libsnapshot: Add IsOrderedOp

Ordered Ops are Cow Ops with source block dependencies.
Currently this is only Copy Ops, but will extend to XOR
blocks when they're added.

Bug: 177104308
Test: Builds, does not impace cow_api_test/cow_snapuserd_test
Change-Id: I0a50dfe3316ec3a3b1d035335f094c62296649a5

fs_mgr/libsnapshot/cow_format.cpp

@@ -90,5 +90,14 @@ bool IsMetadataOp(const CowOperation& op) {
     }
 }
 
+bool IsOrderedOp(const CowOperation& op) {
+    switch (op.type) {
+        case kCowCopyOp:
+            return true;
+        default:
+            return false;
+    }
+}
+
 }  // namespace snapshot
 }  // namespace android

fs_mgr/libsnapshot/include/libsnapshot/cow_format.h

@@ -185,7 +185,10 @@ std::ostream& operator<<(std::ostream& os, CowOperation const& arg);
 int64_t GetNextOpOffset(const CowOperation& op, uint32_t cluster_size);
 int64_t GetNextDataOffset(const CowOperation& op, uint32_t cluster_size);
 
+// Ops that are internal to the Cow Format and not OTA data
 bool IsMetadataOp(const CowOperation& op);
+// Ops that have dependencies on old blocks, and must take care in their merge order
+bool IsOrderedOp(const CowOperation& op);
 
 }  // namespace snapshot
 }  // namespace android

fs_mgr/libsnapshot/snapuserd.cpp

@@ -395,7 +395,7 @@ bool Snapuserd::ReadMetadata() {
         // handling of assigning chunk-id's. Furthermore, we make
         // sure that replace/zero and copy ops are not batch merged; hence,
         // the bump in the chunk_id before break of this loop
-        if (cow_op->type == kCowCopyOp) {
+        if (IsOrderedOp(*cow_op)) {
             data_chunk_id = GetNextAllocatableChunkId(data_chunk_id);
             break;
         }