When you run ls /home/chronos/user/GCache/v1/tmp/, which tmp is preferred?
It behaves randomly?
If we can know if a directory is a pass-through one or not, we can fix Mount::CreateTrackedSubdirectories to stop creating dupes.

As far as I experimented, always the non-pass-through one was taken.
Though I cannot be sure without investigating the ecryptfs impl if it is just by an accident or not.


https://chromium-review.googlesource.com/#/c/526833/ is the CL for stopping to create the dup.
On which I don't have a good idea yet is how to avoid the already created dups.

Seems the behavior depends on the state of cache.

After executing these commands:
 cd /home/.shadow/
 mkdir mount/A; mkdir vault/A;
 rmdir mount/A
 ls vault/
You will see an encrypted directory in vault.

However, after the same commands with drop_caches, you will see the passthrough one left:
 cd /home/.shadow/
 mkdir mount/A; mkdir vault/A;
 echo 3 > /proc/sys/vm/drop_caches
 rmdir mount/A
 ls vault/

Sorry for causing this trouble, as far as I experimented, duplicates can be resolved with the following steps (probably there is a simpler way):
 1. Detect duplicates by checking if a tracked directory's name appears twice in readdir() result.
 2. Rename the passthrough one to a temporary name (e.g. tmp -> tmp_)
 3. echo 3 > /proc/sys/vm/drop_caches to drop cache (otherwise, the next step may delete the passthrough one)
 4. Remove the non-passthrough directory.
 5. Rename the passthrough one again to the original name.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/51dd8de2eea1697ce6f0e4b813751000998cd147

commit 51dd8de2eea1697ce6f0e4b813751000998cd147
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Thu Jun 08 06:45:43 2017

cryptohome: Delete the right path when overriding with a passthrough dir.

The relative path |tracked_dir| now starts from "root/" or "user/",
hence the base directory must be one level up from the "user" directory.

BUG= chromium:729997 
TEST=crs_workon_make cryptohome --test
TEST=Manual step shown in the bug

Change-Id: If91d17c8897c4d4c8c77c86d4e46d62f429c75dd
Reviewed-on: https://chromium-review.googlesource.com/526833
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/51dd8de2eea1697ce6f0e4b813751000998cd147/cryptohome/mount.h
[modify] https://crrev.com/51dd8de2eea1697ce6f0e4b813751000998cd147/cryptohome/mount.cc
[modify] https://crrev.com/51dd8de2eea1697ce6f0e4b813751000998cd147/cryptohome/mount_unittest.cc

Your change meets the bar and is auto-approved for M60. Please go ahead and merge the CL to branch 3112 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), josafat@(ChromeOS), bustamante@(Desktop)

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The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/fd29164a5021651a3232c2812f875b0c4f62b6b9

commit fd29164a5021651a3232c2812f875b0c4f62b6b9
Author: Kazuhiro Inaba <kinaba@chromium.org>
Date: Fri Jun 09 07:16:25 2017

cryptohome: Delete the right path when overriding with a passthrough dir.

The relative path |tracked_dir| now starts from "root/" or "user/",
hence the base directory must be one level up from the "user" directory.

BUG= chromium:729997 
TEST=crs_workon_make cryptohome --test
TEST=Manual step shown in the bug

Change-Id: If91d17c8897c4d4c8c77c86d4e46d62f429c75dd
Reviewed-on: https://chromium-review.googlesource.com/526833
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Tested-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
(cherry picked from commit 51dd8de2eea1697ce6f0e4b813751000998cd147)
Reviewed-on: https://chromium-review.googlesource.com/527744
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Commit-Queue: Kazuhiro Inaba <kinaba@chromium.org>
Trybot-Ready: Kazuhiro Inaba <kinaba@chromium.org>

[modify] https://crrev.com/fd29164a5021651a3232c2812f875b0c4f62b6b9/cryptohome/mount.h
[modify] https://crrev.com/fd29164a5021651a3232c2812f875b0c4f62b6b9/cryptohome/mount.cc
[modify] https://crrev.com/fd29164a5021651a3232c2812f875b0c4f62b6b9/cryptohome/mount_unittest.cc

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