[PATCH 4.2 068/110] dm cache: the CLEAN_SHUTDOWN flag was not being set

[Greg Kroah-Hartman]

4.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Joe Thornber <ejt@xxxxxxxxxx>

commit 3201ac452e84a8a368197d648c9b7011e061804a upstream.

If the CLEAN_SHUTDOWN flag is not set when a cache is loaded then all cache
blocks are marked as dirty and a full writeback occurs.

__commit_transaction() is responsible for setting/clearing
CLEAN_SHUTDOWN (based the flags_mutator that is passed in).

Fix this issue, of the cache's on-disk flags being wrong, by making sure
__commit_transaction() does not reset the flags after the mutator has
altered the flags in preparation for them being serialized to disk.

before:

sb_flags = mutator(le32_to_cpu(disk_super->flags));
disk_super->flags = cpu_to_le32(sb_flags);
disk_super->flags = cpu_to_le32(cmd->flags);

after:

disk_super->flags = cpu_to_le32(cmd->flags);
sb_flags = mutator(le32_to_cpu(disk_super->flags));
disk_super->flags = cpu_to_le32(sb_flags);

Reported-by: Bogdan Vasiliev <bogdan.vasiliev@xxxxxxxxx>
Signed-off-by: Joe Thornber <ejt@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/dm-cache-metadata.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -634,10 +634,10 @@ static int __commit_transaction(struct d
 
 	disk_super = dm_block_data(sblock);
 
+	disk_super->flags = cpu_to_le32(cmd->flags);
 	if (mutator)
 		update_flags(disk_super, mutator);
 
-	disk_super->flags = cpu_to_le32(cmd->flags);
 	disk_super->mapping_root = cpu_to_le64(cmd->root);
 	disk_super->hint_root = cpu_to_le64(cmd->hint_root);
 	disk_super->discard_root = cpu_to_le64(cmd->discard_root);


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