tree 20dc6a74705bf7bb770debbd4bddf04187275574
parent 5d652cdffa70dc772e80548a760e1f0d67de273f
author Julius Werner <jwerner@chromium.org> 1461097252 -0700
committer Philip Chen <philipchen@chromium.org> 1479234760 +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/411475
Reviewed-by: Philip Chen <philipchen@chromium.org>
Commit-Queue: Philip Chen <philipchen@chromium.org>
Tested-by: Philip Chen <philipchen@chromium.org>