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 "g_lock.h"
  22
  23 static NTSTATUS g_lock_force_unlock(struct g_lock_ctx *ctx, const char *name,
  24                                     struct server_id pid);
  25
  26 struct g_lock_ctx {
  27         struct db_context *db;
  28         struct messaging_context *msg;
  29 };
  30
  31 /*
  32  * The "g_lock.tdb" file contains records, indexed by the 0-terminated
  33  * lockname. The record contains an array of "struct g_lock_rec"
  34  * structures. Waiters have the lock_type with G_LOCK_PENDING or'ed.
  35  */
  36
  37 struct g_lock_rec {
  38         enum g_lock_type lock_type;
  39         struct server_id pid;
  40 };
  41
  42 struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
  43                                    struct messaging_context *msg)
  44 {
  45         struct g_lock_ctx *result;
  46
  47         result = talloc(mem_ctx, struct g_lock_ctx);
  48         if (result == NULL) {
  49                 return NULL;
  50         }
  51         result->msg = msg;
  52
  53         result->db = db_open(result, lock_path("g_lock.tdb"), 0,
  54                              TDB_CLEAR_IF_FIRST, O_RDWR|O_CREAT, 0700);
  55         if (result->db == NULL) {
  56                 DEBUG(1, ("g_lock_init: Could not open g_lock.tdb"));
  57                 TALLOC_FREE(result);
  58                 return NULL;
  59         }
  60         return result;
  61 }
  62
  63 static bool g_lock_conflicts(enum g_lock_type lock_type,
  64                              const struct g_lock_rec *rec)
  65 {
  66         enum g_lock_type rec_lock = rec->lock_type;
  67
  68         if ((rec_lock & G_LOCK_PENDING) != 0) {
  69                 return false;
  70         }
  71
  72         /*
  73          * Only tested write locks so far. Very likely this routine
  74          * needs to be fixed for read locks....
  75          */
  76         if ((lock_type == G_LOCK_READ) && (rec_lock == G_LOCK_READ)) {
  77                 return false;
  78         }
  79         return true;
  80 }
  81
  82 static bool g_lock_parse(TALLOC_CTX *mem_ctx, TDB_DATA data,
  83                          int *pnum_locks, struct g_lock_rec **plocks)
  84 {
  85         int i, num_locks;
  86         struct g_lock_rec *locks;
  87
  88         if ((data.dsize % sizeof(struct g_lock_rec)) != 0) {
  89                 DEBUG(1, ("invalid lock record length %d\n", (int)data.dsize));
  90                 return false;
  91         }
  92
  93         num_locks = data.dsize / sizeof(struct g_lock_rec);
  94         locks = talloc_array(mem_ctx, struct g_lock_rec, num_locks);
  95         if (locks == NULL) {
  96                 DEBUG(1, ("talloc failed\n"));
  97                 return false;
  98         }
  99
 100         memcpy(locks, data.dptr, data.dsize);
 101
 102         DEBUG(10, ("locks:\n"));
 103         for (i=0; i<num_locks; i++) {
 104                 DEBUGADD(10, ("%s: %s %s\n",
 105                               procid_str(debug_ctx(), &locks[i].pid),
 106                               ((locks[i].lock_type & 1) == G_LOCK_READ) ?
 107                               "read" : "write",
 108                               (locks[i].lock_type & G_LOCK_PENDING) ?
 109                               "(pending)" : "(owner)"));
 110
 111                 if (((locks[i].lock_type & G_LOCK_PENDING) == 0)
 112                     && !process_exists(locks[i].pid)) {
 113
 114                         DEBUGADD(10, ("lock owner %s died -- discarding\n",
 115                                       procid_str(talloc_tos(),
 116                                                  &locks[i].pid)));
 117
 118                         if (i < (num_locks-1)) {
 119                                 locks[i] = locks[num_locks-1];
 120                         }
 121                         num_locks -= 1;
 122                 }
 123         }
 124
 125         *plocks = locks;
 126         *pnum_locks = num_locks;
 127         return true;
 128 }
 129
 130 static void g_lock_cleanup(int *pnum_locks, struct g_lock_rec *locks)
 131 {
 132         int i, num_locks;
 133
 134         num_locks = *pnum_locks;
 135
 136         DEBUG(10, ("g_lock_cleanup: %d locks\n", num_locks));
 137
 138         for (i=0; i<num_locks; i++) {
 139                 if (process_exists(locks[i].pid)) {
 140                         continue;
 141                 }
 142                 DEBUGADD(10, ("%s does not exist -- discarding\n",
 143                               procid_str(debug_ctx(), &locks[i].pid)));
 144
 145                 if (i < (num_locks-1)) {
 146                         locks[i] = locks[num_locks-1];
 147                 }
 148                 num_locks -= 1;
 149         }
 150         *pnum_locks = num_locks;
 151         return;
 152 }
 153
 154 static struct g_lock_rec *g_lock_addrec(TALLOC_CTX *mem_ctx,
 155                                         struct g_lock_rec *locks,
 156                                         int *pnum_locks,
 157                                         const struct server_id pid,
 158                                         enum g_lock_type lock_type)
 159 {
 160         struct g_lock_rec *result;
 161         int num_locks = *pnum_locks;
 162
 163         result = talloc_realloc(mem_ctx, locks, struct g_lock_rec,
 164                                 num_locks+1);
 165         if (result == NULL) {
 166                 return NULL;
 167         }
 168
 169         result[num_locks].pid = pid;
 170         result[num_locks].lock_type = lock_type;
 171         *pnum_locks += 1;
 172         return result;
 173 }
 174
 175 static void g_lock_got_retry(struct messaging_context *msg,
 176                              void *private_data,
 177                              uint32_t msg_type,
 178                              struct server_id server_id,
 179                              DATA_BLOB *data);
 180 static void g_lock_timedout(struct tevent_context *ev,
 181                             struct tevent_timer *te,
 182                             struct timeval current_time,
 183                             void *private_data);
 184
 185 static NTSTATUS g_lock_trylock(struct g_lock_ctx *ctx, const char *name,
 186                                enum g_lock_type lock_type)
 187 {
 188         struct db_record *rec = NULL;
 189         struct g_lock_rec *locks = NULL;
 190         int i, num_locks;
 191         struct server_id self;
 192         int our_index;
 193         TDB_DATA data;
 194         NTSTATUS status = NT_STATUS_OK;
 195         NTSTATUS store_status;
 196
 197 again:
 198         rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
 199                                     string_term_tdb_data(name));
 200         if (rec == NULL) {
 201                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 202                 status = NT_STATUS_LOCK_NOT_GRANTED;
 203                 goto done;
 204         }
 205
 206         if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
 207                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 208                 status = NT_STATUS_INTERNAL_ERROR;
 209                 goto done;
 210         }
 211
 212         self = procid_self();
 213         our_index = -1;
 214
 215         for (i=0; i<num_locks; i++) {
 216                 if (procid_equal(&self, &locks[i].pid)) {
 217                         if (our_index != -1) {
 218                                 DEBUG(1, ("g_lock_trylock: Added ourself "
 219                                           "twice!\n"));
 220                                 status = NT_STATUS_INTERNAL_ERROR;
 221                                 goto done;
 222                         }
 223                         if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
 224                                 DEBUG(1, ("g_lock_trylock: Found ourself not "
 225                                           "pending!\n"));
 226                                 status = NT_STATUS_INTERNAL_ERROR;
 227                                 goto done;
 228                         }
 229
 230                         our_index = i;
 231
 232                         /* never conflict with ourself */
 233                         continue;
 234                 }
 235                 if (g_lock_conflicts(lock_type, &locks[i])) {
 236                         struct server_id pid = locks[i].pid;
 237
 238                         if (!process_exists(pid)) {
 239                                 TALLOC_FREE(locks);
 240                                 TALLOC_FREE(rec);
 241                                 status = g_lock_force_unlock(ctx, name, pid);
 242                                 if (!NT_STATUS_IS_OK(status)) {
 243                                         DEBUG(1, ("Could not unlock dead lock "
 244                                                   "holder!\n"));
 245                                         goto done;
 246                                 }
 247                                 goto again;
 248                         }
 249                         lock_type |= G_LOCK_PENDING;
 250                 }
 251         }
 252
 253         if (our_index == -1) {
 254                 /* First round, add ourself */
 255
 256                 locks = g_lock_addrec(talloc_tos(), locks, &num_locks,
 257                                       self, lock_type);
 258                 if (locks == NULL) {
 259                         DEBUG(10, ("g_lock_addrec failed\n"));
 260                         status = NT_STATUS_NO_MEMORY;
 261                         goto done;
 262                 }
 263         } else {
 264                 /*
 265                  * Retry. We were pending last time. Overwrite the
 266                  * stored lock_type with what we calculated, we might
 267                  * have acquired the lock this time.
 268                  */
 269                 locks[our_index].lock_type = lock_type;
 270         }
 271
 272         if (NT_STATUS_IS_OK(status) && ((lock_type & G_LOCK_PENDING) == 0)) {
 273                 /*
 274                  * Walk through the list of locks, search for dead entries
 275                  */
 276                 g_lock_cleanup(&num_locks, locks);
 277         }
 278
 279         data = make_tdb_data((uint8_t *)locks, num_locks * sizeof(*locks));
 280         store_status = rec->store(rec, data, 0);
 281         if (!NT_STATUS_IS_OK(store_status)) {
 282                 DEBUG(1, ("rec->store failed: %s\n",
 283                           nt_errstr(store_status)));
 284                 status = store_status;
 285         }
 286
 287 done:
 288         TALLOC_FREE(locks);
 289         TALLOC_FREE(rec);
 290
 291         if (NT_STATUS_IS_OK(status) && (lock_type & G_LOCK_PENDING) != 0) {
 292                 return STATUS_PENDING;
 293         }
 294
 295         return NT_STATUS_OK;
 296 }
 297
 298 NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
 299                      enum g_lock_type lock_type, struct timeval timeout)
 300 {
 301         struct tevent_timer *te = NULL;
 302         NTSTATUS status;
 303         bool retry = false;
 304         struct timeval timeout_end;
 305         struct timeval timeout_remaining;
 306         struct timeval time_now;
 307
 308         DEBUG(10, ("Trying to acquire lock %d for %s\n", (int)lock_type,
 309                    name));
 310
 311         if (lock_type & ~1) {
 312                 DEBUG(1, ("Got invalid lock type %d for %s\n",
 313                           (int)lock_type, name));
 314                 return NT_STATUS_INVALID_PARAMETER;
 315         }
 316
 317 #ifdef CLUSTER_SUPPORT
 318         if (lp_clustering()) {
 319                 status = ctdb_watch_us(messaging_ctdbd_connection());
 320                 if (!NT_STATUS_IS_OK(status)) {
 321                         DEBUG(10, ("could not register retry with ctdb: %s\n",
 322                                    nt_errstr(status)));
 323                         goto done;
 324                 }
 325         }
 326 #endif
 327
 328         status = messaging_register(ctx->msg, &retry, MSG_DBWRAP_G_LOCK_RETRY,
 329                                     g_lock_got_retry);
 330         if (!NT_STATUS_IS_OK(status)) {
 331                 DEBUG(10, ("messaging_register failed: %s\n",
 332                            nt_errstr(status)));
 333                 return status;
 334         }
 335
 336         time_now = timeval_current();
 337         timeout_end = timeval_sum(&time_now, &timeout);
 338
 339         while (true) {
 340                 fd_set _r_fds;
 341                 fd_set *r_fds = NULL;
 342                 int max_fd = 0;
 343                 int ret;
 344
 345                 status = g_lock_trylock(ctx, name, lock_type);
 346                 if (NT_STATUS_IS_OK(status)) {
 347                         DEBUG(10, ("Got lock %s\n", name));
 348                         break;
 349                 }
 350                 if (!NT_STATUS_EQUAL(status, STATUS_PENDING)) {
 351                         DEBUG(10, ("g_lock_trylock failed: %s\n",
 352                                    nt_errstr(status)));
 353                         break;
 354                 }
 355
 356                 DEBUG(10, ("g_lock_trylock: Did not get lock, waiting...\n"));
 357
 358                 /* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 359                  *             !!! HACK ALERT --- FIX ME !!!
 360                  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 361                  * What we really want to do here is to react to
 362                  * MSG_DBWRAP_G_LOCK_RETRY messages that are either sent
 363                  * by a client doing g_lock_unlock or by ourselves when
 364                  * we receive a CTDB_SRVID_SAMBA_NOTIFY or
 365                  * CTDB_SRVID_RECONFIGURE message from ctdbd, i.e. when
 366                  * either a client holding a lock or a complete node
 367                  * has died.
 368                  *
 369                  * Doing this properly involves calling tevent_loop_once(),
 370                  * but doing this here with the main ctdbd messaging context
 371                  * creates a nested event loop when g_lock_lock() is called
 372                  * from the main event loop, e.g. in a tcon_and_X where the
 373                  * share_info.tdb needs to be initialized and is locked by
 374                  * another process, or when the remore registry is accessed
 375                  * for writing and some other process already holds a lock
 376                  * on the registry.tdb.
 377                  *
 378                  * So as a quick fix, we act a little coarsely here: we do
 379                  * a select on the ctdb connection fd and when it is readable
 380                  * or we get EINTR, then we retry without actually parsing
 381                  * any ctdb packages or dispatching messages. This means that
 382                  * we retry more often than intended by design, but this does
 383                  * not harm and it is unobtrusive. When we have finished,
 384                  * the main loop will pick up all the messages and ctdb
 385                  * packets. The only extra twist is that we cannot use timed
 386                  * events here but have to handcode a timeout.
 387                  */
 388
 389 #ifdef CLUSTER_SUPPORT
 390                 if (lp_clustering()) {
 391                         struct ctdbd_connection *conn = messaging_ctdbd_connection();
 392
 393                         r_fds = &_r_fds;
 394                         FD_ZERO(r_fds);
 395                         max_fd = ctdbd_conn_get_fd(conn);
 396                         FD_SET(max_fd, r_fds);
 397                 }
 398 #endif
 399
 400                 time_now = timeval_current();
 401                 timeout_remaining = timeval_until(&time_now, &timeout_end);
 402
 403                 ret = sys_select(max_fd + 1, r_fds, NULL, NULL,
 404                                  &timeout_remaining);
 405
 406                 if (ret == -1) {
 407                         if (errno != EINTR) {
 408                                 DEBUG(1, ("error calling select: %s\n",
 409                                           strerror(errno)));
 410                                 status = NT_STATUS_INTERNAL_ERROR;
 411                                 break;
 412                         }
 413                         /*
 414                          * errno == EINTR:
 415                          * This means a signal was received.
 416                          * It might have been a MSG_DBWRAP_G_LOCK_RETRY message.
 417                          * ==> retry
 418                          */
 419                 } else if (ret == 0) {
 420                         if (timeval_expired(&timeout_end)) {
 421                                 DEBUG(10, ("g_lock_lock timed out\n"));
 422                                 status = NT_STATUS_LOCK_NOT_GRANTED;
 423                                 break;
 424                         } else {
 425                                 DEBUG(10, ("select returned 0 but timeout not "
 426                                            "not expired: strange - retrying\n"));
 427                         }
 428                 } else if (ret != 1) {
 429                         DEBUG(1, ("invalid return code of select: %d\n", ret));
 430                         status = NT_STATUS_INTERNAL_ERROR;
 431                         break;
 432                 }
 433                 /*
 434                  * ret == 1:
 435                  * This means ctdbd has sent us some data.
 436                  * Might be a CTDB_SRVID_RECONFIGURE or a
 437                  * CTDB_SRVID_SAMBA_NOTIFY message.
 438                  * ==> retry
 439                  */
 440         }
 441
 442 done:
 443
 444         if (!NT_STATUS_IS_OK(status)) {
 445                 NTSTATUS unlock_status;
 446
 447                 unlock_status = g_lock_unlock(ctx, name);
 448
 449                 if (!NT_STATUS_IS_OK(unlock_status)) {
 450                         DEBUG(1, ("Could not remove ourself from the locking "
 451                                   "db: %s\n", nt_errstr(status)));
 452                 }
 453         }
 454
 455         messaging_deregister(ctx->msg, MSG_DBWRAP_G_LOCK_RETRY, &retry);
 456         TALLOC_FREE(te);
 457
 458         return status;
 459 }
 460
 461 static void g_lock_got_retry(struct messaging_context *msg,
 462                              void *private_data,
 463                              uint32_t msg_type,
 464                              struct server_id server_id,
 465                              DATA_BLOB *data)
 466 {
 467         bool *pretry = (bool *)private_data;
 468
 469         DEBUG(10, ("Got retry message from pid %s\n",
 470                    procid_str(talloc_tos(), &server_id)));
 471
 472         *pretry = true;
 473 }
 474
 475 static void g_lock_timedout(struct tevent_context *ev,
 476                             struct tevent_timer *te,
 477                             struct timeval current_time,
 478                             void *private_data)
 479 {
 480         bool *ptimedout = (bool *)private_data;
 481         *ptimedout = true;
 482         TALLOC_FREE(te);
 483 }
 484
 485 static NTSTATUS g_lock_force_unlock(struct g_lock_ctx *ctx, const char *name,
 486                                     struct server_id pid)
 487 {
 488         struct db_record *rec = NULL;
 489         struct g_lock_rec *locks = NULL;
 490         int i, num_locks;
 491         enum g_lock_type lock_type;
 492         NTSTATUS status;
 493
 494         rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
 495                                     string_term_tdb_data(name));
 496         if (rec == NULL) {
 497                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 498                 status = NT_STATUS_INTERNAL_ERROR;
 499                 goto done;
 500         }
 501
 502         if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
 503                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 504                 status = NT_STATUS_INTERNAL_ERROR;
 505                 goto done;
 506         }
 507
 508         for (i=0; i<num_locks; i++) {
 509                 if (procid_equal(&pid, &locks[i].pid)) {
 510                         break;
 511                 }
 512         }
 513
 514         if (i == num_locks) {
 515                 DEBUG(10, ("g_lock_force_unlock: Lock not found\n"));
 516                 status = NT_STATUS_INTERNAL_ERROR;
 517                 goto done;
 518         }
 519
 520         lock_type = locks[i].lock_type;
 521
 522         if (i < (num_locks-1)) {
 523                 locks[i] = locks[num_locks-1];
 524         }
 525         num_locks -= 1;
 526
 527         if (num_locks == 0) {
 528                 status = rec->delete_rec(rec);
 529         } else {
 530                 TDB_DATA data;
 531                 data = make_tdb_data((uint8_t *)locks,
 532                                      sizeof(struct g_lock_rec) * num_locks);
 533                 status = rec->store(rec, data, 0);
 534         }
 535
 536         if (!NT_STATUS_IS_OK(status)) {
 537                 DEBUG(1, ("g_lock_force_unlock: Could not store record: %s\n",
 538                           nt_errstr(status)));
 539                 goto done;
 540         }
 541
 542         if ((lock_type & G_LOCK_PENDING) == 0) {
 543                 int num_wakeups = 0;
 544
 545                 /*
 546                  * We've been the lock holder. Others to retry. Don't
 547                  * tell all others to avoid a thundering herd. In case
 548                  * this leads to a complete stall because we miss some
 549                  * processes, the loop in g_lock_lock tries at least
 550                  * once a minute.
 551                  */
 552
 553                 for (i=0; i<num_locks; i++) {
 554                         if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
 555                                 continue;
 556                         }
 557                         if (!process_exists(locks[i].pid)) {
 558                                 continue;
 559                         }
 560
 561                         /*
 562                          * Ping all waiters to retry
 563                          */
 564                         status = messaging_send(ctx->msg, locks[i].pid,
 565                                                 MSG_DBWRAP_G_LOCK_RETRY,
 566                                                 &data_blob_null);
 567                         if (!NT_STATUS_IS_OK(status)) {
 568                                 DEBUG(1, ("sending retry to %s failed: %s\n",
 569                                           procid_str(debug_ctx(),
 570                                                      &locks[i].pid),
 571                                           nt_errstr(status)));
 572                         } else {
 573                                 num_wakeups += 1;
 574                         }
 575                         if (num_wakeups > 5) {
 576                                 break;
 577                         }
 578                 }
 579         }
 580 done:
 581
 582         TALLOC_FREE(locks);
 583         TALLOC_FREE(rec);
 584         return status;
 585 }
 586
 587 NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
 588 {
 589         NTSTATUS status;
 590
 591         status = g_lock_force_unlock(ctx, name, procid_self());
 592
 593 #ifdef CLUSTER_SUPPORT
 594         if (lp_clustering()) {
 595                 ctdb_unwatch(messaging_ctdbd_connection());
 596         }
 597 #endif
 598         return status;
 599 }
 600
 601 struct g_lock_locks_state {
 602         int (*fn)(const char *name, void *private_data);
 603         void *private_data;
 604 };
 605
 606 static int g_lock_locks_fn(struct db_record *rec, void *priv)
 607 {
 608         struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
 609
 610         if ((rec->key.dsize == 0) || (rec->key.dptr[rec->key.dsize-1] != 0)) {
 611                 DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
 612                 return 0;
 613         }
 614         return state->fn((char *)rec->key.dptr, state->private_data);
 615 }
 616
 617 int g_lock_locks(struct g_lock_ctx *ctx,
 618                  int (*fn)(const char *name, void *private_data),
 619                  void *private_data)
 620 {
 621         struct g_lock_locks_state state;
 622
 623         state.fn = fn;
 624         state.private_data = private_data;
 625
 626         return ctx->db->traverse_read(ctx->db, g_lock_locks_fn, &state);
 627 }
 628
 629 NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
 630                      int (*fn)(struct server_id pid,
 631                                enum g_lock_type lock_type,
 632                                void *private_data),
 633                      void *private_data)
 634 {
 635         TDB_DATA data;
 636         int i, num_locks;
 637         struct g_lock_rec *locks = NULL;
 638         bool ret;
 639
 640         if (ctx->db->fetch(ctx->db, talloc_tos(), string_term_tdb_data(name),
 641                            &data) != 0) {
 642                 return NT_STATUS_NOT_FOUND;
 643         }
 644
 645         if ((data.dsize == 0) || (data.dptr == NULL)) {
 646                 return NT_STATUS_OK;
 647         }
 648
 649         ret = g_lock_parse(talloc_tos(), data, &num_locks, &locks);
 650
 651         TALLOC_FREE(data.dptr);
 652
 653         if (!ret) {
 654                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 655                 return NT_STATUS_INTERNAL_ERROR;
 656         }
 657
 658         for (i=0; i<num_locks; i++) {
 659                 if (fn(locks[i].pid, locks[i].lock_type, private_data) != 0) {
 660                         break;
 661                 }
 662         }
 663         TALLOC_FREE(locks);
 664         return NT_STATUS_OK;
 665 }
 666
 667 struct g_lock_get_state {
 668         bool found;
 669         struct server_id *pid;
 670 };
 671
 672 static int g_lock_get_fn(struct server_id pid, enum g_lock_type lock_type,
 673                          void *priv)
 674 {
 675         struct g_lock_get_state *state = (struct g_lock_get_state *)priv;
 676
 677         if ((lock_type & G_LOCK_PENDING) != 0) {
 678                 return 0;
 679         }
 680
 681         state->found = true;
 682         *state->pid = pid;
 683         return 1;
 684 }
 685
 686 NTSTATUS g_lock_get(struct g_lock_ctx *ctx, const char *name,
 687                     struct server_id *pid)
 688 {
 689         struct g_lock_get_state state;
 690         NTSTATUS status;
 691
 692         state.found = false;
 693         state.pid = pid;
 694
 695         status = g_lock_dump(ctx, name, g_lock_get_fn, &state);
 696         if (!NT_STATUS_IS_OK(status)) {
 697                 return status;
 698         }
 699         if (!state.found) {
 700                 return NT_STATUS_NOT_FOUND;
 701         }
 702         return NT_STATUS_OK;
 703 }