Mark block device as read-only before mounting.
Mounting a block device as read-only still allows the filesystem to
write to the block device, while keeping the user-facing filesystem
interface "read-only". This behavior will make dm-verity to fail after
reboot if any block is modified during postinstall.
This patch marks the block device as read-only before mounting it, and
marks them read-only or read-write before using them during the update.
Bug: 27859604
TEST=Added logging and deployed an update to brillo, devices are marked RO/RW as needed during a delta update.
(cherry picked from commit 5fb356cac8a87c62fa83005d99370aa2f8416064)
Change-Id: I8797c35514e1f38c2a0395cedc8e1dce53e28350
diff --git a/common/utils.h b/common/utils.h
index 686f117..88c33b7 100644
--- a/common/utils.h
+++ b/common/utils.h
@@ -178,6 +178,10 @@
// /dev/sda3. Return empty string on error.
std::string MakePartitionNameForMount(const std::string& part_name);
+// Set the read-only attribute on the block device |device| to the value passed
+// in |read_only|. Return whether the operation succeeded.
+bool SetBlockDeviceReadOnly(const std::string& device, bool read_only);
+
// Synchronously mount or unmount a filesystem. Return true on success.
// When mounting, it will attempt to mount the device as the passed filesystem
// type |type|, with the passed |flags| options. If |type| is empty, "ext2",