From b47c02ed8bbd1623a5db9936b33f6d80306d53b9 Mon Sep 17 00:00:00 2001
From: Ming-Hung Tsai <mingnus@gmail.com>
Date: Sat, 27 Feb 2016 01:31:24 +0800
Subject: [PATCH] Show the wanted checksum in bad-superblock-checksum exception

---
 thin-provisioning/superblock.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/thin-provisioning/superblock.cc b/thin-provisioning/superblock.cc
index 9258b53..fb0d17e 100644
--- a/thin-provisioning/superblock.cc
+++ b/thin-provisioning/superblock.cc
@@ -91,8 +91,11 @@ namespace {
 			superblock_disk const *sbd = reinterpret_cast<superblock_disk const *>(raw);
 			crc32c sum(SUPERBLOCK_CSUM_SEED);
 			sum.append(&sbd->flags_, MD_BLOCK_SIZE - sizeof(uint32_t));
-			if (sum.get_sum() != to_cpu<uint32_t>(sbd->csum_))
-				throw checksum_error("bad checksum in superblock");
+			if (sum.get_sum() != to_cpu<uint32_t>(sbd->csum_)) {
+				ostringstream out;
+				out << "bad checksum in superblock, wanted " << sum.get_sum();
+				throw checksum_error(out.str());
+			}
 		}
 
 		virtual void prepare(void *raw, block_address location) const {