libsnapshot: require ex lock for {Create}{CowImage,Snapshot} / DeleteSnapshot
Create / Deleting the COW image / snapshot changes states, so it makes
sense to require an exclusive lock before doing so. If caller doesn't hold
an exclusive lock, parallel calls to MapCowImage / MapSnapshot / UnmapCowImage /
UnmapSnapshot may have weird results.
Test: libsnapshot_test
Change-Id: I4be660df1059ec24144f8baf43a1c8c05d9e372b
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index 8b2c3c6..269b99e 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -183,6 +183,7 @@
bool SnapshotManager::CreateSnapshot(LockedFile* lock, const std::string& name,
SnapshotManager::SnapshotStatus status) {
CHECK(lock);
+ CHECK(lock->lock_mode() == LOCK_EX);
// Sanity check these sizes. Like liblp, we guarantee the partition size
// is respected, which means it has to be sector-aligned. (This guarantee
// is useful for locating avb footers correctly). The COW size, however,
@@ -215,6 +216,7 @@
bool SnapshotManager::CreateCowImage(LockedFile* lock, const std::string& name) {
CHECK(lock);
+ CHECK(lock->lock_mode() == LOCK_EX);
if (!EnsureImageManager()) return false;
SnapshotStatus status;
@@ -415,6 +417,7 @@
bool SnapshotManager::DeleteSnapshot(LockedFile* lock, const std::string& name) {
CHECK(lock);
+ CHECK(lock->lock_mode() == LOCK_EX);
if (!EnsureImageManager()) return false;
auto cow_image_name = GetCowImageDeviceName(name);