tree e69cfcb2c67a7ff46c1fb48f38f78a4cdf5f0142
parent 723b3c09debfa350f7a17e7927116c3535ac081b
author Julius Werner <jwerner@chromium.org> 1461097252 -0700
committer ChromeOS Commit Bot <chromeos-commit-bot@chromium.org> 1466553079 +0000

cgpt: Fully write out primary GPT before starting to write secondary

The point of having two GPTs is to always have a known good one if one
of them gets corrupted. One of the most obvious ways that could happen
is if the write stopped half-way through (e.g. due to a crash or random
power loss).

Unfortunately, the way we currently save modified GPTs can leave both
copies invalid if we stop writing at just the wrong time. Since a GPT
header contains a checksum over the GPT entries, we need to write both
the header and entries for one GPT (and make sure they're synced to
disk) before we start writing the other.

BRANCH=None
BUG=chrome-os-partner:52595
TEST=None

Change-Id: I2d4b56bcfba9a94395af5896f274ebade9e39081
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/340071
Reviewed-by: Nam Nguyen <namnguyen@google.com>
(cherry picked from commit 5de0000ece70bf419130db9bdbaf444ffc98bf30)
Reviewed-on: https://chromium-review.googlesource.com/354565
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>