dm exception store: separate type from instance

Introduce struct dm_exception_store_type.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-exception-store.h

@@ -37,11 +37,15 @@ struct dm_snap_exception {
  * Abstraction to handle the meta/layout of exception stores (the
  * COW device).
  */
-struct dm_exception_store {
+struct dm_exception_store;
+struct dm_exception_store_type {
+	int (*ctr) (struct dm_exception_store *store,
+		    unsigned argc, char **argv);
+
 	/*
 	 * Destroys this object when you've finished with it.
 	 */
-	void (*destroy) (struct dm_exception_store *store);
+	void (*dtr) (struct dm_exception_store *store);
 
 	/*
 	 * The target shouldn't read the COW device until this is
@@ -81,8 +85,13 @@ struct dm_exception_store {
 	void (*fraction_full) (struct dm_exception_store *store,
 			       sector_t *numerator,
 			       sector_t *denominator);
+};
+
+struct dm_exception_store {
+	struct dm_exception_store_type type;
 
 	struct dm_snapshot *snap;
+
 	void *context;
 };
 

drivers/md/dm-snap-persistent.c

@@ -683,12 +683,13 @@ int dm_create_persistent(struct dm_exception_store *store)
 		return -ENOMEM;
 	}
 
-	store->destroy = persistent_destroy;
-	store->read_metadata = persistent_read_metadata;
-	store->prepare_exception = persistent_prepare_exception;
-	store->commit_exception = persistent_commit_exception;
-	store->drop_snapshot = persistent_drop_snapshot;
-	store->fraction_full = persistent_fraction_full;
+	store->type.dtr = persistent_destroy;
+	store->type.read_metadata = persistent_read_metadata;
+	store->type.prepare_exception = persistent_prepare_exception;
+	store->type.commit_exception = persistent_commit_exception;
+	store->type.drop_snapshot = persistent_drop_snapshot;
+	store->type.fraction_full = persistent_fraction_full;
+
 	store->context = ps;
 
 	return 0;

drivers/md/dm-snap-transient.c

@@ -39,7 +39,7 @@ static int transient_read_metadata(struct dm_exception_store *store,
 static int transient_prepare_exception(struct dm_exception_store *store,
 				       struct dm_snap_exception *e)
 {
-	struct transient_c *tc = (struct transient_c *) store->context;
+	struct transient_c *tc = store->context;
 	sector_t size = get_dev_size(store->snap->cow->bdev);
 
 	if (size < (tc->next_free + store->snap->chunk_size))
@@ -71,12 +71,12 @@ int dm_create_transient(struct dm_exception_store *store)
 {
 	struct transient_c *tc;
 
-	store->destroy = transient_destroy;
-	store->read_metadata = transient_read_metadata;
-	store->prepare_exception = transient_prepare_exception;
-	store->commit_exception = transient_commit_exception;
-	store->drop_snapshot = NULL;
-	store->fraction_full = transient_fraction_full;
+	store->type.dtr = transient_destroy;
+	store->type.read_metadata = transient_read_metadata;
+	store->type.prepare_exception = transient_prepare_exception;
+	store->type.commit_exception = transient_commit_exception;
+	store->type.drop_snapshot = NULL;
+	store->type.fraction_full = transient_fraction_full;
 
 	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
 	if (!tc)

drivers/md/dm-snap.c

@@ -665,7 +665,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	spin_lock_init(&s->tracked_chunk_lock);
 
 	/* Metadata must only be loaded into one table at once */
-	r = s->store.read_metadata(&s->store, dm_add_exception, (void *)s);
+	r = s->store.type.read_metadata(&s->store, dm_add_exception, (void *)s);
 	if (r < 0) {
 		ti->error = "Failed to read snapshot metadata";
 		goto bad_load_and_register;
@@ -700,7 +700,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	dm_kcopyd_client_destroy(s->kcopyd_client);
 
  bad5:
-	s->store.destroy(&s->store);
+	s->store.type.dtr(&s->store);
 
  bad4:
 	exit_exception_table(&s->pending, pending_cache);
@@ -725,7 +725,7 @@ static void __free_exceptions(struct dm_snapshot *s)
 	exit_exception_table(&s->pending, pending_cache);
 	exit_exception_table(&s->complete, exception_cache);
 
-	s->store.destroy(&s->store);
+	s->store.type.dtr(&s->store);
 }
 
 static void snapshot_dtr(struct dm_target *ti)
@@ -820,8 +820,8 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err)
 	else if (err == -ENOMEM)
 		DMERR("Invalidating snapshot: Unable to allocate exception.");
 
-	if (s->store.drop_snapshot)
-		s->store.drop_snapshot(&s->store);
+	if (s->store.type.drop_snapshot)
+		s->store.type.drop_snapshot(&s->store);
 
 	s->valid = 0;
 
@@ -943,8 +943,8 @@ static void copy_callback(int read_err, unsigned long write_err, void *context)
 
 	else
 		/* Update the metadata if we are persistent */
-		s->store.commit_exception(&s->store, &pe->e, commit_callback,
-					  pe);
+		s->store.type.commit_exception(&s->store, &pe->e,
+					       commit_callback, pe);
 }
 
 /*
@@ -1010,7 +1010,7 @@ __find_pending_exception(struct dm_snapshot *s,
 	atomic_set(&pe->ref_count, 0);
 	pe->started = 0;
 
-	if (s->store.prepare_exception(&s->store, &pe->e)) {
+	if (s->store.type.prepare_exception(&s->store, &pe->e)) {
 		free_pending_exception(pe);
 		return NULL;
 	}
@@ -1149,9 +1149,9 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
 		if (!snap->valid)
 			snprintf(result, maxlen, "Invalid");
 		else {
-			if (snap->store.fraction_full) {
+			if (snap->store.type.fraction_full) {
 				sector_t numerator, denominator;
-				snap->store.fraction_full(&snap->store,
+				snap->store.type.fraction_full(&snap->store,
 							  &numerator,
 							  &denominator);
 				snprintf(result, maxlen, "%llu/%llu",