tree 6a8ca1dc6a8567ae74e2e80839c6863b5d2d928d
parent cbd67f8c4bf76a6e5663f9fef7c40975d7f996b1
author Sandeep Dhavale <dhavale@google.com> 1757104244 -0700
committer Sandeep Dhavale <dhavale@google.com> 1757104244 -0700

snapuserd: fix race condition during merge-resume

When resuming a merge after a crash, a race condition can occur where
a block is written to both the scratch space and the base device, but
the merge is not yet committed.

This change ensures that when a merge is resumed, the scratch space is
always checked first. Data from the scratch space is prioritized over
the source block to handle overlapping blocks and XOR ops correctly.

This prevents returning wrong data by ensuring that the most up-to-date
block is used when serving the io.

Bug: 441666433
Test: th, manual OTA and reboots
Change-Id: Idacef9726d3f91a3e416f2b56e531a208d213232
Signed-off-by: Sandeep Dhavale <dhavale@google.com>