dm space map metadata: fix 'struct sm_metadata' leak on failed create

In dm_sm_metadata_create() we temporarily change the dm_space_map
operations from 'ops' (whose .destroy function deallocates the
sm_metadata) to 'bootstrap_ops' (whose .destroy function doesn't).

If dm_sm_metadata_create() fails in sm_ll_new_metadata() or
sm_ll_extend(), it exits back to dm_tm_create_internal(), which calls
dm_sm_destroy() with the intention of freeing the sm_metadata, but it
doesn't (because the dm_space_map operations is still set to
'bootstrap_ops').

Fix this by setting the dm_space_map operations back to 'ops' if
dm_sm_metadata_create() fails when it is set to 'bootstrap_ops'.

Signed-off-by: Benjamin Marzinski <[e-mail]>
Acked-by: Joe Thornber <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>
Cc: [e-mail]

drivers/md/persistent-data/dm-space-map-metadata.c

···
 	memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
 
 	r = sm_ll_new_metadata(&smm->ll, tm);
-	if (r)
-		return r;
-
-	if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
-		nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
-	r = sm_ll_extend(&smm->ll, nr_blocks);
-	if (r)
-		return r;
-
+	if (!r) {
+		if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
+			nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
+		r = sm_ll_extend(&smm->ll, nr_blocks);
+	}
 	memcpy(&smm->sm, &ops, sizeof(smm->sm));
+	if (r)
+		return r;
 
 	/*
 	 * Now we need to update the newly created data structures with the