libsnapshot: update write error logs

We want to print how much total data we are attempting to write if a
failure occurs

Bug: 336461151
Test: th
Change-Id: I269b7e280df34994c80fa8ef7d39163d053fa9ea
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.cpp
index 95398e4..1117ec9 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.cpp
@@ -731,7 +731,8 @@
             i += chunk;
         }
         if (total_written != total_data_size) {
-            PLOG(ERROR) << "write failed for data of size: " << data.size()
+            PLOG(ERROR) << "write failed for data vector of size: " << data.size()
+                        << " and total data length: " << total_data_size
                         << " at offset: " << next_data_pos_ << " " << errno
                         << ", only wrote: " << total_written;
             return false;