[PATCH 3.16 079/134] dm era: save spacemap metadata root after the pre-commit

[Ben Hutchings]

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Somasundaram Krishnasamy <somasundaram.krishnasamy@xxxxxxxxxx>

commit 117aceb030307dcd431fdcff87ce988d3016c34a upstream.

When committing era metadata to disk, it doesn't always save the latest
spacemap metadata root in superblock. Due to this, metadata is getting
corrupted sometimes when reopening the device. The correct order of update
should be, pre-commit (shadows spacemap root), save the spacemap root
(newly shadowed block) to in-core superblock and then the final commit.

Signed-off-by: Somasundaram Krishnasamy <somasundaram.krishnasamy@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/md/dm-era-target.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/md/dm-era-target.c
+++ b/drivers/md/dm-era-target.c
@@ -957,15 +957,15 @@ static int metadata_commit(struct era_me
 		}
 	}
 
-	r = save_sm_root(md);
+	r = dm_tm_pre_commit(md->tm);
 	if (r) {
-		DMERR("%s: save_sm_root failed", __func__);
+		DMERR("%s: pre commit failed", __func__);
 		return r;
 	}
 
-	r = dm_tm_pre_commit(md->tm);
+	r = save_sm_root(md);
 	if (r) {
-		DMERR("%s: pre commit failed", __func__);
+		DMERR("%s: save_sm_root failed", __func__);
 		return r;
 	}