Implement basic libsnapshot functionality.
This CL implements some of the libsnapshot internals necessary to work
with update_engine. In particular it implements snapshot and update
state, as well as creating and mapping snapshot devices. It does not
implement anything related to merging, nor does it implement the full
update_engine flow.
Update state is stored in /metadata/ota/state. To synchronize callers of
libsnapshot, we always flock() this file at the top of public functions
in SnapshotManager. Internal functions are only called while the lock is
held, and a "LockedFile" guard object is always passed through to
indicate proof-of-lock.
Low-level functions, such as snapshot management, have been moved to
private methods. Higher-level methods designed for update_engine will
ultimately call into these.
This CL also adds some functional tests for SnapshotManager. Test state
is stored in /metadata/ota/test to avoid conflicts with the rest of the
system.
Bug: 136678799
Test: libsnapshot_test gtest
Change-Id: I78c769ed33b307d5214ee386bb13648e35db6cc6
diff --git a/rootdir/init.rc b/rootdir/init.rc
index d22e9a7..86d8042 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -415,6 +415,7 @@
chmod 0700 /metadata/vold
mkdir /metadata/password_slots 0771 root system
mkdir /metadata/ota 0700 root system
+ mkdir /metadata/ota/snapshots 0700 root system
mkdir /metadata/apex 0700 root system
mkdir /metadata/apex/sessions 0700 root system