4 files changed, 35 insertions, 25 deletions

diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index bb9f33d5daa2..aed1f1172f9e 100644
--- a/drivers/md/dm-exception-store.h
+++ b/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;
 };
 
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 936b34e0959f..0bbbe3b7431e 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/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;
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 7f6e2e6dcb0d..b558176ff020 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/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)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 462750c66319..dabd58e9aafc 100644
--- a/drivers/md/dm-snap.c
+++ b/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",