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(talloc_tos(), &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(talloc_tos(), &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
 181 static NTSTATUS g_lock_trylock(struct g_lock_ctx *ctx, const char *name,
 182                                enum g_lock_type lock_type)
 183 {
 184         struct db_record *rec = NULL;
 185         struct g_lock_rec *locks = NULL;
 186         int i, num_locks;
 187         struct server_id self;
 188         int our_index;
 189         TDB_DATA data;
 190         NTSTATUS status = NT_STATUS_OK;
 191         NTSTATUS store_status;
 192
 193 again:
 194         rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
 195                                     string_term_tdb_data(name));
 196         if (rec == NULL) {
 197                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 198                 status = NT_STATUS_LOCK_NOT_GRANTED;
 199                 goto done;
 200         }
 201
 202         if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
 203                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 204                 status = NT_STATUS_INTERNAL_ERROR;
 205                 goto done;
 206         }
 207
 208         self = procid_self();
 209         our_index = -1;
 210
 211         for (i=0; i<num_locks; i++) {
 212                 if (procid_equal(&self, &locks[i].pid)) {
 213                         if (our_index != -1) {
 214                                 DEBUG(1, ("g_lock_trylock: Added ourself "
 215                                           "twice!\n"));
 216                                 status = NT_STATUS_INTERNAL_ERROR;
 217                                 goto done;
 218                         }
 219                         if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
 220                                 DEBUG(1, ("g_lock_trylock: Found ourself not "
 221                                           "pending!\n"));
 222                                 status = NT_STATUS_INTERNAL_ERROR;
 223                                 goto done;
 224                         }
 225
 226                         our_index = i;
 227
 228                         /* never conflict with ourself */
 229                         continue;
 230                 }
 231                 if (g_lock_conflicts(lock_type, &locks[i])) {
 232                         struct server_id pid = locks[i].pid;
 233
 234                         if (!process_exists(pid)) {
 235                                 TALLOC_FREE(locks);
 236                                 TALLOC_FREE(rec);
 237                                 status = g_lock_force_unlock(ctx, name, pid);
 238                                 if (!NT_STATUS_IS_OK(status)) {
 239                                         DEBUG(1, ("Could not unlock dead lock "
 240                                                   "holder!\n"));
 241                                         goto done;
 242                                 }
 243                                 goto again;
 244                         }
 245                         lock_type |= G_LOCK_PENDING;
 246                 }
 247         }
 248
 249         if (our_index == -1) {
 250                 /* First round, add ourself */
 251
 252                 locks = g_lock_addrec(talloc_tos(), locks, &num_locks,
 253                                       self, lock_type);
 254                 if (locks == NULL) {
 255                         DEBUG(10, ("g_lock_addrec failed\n"));
 256                         status = NT_STATUS_NO_MEMORY;
 257                         goto done;
 258                 }
 259         } else {
 260                 /*
 261                  * Retry. We were pending last time. Overwrite the
 262                  * stored lock_type with what we calculated, we might
 263                  * have acquired the lock this time.
 264                  */
 265                 locks[our_index].lock_type = lock_type;
 266         }
 267
 268         if (NT_STATUS_IS_OK(status) && ((lock_type & G_LOCK_PENDING) == 0)) {
 269                 /*
 270                  * Walk through the list of locks, search for dead entries
 271                  */
 272                 g_lock_cleanup(&num_locks, locks);
 273         }
 274
 275         data = make_tdb_data((uint8_t *)locks, num_locks * sizeof(*locks));
 276         store_status = rec->store(rec, data, 0);
 277         if (!NT_STATUS_IS_OK(store_status)) {
 278                 DEBUG(1, ("rec->store failed: %s\n",
 279                           nt_errstr(store_status)));
 280                 status = store_status;
 281         }
 282
 283 done:
 284         TALLOC_FREE(locks);
 285         TALLOC_FREE(rec);
 286
 287         if (NT_STATUS_IS_OK(status) && (lock_type & G_LOCK_PENDING) != 0) {
 288                 return STATUS_PENDING;
 289         }
 290
 291         return NT_STATUS_OK;
 292 }
 293
 294 NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
 295                      enum g_lock_type lock_type, struct timeval timeout)
 296 {
 297         struct tevent_timer *te = NULL;
 298         NTSTATUS status;
 299         bool retry = false;
 300         struct timeval timeout_end;
 301         struct timeval time_now;
 302
 303         DEBUG(10, ("Trying to acquire lock %d for %s\n", (int)lock_type,
 304                    name));
 305
 306         if (lock_type & ~1) {
 307                 DEBUG(1, ("Got invalid lock type %d for %s\n",
 308                           (int)lock_type, name));
 309                 return NT_STATUS_INVALID_PARAMETER;
 310         }
 311
 312 #ifdef CLUSTER_SUPPORT
 313         if (lp_clustering()) {
 314                 status = ctdb_watch_us(messaging_ctdbd_connection());
 315                 if (!NT_STATUS_IS_OK(status)) {
 316                         DEBUG(10, ("could not register retry with ctdb: %s\n",
 317                                    nt_errstr(status)));
 318                         goto done;
 319                 }
 320         }
 321 #endif
 322
 323         status = messaging_register(ctx->msg, &retry, MSG_DBWRAP_G_LOCK_RETRY,
 324                                     g_lock_got_retry);
 325         if (!NT_STATUS_IS_OK(status)) {
 326                 DEBUG(10, ("messaging_register failed: %s\n",
 327                            nt_errstr(status)));
 328                 return status;
 329         }
 330
 331         time_now = timeval_current();
 332         timeout_end = timeval_sum(&time_now, &timeout);
 333
 334         while (true) {
 335 #ifdef CLUSTER_SUPPORT
 336                 fd_set _r_fds;
 337 #endif
 338                 fd_set *r_fds = NULL;
 339                 int max_fd = 0;
 340                 int ret;
 341                 struct timeval select_timeout;
 342
 343                 status = g_lock_trylock(ctx, name, lock_type);
 344                 if (NT_STATUS_IS_OK(status)) {
 345                         DEBUG(10, ("Got lock %s\n", name));
 346                         break;
 347                 }
 348                 if (!NT_STATUS_EQUAL(status, STATUS_PENDING)) {
 349                         DEBUG(10, ("g_lock_trylock failed: %s\n",
 350                                    nt_errstr(status)));
 351                         break;
 352                 }
 353
 354                 DEBUG(10, ("g_lock_trylock: Did not get lock, waiting...\n"));
 355
 356                 /* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 357                  *             !!! HACK ALERT --- FIX ME !!!
 358                  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 359                  * What we really want to do here is to react to
 360                  * MSG_DBWRAP_G_LOCK_RETRY messages that are either sent
 361                  * by a client doing g_lock_unlock or by ourselves when
 362                  * we receive a CTDB_SRVID_SAMBA_NOTIFY or
 363                  * CTDB_SRVID_RECONFIGURE message from ctdbd, i.e. when
 364                  * either a client holding a lock or a complete node
 365                  * has died.
 366                  *
 367                  * Doing this properly involves calling tevent_loop_once(),
 368                  * but doing this here with the main ctdbd messaging context
 369                  * creates a nested event loop when g_lock_lock() is called
 370                  * from the main event loop, e.g. in a tcon_and_X where the
 371                  * share_info.tdb needs to be initialized and is locked by
 372                  * another process, or when the remore registry is accessed
 373                  * for writing and some other process already holds a lock
 374                  * on the registry.tdb.
 375                  *
 376                  * So as a quick fix, we act a little coarsely here: we do
 377                  * a select on the ctdb connection fd and when it is readable
 378                  * or we get EINTR, then we retry without actually parsing
 379                  * any ctdb packages or dispatching messages. This means that
 380                  * we retry more often than intended by design, but this does
 381                  * not harm and it is unobtrusive. When we have finished,
 382                  * the main loop will pick up all the messages and ctdb
 383                  * packets. The only extra twist is that we cannot use timed
 384                  * events here but have to handcode a timeout.
 385                  */
 386
 387 #ifdef CLUSTER_SUPPORT
 388                 if (lp_clustering()) {
 389                         struct ctdbd_connection *conn = messaging_ctdbd_connection();
 390
 391                         r_fds = &_r_fds;
 392                         FD_ZERO(r_fds);
 393                         max_fd = ctdbd_conn_get_fd(conn);
 394                         FD_SET(max_fd, r_fds);
 395                 }
 396 #endif
 397
 398                 select_timeout = timeval_set(60, 0);
 399
 400                 ret = sys_select(max_fd + 1, r_fds, NULL, NULL,
 401                                  &select_timeout);
 402                 if (ret == -1) {
 403                         if (errno != EINTR) {
 404                                 DEBUG(1, ("error calling select: %s\n",
 405                                           strerror(errno)));
 406                                 status = NT_STATUS_INTERNAL_ERROR;
 407                                 break;
 408                         }
 409                         /*
 410                          * errno == EINTR:
 411                          * This means a signal was received.
 412                          * It might have been a MSG_DBWRAP_G_LOCK_RETRY message.
 413                          * ==> retry
 414                          */
 415                 } else if (ret == 0) {
 416                         if (timeval_expired(&timeout_end)) {
 417                                 DEBUG(10, ("g_lock_lock timed out\n"));
 418                                 status = NT_STATUS_LOCK_NOT_GRANTED;
 419                                 break;
 420                         } else {
 421                                 DEBUG(10, ("select returned 0 but timeout not "
 422                                            "not expired, retrying\n"));
 423                         }
 424                 } else if (ret != 1) {
 425                         DEBUG(1, ("invalid return code of select: %d\n", ret));
 426                         status = NT_STATUS_INTERNAL_ERROR;
 427                         break;
 428                 }
 429                 /*
 430                  * ret == 1:
 431                  * This means ctdbd has sent us some data.
 432                  * Might be a CTDB_SRVID_RECONFIGURE or a
 433                  * CTDB_SRVID_SAMBA_NOTIFY message.
 434                  * ==> retry
 435                  */
 436         }
 437
 438 #ifdef CLUSTER_SUPPORT
 439 done:
 440 #endif
 441
 442         if (!NT_STATUS_IS_OK(status)) {
 443                 NTSTATUS unlock_status;
 444
 445                 unlock_status = g_lock_unlock(ctx, name);
 446
 447                 if (!NT_STATUS_IS_OK(unlock_status)) {
 448                         DEBUG(1, ("Could not remove ourself from the locking "
 449                                   "db: %s\n", nt_errstr(status)));
 450                 }
 451         }
 452
 453         messaging_deregister(ctx->msg, MSG_DBWRAP_G_LOCK_RETRY, &retry);
 454         TALLOC_FREE(te);
 455
 456         return status;
 457 }
 458
 459 static void g_lock_got_retry(struct messaging_context *msg,
 460                              void *private_data,
 461                              uint32_t msg_type,
 462                              struct server_id server_id,
 463                              DATA_BLOB *data)
 464 {
 465         bool *pretry = (bool *)private_data;
 466
 467         DEBUG(10, ("Got retry message from pid %s\n",
 468                    procid_str(talloc_tos(), &server_id)));
 469
 470         *pretry = true;
 471 }
 472
 473 static NTSTATUS g_lock_force_unlock(struct g_lock_ctx *ctx, const char *name,
 474                                     struct server_id pid)
 475 {
 476         struct db_record *rec = NULL;
 477         struct g_lock_rec *locks = NULL;
 478         int i, num_locks;
 479         enum g_lock_type lock_type;
 480         NTSTATUS status;
 481
 482         rec = ctx->db->fetch_locked(ctx->db, talloc_tos(),
 483                                     string_term_tdb_data(name));
 484         if (rec == NULL) {
 485                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 486                 status = NT_STATUS_INTERNAL_ERROR;
 487                 goto done;
 488         }
 489
 490         if (!g_lock_parse(talloc_tos(), rec->value, &num_locks, &locks)) {
 491                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 492                 status = NT_STATUS_INTERNAL_ERROR;
 493                 goto done;
 494         }
 495
 496         for (i=0; i<num_locks; i++) {
 497                 if (procid_equal(&pid, &locks[i].pid)) {
 498                         break;
 499                 }
 500         }
 501
 502         if (i == num_locks) {
 503                 DEBUG(10, ("g_lock_force_unlock: Lock not found\n"));
 504                 status = NT_STATUS_INTERNAL_ERROR;
 505                 goto done;
 506         }
 507
 508         lock_type = locks[i].lock_type;
 509
 510         if (i < (num_locks-1)) {
 511                 locks[i] = locks[num_locks-1];
 512         }
 513         num_locks -= 1;
 514
 515         if (num_locks == 0) {
 516                 status = rec->delete_rec(rec);
 517         } else {
 518                 TDB_DATA data;
 519                 data = make_tdb_data((uint8_t *)locks,
 520                                      sizeof(struct g_lock_rec) * num_locks);
 521                 status = rec->store(rec, data, 0);
 522         }
 523
 524         if (!NT_STATUS_IS_OK(status)) {
 525                 DEBUG(1, ("g_lock_force_unlock: Could not store record: %s\n",
 526                           nt_errstr(status)));
 527                 goto done;
 528         }
 529
 530         TALLOC_FREE(rec);
 531
 532         if ((lock_type & G_LOCK_PENDING) == 0) {
 533                 int num_wakeups = 0;
 534
 535                 /*
 536                  * We've been the lock holder. Others to retry. Don't
 537                  * tell all others to avoid a thundering herd. In case
 538                  * this leads to a complete stall because we miss some
 539                  * processes, the loop in g_lock_lock tries at least
 540                  * once a minute.
 541                  */
 542
 543                 for (i=0; i<num_locks; i++) {
 544                         if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
 545                                 continue;
 546                         }
 547                         if (!process_exists(locks[i].pid)) {
 548                                 continue;
 549                         }
 550
 551                         /*
 552                          * Ping all waiters to retry
 553                          */
 554                         status = messaging_send(ctx->msg, locks[i].pid,
 555                                                 MSG_DBWRAP_G_LOCK_RETRY,
 556                                                 &data_blob_null);
 557                         if (!NT_STATUS_IS_OK(status)) {
 558                                 DEBUG(1, ("sending retry to %s failed: %s\n",
 559                                           procid_str(talloc_tos(),
 560                                                      &locks[i].pid),
 561                                           nt_errstr(status)));
 562                         } else {
 563                                 num_wakeups += 1;
 564                         }
 565                         if (num_wakeups > 5) {
 566                                 break;
 567                         }
 568                 }
 569         }
 570 done:
 571         /*
 572          * For the error path, TALLOC_FREE(rec) as well. In the good
 573          * path we have already freed it.
 574          */
 575         TALLOC_FREE(rec);
 576
 577         TALLOC_FREE(locks);
 578         return status;
 579 }
 580
 581 NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
 582 {
 583         NTSTATUS status;
 584
 585         status = g_lock_force_unlock(ctx, name, procid_self());
 586
 587 #ifdef CLUSTER_SUPPORT
 588         if (lp_clustering()) {
 589                 ctdb_unwatch(messaging_ctdbd_connection());
 590         }
 591 #endif
 592         return status;
 593 }
 594
 595 struct g_lock_locks_state {
 596         int (*fn)(const char *name, void *private_data);
 597         void *private_data;
 598 };
 599
 600 static int g_lock_locks_fn(struct db_record *rec, void *priv)
 601 {
 602         struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
 603
 604         if ((rec->key.dsize == 0) || (rec->key.dptr[rec->key.dsize-1] != 0)) {
 605                 DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
 606                 return 0;
 607         }
 608         return state->fn((char *)rec->key.dptr, state->private_data);
 609 }
 610
 611 int g_lock_locks(struct g_lock_ctx *ctx,
 612                  int (*fn)(const char *name, void *private_data),
 613                  void *private_data)
 614 {
 615         struct g_lock_locks_state state;
 616
 617         state.fn = fn;
 618         state.private_data = private_data;
 619
 620         return ctx->db->traverse_read(ctx->db, g_lock_locks_fn, &state);
 621 }
 622
 623 NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
 624                      int (*fn)(struct server_id pid,
 625                                enum g_lock_type lock_type,
 626                                void *private_data),
 627                      void *private_data)
 628 {
 629         TDB_DATA data;
 630         int i, num_locks;
 631         struct g_lock_rec *locks = NULL;
 632         bool ret;
 633
 634         if (ctx->db->fetch(ctx->db, talloc_tos(), string_term_tdb_data(name),
 635                            &data) != 0) {
 636                 return NT_STATUS_NOT_FOUND;
 637         }
 638
 639         if ((data.dsize == 0) || (data.dptr == NULL)) {
 640                 return NT_STATUS_OK;
 641         }
 642
 643         ret = g_lock_parse(talloc_tos(), data, &num_locks, &locks);
 644
 645         TALLOC_FREE(data.dptr);
 646
 647         if (!ret) {
 648                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 649                 return NT_STATUS_INTERNAL_ERROR;
 650         }
 651
 652         for (i=0; i<num_locks; i++) {
 653                 if (fn(locks[i].pid, locks[i].lock_type, private_data) != 0) {
 654                         break;
 655                 }
 656         }
 657         TALLOC_FREE(locks);
 658         return NT_STATUS_OK;
 659 }
 660
 661 struct g_lock_get_state {
 662         bool found;
 663         struct server_id *pid;
 664 };
 665
 666 static int g_lock_get_fn(struct server_id pid, enum g_lock_type lock_type,
 667                          void *priv)
 668 {
 669         struct g_lock_get_state *state = (struct g_lock_get_state *)priv;
 670
 671         if ((lock_type & G_LOCK_PENDING) != 0) {
 672                 return 0;
 673         }
 674
 675         state->found = true;
 676         *state->pid = pid;
 677         return 1;
 678 }
 679
 680 NTSTATUS g_lock_get(struct g_lock_ctx *ctx, const char *name,
 681                     struct server_id *pid)
 682 {
 683         struct g_lock_get_state state;
 684         NTSTATUS status;
 685
 686         state.found = false;
 687         state.pid = pid;
 688
 689         status = g_lock_dump(ctx, name, g_lock_get_fn, &state);
 690         if (!NT_STATUS_IS_OK(status)) {
 691                 return status;
 692         }
 693         if (!state.found) {
 694                 return NT_STATUS_NOT_FOUND;
 695         }
 696         return NT_STATUS_OK;
 697 }