Fix wrong dedup_table_size for legacy dedup

If we call ddt_log_load() for legacy ddt, we will end up going into
ddt_log_update_stats() and filling uninitialized value into ddo_dspace.
This value will then get added to dedup_table_size during
ddt_get_dedup_object_stats().

Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Fixes openzfs#17019

Author: davidchenntnx

module/zfs/ddt.c

@@ -1701,9 +1701,11 @@ ddt_load(spa_t *spa)
 			}
 		}
 
-		error = ddt_log_load(ddt);
-		if (error != 0 && error != ENOENT)
-			return (error);
+		if (ddt->ddt_flags & DDT_FLAG_LOG) {
+			error = ddt_log_load(ddt);
+			if (error != 0 && error != ENOENT)
+				return (error);
+		}
 
 		DDT_KSTAT_SET(ddt, dds_log_active_entries,
 		    avl_numnodes(&ddt->ddt_log_active->ddl_tree));

module/zfs/ddt_log.c

@@ -176,11 +176,13 @@ ddt_log_update_stats(ddt_t *ddt)
 	 * that's reasonable to expect anyway.
 	 */
 	dmu_object_info_t doi;
-	uint64_t nblocks;
-	dmu_object_info(ddt->ddt_os, ddt->ddt_log_active->ddl_object, &doi);
-	nblocks = doi.doi_physical_blocks_512;
-	dmu_object_info(ddt->ddt_os, ddt->ddt_log_flushing->ddl_object, &doi);
-	nblocks += doi.doi_physical_blocks_512;
+	uint64_t nblocks = 0;
+	if (dmu_object_info(ddt->ddt_os, ddt->ddt_log_active->ddl_object,
+	    &doi) == 0)
+		nblocks += doi.doi_physical_blocks_512;
+	if (dmu_object_info(ddt->ddt_os, ddt->ddt_log_flushing->ddl_object,
+	    &doi) == 0)
+		nblocks += doi.doi_physical_blocks_512;
 
 	ddt_object_t *ddo = &ddt->ddt_log_stats;
 	ddo->ddo_count =