source3/lib/g_lock.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    global locks based on dbwrap and messaging
   4    Copyright (C) 2009 by Volker Lendecke
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21 #include "system/filesys.h"
  22 #include "lib/util/server_id.h"
  23 #include "dbwrap/dbwrap.h"
  24 #include "dbwrap/dbwrap_open.h"
  25 #include "dbwrap/dbwrap_watch.h"
  26 #include "g_lock.h"
  27 #include "util_tdb.h"
  28 #include "../lib/util/tevent_ntstatus.h"
  29 #include "messages.h"
  30 #include "serverid.h"
  31
  32 struct g_lock_ctx {
  33         struct db_context *db;
  34         struct messaging_context *msg;
  35 };
  36
  37 /*
  38  * The "g_lock.tdb" file contains records, indexed by the 0-terminated
  39  * lockname. The record contains an array of "struct g_lock_rec"
  40  * structures.
  41  */
  42
  43 #define G_LOCK_REC_LENGTH (SERVER_ID_BUF_LENGTH+1)
  44
  45 static void g_lock_rec_put(uint8_t buf[G_LOCK_REC_LENGTH],
  46                            const struct g_lock_rec rec)
  47 {
  48         SCVAL(buf, 0, rec.lock_type);
  49         server_id_put(buf+1, rec.pid);
  50 }
  51
  52 static void g_lock_rec_get(struct g_lock_rec *rec,
  53                            const uint8_t buf[G_LOCK_REC_LENGTH])
  54 {
  55         rec->lock_type = CVAL(buf, 0);
  56         server_id_get(&rec->pid, buf+1);
  57 }
  58
  59 static ssize_t g_lock_put(uint8_t *buf, size_t buflen,
  60                           const struct g_lock_rec *locks,
  61                           size_t num_locks,
  62                           const uint8_t *data, size_t datalen)
  63 {
  64         size_t i, len, ofs;
  65
  66         if (num_locks > UINT32_MAX/G_LOCK_REC_LENGTH) {
  67                 return -1;
  68         }
  69
  70         len = num_locks * G_LOCK_REC_LENGTH;
  71
  72         len += sizeof(uint32_t);
  73         if (len < sizeof(uint32_t)) {
  74                 return -1;
  75         }
  76
  77         len += datalen;
  78         if (len < datalen) {
  79                 return -1;
  80         }
  81
  82         if (len > buflen) {
  83                 return len;
  84         }
  85
  86         ofs = 0;
  87         SIVAL(buf, ofs, num_locks);
  88         ofs += sizeof(uint32_t);
  89
  90         for (i=0; i<num_locks; i++) {
  91                 g_lock_rec_put(buf+ofs, locks[i]);
  92                 ofs += G_LOCK_REC_LENGTH;
  93         }
  94
  95         if ((data != NULL) && (datalen != 0)) {
  96                 memcpy(buf+ofs, data, datalen);
  97         }
  98
  99         return len;
 100 }
 101
 102 static ssize_t g_lock_get(TDB_DATA recval,
 103                           struct g_lock_rec *locks, size_t num_locks,
 104                           uint8_t **data, size_t *datalen)
 105 {
 106         size_t found_locks;
 107
 108         if (recval.dsize < sizeof(uint32_t)) {
 109                 /* Fresh or invalid record */
 110                 found_locks = 0;
 111                 goto done;
 112         }
 113
 114         found_locks = IVAL(recval.dptr, 0);
 115         recval.dptr += sizeof(uint32_t);
 116         recval.dsize -= sizeof(uint32_t);
 117
 118         if (found_locks > recval.dsize/G_LOCK_REC_LENGTH) {
 119                 /* Invalid record */
 120                 return 0;
 121         }
 122
 123         if (found_locks <= num_locks) {
 124                 size_t i;
 125
 126                 for (i=0; i<found_locks; i++) {
 127                         g_lock_rec_get(&locks[i], recval.dptr);
 128                         recval.dptr += G_LOCK_REC_LENGTH;
 129                         recval.dsize -= G_LOCK_REC_LENGTH;
 130                 }
 131         } else {
 132                 /*
 133                  * Not enough space passed in by the caller, don't
 134                  * parse the locks.
 135                  */
 136                 recval.dptr += found_locks * G_LOCK_REC_LENGTH;
 137                 recval.dsize -= found_locks * G_LOCK_REC_LENGTH;
 138         }
 139
 140 done:
 141         if (data != NULL) {
 142                 *data = recval.dptr;
 143         }
 144         if (datalen != NULL) {
 145                 *datalen = recval.dsize;
 146         }
 147         return found_locks;
 148 }
 149
 150 static NTSTATUS g_lock_get_talloc(TALLOC_CTX *mem_ctx, TDB_DATA recval,
 151                                   struct g_lock_rec **plocks,
 152                                   size_t *pnum_locks,
 153                                   uint8_t **data, size_t *datalen)
 154 {
 155         struct g_lock_rec *locks;
 156         ssize_t num_locks;
 157
 158         num_locks = g_lock_get(recval, NULL, 0, NULL, NULL);
 159         if (num_locks == -1) {
 160                 return NT_STATUS_INTERNAL_DB_CORRUPTION;
 161         }
 162         locks = talloc_array(mem_ctx, struct g_lock_rec, num_locks);
 163         if (locks == NULL) {
 164                 return NT_STATUS_NO_MEMORY;
 165         }
 166         g_lock_get(recval, locks, num_locks, data, datalen);
 167
 168         *plocks = locks;
 169         *pnum_locks = num_locks;
 170
 171         return NT_STATUS_OK;
 172 }
 173
 174 struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
 175                                    struct messaging_context *msg)
 176 {
 177         struct g_lock_ctx *result;
 178         struct db_context *backend;
 179         char *db_path;
 180
 181         result = talloc(mem_ctx, struct g_lock_ctx);
 182         if (result == NULL) {
 183                 return NULL;
 184         }
 185         result->msg = msg;
 186
 187         db_path = lock_path("g_lock.tdb");
 188         if (db_path == NULL) {
 189                 TALLOC_FREE(result);
 190                 return NULL;
 191         }
 192
 193         backend = db_open(result, db_path, 0,
 194                           TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH,
 195                           O_RDWR|O_CREAT, 0600,
 196                           DBWRAP_LOCK_ORDER_3,
 197                           DBWRAP_FLAG_NONE);
 198         TALLOC_FREE(db_path);
 199         if (backend == NULL) {
 200                 DEBUG(1, ("g_lock_init: Could not open g_lock.tdb\n"));
 201                 TALLOC_FREE(result);
 202                 return NULL;
 203         }
 204
 205         result->db = db_open_watched(result, backend, msg);
 206         if (result->db == NULL) {
 207                 DBG_WARNING("g_lock_init: db_open_watched failed\n");
 208                 TALLOC_FREE(result);
 209                 return NULL;
 210         }
 211         return result;
 212 }
 213
 214 static bool g_lock_conflicts(enum g_lock_type l1, enum g_lock_type l2)
 215 {
 216         /*
 217          * Only tested write locks so far. Very likely this routine
 218          * needs to be fixed for read locks....
 219          */
 220         if ((l1 == G_LOCK_READ) && (l2 == G_LOCK_READ)) {
 221                 return false;
 222         }
 223         return true;
 224 }
 225
 226 static NTSTATUS g_lock_record_store(struct db_record *rec,
 227                                     const struct g_lock_rec *locks,
 228                                     size_t num_locks,
 229                                     const uint8_t *data, size_t datalen)
 230 {
 231         ssize_t len;
 232         uint8_t *buf;
 233         NTSTATUS status;
 234
 235         len = g_lock_put(NULL, 0, locks, num_locks, data, datalen);
 236         if (len == -1) {
 237                 return NT_STATUS_BUFFER_TOO_SMALL;
 238         }
 239
 240         buf = talloc_array(rec, uint8_t, len);
 241         if (buf == NULL) {
 242                 return NT_STATUS_NO_MEMORY;
 243         }
 244
 245         g_lock_put(buf, len, locks, num_locks, data, datalen);
 246
 247         status = dbwrap_record_store(
 248                 rec, (TDB_DATA) { .dptr = buf, .dsize = len }, 0);
 249
 250         TALLOC_FREE(buf);
 251
 252         return status;
 253 }
 254
 255 static NTSTATUS g_lock_trylock(struct db_record *rec, struct server_id self,
 256                                enum g_lock_type type,
 257                                struct server_id *blocker)
 258 {
 259         TDB_DATA data, userdata;
 260         size_t i, num_locks, my_lock;
 261         struct g_lock_rec *locks, *tmp;
 262         NTSTATUS status;
 263         bool modified = false;
 264
 265         data = dbwrap_record_get_value(rec);
 266
 267         status = g_lock_get_talloc(talloc_tos(), data, &locks, &num_locks,
 268                                    &userdata.dptr, &userdata.dsize);
 269         if (!NT_STATUS_IS_OK(status)) {
 270                 return status;
 271         }
 272
 273         my_lock = num_locks;    /* doesn't exist yet */
 274
 275         if ((type == G_LOCK_READ) && (num_locks > 0)) {
 276                 /*
 277                  * Read locks can stay around forever if the process
 278                  * dies. Do a heuristic check for process existence:
 279                  * Check one random process for existence. Hopefully
 280                  * this will keep runaway read locks under control.
 281                  */
 282                 i = generate_random() % num_locks;
 283
 284                 if (!serverid_exists(&locks[i].pid)) {
 285                         locks[i] = locks[num_locks-1];
 286                         num_locks -=1;
 287                         modified = true;
 288                 }
 289         }
 290
 291         for (i=0; i<num_locks; i++) {
 292                 struct g_lock_rec *lock = &locks[i];
 293
 294                 if (serverid_equal(&self, &lock->pid)) {
 295                         if (lock->lock_type == type) {
 296                                 status = NT_STATUS_WAS_LOCKED;
 297                                 goto done;
 298                         }
 299                         my_lock = i;
 300                         break;
 301                 }
 302         }
 303
 304         i=0;
 305
 306         while (i < num_locks) {
 307                 if (i == my_lock) {
 308                         i++;
 309                         continue;
 310                 }
 311
 312                 if (g_lock_conflicts(type, locks[i].lock_type)) {
 313                         struct server_id pid = locks[i].pid;
 314
 315                         /*
 316                          * As the serverid_exists might recurse into
 317                          * the g_lock code, we use
 318                          * SERVERID_UNIQUE_ID_NOT_TO_VERIFY to avoid the loop
 319                          */
 320                         pid.unique_id = SERVERID_UNIQUE_ID_NOT_TO_VERIFY;
 321
 322                         if (serverid_exists(&pid)) {
 323                                 status = NT_STATUS_LOCK_NOT_GRANTED;
 324                                 *blocker = locks[i].pid;
 325                                 goto done;
 326                         }
 327
 328                         /*
 329                          * Delete stale conflicting entry
 330                          */
 331                         locks[i] = locks[num_locks-1];
 332                         num_locks -= 1;
 333                         modified = true;
 334                         continue;
 335                 }
 336                 i++;
 337         }
 338
 339         if (my_lock >= num_locks) {
 340                 tmp = talloc_realloc(talloc_tos(), locks, struct g_lock_rec,
 341                                      num_locks+1);
 342                 if (tmp == NULL) {
 343                         status = NT_STATUS_NO_MEMORY;
 344                         goto done;
 345                 }
 346                 locks = tmp;
 347                 my_lock = num_locks;
 348                 num_locks += 1;
 349         }
 350
 351         locks[my_lock] = (struct g_lock_rec){ .pid = self, .lock_type = type };
 352         modified = true;
 353
 354         status = NT_STATUS_OK;
 355 done:
 356         if (modified) {
 357                 NTSTATUS store_status;
 358                 store_status = g_lock_record_store(
 359                         rec, locks, num_locks, userdata.dptr, userdata.dsize);
 360                 if (!NT_STATUS_IS_OK(store_status)) {
 361                         DBG_WARNING("g_lock_record_store failed: %s\n",
 362                                     nt_errstr(store_status));
 363                         status = store_status;
 364                 }
 365         }
 366         TALLOC_FREE(locks);
 367         return status;
 368 }
 369
 370 struct g_lock_lock_state {
 371         struct tevent_context *ev;
 372         struct g_lock_ctx *ctx;
 373         const char *name;
 374         enum g_lock_type type;
 375 };
 376
 377 static void g_lock_lock_retry(struct tevent_req *subreq);
 378
 379 struct tevent_req *g_lock_lock_send(TALLOC_CTX *mem_ctx,
 380                                     struct tevent_context *ev,
 381                                     struct g_lock_ctx *ctx,
 382                                     const char *name,
 383                                     enum g_lock_type type)
 384 {
 385         struct tevent_req *req, *subreq;
 386         struct g_lock_lock_state *state;
 387         struct db_record *rec;
 388         struct server_id self, blocker;
 389         NTSTATUS status;
 390
 391         req = tevent_req_create(mem_ctx, &state, struct g_lock_lock_state);
 392         if (req == NULL) {
 393                 return NULL;
 394         }
 395         state->ev = ev;
 396         state->ctx = ctx;
 397         state->name = name;
 398         state->type = type;
 399
 400         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 401                                   string_term_tdb_data(state->name));
 402         if (rec == NULL) {
 403                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 404                 tevent_req_nterror(req, NT_STATUS_LOCK_NOT_GRANTED);
 405                 return tevent_req_post(req, ev);
 406         }
 407
 408         self = messaging_server_id(state->ctx->msg);
 409
 410         status = g_lock_trylock(rec, self, state->type, &blocker);
 411         if (NT_STATUS_IS_OK(status)) {
 412                 TALLOC_FREE(rec);
 413                 tevent_req_done(req);
 414                 return tevent_req_post(req, ev);
 415         }
 416         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 417                 TALLOC_FREE(rec);
 418                 tevent_req_nterror(req, status);
 419                 return tevent_req_post(req, ev);
 420         }
 421         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 422         TALLOC_FREE(rec);
 423         if (tevent_req_nomem(subreq, req)) {
 424                 return tevent_req_post(req, ev);
 425         }
 426         if (!tevent_req_set_endtime(
 427                     subreq, state->ev,
 428                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 429                 tevent_req_oom(req);
 430                 return tevent_req_post(req, ev);
 431         }
 432         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 433         return req;
 434 }
 435
 436 static void g_lock_lock_retry(struct tevent_req *subreq)
 437 {
 438         struct tevent_req *req = tevent_req_callback_data(
 439                 subreq, struct tevent_req);
 440         struct g_lock_lock_state *state = tevent_req_data(
 441                 req, struct g_lock_lock_state);
 442         struct server_id self = messaging_server_id(state->ctx->msg);
 443         struct server_id blocker;
 444         struct db_record *rec;
 445         NTSTATUS status;
 446
 447         status = dbwrap_watched_watch_recv(subreq, talloc_tos(), &rec, NULL,
 448                                            NULL);
 449         TALLOC_FREE(subreq);
 450
 451         if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT)) {
 452                 rec = dbwrap_fetch_locked(
 453                         state->ctx->db, talloc_tos(),
 454                         string_term_tdb_data(state->name));
 455                 if (rec == NULL) {
 456                         status = map_nt_error_from_unix(errno);
 457                 } else {
 458                         status = NT_STATUS_OK;
 459                 }
 460         }
 461
 462         if (tevent_req_nterror(req, status)) {
 463                 return;
 464         }
 465         status = g_lock_trylock(rec, self, state->type, &blocker);
 466         if (NT_STATUS_IS_OK(status)) {
 467                 TALLOC_FREE(rec);
 468                 tevent_req_done(req);
 469                 return;
 470         }
 471         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 472                 TALLOC_FREE(rec);
 473                 tevent_req_nterror(req, status);
 474                 return;
 475         }
 476         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 477         TALLOC_FREE(rec);
 478         if (tevent_req_nomem(subreq, req)) {
 479                 return;
 480         }
 481         if (!tevent_req_set_endtime(
 482                     subreq, state->ev,
 483                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 484                 tevent_req_oom(req);
 485                 return;
 486         }
 487         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 488         return;
 489
 490 }
 491
 492 NTSTATUS g_lock_lock_recv(struct tevent_req *req)
 493 {
 494         return tevent_req_simple_recv_ntstatus(req);
 495 }
 496
 497 NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
 498                      enum g_lock_type type, struct timeval timeout)
 499 {
 500         TALLOC_CTX *frame = talloc_stackframe();
 501         struct tevent_context *ev;
 502         struct tevent_req *req;
 503         struct timeval end;
 504         NTSTATUS status = NT_STATUS_NO_MEMORY;
 505
 506         ev = samba_tevent_context_init(frame);
 507         if (ev == NULL) {
 508                 goto fail;
 509         }
 510         req = g_lock_lock_send(frame, ev, ctx, name, type);
 511         if (req == NULL) {
 512                 goto fail;
 513         }
 514         end = timeval_current_ofs(timeout.tv_sec, timeout.tv_usec);
 515         if (!tevent_req_set_endtime(req, ev, end)) {
 516                 goto fail;
 517         }
 518         if (!tevent_req_poll_ntstatus(req, ev, &status)) {
 519                 goto fail;
 520         }
 521         status = g_lock_lock_recv(req);
 522  fail:
 523         TALLOC_FREE(frame);
 524         return status;
 525 }
 526
 527 NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
 528 {
 529         struct server_id self = messaging_server_id(ctx->msg);
 530         struct db_record *rec = NULL;
 531         struct g_lock_rec *locks = NULL;
 532         size_t i, num_locks;
 533         NTSTATUS status;
 534         TDB_DATA value, userdata;
 535
 536         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 537                                   string_term_tdb_data(name));
 538         if (rec == NULL) {
 539                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 540                 status = NT_STATUS_INTERNAL_ERROR;
 541                 goto done;
 542         }
 543
 544         value = dbwrap_record_get_value(rec);
 545
 546         status = g_lock_get_talloc(talloc_tos(), value, &locks, &num_locks,
 547                                    &userdata.dptr, &userdata.dsize);
 548         if (!NT_STATUS_IS_OK(status)) {
 549                 DBG_DEBUG("g_lock_get for %s failed: %s\n", name,
 550                           nt_errstr(status));
 551                 status = NT_STATUS_FILE_INVALID;
 552                 goto done;
 553         }
 554         for (i=0; i<num_locks; i++) {
 555                 if (serverid_equal(&self, &locks[i].pid)) {
 556                         break;
 557                 }
 558         }
 559         if (i == num_locks) {
 560                 DBG_DEBUG("Lock not found, num_locks=%zu\n", num_locks);
 561                 status = NT_STATUS_NOT_FOUND;
 562                 goto done;
 563         }
 564
 565         locks[i] = locks[num_locks-1];
 566         num_locks -= 1;
 567
 568         if ((num_locks == 0) && (userdata.dsize == 0)) {
 569                 status = dbwrap_record_delete(rec);
 570         } else {
 571                 status = g_lock_record_store(
 572                         rec, locks, num_locks, userdata.dptr, userdata.dsize);
 573         }
 574         if (!NT_STATUS_IS_OK(status)) {
 575                 DBG_WARNING("Could not store record: %s\n", nt_errstr(status));
 576                 goto done;
 577         }
 578
 579         status = NT_STATUS_OK;
 580 done:
 581         TALLOC_FREE(rec);
 582         TALLOC_FREE(locks);
 583         return status;
 584 }
 585
 586 NTSTATUS g_lock_write_data(struct g_lock_ctx *ctx, const char *name,
 587                            const uint8_t *buf, size_t buflen)
 588 {
 589         struct server_id self = messaging_server_id(ctx->msg);
 590         struct db_record *rec = NULL;
 591         struct g_lock_rec *locks = NULL;
 592         size_t i, num_locks;
 593         NTSTATUS status;
 594         TDB_DATA value;
 595
 596         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 597                                   string_term_tdb_data(name));
 598         if (rec == NULL) {
 599                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 600                 status = NT_STATUS_INTERNAL_ERROR;
 601                 goto done;
 602         }
 603
 604         value = dbwrap_record_get_value(rec);
 605
 606         status = g_lock_get_talloc(talloc_tos(), value, &locks, &num_locks,
 607                                    NULL, NULL);
 608         if (!NT_STATUS_IS_OK(status)) {
 609                 DBG_DEBUG("g_lock_get for %s failed: %s\n", name,
 610                           nt_errstr(status));
 611                 status = NT_STATUS_FILE_INVALID;
 612                 goto done;
 613         }
 614
 615         for (i=0; i<num_locks; i++) {
 616                 if (server_id_equal(&self, &locks[i].pid) &&
 617                     (locks[i].lock_type == G_LOCK_WRITE)) {
 618                         break;
 619                 }
 620         }
 621         if (i == num_locks) {
 622                 DBG_DEBUG("Not locked by us\n");
 623                 status = NT_STATUS_NOT_LOCKED;
 624                 goto done;
 625         }
 626
 627         status = g_lock_record_store(rec, locks, num_locks, buf, buflen);
 628
 629 done:
 630         TALLOC_FREE(locks);
 631         TALLOC_FREE(rec);
 632         return status;
 633 }
 634
 635 struct g_lock_locks_state {
 636         int (*fn)(const char *name, void *private_data);
 637         void *private_data;
 638 };
 639
 640 static int g_lock_locks_fn(struct db_record *rec, void *priv)
 641 {
 642         TDB_DATA key;
 643         struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
 644
 645         key = dbwrap_record_get_key(rec);
 646         if ((key.dsize == 0) || (key.dptr[key.dsize-1] != 0)) {
 647                 DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
 648                 return 0;
 649         }
 650         return state->fn((char *)key.dptr, state->private_data);
 651 }
 652
 653 int g_lock_locks(struct g_lock_ctx *ctx,
 654                  int (*fn)(const char *name, void *private_data),
 655                  void *private_data)
 656 {
 657         struct g_lock_locks_state state;
 658         NTSTATUS status;
 659         int count;
 660
 661         state.fn = fn;
 662         state.private_data = private_data;
 663
 664         status = dbwrap_traverse_read(ctx->db, g_lock_locks_fn, &state, &count);
 665         if (!NT_STATUS_IS_OK(status)) {
 666                 return -1;
 667         }
 668         return count;
 669 }
 670
 671 NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
 672                      void (*fn)(const struct g_lock_rec *locks,
 673                                 size_t num_locks,
 674                                 const uint8_t *data,
 675                                 size_t datalen,
 676                                 void *private_data),
 677                      void *private_data)
 678 {
 679         TDB_DATA data;
 680         size_t num_locks;
 681         struct g_lock_rec *locks = NULL;
 682         uint8_t *userdata;
 683         size_t userdatalen;
 684         NTSTATUS status;
 685
 686         status = dbwrap_fetch_bystring(ctx->db, talloc_tos(), name, &data);
 687         if (!NT_STATUS_IS_OK(status)) {
 688                 return status;
 689         }
 690
 691         if ((data.dsize == 0) || (data.dptr == NULL)) {
 692                 return NT_STATUS_OK;
 693         }
 694
 695         status = g_lock_get_talloc(talloc_tos(), data, &locks, &num_locks,
 696                                    &userdata, &userdatalen);
 697
 698         if (!NT_STATUS_IS_OK(status)) {
 699                 DBG_DEBUG("g_lock_get for %s failed: %s\n", name,
 700                           nt_errstr(status));
 701                 TALLOC_FREE(data.dptr);
 702                 return NT_STATUS_INTERNAL_ERROR;
 703         }
 704
 705         fn(locks, num_locks, userdata, userdatalen, private_data);
 706
 707         TALLOC_FREE(locks);
 708         TALLOC_FREE(data.dptr);
 709         return NT_STATUS_OK;
 710 }
 711
 712 static bool g_lock_init_all(TALLOC_CTX *mem_ctx,
 713                             struct tevent_context **pev,
 714                             struct messaging_context **pmsg,
 715                             struct g_lock_ctx **pg_ctx)
 716 {
 717         struct tevent_context *ev = NULL;
 718         struct messaging_context *msg = NULL;
 719         struct g_lock_ctx *g_ctx = NULL;
 720
 721         ev = samba_tevent_context_init(mem_ctx);
 722         if (ev == NULL) {
 723                 d_fprintf(stderr, "ERROR: could not init event context\n");
 724                 goto fail;
 725         }
 726         msg = messaging_init(mem_ctx, ev);
 727         if (msg == NULL) {
 728                 d_fprintf(stderr, "ERROR: could not init messaging context\n");
 729                 goto fail;
 730         }
 731         g_ctx = g_lock_ctx_init(mem_ctx, msg);
 732         if (g_ctx == NULL) {
 733                 d_fprintf(stderr, "ERROR: could not init g_lock context\n");
 734                 goto fail;
 735         }
 736
 737         *pev = ev;
 738         *pmsg = msg;
 739         *pg_ctx = g_ctx;
 740         return true;
 741 fail:
 742         TALLOC_FREE(g_ctx);
 743         TALLOC_FREE(msg);
 744         TALLOC_FREE(ev);
 745         return false;
 746 }
 747
 748 NTSTATUS g_lock_do(const char *name, enum g_lock_type lock_type,
 749                    struct timeval timeout,
 750                    void (*fn)(void *private_data), void *private_data)
 751 {
 752         struct tevent_context *ev = NULL;
 753         struct messaging_context *msg = NULL;
 754         struct g_lock_ctx *g_ctx = NULL;
 755         NTSTATUS status;
 756
 757         if (!g_lock_init_all(talloc_tos(), &ev, &msg, &g_ctx)) {
 758                 status = NT_STATUS_ACCESS_DENIED;
 759                 goto done;
 760         }
 761
 762         status = g_lock_lock(g_ctx, name, lock_type, timeout);
 763         if (!NT_STATUS_IS_OK(status)) {
 764                 goto done;
 765         }
 766         fn(private_data);
 767         g_lock_unlock(g_ctx, name);
 768
 769 done:
 770         TALLOC_FREE(g_ctx);
 771         TALLOC_FREE(msg);
 772         TALLOC_FREE(ev);
 773         return status;
 774 }