekFile(file_, whence, offset, &result, record_uma_, bound_net_log_);
-  return result;
+  DCHECK(!is_async() || !context_->async_in_progress());
+  return context_->SeekSync(whence, offset);
 }
 
 int64 FileStreamPosix::Available() {
@@ -439,12 +582,8 @@
     return cur_pos;
 
   struct stat info;
-  if (fstat(file_, &info) != 0) {
-    return RecordAndMapError(errno,
-                             FILE_ERROR_SOURCE_GET_SIZE,
-                             record_uma_,
-                             bound_net_log_);
-  }
+  if (fstat(context_->file(), &info) != 0)
+    return context_->RecordAndMapError(errno, FILE_ERROR_SOURCE_GET_SIZE);
 
   int64 size = static_cast<int64>(info.st_size);
   DCHECK_GT(size, cur_pos);
@@ -452,34 +591,18 @@
   return size - cur_pos;
 }
 
-int FileStreamPosix::Read(
-    IOBuffer* in_buf, int buf_len, const CompletionCallback& callback) {
+int FileStreamPosix::Read(IOBuffer* buf,
+                          int buf_len,
+                          const CompletionCallback& callback) {
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
   // read(..., 0) will return 0, which indicates end-of-file.
   DCHECK_GT(buf_len, 0);
   DCHECK(open_flags_ & base::PLATFORM_FILE_READ);
-  DCHECK(open_flags_ & base::PLATFORM_FILE_ASYNC);
+  DCHECK(is_async());
 
-  // Make sure we don't have a request in flight.
-  DCHECK(!weak_ptr_factory_.HasWeakPtrs());
-  DCHECK(!on_io_complete_.get());
-
-  on_io_complete_.reset(new base::WaitableEvent(
-      false  /* manual_reset */, false  /* initially_signaled */));
-
-  int* result = new int(OK);
-  scoped_refptr<IOBuffer> buf = in_buf;
-  const bool posted = base::WorkerPool::PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&ReadFileAndSignal, file_, buf, buf_len,
-                 record_uma_, result, on_io_complete_.get(), bound_net_log_),
-      base::Bind(&OnIOComplete<int>,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 callback, base::Owned(result)),
-      true /* task is slow */);
-  DCHECK(posted);
+  context_->ReadAsync(buf, buf_len, callback);
   return ERR_IO_PENDING;
 }
 
@@ -487,14 +610,12 @@
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
-  DCHECK(!(open_flags_ & base::PLATFORM_FILE_ASYNC));
+  DCHECK(!is_async());
   // read(..., 0) will return 0, which indicates end-of-file.
   DCHECK_GT(buf_len, 0);
   DCHECK(open_flags_ & base::PLATFORM_FILE_READ);
 
-  int result = OK;
-  ReadFile(file_, buf, buf_len, record_uma_, &result, bound_net_log_);
-  return result;
+  return context_->ReadSync(buf, buf_len);
 }
 
 int FileStreamPosix::ReadUntilComplete(char *buf, int buf_len) {
@@ -518,49 +639,31 @@
   return bytes_total;
 }
 
-int FileStreamPosix::Write(
-    IOBuffer* in_buf, int buf_len, const CompletionCallback& callback) {
+int FileStreamPosix::Write(IOBuffer* buf,
+                           int buf_len,
+                           const CompletionCallback& callback) {
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
-  DCHECK(open_flags_ & base::PLATFORM_FILE_ASYNC);
+  DCHECK(is_async());
   DCHECK(open_flags_ & base::PLATFORM_FILE_WRITE);
   // write(..., 0) will return 0, which indicates end-of-file.
   DCHECK_GT(buf_len, 0);
 
-  // Make sure we don't have a request in flight.
-  DCHECK(!weak_ptr_factory_.HasWeakPtrs());
-  DCHECK(!on_io_complete_.get());
-  on_io_complete_.reset(new base::WaitableEvent(
-      false  /* manual_reset */, false  /* initially_signaled */));
-
-  int* result = new int(OK);
-  scoped_refptr<IOBuffer> buf = in_buf;
-  const bool posted = base::WorkerPool::PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&WriteFileAndSignal, file_, buf, buf_len,
-                 record_uma_, result, on_io_complete_.get(), bound_net_log_),
-      base::Bind(&OnIOComplete<int>,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 callback, base::Owned(result)),
-      true /* task is slow */);
-  DCHECK(posted);
+  context_->WriteAsync(buf, buf_len, callback);
   return ERR_IO_PENDING;
 }
 
-int FileStreamPosix::WriteSync(
-    const char* buf, int buf_len) {
+int FileStreamPosix::WriteSync(const char* buf, int buf_len) {
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
-  DCHECK(!(open_flags_ & base::PLATFORM_FILE_ASYNC));
+  DCHECK(!is_async());
   DCHECK(open_flags_ & base::PLATFORM_FILE_WRITE);
   // write(..., 0) will return 0, which indicates end-of-file.
   DCHECK_GT(buf_len, 0);
 
-  int result = OK;
-  WriteFile(file_, buf, buf_len, record_uma_, &result, bound_net_log_);
-  return result;
+  return context_->WriteSync(buf, buf_len);
 }
 
 int64 FileStreamPosix::Truncate(int64 bytes) {
@@ -578,25 +681,27 @@
     return ERR_UNEXPECTED;
 
   // And truncate the file.
-  int result = ftruncate(file_, bytes);
+  int result = ftruncate(context_->file(), bytes);
   if (result == 0)
     return seek_position;
 
-  return RecordAndMapError(errno,
-                           FILE_ERROR_SOURCE_SET_EOF,
-                           record_uma_,
-                           bound_net_log_);
+  return context_->RecordAndMapError(errno, FILE_ERROR_SOURCE_SET_EOF);
 }
 
 int FileStreamPosix::Flush() {
+  base::ThreadRestrictions::AssertIOAllowed();
+
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
-  return FlushFile(file_, record_uma_, bound_net_log_);
+  ssize_t res = HANDLE_EINTR(fsync(context_->file()));
+  if (res == -1)
+    res = context_->RecordAndMapError(errno, FILE_ERROR_SOURCE_FLUSH);
+  return res;
 }
 
 void FileStreamPosix::EnableErrorStatistics() {
-  record_uma_ = true;
+  context_->set_record_uma(true);
 }
 
 void FileStreamPosix::SetBoundNetLogSource(
@@ -620,29 +725,7 @@
 }
 
 base::PlatformFile FileStreamPosix::GetPlatformFileForTesting() {
-  return file_;
+  return context_->file();
 }
 
-void FileStreamPosix::ResetOnIOComplete() {
-  on_io_complete_.reset();
-  weak_ptr_factory_.InvalidateWeakPtrs();
-}
-
-void FileStreamPosix::OnClosed(const CompletionCallback& callback) {
-  file_ = base::kInvalidPlatformFileValue;
-
-  // Reset this before Run() as Run() may issue a new async operation.
-  ResetOnIOComplete();
-  callback.Run(OK);
-}
-
-void FileStreamPosix::WaitForIOCompletion() {
-  // http://crbug.com/115067
-  base::ThreadRestrictions::ScopedAllowWait allow_wait;
-  if (on_io_complete_.get()) {
-    on_io_complete_->Wait();
-    on_io_complete_.reset();
-  }
-}
-
 }  // namespace net