One tricky point is that it already has a so-called "force ecryptfs" flag. We need to merge them nicely.

If it's going to be complicated, one thing we can do is remove force_ecryptfs from mount arguments by injecting the value via Mount's ctor (this should result in cleaner code as force_cryptfs value never changes during crypothome process's lifetime).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/system_api/+/e86bc673db5c34560e86ce1ceac5b8029584149d

commit e86bc673db5c34560e86ce1ceac5b8029584149d
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Mon Mar 13 09:54:13 2017

cryptohome: Add a new flag and an error code for forcing new encryption.

New encryption scheme is required for running ARC for Android N,
so we want to force it, and in case of an error we navigate the user
to migration UI. Some other cases (including when the user chose
"do it later"), we are not forcing it. In addition, if for any reason
the migration step is aborted in the middle and the user tried to
re-login, we cannot let "do it later" and do need to force migration.
An additional error code for this state is also necessary.

This CL adds a flag and an error code for that purpose.
Actual code using them will follow later.

BUG= chromium:699436 
TEST=manually checked log-in to new/existing accounts.

Change-Id: Ibf5e40815fb50f74badfc95808c9c401a0b35a05
Reviewed-on: https://chromium-review.googlesource.com/452097
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>

[modify] https://crrev.com/e86bc673db5c34560e86ce1ceac5b8029584149d/dbus/cryptohome/rpc.proto
[modify] https://crrev.com/e86bc673db5c34560e86ce1ceac5b8029584149d/dbus/cryptohome/dbus-constants.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8a9749142275a2eae0ab63da86ec41905d199812

commit 8a9749142275a2eae0ab63da86ec41905d199812
Author: kinaba <kinaba@chromium.org>
Date: Mon Mar 13 12:50:03 2017

cryptohome: Add the conversion for a new error code.

This CL depends on
https://chromium-review.googlesource.com/c/452097/

BUG= 699436 
TEST=none (no behavior change at this point.)

Review-Url: https://codereview.chromium.org/2740883002
Cr-Commit-Position: refs/heads/master@{#456357}

[modify] https://crrev.com/8a9749142275a2eae0ab63da86ec41905d199812/DEPS
[modify] https://crrev.com/8a9749142275a2eae0ab63da86ec41905d199812/chromeos/cryptohome/homedir_methods.cc

Dbus interface has landed. I'll move on to the implementation (of properly returning the error codes) next.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/17f9ea4fc88f34cd58ce24375dfb46b5fa0874f3

commit 17f9ea4fc88f34cd58ce24375dfb46b5fa0874f3
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Mon Mar 13 14:36:17 2017

cryptohome: Add a new error code for forcing new encryption.

Just adding the conversion to protobuf enum. Actual change generating
this new error code is coming very soon.

CQ-DEPEND=CL:452097
BUG= chromium:699436 
TEST=manually checked log-in to new/existing accounts.

Change-Id: I8ae4d1bc77fdac95d332481c129f464ed01dad43
Reviewed-on: https://chromium-review.googlesource.com/452117
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>

[modify] https://crrev.com/17f9ea4fc88f34cd58ce24375dfb46b5fa0874f3/cryptohome/service.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/46b030f7e44f77f9c22dde9ee341217da3d164c3

commit 46b030f7e44f77f9c22dde9ee341217da3d164c3
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Wed Mar 22 15:21:00 2017

cryptohome: PREVIOUS_MIGRATION_INCOMPLETE error when both directories found.

When both the old vault/ directory for ecryptfs and the new mount/
directory is ext4 encryption key set are found, regard it as an
incomplete migration and raises an error.

BUG= chromium:699436 
TEST=cros_workon_make --board=samus-cheets cryptohome --test
TEST=Manually checked 3 types of situations.

Change-Id: Ida253a334b92a7e7935b10fb6a84169dc62e2ff4
Reviewed-on: https://chromium-review.googlesource.com/456671
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>

[modify] https://crrev.com/46b030f7e44f77f9c22dde9ee341217da3d164c3/cryptohome/mount.h
[modify] https://crrev.com/46b030f7e44f77f9c22dde9ee341217da3d164c3/cryptohome/mount.cc
[modify] https://crrev.com/46b030f7e44f77f9c22dde9ee341217da3d164c3/cryptohome/mount_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/7ac52416e8a23c717b1c17d23cef1ae0462842c8

commit 7ac52416e8a23c717b1c17d23cef1ae0462842c8
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Thu Mar 23 13:38:00 2017

cryptohome: OLD_ENCRYPTION error when mounting ecryptfs with force_dircrypto.

BUG= chromium:699436 
TEST=cros_workon_make --board=samus-cheets cryptohome --test
TEST=Manually checked mounting both types of cryptohome.

Change-Id: I2440d6cc62fe843341830bba64617796c5c00209
Reviewed-on: https://chromium-review.googlesource.com/458317
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>

[modify] https://crrev.com/7ac52416e8a23c717b1c17d23cef1ae0462842c8/cryptohome/mount.cc
[modify] https://crrev.com/7ac52416e8a23c717b1c17d23cef1ae0462842c8/cryptohome/mount_unittest.cc

The option, corresponding error codes, as well as the implementation to return the error codes in necessary situation has all landed.

Closing.