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>

6 files changed, 36 insertions, 6 deletions

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 1bb91802b22a..74213d1f1db5 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -83,6 +83,8 @@ struct cache_disk_superblock {
         __le32 read_misses;
         __le32 write_hits;
         __le32 write_misses;
+
+        __le32 policy_version[CACHE_POLICY_VERSION_SIZE];
 } __packed;
 
 struct dm_cache_metadata {
@@ -109,6 +111,7 @@ struct dm_cache_metadata {
         bool clean_when_opened:1;
 
         char policy_name[CACHE_POLICY_NAME_SIZE];
+        unsigned policy_version[CACHE_POLICY_VERSION_SIZE];
         size_t policy_hint_size;
         struct dm_cache_statistics stats;
 };
@@ -268,7 +271,8 @@ static int __write_initial_superblock(struct dm_cache_metadata *cmd)
         memset(disk_super->uuid, 0, sizeof(disk_super->uuid));
         disk_super->magic = cpu_to_le64(CACHE_SUPERBLOCK_MAGIC);
         disk_super->version = cpu_to_le32(CACHE_VERSION);
-        memset(disk_super->policy_name, 0, CACHE_POLICY_NAME_SIZE);
+        memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name));
+        memset(disk_super->policy_version, 0, sizeof(disk_super->policy_version));
         disk_super->policy_hint_size = 0;
 
         r = dm_sm_copy_root(cmd->metadata_sm, &disk_super->metadata_space_map_root,
@@ -284,7 +288,6 @@ static int __write_initial_superblock(struct dm_cache_metadata *cmd)
         disk_super->metadata_block_size = cpu_to_le32(DM_CACHE_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
         disk_super->data_block_size = cpu_to_le32(cmd->data_block_size);
         disk_super->cache_blocks = cpu_to_le32(0);
-        memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name));
 
         disk_super->read_hits = cpu_to_le32(0);
         disk_super->read_misses = cpu_to_le32(0);
@@ -478,6 +481,9 @@ static void read_superblock_fields(struct dm_cache_metadata *cmd,
         cmd->data_block_size = le32_to_cpu(disk_super->data_block_size);
         cmd->cache_blocks = to_cblock(le32_to_cpu(disk_super->cache_blocks));
         strncpy(cmd->policy_name, disk_super->policy_name, sizeof(cmd->policy_name));
+        cmd->policy_version[0] = le32_to_cpu(disk_super->policy_version[0]);
+        cmd->policy_version[1] = le32_to_cpu(disk_super->policy_version[1]);
+        cmd->policy_version[2] = le32_to_cpu(disk_super->policy_version[2]);
         cmd->policy_hint_size = le32_to_cpu(disk_super->policy_hint_size);
 
         cmd->stats.read_hits = le32_to_cpu(disk_super->read_hits);
@@ -572,6 +578,9 @@ static int __commit_transaction(struct dm_cache_metadata *cmd,
         disk_super->discard_nr_blocks = cpu_to_le64(from_dblock(cmd->discard_nr_blocks));
         disk_super->cache_blocks = cpu_to_le32(from_cblock(cmd->cache_blocks));
         strncpy(disk_super->policy_name, cmd->policy_name, sizeof(disk_super->policy_name));
+        disk_super->policy_version[0] = cpu_to_le32(cmd->policy_version[0]);
+        disk_super->policy_version[1] = cpu_to_le32(cmd->policy_version[1]);
+        disk_super->policy_version[2] = cpu_to_le32(cmd->policy_version[2]);
 
         disk_super->read_hits = cpu_to_le32(cmd->stats.read_hits);
         disk_super->read_misses = cpu_to_le32(cmd->stats.read_misses);
@@ -1070,6 +1079,7 @@ static int begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *po
         __le32 value;
         size_t hint_size;
         const char *policy_name = dm_cache_policy_get_name(policy);
+        const unsigned *policy_version = dm_cache_policy_get_version(policy);
 
         if (!policy_name[0] ||
             (strlen(policy_name) > sizeof(cmd->policy_name) - 1))
@@ -1077,6 +1087,7 @@ static int begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *po
 
         if (strcmp(cmd->policy_name, policy_name)) {
                 strncpy(cmd->policy_name, policy_name, sizeof(cmd->policy_name));
+                memcpy(cmd->policy_version, policy_version, sizeof(cmd->policy_version));
 
                 hint_size = dm_cache_policy_get_hint_size(policy);
                 if (!hint_size)
diff --git a/drivers/md/dm-cache-policy-cleaner.c b/drivers/md/dm-cache-policy-cleaner.c
index cc05d70b3cb8..b04d1f904d07 100644
--- a/drivers/md/dm-cache-policy-cleaner.c
+++ b/drivers/md/dm-cache-policy-cleaner.c
@@ -17,7 +17,6 @@
 /*----------------------------------------------------------------*/
 
 #define DM_MSG_PREFIX "cache cleaner"
-#define CLEANER_VERSION "1.0.0"
 
 /* Cache entry struct. */
 struct wb_cache_entry {
@@ -434,6 +433,7 @@ static struct dm_cache_policy *wb_create(dm_cblock_t cache_size,
 
 static struct dm_cache_policy_type wb_policy_type = {
         .name = "cleaner",
+        .version = {1, 0, 0},
         .hint_size = 0,
         .owner = THIS_MODULE,
         .create = wb_create
@@ -446,7 +446,10 @@ static int __init wb_init(void)
         if (r < 0)
                 DMERR("register failed %d", r);
         else
-                DMINFO("version " CLEANER_VERSION " loaded");
+                DMINFO("version %u.%u.%u loaded",
+                       wb_policy_type.version[0],
+                       wb_policy_type.version[1],
+                       wb_policy_type.version[2]);
 
         return r;
 }
diff --git a/drivers/md/dm-cache-policy-internal.h b/drivers/md/dm-cache-policy-internal.h
index 52a75beeced5..0928abdc49f0 100644
--- a/drivers/md/dm-cache-policy-internal.h
+++ b/drivers/md/dm-cache-policy-internal.h
@@ -117,6 +117,8 @@ void dm_cache_policy_destroy(struct dm_cache_policy *p);
  */
 const char *dm_cache_policy_get_name(struct dm_cache_policy *p);
 
+const unsigned *dm_cache_policy_get_version(struct dm_cache_policy *p);
+
 size_t dm_cache_policy_get_hint_size(struct dm_cache_policy *p);
 
 /*----------------------------------------------------------------*/
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index 964153255076..dc112a7137fe 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -14,7 +14,6 @@
 #include <linux/vmalloc.h>
 
 #define DM_MSG_PREFIX "cache-policy-mq"
-#define MQ_VERSION      "1.0.0"
 
 static struct kmem_cache *mq_entry_cache;
 
@@ -1133,6 +1132,7 @@ bad_cache_alloc:
 
 static struct dm_cache_policy_type mq_policy_type = {
         .name = "mq",
+        .version = {1, 0, 0},
         .hint_size = 4,
         .owner = THIS_MODULE,
         .create = mq_create
@@ -1140,6 +1140,7 @@ static struct dm_cache_policy_type mq_policy_type = {
 
 static struct dm_cache_policy_type default_policy_type = {
         .name = "default",
+        .version = {1, 0, 0},
         .hint_size = 4,
         .owner = THIS_MODULE,
         .create = mq_create
@@ -1164,7 +1165,10 @@ static int __init mq_init(void)
 
         r = dm_cache_policy_register(&default_policy_type);
         if (!r) {
-                DMINFO("version " MQ_VERSION " loaded");
+                DMINFO("version %u.%u.%u loaded",
+                       mq_policy_type.version[0],
+                       mq_policy_type.version[1],
+                       mq_policy_type.version[2]);
                 return 0;
         }
 
diff --git a/drivers/md/dm-cache-policy.c b/drivers/md/dm-cache-policy.c
index 2cbf5fdaac52..21c03c570c06 100644
--- a/drivers/md/dm-cache-policy.c
+++ b/drivers/md/dm-cache-policy.c
@@ -150,6 +150,14 @@ const char *dm_cache_policy_get_name(struct dm_cache_policy *p)
 }
 EXPORT_SYMBOL_GPL(dm_cache_policy_get_name);
 
+const unsigned *dm_cache_policy_get_version(struct dm_cache_policy *p)
+{
+        struct dm_cache_policy_type *t = p->private;
+
+        return t->version;
+}
+EXPORT_SYMBOL_GPL(dm_cache_policy_get_version);
+
 size_t dm_cache_policy_get_hint_size(struct dm_cache_policy *p)
 {
         struct dm_cache_policy_type *t = p->private;
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.