code: public Set<Long> getLockedBlocks() {
      synchronized (mSharedMapsLock) {
        Set<Long> set = new HashSet<>();
        for (LockRecord lockRecord : mLockIdToRecordMap.values()) {
          set.add(lockRecord.getBlockId());
        }
        return set;
      }
    }
docs: Gets a set of currently locked blocks.
  
  @return a set of locked blocks