Let ImportantFileWriter Use fdatasync

base/files/file_posix.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/file.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ skipping 415 matching lines @@
   DCHECK(IsValid());
   return !CallFtruncate(file_.get(), length);
 }
 
 bool File::Flush() {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(IsValid());
   return !CallFsync(file_.get());
 }
 
+bool File::FlushData() {
+#if defined(OS_LINUX) || defined(OS_ANDROID)
+  base::ThreadRestrictions::AssertIOAllowed();
+  DCHECK(IsValid());
+  return !HANDLE_EINTR(fdatasync(file_.get()));

[rvargas (doing something else), 2015/03/20 18:56:05]

is fdatasync a Linux-only thing? What's the behavior on BSD?

[hashimoto, 2015/03/20 19:38:57]

fdatasync is a part of POSIX, but it's not mandatory.
According to what I get from casual searching, Mac OS does not implement
fdatasync.

+#else
+  return Flush();
+#endif
+}
+
 bool File::SetTimes(Time last_access_time, Time last_modified_time) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(IsValid());
 
   timeval times[2];
   times[0] = last_access_time.ToTimeVal();
   times[1] = last_modified_time.ToTimeVal();
 
   return !CallFutimes(file_.get(), times);
 }
@@ skipping 111 matching lines @@
 }
 
 void File::SetPlatformFile(PlatformFile file) {
   CHECK(!file_.is_valid());
   file_.reset(file);
   if (file_.is_valid())
     ProtectFileDescriptor(GetPlatformFile());
 }
 
 }  // namespace base