ovsdb/transaction.c

   1 /* Copyright (c) 2009, 2010 Nicira Networks
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #include <config.h>
  17
  18 #include "transaction.h"
  19
  20 #include <assert.h>
  21
  22 #include "bitmap.h"
  23 #include "dynamic-string.h"
  24 #include "hash.h"
  25 #include "hmap.h"
  26 #include "json.h"
  27 #include "list.h"
  28 #include "ovsdb-error.h"
  29 #include "ovsdb.h"
  30 #include "row.h"
  31 #include "table.h"
  32 #include "uuid.h"
  33
  34 struct ovsdb_txn {
  35     struct ovsdb *db;
  36     struct list txn_tables;     /* Contains "struct ovsdb_txn_table"s. */
  37     struct ds comment;
  38 };
  39
  40 /* A table modified by a transaction. */
  41 struct ovsdb_txn_table {
  42     struct list node;           /* Element in ovsdb_txn's txn_tables list. */
  43     struct ovsdb_table *table;
  44     struct hmap txn_rows;       /* Contains "struct ovsdb_txn_row"s. */
  45
  46     /* Used by for_each_txn_row(). */
  47     unsigned int serial;        /* Serial number of in-progress iteration. */
  48     unsigned int n_processed;   /* Number of rows processed. */
  49 };
  50
  51 /* A row modified by the transaction:
  52  *
  53  *      - A row added by a transaction will have null 'old' and non-null 'new'.
  54  *
  55  *      - A row deleted by a transaction will have non-null 'old' and null
  56  *        'new'.
  57  *
  58  *      - A row modified by a transaction will have non-null 'old' and 'new'.
  59  *
  60  *      - 'old' and 'new' both null is invalid.  It would indicate that a row
  61  *        was added then deleted within a single transaction, but we instead
  62  *        handle that case by deleting the txn_row entirely.
  63  */
  64 struct ovsdb_txn_row {
  65     struct hmap_node hmap_node; /* In ovsdb_txn_table's txn_rows hmap. */
  66     struct ovsdb_row *old;      /* The old row. */
  67     struct ovsdb_row *new;      /* The new row. */
  68     size_t n_refs;              /* Number of remaining references. */
  69
  70     /* Used by for_each_txn_row(). */
  71     unsigned int serial;        /* Serial number of in-progress commit. */
  72
  73     unsigned long changed[];    /* Bits set to 1 for columns that changed. */
  74 };
  75
  76 static void ovsdb_txn_row_prefree(struct ovsdb_txn_row *);
  77 static struct ovsdb_error * WARN_UNUSED_RESULT
  78 for_each_txn_row(struct ovsdb_txn *txn,
  79                       struct ovsdb_error *(*)(struct ovsdb_txn *,
  80                                               struct ovsdb_txn_row *));
  81
  82 /* Used by for_each_txn_row() to track tables and rows that have been
  83  * processed.  */
  84 static unsigned int serial;
  85
  86 struct ovsdb_txn *
  87 ovsdb_txn_create(struct ovsdb *db)
  88 {
  89     struct ovsdb_txn *txn = xmalloc(sizeof *txn);
  90     txn->db = db;
  91     list_init(&txn->txn_tables);
  92     ds_init(&txn->comment);
  93     return txn;
  94 }
  95
  96 static void
  97 ovsdb_txn_free(struct ovsdb_txn *txn)
  98 {
  99     assert(list_is_empty(&txn->txn_tables));
 100     ds_destroy(&txn->comment);
 101     free(txn);
 102 }
 103
 104 static struct ovsdb_error *
 105 ovsdb_txn_row_abort(struct ovsdb_txn *txn OVS_UNUSED,
 106                     struct ovsdb_txn_row *txn_row)
 107 {
 108     struct ovsdb_row *old = txn_row->old;
 109     struct ovsdb_row *new = txn_row->new;
 110
 111     ovsdb_txn_row_prefree(txn_row);
 112     if (!old) {
 113         hmap_remove(&new->table->rows, &new->hmap_node);
 114     } else if (!new) {
 115         hmap_insert(&old->table->rows, &old->hmap_node, ovsdb_row_hash(old));
 116     } else {
 117         hmap_replace(&new->table->rows, &new->hmap_node, &old->hmap_node);
 118     }
 119     ovsdb_row_destroy(new);
 120     free(txn_row);
 121
 122     return NULL;
 123 }
 124
 125 void
 126 ovsdb_txn_abort(struct ovsdb_txn *txn)
 127 {
 128     ovsdb_error_assert(for_each_txn_row(txn, ovsdb_txn_row_abort));
 129     ovsdb_txn_free(txn);
 130 }
 131
 132 static struct ovsdb_txn_row *
 133 find_txn_row(const struct ovsdb_table *table, const struct uuid *uuid)
 134 {
 135     struct ovsdb_txn_row *txn_row;
 136
 137     if (!table->txn_table) {
 138         return NULL;
 139     }
 140
 141     HMAP_FOR_EACH_WITH_HASH (txn_row, struct ovsdb_txn_row, hmap_node,
 142                              uuid_hash(uuid), &table->txn_table->txn_rows) {
 143         const struct ovsdb_row *row;
 144
 145         row = txn_row->old ? txn_row->old : txn_row->new;
 146         if (uuid_equals(uuid, ovsdb_row_get_uuid(row))) {
 147             return txn_row;
 148         }
 149     }
 150
 151     return NULL;
 152 }
 153
 154 static struct ovsdb_error * WARN_UNUSED_RESULT
 155 ovsdb_txn_adjust_atom_refs(struct ovsdb_txn *txn,
 156                            const struct ovsdb_base_type *base,
 157                            const union ovsdb_atom *atoms, unsigned int n,
 158                            int delta)
 159 {
 160     const struct ovsdb_table *table;
 161     unsigned int i;
 162
 163     if (!ovsdb_base_type_is_strong_ref(base)) {
 164         return NULL;
 165     }
 166
 167     table = base->u.uuid.refTable;
 168     for (i = 0; i < n; i++) {
 169         const struct uuid *uuid = &atoms[i].uuid;
 170         struct ovsdb_txn_row *txn_row = find_txn_row(table, uuid);
 171         if (!txn_row) {
 172             const struct ovsdb_row *row = ovsdb_table_get_row(table, uuid);
 173             if (row) {
 174                 txn_row = ovsdb_txn_row_modify(txn, row)->txn_row;
 175             } else {
 176                 return ovsdb_error("referential integrity violation",
 177                                    "reference to nonexistent row "
 178                                    UUID_FMT, UUID_ARGS(uuid));
 179             }
 180         }
 181         txn_row->n_refs += delta;
 182     }
 183
 184     return NULL;
 185 }
 186
 187 static struct ovsdb_error * WARN_UNUSED_RESULT
 188 ovsdb_txn_adjust_row_refs(struct ovsdb_txn *txn, const struct ovsdb_row *r,
 189                           const struct ovsdb_column *column, int delta)
 190 {
 191     const struct ovsdb_datum *field = &r->fields[column->index];
 192     struct ovsdb_error *error;
 193
 194     error = ovsdb_txn_adjust_atom_refs(txn, &column->type.key,
 195                                        field->keys, field->n, delta);
 196     if (!error) {
 197         error = ovsdb_txn_adjust_atom_refs(txn, &column->type.value,
 198                                            field->values, field->n, delta);
 199     }
 200     return error;
 201 }
 202
 203 static struct ovsdb_error * WARN_UNUSED_RESULT
 204 update_row_ref_count(struct ovsdb_txn *txn, struct ovsdb_txn_row *r)
 205 {
 206     struct ovsdb_table *table = r->old ? r->old->table : r->new->table;
 207     struct shash_node *node;
 208
 209     SHASH_FOR_EACH (node, &table->schema->columns) {
 210         const struct ovsdb_column *column = node->data;
 211         struct ovsdb_error *error;
 212
 213         if (r->old) {
 214             error = ovsdb_txn_adjust_row_refs(txn, r->old, column, -1);
 215             if (error) {
 216                 ovsdb_error_destroy(error);
 217                 return OVSDB_BUG("error decreasing refcount");
 218             }
 219         }
 220         if (r->new) {
 221             error = ovsdb_txn_adjust_row_refs(txn, r->new, column, 1);
 222             if (error) {
 223                 return error;
 224             }
 225         }
 226     }
 227
 228     return NULL;
 229 }
 230
 231 static struct ovsdb_error * WARN_UNUSED_RESULT
 232 check_ref_count(struct ovsdb_txn *txn OVS_UNUSED, struct ovsdb_txn_row *r)
 233 {
 234     if (r->new || !r->n_refs) {
 235         return NULL;
 236     } else {
 237         return ovsdb_error("referential integrity violation",
 238                            "cannot delete %s row "UUID_FMT" because "
 239                            "of %zu remaining reference(s)",
 240                            r->old->table->schema->name,
 241                            UUID_ARGS(ovsdb_row_get_uuid(r->old)),
 242                            r->n_refs);
 243     }
 244 }
 245
 246 static struct ovsdb_error * WARN_UNUSED_RESULT
 247 update_ref_counts(struct ovsdb_txn *txn)
 248 {
 249     struct ovsdb_error *error;
 250
 251     error = for_each_txn_row(txn, update_row_ref_count);
 252     if (error) {
 253         return error;
 254     }
 255
 256     return for_each_txn_row(txn, check_ref_count);
 257 }
 258
 259 static struct ovsdb_error *
 260 ovsdb_txn_row_commit(struct ovsdb_txn *txn OVS_UNUSED,
 261                      struct ovsdb_txn_row *txn_row)
 262 {
 263     ovsdb_txn_row_prefree(txn_row);
 264     if (txn_row->new) {
 265         txn_row->new->n_refs = txn_row->n_refs;
 266     }
 267     ovsdb_row_destroy(txn_row->old);
 268     free(txn_row);
 269
 270     return NULL;
 271 }
 272
 273 static void
 274 add_weak_ref(struct ovsdb_txn *txn,
 275              const struct ovsdb_row *src_, const struct ovsdb_row *dst_)
 276 {
 277     struct ovsdb_row *src = (struct ovsdb_row *) src_;
 278     struct ovsdb_row *dst = (struct ovsdb_row *) dst_;
 279     struct ovsdb_weak_ref *weak;
 280
 281     if (src == dst) {
 282         return;
 283     }
 284
 285     dst = ovsdb_txn_row_modify(txn, dst);
 286
 287     if (!list_is_empty(&dst->dst_refs)) {
 288         /* Omit duplicates. */
 289         weak = CONTAINER_OF(list_back(&dst->dst_refs),
 290                             struct ovsdb_weak_ref, dst_node);
 291         if (weak->src == src) {
 292             return;
 293         }
 294     }
 295
 296     weak = xmalloc(sizeof *weak);
 297     weak->src = src;
 298     list_push_back(&dst->dst_refs, &weak->dst_node);
 299     list_push_back(&src->src_refs, &weak->src_node);
 300 }
 301
 302 static struct ovsdb_error * WARN_UNUSED_RESULT
 303 assess_weak_refs(struct ovsdb_txn *txn, struct ovsdb_txn_row *txn_row)
 304 {
 305     struct ovsdb_table *table;
 306     struct shash_node *node;
 307
 308     if (txn_row->old) {
 309         /* Mark rows that have weak references to 'txn_row' as modified, so
 310          * that their weak references will get reassessed. */
 311         struct ovsdb_weak_ref *weak, *next;
 312
 313         LIST_FOR_EACH_SAFE (weak, next, struct ovsdb_weak_ref, dst_node,
 314                             &txn_row->old->dst_refs) {
 315             if (!weak->src->txn_row) {
 316                 ovsdb_txn_row_modify(txn, weak->src);
 317             }
 318         }
 319     }
 320
 321     if (!txn_row->new) {
 322         /* We don't have to do anything about references that originate at
 323          * 'txn_row', because ovsdb_row_destroy() will remove those weak
 324          * references. */
 325         return NULL;
 326     }
 327
 328     table = txn_row->new->table;
 329     SHASH_FOR_EACH (node, &table->schema->columns) {
 330         const struct ovsdb_column *column = node->data;
 331         struct ovsdb_datum *datum = &txn_row->new->fields[column->index];
 332         unsigned int orig_n, i;
 333         bool zero = false;
 334
 335         orig_n = datum->n;
 336
 337         if (ovsdb_base_type_is_weak_ref(&column->type.key)) {
 338             for (i = 0; i < datum->n; ) {
 339                 const struct ovsdb_row *row;
 340
 341                 row = ovsdb_table_get_row(column->type.key.u.uuid.refTable,
 342                                           &datum->keys[i].uuid);
 343                 if (row) {
 344                     add_weak_ref(txn, txn_row->new, row);
 345                     i++;
 346                 } else {
 347                     if (uuid_is_zero(&datum->keys[i].uuid)) {
 348                         zero = true;
 349                     }
 350                     ovsdb_datum_remove_unsafe(datum, i, &column->type);
 351                 }
 352             }
 353         }
 354
 355         if (ovsdb_base_type_is_weak_ref(&column->type.value)) {
 356             for (i = 0; i < datum->n; ) {
 357                 const struct ovsdb_row *row;
 358
 359                 row = ovsdb_table_get_row(column->type.value.u.uuid.refTable,
 360                                           &datum->values[i].uuid);
 361                 if (row) {
 362                     add_weak_ref(txn, txn_row->new, row);
 363                     i++;
 364                 } else {
 365                     if (uuid_is_zero(&datum->values[i].uuid)) {
 366                         zero = true;
 367                     }
 368                     ovsdb_datum_remove_unsafe(datum, i, &column->type);
 369                 }
 370             }
 371         }
 372
 373         if (datum->n != orig_n) {
 374             bitmap_set1(txn_row->changed, column->index);
 375             ovsdb_datum_sort_assert(datum, column->type.key.type);
 376             if (datum->n < column->type.n_min) {
 377                 const struct uuid *row_uuid = ovsdb_row_get_uuid(txn_row->new);
 378                 if (zero && !txn_row->old) {
 379                     return ovsdb_error(
 380                         "constraint violation",
 381                         "Weak reference column \"%s\" in \"%s\" row "UUID_FMT
 382                         " (inserted within this transaction) contained "
 383                         "all-zeros UUID (probably as the default value for "
 384                         "this column) but deleting this value caused a "
 385                         "constraint volation because this column is not "
 386                         "allowed to be empty.", column->name,
 387                         table->schema->name, UUID_ARGS(row_uuid));
 388                 } else {
 389                     return ovsdb_error(
 390                         "constraint violation",
 391                         "Deletion of %u weak reference(s) to deleted (or "
 392                         "never-existing) rows from column \"%s\" in \"%s\" "
 393                         "row "UUID_FMT" %scaused this column to become empty, "
 394                         "but constraints on this column disallow an "
 395                         "empty column.",
 396                         orig_n - datum->n, column->name, table->schema->name,
 397                         UUID_ARGS(row_uuid),
 398                         (txn_row->old
 399                          ? ""
 400                          : "(inserted within this transaction) "));
 401                 }
 402             }
 403         }
 404     }
 405
 406     return NULL;
 407 }
 408
 409 static struct ovsdb_error * WARN_UNUSED_RESULT
 410 determine_changes(struct ovsdb_txn *txn, struct ovsdb_txn_row *txn_row)
 411 {
 412     struct ovsdb_table *table;
 413
 414     table = (txn_row->old ? txn_row->old : txn_row->new)->table;
 415     if (txn_row->old && txn_row->new) {
 416         struct shash_node *node;
 417         bool changed = false;
 418
 419         SHASH_FOR_EACH (node, &table->schema->columns) {
 420             const struct ovsdb_column *column = node->data;
 421             const struct ovsdb_type *type = &column->type;
 422             unsigned int idx = column->index;
 423
 424             if (!ovsdb_datum_equals(&txn_row->old->fields[idx],
 425                                     &txn_row->new->fields[idx],
 426                                     type)) {
 427                 bitmap_set1(txn_row->changed, idx);
 428                 changed = true;
 429             }
 430         }
 431
 432         if (!changed) {
 433             /* Nothing actually changed in this row, so drop it. */
 434             ovsdb_txn_row_abort(txn, txn_row);
 435         }
 436     } else {
 437         bitmap_set_multiple(txn_row->changed, 0,
 438                             shash_count(&table->schema->columns), 1);
 439     }
 440
 441     return NULL;
 442 }
 443
 444 static struct ovsdb_error * WARN_UNUSED_RESULT
 445 check_max_rows(struct ovsdb_txn *txn)
 446 {
 447     struct ovsdb_txn_table *t;
 448
 449     LIST_FOR_EACH (t, struct ovsdb_txn_table, node, &txn->txn_tables) {
 450         size_t n_rows = hmap_count(&t->table->rows);
 451         unsigned int max_rows = t->table->schema->max_rows;
 452
 453         if (n_rows > max_rows) {
 454             return ovsdb_error("constraint violation",
 455                                "transaction causes \"%s\" table to contain "
 456                                "%zu rows, greater than the schema-defined "
 457                                "limit of %u row(s)",
 458                                t->table->schema->name, n_rows, max_rows);
 459         }
 460     }
 461
 462     return NULL;
 463 }
 464
 465 struct ovsdb_error *
 466 ovsdb_txn_commit(struct ovsdb_txn *txn, bool durable)
 467 {
 468     struct ovsdb_replica *replica;
 469     struct ovsdb_error *error;
 470
 471     /* Figure out what actually changed, and abort early if the transaction
 472      * was really a no-op. */
 473     error = for_each_txn_row(txn, determine_changes);
 474     if (error) {
 475         ovsdb_error_destroy(error);
 476         return OVSDB_BUG("can't happen");
 477     }
 478     if (list_is_empty(&txn->txn_tables)) {
 479         ovsdb_txn_abort(txn);
 480         return NULL;
 481     }
 482
 483     /* Check maximum rows table constraints. */
 484     error = check_max_rows(txn);
 485     if (error) {
 486         ovsdb_txn_abort(txn);
 487         return error;
 488     }
 489
 490     /* Update reference counts and check referential integrity. */
 491     error = update_ref_counts(txn);
 492     if (error) {
 493         ovsdb_txn_abort(txn);
 494         return error;
 495     }
 496
 497     /* Check reference counts and remove bad reference for "weak" referential
 498      * integrity. */
 499     error = for_each_txn_row(txn, assess_weak_refs);
 500     if (error) {
 501         ovsdb_txn_abort(txn);
 502         return error;
 503     }
 504
 505     /* Send the commit to each replica. */
 506     LIST_FOR_EACH (replica, struct ovsdb_replica, node, &txn->db->replicas) {
 507         error = (replica->class->commit)(replica, txn, durable);
 508         if (error) {
 509             /* We don't support two-phase commit so only the first replica is
 510              * allowed to report an error. */
 511             assert(&replica->node == txn->db->replicas.next);
 512
 513             ovsdb_txn_abort(txn);
 514             return error;
 515         }
 516     }
 517
 518     /* Finalize commit. */
 519     txn->db->run_triggers = true;
 520     ovsdb_error_assert(for_each_txn_row(txn, ovsdb_txn_row_commit));
 521     ovsdb_txn_free(txn);
 522
 523     return NULL;
 524 }
 525
 526 void
 527 ovsdb_txn_for_each_change(const struct ovsdb_txn *txn,
 528                           ovsdb_txn_row_cb_func *cb, void *aux)
 529 {
 530     struct ovsdb_txn_table *t;
 531     struct ovsdb_txn_row *r;
 532
 533     LIST_FOR_EACH (t, struct ovsdb_txn_table, node, &txn->txn_tables) {
 534         HMAP_FOR_EACH (r, struct ovsdb_txn_row, hmap_node, &t->txn_rows) {
 535             if (!cb(r->old, r->new, r->changed, aux)) {
 536                 break;
 537             }
 538         }
 539    }
 540 }
 541
 542 static struct ovsdb_txn_table *
 543 ovsdb_txn_create_txn_table(struct ovsdb_txn *txn, struct ovsdb_table *table)
 544 {
 545     if (!table->txn_table) {
 546         struct ovsdb_txn_table *txn_table;
 547
 548         table->txn_table = txn_table = xmalloc(sizeof *table->txn_table);
 549         txn_table->table = table;
 550         hmap_init(&txn_table->txn_rows);
 551         txn_table->serial = serial - 1;
 552         list_push_back(&txn->txn_tables, &txn_table->node);
 553     }
 554     return table->txn_table;
 555 }
 556
 557 static struct ovsdb_txn_row *
 558 ovsdb_txn_row_create(struct ovsdb_txn *txn, struct ovsdb_table *table,
 559                      const struct ovsdb_row *old_, struct ovsdb_row *new)
 560 {
 561     struct ovsdb_row *old = (struct ovsdb_row *) old_;
 562     size_t n_columns = shash_count(&table->schema->columns);
 563     struct ovsdb_txn_table *txn_table;
 564     struct ovsdb_txn_row *txn_row;
 565
 566     txn_row = xzalloc(offsetof(struct ovsdb_txn_row, changed)
 567                       + bitmap_n_bytes(n_columns));
 568     txn_row->old = (struct ovsdb_row *) old;
 569     txn_row->new = new;
 570     txn_row->n_refs = old ? old->n_refs : 0;
 571     txn_row->serial = serial - 1;
 572
 573     if (old) {
 574         old->txn_row = txn_row;
 575     }
 576     if (new) {
 577         new->txn_row = txn_row;
 578     }
 579
 580     txn_table = ovsdb_txn_create_txn_table(txn, table);
 581     hmap_insert(&txn_table->txn_rows, &txn_row->hmap_node,
 582                 ovsdb_row_hash(old ? old : new));
 583
 584     return txn_row;
 585 }
 586
 587 struct ovsdb_row *
 588 ovsdb_txn_row_modify(struct ovsdb_txn *txn, const struct ovsdb_row *ro_row_)
 589 {
 590     struct ovsdb_row *ro_row = (struct ovsdb_row *) ro_row_;
 591
 592     if (ro_row->txn_row) {
 593         assert(ro_row == ro_row->txn_row->new);
 594         return ro_row;
 595     } else {
 596         struct ovsdb_table *table = ro_row->table;
 597         struct ovsdb_row *rw_row;
 598
 599         rw_row = ovsdb_row_clone(ro_row);
 600         rw_row->n_refs = ro_row->n_refs;
 601         uuid_generate(ovsdb_row_get_version_rw(rw_row));
 602         ovsdb_txn_row_create(txn, table, ro_row, rw_row);
 603         hmap_replace(&table->rows, &ro_row->hmap_node, &rw_row->hmap_node);
 604
 605         return rw_row;
 606     }
 607 }
 608
 609 void
 610 ovsdb_txn_row_insert(struct ovsdb_txn *txn, struct ovsdb_row *row)
 611 {
 612     uint32_t hash = ovsdb_row_hash(row);
 613     struct ovsdb_table *table = row->table;
 614
 615     uuid_generate(ovsdb_row_get_version_rw(row));
 616
 617     ovsdb_txn_row_create(txn, table, NULL, row);
 618     hmap_insert(&table->rows, &row->hmap_node, hash);
 619 }
 620
 621 /* 'row' must be assumed destroyed upon return; the caller must not reference
 622  * it again. */
 623 void
 624 ovsdb_txn_row_delete(struct ovsdb_txn *txn, const struct ovsdb_row *row_)
 625 {
 626     struct ovsdb_row *row = (struct ovsdb_row *) row_;
 627     struct ovsdb_table *table = row->table;
 628     struct ovsdb_txn_row *txn_row = row->txn_row;
 629
 630     hmap_remove(&table->rows, &row->hmap_node);
 631
 632     if (!txn_row) {
 633         ovsdb_txn_row_create(txn, table, row, NULL);
 634     } else {
 635         assert(txn_row->new == row);
 636         if (txn_row->old) {
 637             txn_row->new = NULL;
 638         } else {
 639             hmap_remove(&table->txn_table->txn_rows, &txn_row->hmap_node);
 640             free(txn_row);
 641         }
 642         ovsdb_row_destroy(row);
 643     }
 644 }
 645
 646 void
 647 ovsdb_txn_add_comment(struct ovsdb_txn *txn, const char *s)
 648 {
 649     if (txn->comment.length) {
 650         ds_put_char(&txn->comment, '\n');
 651     }
 652     ds_put_cstr(&txn->comment, s);
 653 }
 654
 655 const char *
 656 ovsdb_txn_get_comment(const struct ovsdb_txn *txn)
 657 {
 658     return txn->comment.length ? ds_cstr_ro(&txn->comment) : NULL;
 659 }
 660 \f
 661 static void
 662 ovsdb_txn_row_prefree(struct ovsdb_txn_row *txn_row)
 663 {
 664     struct ovsdb_row *row = txn_row->old ? txn_row->old : txn_row->new;
 665     struct ovsdb_txn_table *txn_table = row->table->txn_table;
 666
 667     txn_table->n_processed--;
 668     hmap_remove(&txn_table->txn_rows, &txn_row->hmap_node);
 669
 670     if (txn_row->old) {
 671         txn_row->old->txn_row = NULL;
 672     }
 673     if (txn_row->new) {
 674         txn_row->new->txn_row = NULL;
 675     }
 676 }
 677
 678 static void
 679 ovsdb_txn_table_destroy(struct ovsdb_txn_table *txn_table)
 680 {
 681     assert(hmap_is_empty(&txn_table->txn_rows));
 682     txn_table->table->txn_table = NULL;
 683     hmap_destroy(&txn_table->txn_rows);
 684     list_remove(&txn_table->node);
 685     free(txn_table);
 686 }
 687
 688 /* Calls 'cb' for every txn_row within 'txn'.  If 'cb' returns nonnull, this
 689  * aborts the iteration and for_each_txn_row() passes the error up.  Otherwise,
 690  * returns a null pointer after iteration is complete.
 691  *
 692  * 'cb' may insert new txn_rows and new txn_tables into 'txn'.  It may delete
 693  * the txn_row that it is passed in, or txn_rows in txn_tables other than the
 694  * one passed to 'cb'.  It may *not* delete txn_rows other than the one passed
 695  * in within the same txn_table.  It may *not* delete any txn_tables.  As long
 696  * as these rules are followed, 'cb' will be called exactly once for each
 697  * txn_row in 'txn', even those added by 'cb'.
 698  */
 699 static struct ovsdb_error * WARN_UNUSED_RESULT
 700 for_each_txn_row(struct ovsdb_txn *txn,
 701                  struct ovsdb_error *(*cb)(struct ovsdb_txn *,
 702                                            struct ovsdb_txn_row *))
 703 {
 704     bool any_work;
 705
 706     serial++;
 707
 708     do {
 709         struct ovsdb_txn_table *t, *next_txn_table;
 710
 711         any_work = false;
 712         LIST_FOR_EACH_SAFE (t, next_txn_table, struct ovsdb_txn_table, node,
 713                             &txn->txn_tables) {
 714             if (t->serial != serial) {
 715                 t->serial = serial;
 716                 t->n_processed = 0;
 717             }
 718
 719             while (t->n_processed < hmap_count(&t->txn_rows)) {
 720                 struct ovsdb_txn_row *r, *next_txn_row;
 721
 722                 HMAP_FOR_EACH_SAFE (r, next_txn_row,
 723                                     struct ovsdb_txn_row, hmap_node,
 724                                     &t->txn_rows) {
 725                     if (r->serial != serial) {
 726                         struct ovsdb_error *error;
 727
 728                         r->serial = serial;
 729                         t->n_processed++;
 730                         any_work = true;
 731
 732                         error = cb(txn, r);
 733                         if (error) {
 734                             return error;
 735                         }
 736                     }
 737                 }
 738             }
 739             if (hmap_is_empty(&t->txn_rows)) {
 740                 /* Table is empty.  Drop it. */
 741                 ovsdb_txn_table_destroy(t);
 742             }
 743         }
 744     } while (any_work);
 745
 746     return NULL;
 747 }