Zero out blocks that may be touched by dm-verity.
dm-verity may touch some blocks that are not in the care_map due to
block device read-ahead. It will fail if such blocks contain
non-zeroes. As a workaround, we mark them as extended blocks and
zero out explicitly to avoid dm-verity failures.
Bug: 20881595
Change-Id: I54e24e70ad822c0d6d7af43301f74d24505f4461
diff --git a/tools/releasetools/sparse_img.py b/tools/releasetools/sparse_img.py
index 7019f00..07f3c1c 100644
--- a/tools/releasetools/sparse_img.py
+++ b/tools/releasetools/sparse_img.py
@@ -110,6 +110,17 @@
self.care_map = rangelib.RangeSet(care_data)
self.offset_index = [i[0] for i in offset_map]
+ # Bug: 20881595
+ # Introduce extended blocks as a workaround for the bug. dm-verity may
+ # touch blocks that are not in the care_map due to block device
+ # read-ahead. It will fail if such blocks contain non-zeroes. We zero out
+ # the extended blocks explicitly to avoid dm-verity failures. 512 blocks
+ # are the maximum read-ahead we configure for dm-verity block devices.
+ extended = self.care_map.extend(512)
+ all_blocks = rangelib.RangeSet(data=(0, self.total_blocks))
+ extended = extended.intersect(all_blocks).subtract(self.care_map)
+ self.extended = extended
+
if file_map_fn:
self.LoadFileBlockMap(file_map_fn, self.clobbered_blocks)
else: