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 <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-cache-metadata.c

···
 	__le32 read_misses;
 	__le32 write_hits;
 	__le32 write_misses;
+
+	__le32 policy_version[CACHE_POLICY_VERSION_SIZE];
 } __packed;
 
 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;
 };
···
 	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,
···
 	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);
···
 	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);
···
 	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);
···
 	__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))
···
 
 	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)

drivers/md/dm-cache-policy-cleaner.c

···
 /*----------------------------------------------------------------*/
 
 #define DM_MSG_PREFIX "cache cleaner"
-#define CLEANER_VERSION "1.0.0"
 
 /* Cache entry struct. */
 struct wb_cache_entry {
···
 
 static struct dm_cache_policy_type wb_policy_type = {
 	.name = "cleaner",
+	.version = {1, 0, 0},
 	.hint_size = 0,
 	.owner = THIS_MODULE,
 	.create = wb_create
···
 	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;
 }

drivers/md/dm-cache-policy-internal.h

···
  */
 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);
 
 /*----------------------------------------------------------------*/

drivers/md/dm-cache-policy-mq.c

···
 #include <linux/vmalloc.h>
 
 #define DM_MSG_PREFIX "cache-policy-mq"
-#define MQ_VERSION	"1.0.0"
 
 static struct kmem_cache *mq_entry_cache;
 
···
 
 static struct dm_cache_policy_type mq_policy_type = {
 	.name = "mq",
+	.version = {1, 0, 0},
 	.hint_size = 4,
 	.owner = THIS_MODULE,
 	.create = mq_create
···
 
 static struct dm_cache_policy_type default_policy_type = {
 	.name = "default",
+	.version = {1, 0, 0},
 	.hint_size = 4,
 	.owner = THIS_MODULE,
 	.create = mq_create
···
 
 	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;
 	}
 

drivers/md/dm-cache-policy.c

···
 }
 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;

drivers/md/dm-cache-policy.h

···
  * 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. */
···
 	 * 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.