ovsdb-idl: Tracking - preserve data for deleted rows.

OVSDB IDL can track changes, but for deleted rows, the data is
destroyed and only uuid is tracked. In some cases we need to
check the data of the deleted rows. This patch preserves data
for deleted rows until track clear is called.

Signed-off-by: Han Zhou <hzhou8@ebay.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

lib/ovsdb-idl-provider.h

@@ -73,6 +73,7 @@ struct ovsdb_idl_row {
     struct ovs_list dst_arcs;   /* Backward arcs (ovsdb_idl_arc.dst_node). */
     struct ovsdb_idl_table *table; /* Containing table. */
     struct ovsdb_datum *old_datum; /* Committed data (null if orphaned). */
+    bool parsed; /* Whether the row is parsed. */
 
     /* Transactional data. */
     struct ovsdb_datum *new_datum; /* Modified data (null to delete row). */
@@ -88,6 +89,7 @@ struct ovsdb_idl_row {
     unsigned int change_seqno[OVSDB_IDL_CHANGE_MAX];
     struct ovs_list track_node; /* Rows modified/added/deleted by IDL */
     unsigned long int *updated; /* Bitmap of columns updated by IDL */
+    struct ovsdb_datum *tracked_old_datum; /* Old deleted data. */
 };
 
 struct ovsdb_idl_column {

lib/ovsdb-idl.c

@@ -1828,7 +1828,16 @@ ovsdb_idl_db_track_clear(struct ovsdb_idl_db *db)
                 }
                 ovs_list_remove(&row->track_node);
                 ovs_list_init(&row->track_node);
-                if (ovsdb_idl_row_is_orphan(row)) {
+                if (ovsdb_idl_row_is_orphan(row) && row->tracked_old_datum) {
+                    ovsdb_idl_row_unparse(row);
+                    const struct ovsdb_idl_table_class *class =
+                                                        row->table->class_;
+                    for (size_t c = 0; c < class->n_columns; c++) {
+                        ovsdb_datum_destroy(&row->tracked_old_datum[c],
+                                            &class->columns[c].type);
+                    }
+                    free(row->tracked_old_datum);
+                    row->tracked_old_datum = NULL;
                     free(row);
                 }
             }
@@ -2665,10 +2674,14 @@ ovsdb_idl_row_parse(struct ovsdb_idl_row *row)
     const struct ovsdb_idl_table_class *class = row->table->class_;
     size_t i;
 
+    if (row->parsed) {
+        ovsdb_idl_row_unparse(row);
+    }
     for (i = 0; i < class->n_columns; i++) {
         const struct ovsdb_idl_column *c = &class->columns[i];
         (c->parse)(row, &row->old_datum[i]);
     }
+    row->parsed = true;
 }
 
 static void
@@ -2677,10 +2690,14 @@ ovsdb_idl_row_unparse(struct ovsdb_idl_row *row)
     const struct ovsdb_idl_table_class *class = row->table->class_;
     size_t i;
 
+    if (!row->parsed) {
+        return;
+    }
     for (i = 0; i < class->n_columns; i++) {
         const struct ovsdb_idl_column *c = &class->columns[i];
         (c->unparse)(row);
     }
+    row->parsed = false;
 }
 
 /* The OVSDB-IDL Compound Indexes feature allows for the creation of custom
@@ -3008,13 +3025,18 @@ ovsdb_idl_row_clear_old(struct ovsdb_idl_row *row)
 {
     ovs_assert(row->old_datum == row->new_datum);
     if (!ovsdb_idl_row_is_orphan(row)) {
-        const struct ovsdb_idl_table_class *class = row->table->class_;
-        size_t i;
+        if (ovsdb_idl_track_is_set(row->table)) {
+            row->tracked_old_datum = row->old_datum;
+        } else {
+            const struct ovsdb_idl_table_class *class = row->table->class_;
+            size_t i;
 
-        for (i = 0; i < class->n_columns; i++) {
-            ovsdb_datum_destroy(&row->old_datum[i], &class->columns[i].type);
+            for (i = 0; i < class->n_columns; i++) {
+                ovsdb_datum_destroy(&row->old_datum[i],
+                                    &class->columns[i].type);
+            }
+            free(row->old_datum);
         }
-        free(row->old_datum);
         row->old_datum = row->new_datum = NULL;
     }
 }
@@ -3187,6 +3209,7 @@ ovsdb_idl_row_destroy_postprocess(struct ovsdb_idl_db *db)
             LIST_FOR_EACH_SAFE(row, next, track_node, &table->track_list) {
                 if (!ovsdb_idl_track_is_set(row->table)) {
                     ovs_list_remove(&row->track_node);
+                    ovsdb_idl_row_unparse(row);
                     free(row);
                 }
             }
@@ -3217,7 +3240,6 @@ static void
 ovsdb_idl_delete_row(struct ovsdb_idl_row *row)
 {
     ovsdb_idl_remove_from_indexes(row);
-    ovsdb_idl_row_unparse(row);
     ovsdb_idl_row_clear_arcs(row, true);
     ovsdb_idl_row_clear_old(row);
     if (ovs_list_is_empty(&row->dst_arcs)) {