[ovs-dev] [PATCH] ovsdb-idl: Fix *_is_new() IDL functions

Mark Gray mark.d.gray at redhat.com
Thu Oct 1 09:32:18 UTC 2020


On 30/09/2020 10:32, Dumitru Ceara wrote:
> On 9/30/20 11:21 AM, Dumitru Ceara wrote:
>> On 9/29/20 8:34 PM, Mark Gray wrote:
>>> Currently all functions of the type *_is_new() always return
>>> 'false'. This patch resolves this issue by using the
>>> 'OVSDB_IDL_CHANGE_INSERT' 'change_seqno' instead of the
>>> 'OVSDB_IDL_CHANGE_MODIFY' 'change_seqno' to determine if a row
>>> is new and by resetting the 'OVSDB_IDL_CHANGE_INSERT'
>>> 'change_seqno' on clear.
>>>
>>> Further to this, the code is also updated to match this
>>> behaviour:
>>>
>>> When a row is inserted, the 'OVSDB_IDL_CHANGE_INSERT'
>>> 'change_seqno' is updated to match the new database
>>> change_seqno. The 'OVSDB_IDL_CHANGE_MODIFY' 'change_seqno'
>>> is not set for inserted rows (only for updated rows).
>>>
>>> At the end of a run, ovsdb_idl_db_track_clear() should be
>>> called to clear all tracking information, this includes
>>> resetting all row 'change_seqno' to zero. This will ensure
>>> that subsequent runs will not see a previously 'new' row.
>>>
>>> add_tracked_change_for_references() is updated to only
>>> track rows that reference the current row.
>>>
>>> Signed-off-by: Mark Gray <mark.d.gray at redhat.com>
>>> Suggested-by: Dumitru Ceara <dceara at redhat.com>
>>> Reported-at: https://bugzilla.redhat.com/1883562
>>
>> Hi Mark,
>>
>> Thanks for working on this, it definitely looks like a nasty bug to me!
>>
>> We were lucky to not hit it in ovn-controller before. That's just
>> because all the "update" operations were handled there as "delete" +
>> "insert" but that is not mandatory and might change.

Very lucky!

>>
>>> ---
>>>  lib/ovsdb-idl.c     | 39 +++++++++++++++++++++++++++------------
>>>  ovsdb/ovsdb-idlc.in |  2 +-
>>>  2 files changed, 28 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
>>> index d8f221ca6..3cfd73871 100644
>>> --- a/lib/ovsdb-idl.c
>>> +++ b/lib/ovsdb-idl.c
>>> @@ -1959,6 +1959,11 @@ ovsdb_idl_db_track_clear(struct ovsdb_idl_db *db)
>>>                      free(row->updated);
>>>                      row->updated = NULL;
>>>                  }
>>> +
>>> +                row->change_seqno[OVSDB_IDL_CHANGE_INSERT] =
>>> +                    row->change_seqno[OVSDB_IDL_CHANGE_MODIFY] =
>>> +                    row->change_seqno[OVSDB_IDL_CHANGE_DELETE] = 0;
>>> +
>>>                  ovs_list_remove(&row->track_node);
>>>                  ovs_list_init(&row->track_node);
>>>                  if (ovsdb_idl_row_is_orphan(row) && row->tracked_old_datum) {
>>> @@ -2684,24 +2689,27 @@ ovsdb_idl_process_update2(struct ovsdb_idl_table *table,
>>>      return OVSDB_IDL_UPDATE_DB_CHANGED;
>>>  }
>>>  
>>> -/* Recursively add rows to tracked change lists for current row
>>> - * and the rows that reference this row. */
>>> +/* Recursively add rows to tracked change lists for all rows that reference
>>> +   'row'. */
>>>  static void
>>>  add_tracked_change_for_references(struct ovsdb_idl_row *row)
>>>  {
>>> -    if (ovs_list_is_empty(&row->track_node) &&
>>> -            ovsdb_idl_track_is_set(row->table)) {
>>> -        ovs_list_push_back(&row->table->track_list,
>>> -                           &row->track_node);
>>> -        row->change_seqno[OVSDB_IDL_CHANGE_MODIFY]
>>> -            = row->table->change_seqno[OVSDB_IDL_CHANGE_MODIFY]
>>> -            = row->table->db->change_seqno + 1;
>>> -
>>>          const struct ovsdb_idl_arc *arc;
>>>          LIST_FOR_EACH (arc, dst_node, &row->dst_arcs) {
>>> -            add_tracked_change_for_references(arc->src);
>>> +            struct ovsdb_idl_row *ref = arc->src;
>>> +
>>> +            if (ovs_list_is_empty(&ref->track_node) &&
>>> +                ovsdb_idl_track_is_set(ref->table)) {
>>> +                    ovs_list_push_back(&ref->table->track_list,
>>> +                                       &ref->track_node);
>>> +
>>> +                ref->change_seqno[OVSDB_IDL_CHANGE_MODIFY]
>>> +                    = ref->table->change_seqno[OVSDB_IDL_CHANGE_MODIFY]
>>> +                    = ref->table->db->change_seqno + 1;
>>> +
>>> +                add_tracked_change_for_references(ref);
>>> +            }
>>>          }
>>> -    }
>>>  }
>>>  
>>>  
>>> @@ -2767,7 +2775,14 @@ ovsdb_idl_row_change__(struct ovsdb_idl_row *row, const struct json *row_json,
>>>                      row->change_seqno[change]
>>>                          = row->table->change_seqno[change]
>>>                          = row->table->db->change_seqno + 1;
>>> +
>>>                      if (table->modes[column_idx] & OVSDB_IDL_TRACK) {
>>> +                        if (ovs_list_is_empty(&row->track_node) &&
>>> +                            ovsdb_idl_track_is_set(row->table)) {
>>> +                            ovs_list_push_back(&row->table->track_list,
>>> +                                               &row->track_node);
>>> +                        }
>>> +
>>>                          add_tracked_change_for_references(row);
>>>                          if (!row->updated) {
>>>                              row->updated = bitmap_allocate(class->n_columns);
>>> diff --git a/ovsdb/ovsdb-idlc.in b/ovsdb/ovsdb-idlc.in
>>> index 698fe25f3..89c3eb682 100755
>>> --- a/ovsdb/ovsdb-idlc.in
>>> +++ b/ovsdb/ovsdb-idlc.in
>>> @@ -282,7 +282,7 @@ const struct %(s)s *%(s)s_table_track_get_first(const struct %(s)s_table *);
>>>  /* Returns true if 'row' was inserted since the last change tracking reset. */
>>>  static inline bool %(s)s_is_new(const struct %(s)s *row)
>>>  {
>>> -    return %(s)s_row_get_seqno(row, OVSDB_IDL_CHANGE_MODIFY) == 0;
>>> +    return %(s)s_row_get_seqno(row, OVSDB_IDL_CHANGE_INSERT) > 0;
>>
>> This causes some issues with records created by the IDL client (e.g.,
>> ovn-controller). Those are created with ovsdb_idl_txn_insert() and we
>> don't set the OVSDB_IDL_CHANGE_INSERT change_seqno in that case.
>>
>> Essentially *_is_new() will never return true for rows inserted locally.
>>
> 
> It would also be nice if we could add some OVS self tests in
> ovsdb-idl.at for all these changes.

Good idea, I will have a look at this suite of tests and see what can be
done. Thanks for the suggestion and review.
> 
> Thanks,
> Dumitru
> 



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