dm cache: policy change version from string to integer set

Separate dm cache policy version string into 3 unsigned numbers
corresponding to major, minor and patchlevel and store them at the end
of the on-disk metadata so we know which version of the policy generated
the hints in case a future version wants to use them differently.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/dm-cache-policy.h b/drivers/md/dm-cache-policy.h
index f0f51b260544..558bdfdabf5f 100644
--- a/drivers/md/dm-cache-policy.h
+++ b/drivers/md/dm-cache-policy.h
@@ -196,6 +196,7 @@ struct dm_cache_policy {
  * We maintain a little register of the different policy types.
  */
 #define CACHE_POLICY_NAME_SIZE 16
+#define CACHE_POLICY_VERSION_SIZE 3
 
 struct dm_cache_policy_type {
         /* For use by the register code only. */
@@ -206,6 +207,7 @@ struct dm_cache_policy_type {
          * what gets passed on the target line to select your policy.
          */
         char name[CACHE_POLICY_NAME_SIZE];
+        unsigned version[CACHE_POLICY_VERSION_SIZE];
 
         /*
          * Policies may store a hint for each each cache block.