Unmounts volumes before writing to a drive.

chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc

Index: chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc
diff --git a/chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc b/chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc
index ceaf76bc30911c395fe0dcc3e05c849ff3af505f..c36abd3d2a22eb4ba0c139cba66802b92de45aa4 100644
--- a/chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc
+++ b/chrome/browser/extensions/api/image_writer_private/operation_chromeos.cc
@@ -6,11 +6,13 @@
 #include "chrome/browser/extensions/api/image_writer_private/operation.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/image_burner_client.h"
+#include "chromeos/disks/disk_mount_manager.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace extensions {
 namespace image_writer {
 
+using chromeos::disks::DiskMountManager;
 using chromeos::ImageBurnerClient;
 using content::BrowserThread;
 
@@ -38,9 +40,7 @@ void Operation::Write(const base::Closure& continuation) {
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
-      base::Bind(&Operation::StartWriteOnUIThread, this, continuation));
-
-  AddCleanUpFunction(base::Bind(&ClearImageBurner));
+      base::Bind(&Operation::UnmountVolumes, this, continuation));
 }
 
 void Operation::VerifyWrite(const base::Closure& continuation) {
@@ -50,18 +50,51 @@ void Operation::VerifyWrite(const base::Closure& continuation) {
   continuation.Run();
 }
 
-void Operation::StartWriteOnUIThread(const base::Closure& continuation) {
+void Operation::UnmountVolumes(const base::Closure& continuation) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DiskMountManager::GetInstance()->UnmountDeviceRecursively(
+      device_path_.value(),
+      base::Bind(&Operation::UnmountVolumesCallback, this, continuation));
+}
+
+void Operation::UnmountVolumesCallback(const base::Closure& continuation,
+                                       bool success) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  if (!success) {
+    LOG(ERROR) << "Volume unmounting failed.";
+    Error(error::kUnmountVolumesError);
+    return;
+  }
+
+  const DiskMountManager::DiskMap& disks =
+      DiskMountManager::GetInstance()->disks();
+  DiskMountManager::DiskMap::const_iterator iter =
+      disks.find(device_path_.value());
+
+  if (iter == disks.end()) {
+    LOG(ERROR) << "Disk not found in disk list after unmounting volumes.";
+    Error(error::kUnmountVolumesError);
+    return;
+  }
+
+  StartWriteOnUIThread(iter->second->file_path(), continuation);
+}
+
+void Operation::StartWriteOnUIThread(const std::string& target_path,
+                                     const base::Closure& continuation) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   ImageBurnerClient* burner =
       chromeos::DBusThreadManager::Get()->GetImageBurnerClient();
 
+  AddCleanUpFunction(base::Bind(&ClearImageBurner));

[tbarzic, 2014/05/15 00:58:58]

AddCleanupFunction has DCHECK that it's on file thread

[Drew Haven, 2014/05/15 02:00:28]

Oh, I built release mode when I tested, so I didn't catch that.  You're right. 
It needs to be on the FILE thread so we don't get concurrent access to the
cleanup function list or try to run them while I'm trying to add to them.

I'm going to add the cleanup way before the write.  I believe it should be fine
to call it that early because even if the operation is interrupted the cleanup
call should not cause harm unless another burn operation was already in progress
somehow.  I've done my best to stop that as no one can use the API twice at the
same time, but I don't think I can stop someone from using the Image Burner at
the same time.

   burner->SetEventHandlers(
       base::Bind(&Operation::OnBurnFinished, this, continuation),
       base::Bind(&Operation::OnBurnProgress, this));
 
   burner->BurnImage(image_path_.value(),
-                    device_path_.value(),
+                    target_path,
                     base::Bind(&Operation::OnBurnError, this));
 }