src/common/trace-chunk.c

   1 /*
   2  * Copyright (C) 2019 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This library is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #include <lttng/constant.h>
  19 #include <common/string-utils/format.h>
  20 #include <common/trace-chunk.h>
  21 #include <common/trace-chunk-registry.h>
  22 #include <common/hashtable/utils.h>
  23 #include <common/hashtable/hashtable.h>
  24 #include <common/error.h>
  25 #include <common/utils.h>
  26 #include <common/time.h>
  27 #include <common/optional.h>
  28 #include <common/compat/directory-handle.h>
  29 #include <common/credentials.h>
  30 #include <common/defaults.h>
  31 #include <common/dynamic-array.h>
  32
  33 #include <urcu/ref.h>
  34 #include <urcu/rculfhash.h>
  35 #include <sys/stat.h>
  36 #include <inttypes.h>
  37 #include <pthread.h>
  38 #include <stdio.h>
  39
  40 /*
  41  * Two ISO 8601-compatible timestamps, separated by a hypen, followed an
  42  * index, i.e. <start-iso-8601>-<end-iso-8601>-<id-uint64_t>.
  43  */
  44 #define GENERATED_CHUNK_NAME_LEN (2 * sizeof("YYYYmmddTHHMMSS+HHMM") + MAX_INT_DEC_LEN(uint64_t))
  45 #define DIR_CREATION_MODE (S_IRWXU | S_IRWXG)
  46
  47 enum trace_chunk_mode {
  48         TRACE_CHUNK_MODE_USER,
  49         TRACE_CHUNK_MODE_OWNER,
  50 };
  51
  52 /*
  53  * Callback to invoke on release of a trace chunk. Note that there is no
  54  * need to 'lock' the trace chunk during the execution of these callbacks
  55  * since only one thread may access a chunk during its destruction (the last
  56  * to release its reference to the chunk).
  57  */
  58 typedef void (*chunk_close_command)(struct lttng_trace_chunk *trace_chunk);
  59
  60 /* Move a completed trace chunk to the 'completed' trace archive folder. */
  61 static
  62 void lttng_trace_chunk_move_to_completed(struct lttng_trace_chunk *trace_chunk);
  63
  64 struct chunk_credentials {
  65         bool use_current_user;
  66         struct lttng_credentials user;
  67 };
  68
  69 struct lttng_trace_chunk {
  70         pthread_mutex_t lock;
  71         struct urcu_ref ref;
  72         LTTNG_OPTIONAL(enum trace_chunk_mode) mode;
  73         /*
  74          * First-level directories created within the trace chunk.
  75          * Elements are of type 'char *'.
  76          */
  77         struct lttng_dynamic_pointer_array top_level_directories;
  78         /* Is contained within an lttng_trace_chunk_registry_element? */
  79         bool in_registry_element;
  80         bool name_overriden;
  81         char *name;
  82         /* An unset id means the chunk is anonymous. */
  83         LTTNG_OPTIONAL(uint64_t) id;
  84         LTTNG_OPTIONAL(time_t) timestamp_creation;
  85         LTTNG_OPTIONAL(time_t) timestamp_close;
  86         LTTNG_OPTIONAL(struct chunk_credentials) credentials;
  87         LTTNG_OPTIONAL(struct lttng_directory_handle) session_output_directory;
  88         LTTNG_OPTIONAL(struct lttng_directory_handle) chunk_directory;
  89         LTTNG_OPTIONAL(enum lttng_trace_chunk_command_type) close_command;
  90 };
  91
  92 /* A trace chunk is uniquely identified by its (session id, chunk id) tuple. */
  93 struct lttng_trace_chunk_registry_element {
  94         uint64_t session_id;
  95         struct lttng_trace_chunk chunk;
  96         /* Weak and only set when added. */
  97         struct lttng_trace_chunk_registry *registry;
  98         struct cds_lfht_node trace_chunk_registry_ht_node;
  99         /* call_rcu delayed reclaim. */
 100         struct rcu_head rcu_node;
 101 };
 102
 103 struct lttng_trace_chunk_registry {
 104         struct cds_lfht *ht;
 105 };
 106
 107 const char *close_command_names[] = {
 108         [LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED] =
 109                 "move to completed chunk folder",
 110 };
 111
 112 chunk_close_command close_command_funcs[] = {
 113         [LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED] =
 114                         lttng_trace_chunk_move_to_completed,
 115 };
 116
 117 static
 118 bool lttng_trace_chunk_registry_element_equals(
 119                 const struct lttng_trace_chunk_registry_element *a,
 120                 const struct lttng_trace_chunk_registry_element *b)
 121 {
 122         if (a->session_id != b->session_id) {
 123                 goto not_equal;
 124         }
 125         if (a->chunk.id.is_set != b->chunk.id.is_set) {
 126                 goto not_equal;
 127         }
 128         if (a->chunk.id.is_set && a->chunk.id.value != b->chunk.id.value) {
 129                 goto not_equal;
 130         }
 131         return true;
 132 not_equal:
 133         return false;
 134 }
 135
 136 static
 137 int lttng_trace_chunk_registry_element_match(struct cds_lfht_node *node,
 138                 const void *key)
 139 {
 140         const struct lttng_trace_chunk_registry_element *element_a, *element_b;
 141
 142         element_a = (const struct lttng_trace_chunk_registry_element *) key;
 143         element_b = caa_container_of(node, typeof(*element_b),
 144                         trace_chunk_registry_ht_node);
 145         return lttng_trace_chunk_registry_element_equals(element_a, element_b);
 146 }
 147
 148 static
 149 unsigned long lttng_trace_chunk_registry_element_hash(
 150                 const struct lttng_trace_chunk_registry_element *element)
 151 {
 152         unsigned long hash = hash_key_u64(&element->session_id,
 153                         lttng_ht_seed);
 154
 155         if (element->chunk.id.is_set) {
 156                 hash ^= hash_key_u64(&element->chunk.id.value, lttng_ht_seed);
 157         }
 158
 159         return hash;
 160 }
 161
 162 static
 163 char *generate_chunk_name(uint64_t chunk_id, time_t creation_timestamp,
 164                 const time_t *close_timestamp)
 165 {
 166         int ret = 0;
 167         char *new_name= NULL;
 168         char start_datetime[sizeof("YYYYmmddTHHMMSS+HHMM")] = {};
 169         char end_datetime_suffix[sizeof("-YYYYmmddTHHMMSS+HHMM")] = {};
 170
 171         ret = time_to_iso8601_str(
 172                         creation_timestamp,
 173                         start_datetime, sizeof(start_datetime));
 174         if (ret) {
 175                 ERR("Failed to format trace chunk start date time");
 176                 goto error;
 177         }
 178         if (close_timestamp) {
 179                 *end_datetime_suffix = '-';
 180                 ret = time_to_iso8601_str(
 181                                 *close_timestamp,
 182                                 end_datetime_suffix + 1,
 183                                 sizeof(end_datetime_suffix));
 184                 if (ret) {
 185                         ERR("Failed to format trace chunk end date time");
 186                         goto error;
 187                 }
 188         }
 189         new_name = zmalloc(GENERATED_CHUNK_NAME_LEN);
 190         if (!new_name) {
 191                 ERR("Failed to allocate buffer for automatically-generated trace chunk name");
 192                 goto error;
 193         }
 194         ret = snprintf(new_name, GENERATED_CHUNK_NAME_LEN, "%s%s-%" PRIu64,
 195                         start_datetime, end_datetime_suffix, chunk_id);
 196         if (ret >= GENERATED_CHUNK_NAME_LEN || ret == -1) {
 197                 ERR("Failed to format trace chunk name");
 198                 goto error;
 199         }
 200
 201         return new_name;
 202 error:
 203         free(new_name);
 204         return NULL;
 205 }
 206
 207 static
 208 void lttng_trace_chunk_init(struct lttng_trace_chunk *chunk)
 209 {
 210         urcu_ref_init(&chunk->ref);
 211         pthread_mutex_init(&chunk->lock, NULL);
 212         lttng_dynamic_pointer_array_init(&chunk->top_level_directories, free);
 213 }
 214
 215 static
 216 void lttng_trace_chunk_fini(struct lttng_trace_chunk *chunk)
 217 {
 218         if (chunk->session_output_directory.is_set) {
 219                 lttng_directory_handle_fini(
 220                                 &chunk->session_output_directory.value);
 221         }
 222         if (chunk->chunk_directory.is_set) {
 223                 lttng_directory_handle_fini(&chunk->chunk_directory.value);
 224         }
 225         free(chunk->name);
 226         chunk->name = NULL;
 227         lttng_dynamic_pointer_array_reset(&chunk->top_level_directories);
 228         pthread_mutex_destroy(&chunk->lock);
 229 }
 230
 231 static
 232 struct lttng_trace_chunk *lttng_trace_chunk_allocate(void)
 233 {
 234         struct lttng_trace_chunk *chunk = NULL;
 235
 236         chunk = zmalloc(sizeof(*chunk));
 237         if (!chunk) {
 238                 ERR("Failed to allocate trace chunk");
 239                 goto end;
 240         }
 241         lttng_trace_chunk_init(chunk);
 242 end:
 243         return chunk;
 244 }
 245
 246 LTTNG_HIDDEN
 247 struct lttng_trace_chunk *lttng_trace_chunk_create_anonymous(void)
 248 {
 249         DBG("Creating anonymous trace chunk");
 250         return lttng_trace_chunk_allocate();
 251 }
 252
 253 LTTNG_HIDDEN
 254 struct lttng_trace_chunk *lttng_trace_chunk_create(
 255                 uint64_t chunk_id, time_t chunk_creation_time)
 256 {
 257         struct lttng_trace_chunk *chunk;
 258         char chunk_creation_datetime_buf[16] = {};
 259         const char *chunk_creation_datetime_str = "(formatting error)";
 260         struct tm timeinfo_buf, *timeinfo;
 261
 262         timeinfo = localtime_r(&chunk_creation_time, &timeinfo_buf);
 263         if (timeinfo) {
 264                 size_t strftime_ret;
 265
 266                 /* Don't fail because of this; it is only used for logging. */
 267                 strftime_ret = strftime(chunk_creation_datetime_buf,
 268                                 sizeof(chunk_creation_datetime_buf),
 269                                 "%Y%m%d-%H%M%S", timeinfo);
 270                 if (strftime_ret) {
 271                         chunk_creation_datetime_str =
 272                                         chunk_creation_datetime_buf;
 273                 }
 274         }
 275
 276         DBG("Creating trace chunk: chunk_id = %" PRIu64 ", creation time = %s",
 277                         chunk_id, chunk_creation_datetime_str);
 278         chunk = lttng_trace_chunk_allocate();
 279         if (!chunk) {
 280                 goto end;
 281         }
 282
 283         LTTNG_OPTIONAL_SET(&chunk->id, chunk_id);
 284         LTTNG_OPTIONAL_SET(&chunk->timestamp_creation, chunk_creation_time);
 285         if (chunk_id != 0) {
 286                 chunk->name = generate_chunk_name(chunk_id,
 287                                 chunk_creation_time, NULL);
 288                 if (!chunk->name) {
 289                         ERR("Failed to allocate trace chunk name storage");
 290                         goto error;
 291                 }
 292         }
 293
 294         DBG("Chunk name set to \"%s\"", chunk->name ? : "(none)");
 295 end:
 296         return chunk;
 297 error:
 298         lttng_trace_chunk_put(chunk);
 299         return NULL;
 300 }
 301
 302 LTTNG_HIDDEN
 303 enum lttng_trace_chunk_status lttng_trace_chunk_get_id(
 304                 struct lttng_trace_chunk *chunk, uint64_t *id)
 305 {
 306         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 307
 308         pthread_mutex_lock(&chunk->lock);
 309         if (chunk->id.is_set) {
 310                 *id = chunk->id.value;
 311         } else {
 312                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 313         }
 314         pthread_mutex_unlock(&chunk->lock);
 315         return status;
 316 }
 317
 318 LTTNG_HIDDEN
 319 enum lttng_trace_chunk_status lttng_trace_chunk_get_creation_timestamp(
 320                 struct lttng_trace_chunk *chunk, time_t *creation_ts)
 321
 322 {
 323         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 324
 325         pthread_mutex_lock(&chunk->lock);
 326         if (chunk->timestamp_creation.is_set) {
 327                 *creation_ts = chunk->timestamp_creation.value;
 328         } else {
 329                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 330         }
 331         pthread_mutex_unlock(&chunk->lock);
 332         return status;
 333 }
 334
 335 LTTNG_HIDDEN
 336 enum lttng_trace_chunk_status lttng_trace_chunk_get_close_timestamp(
 337                 struct lttng_trace_chunk *chunk, time_t *close_ts)
 338 {
 339         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 340
 341         pthread_mutex_lock(&chunk->lock);
 342         if (chunk->timestamp_close.is_set) {
 343                 *close_ts = chunk->timestamp_close.value;
 344         } else {
 345                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 346         }
 347         pthread_mutex_unlock(&chunk->lock);
 348         return status;
 349 }
 350
 351 LTTNG_HIDDEN
 352 enum lttng_trace_chunk_status lttng_trace_chunk_set_close_timestamp(
 353                 struct lttng_trace_chunk *chunk, time_t close_ts)
 354 {
 355         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 356
 357         pthread_mutex_lock(&chunk->lock);
 358         if (!chunk->timestamp_creation.is_set) {
 359                 ERR("Failed to set trace chunk close timestamp: creation timestamp is unset");
 360                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
 361                 goto end;
 362         }
 363         if (chunk->timestamp_creation.value > close_ts) {
 364                 ERR("Failed to set trace chunk close timestamp: close timestamp is before creation timestamp");
 365                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
 366                 goto end;
 367         }
 368         LTTNG_OPTIONAL_SET(&chunk->timestamp_close, close_ts);
 369         free(chunk->name);
 370         chunk->name = generate_chunk_name(LTTNG_OPTIONAL_GET(chunk->id),
 371                         LTTNG_OPTIONAL_GET(chunk->timestamp_creation),
 372                         &close_ts);
 373         if (!chunk->name) {
 374                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 375         }
 376 end:
 377         pthread_mutex_unlock(&chunk->lock);
 378         return status;
 379 }
 380
 381 LTTNG_HIDDEN
 382 enum lttng_trace_chunk_status lttng_trace_chunk_get_name(
 383                 struct lttng_trace_chunk *chunk, const char **name,
 384                 bool *name_overriden)
 385 {
 386         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 387
 388         pthread_mutex_lock(&chunk->lock);
 389         if (name_overriden) {
 390                 *name_overriden = chunk->name_overriden;
 391         }
 392         if (!chunk->name) {
 393                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 394                 goto end;
 395         }
 396         *name = chunk->name;
 397 end:
 398         pthread_mutex_unlock(&chunk->lock);
 399         return status;
 400 }
 401
 402 static
 403 bool is_valid_chunk_name(const char *name)
 404 {
 405         size_t len;
 406
 407         if (!name) {
 408                 return false;
 409         }
 410
 411         len = strnlen(name, LTTNG_NAME_MAX);
 412         if (len == 0 || len == LTTNG_NAME_MAX) {
 413                 return false;
 414         }
 415
 416         if (strchr(name, '/') || strchr(name, '.')) {
 417                 return false;
 418         }
 419
 420         return true;
 421 }
 422
 423 LTTNG_HIDDEN
 424 enum lttng_trace_chunk_status lttng_trace_chunk_override_name(
 425                 struct lttng_trace_chunk *chunk, const char *name)
 426
 427 {
 428         char *new_name;
 429         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 430
 431         if (!is_valid_chunk_name(name)) {
 432                 ERR("Attempted to set an invalid name on a trace chunk: name = %s",
 433                                 name ? : "NULL");
 434                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
 435                 goto end;
 436         }
 437
 438         pthread_mutex_lock(&chunk->lock);
 439         if (!chunk->id.is_set) {
 440                 ERR("Attempted to set an override name on an anonymous trace chunk: name = %s",
 441                                 name);
 442                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
 443                 goto end_unlock;
 444         }
 445         new_name = strdup(name);
 446         if (!new_name) {
 447                 ERR("Failed to allocate new trace chunk name");
 448                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 449                 goto end_unlock;
 450         }
 451         free(chunk->name);
 452         chunk->name = new_name;
 453         chunk->name_overriden = true;
 454 end_unlock:
 455         pthread_mutex_unlock(&chunk->lock);
 456 end:
 457         return status;
 458 }
 459
 460 LTTNG_HIDDEN
 461 enum lttng_trace_chunk_status lttng_trace_chunk_get_credentials(
 462                 struct lttng_trace_chunk *chunk,
 463                 struct lttng_credentials *credentials)
 464 {
 465         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 466
 467         pthread_mutex_lock(&chunk->lock);
 468         if (chunk->credentials.is_set) {
 469                 if (chunk->credentials.value.use_current_user) {
 470                         credentials->uid = geteuid();
 471                         credentials->gid = getegid();
 472                 } else {
 473                         *credentials = chunk->credentials.value.user;
 474                 }
 475         } else {
 476                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 477         }
 478         pthread_mutex_unlock(&chunk->lock);
 479         return status;
 480 }
 481
 482 LTTNG_HIDDEN
 483 enum lttng_trace_chunk_status lttng_trace_chunk_set_credentials(
 484                 struct lttng_trace_chunk *chunk,
 485                 const struct lttng_credentials *user_credentials)
 486 {
 487         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 488         const struct chunk_credentials credentials = {
 489                 .user = *user_credentials,
 490                 .use_current_user = false,
 491         };
 492
 493         pthread_mutex_lock(&chunk->lock);
 494         if (chunk->credentials.is_set) {
 495                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 496                 goto end;
 497         }
 498         LTTNG_OPTIONAL_SET(&chunk->credentials, credentials);
 499 end:
 500         pthread_mutex_unlock(&chunk->lock);
 501         return status;
 502 }
 503
 504 LTTNG_HIDDEN
 505 enum lttng_trace_chunk_status lttng_trace_chunk_set_credentials_current_user(
 506                 struct lttng_trace_chunk *chunk)
 507 {
 508         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 509         const struct chunk_credentials credentials = {
 510                 .use_current_user = true,
 511         };
 512
 513         pthread_mutex_lock(&chunk->lock);
 514         if (chunk->credentials.is_set) {
 515                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 516                 goto end;
 517         }
 518         LTTNG_OPTIONAL_SET(&chunk->credentials, credentials);
 519 end:
 520         pthread_mutex_unlock(&chunk->lock);
 521         return status;
 522 }
 523
 524
 525 LTTNG_HIDDEN
 526 enum lttng_trace_chunk_status lttng_trace_chunk_set_as_owner(
 527                 struct lttng_trace_chunk *chunk,
 528                 struct lttng_directory_handle *session_output_directory)
 529 {
 530         int ret;
 531         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 532         struct lttng_directory_handle chunk_directory_handle;
 533
 534         pthread_mutex_lock(&chunk->lock);
 535         if (chunk->mode.is_set) {
 536                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
 537                 goto end;
 538         }
 539         if (!chunk->credentials.is_set) {
 540                 /*
 541                  * Fatal error, credentials must be set before a
 542                  * directory is created.
 543                  */
 544                 ERR("Credentials of trace chunk are unset: refusing to set session output directory");
 545                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 546                 goto end;
 547         }
 548
 549         if (chunk->name) {
 550                 /*
 551                  * A nameless chunk does not need its own output directory.
 552                  * The session's output directory will be used.
 553                  */
 554                 ret = lttng_directory_handle_create_subdirectory_as_user(
 555                                 session_output_directory,
 556                                 chunk->name,
 557                                 DIR_CREATION_MODE,
 558                                 !chunk->credentials.value.use_current_user ?
 559                                         &chunk->credentials.value.user : NULL);
 560                 if (ret) {
 561                         PERROR("Failed to create chunk output directory \"%s\"",
 562                                 chunk->name);
 563                         status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 564                         goto end;
 565                 }
 566         }
 567         ret = lttng_directory_handle_init_from_handle(&chunk_directory_handle,
 568                         chunk->name,
 569                         session_output_directory);
 570         if (ret) {
 571                 /* The function already logs on all error paths. */
 572                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 573                 goto end;
 574         }
 575         LTTNG_OPTIONAL_SET(&chunk->session_output_directory,
 576                         lttng_directory_handle_move(session_output_directory));
 577         LTTNG_OPTIONAL_SET(&chunk->chunk_directory,
 578                         lttng_directory_handle_move(&chunk_directory_handle));
 579         LTTNG_OPTIONAL_SET(&chunk->mode, TRACE_CHUNK_MODE_OWNER);
 580 end:
 581         pthread_mutex_unlock(&chunk->lock);
 582         return status;
 583 }
 584
 585 LTTNG_HIDDEN
 586 enum lttng_trace_chunk_status lttng_trace_chunk_set_as_user(
 587                 struct lttng_trace_chunk *chunk,
 588                 struct lttng_directory_handle *chunk_directory)
 589 {
 590         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 591
 592         pthread_mutex_lock(&chunk->lock);
 593         if (chunk->mode.is_set) {
 594                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
 595                 goto end;
 596         }
 597         if (!chunk->credentials.is_set) {
 598                 ERR("Credentials of trace chunk are unset: refusing to set chunk output directory");
 599                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 600                 goto end;
 601         }
 602         LTTNG_OPTIONAL_SET(&chunk->chunk_directory,
 603                         lttng_directory_handle_move(chunk_directory));
 604         LTTNG_OPTIONAL_SET(&chunk->mode, TRACE_CHUNK_MODE_USER);
 605 end:
 606         pthread_mutex_unlock(&chunk->lock);
 607         return status;
 608 }
 609
 610 LTTNG_HIDDEN
 611 enum lttng_trace_chunk_status lttng_trace_chunk_get_chunk_directory_handle(
 612                 struct lttng_trace_chunk *chunk,
 613                 const struct lttng_directory_handle **handle)
 614 {
 615         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 616
 617         pthread_mutex_lock(&chunk->lock);
 618         if (!chunk->chunk_directory.is_set) {
 619                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 620                 goto end;
 621         }
 622
 623         *handle = &chunk->chunk_directory.value;
 624 end:
 625         pthread_mutex_unlock(&chunk->lock);
 626         return status;
 627 }
 628
 629 /* Add a top-level directory to the trace chunk if it was previously unknown. */
 630 static
 631 int add_top_level_directory_unique(struct lttng_trace_chunk *chunk,
 632                 const char *new_path)
 633 {
 634         int ret = 0;
 635         bool found = false;
 636         size_t i, count = lttng_dynamic_pointer_array_get_count(
 637                         &chunk->top_level_directories);
 638         const char *new_path_separator_pos = strchr(new_path, '/');
 639         const ptrdiff_t new_path_top_level_len = new_path_separator_pos ?
 640                         new_path_separator_pos - new_path : strlen(new_path);
 641
 642         for (i = 0; i < count; i++) {
 643                 const char *path = lttng_dynamic_pointer_array_get_pointer(
 644                                 &chunk->top_level_directories, i);
 645                 const ptrdiff_t path_top_level_len = strlen(path);
 646
 647                 if (path_top_level_len != new_path_top_level_len) {
 648                         continue;
 649                 }
 650                 if (!strncmp(path, new_path, path_top_level_len)) {
 651                         found = true;
 652                         break;
 653                 }
 654         }
 655
 656         if (!found) {
 657                 char *copy = strndup(new_path, new_path_top_level_len);
 658
 659                 DBG("Adding new top-level directory \"%s\" to trace chunk \"%s\"",
 660                                 new_path, chunk->name ? : "(unnamed)");
 661                 if (!copy) {
 662                         PERROR("Failed to copy path");
 663                         ret = -1;
 664                         goto end;
 665                 }
 666                 ret = lttng_dynamic_pointer_array_add_pointer(
 667                                 &chunk->top_level_directories, copy);
 668                 if (ret) {
 669                         ERR("Allocation failure while adding top-level directory entry to a trace chunk");
 670                         free(copy);
 671                         goto end;
 672                 }
 673         }
 674 end:
 675         return ret;
 676 }
 677
 678 LTTNG_HIDDEN
 679 enum lttng_trace_chunk_status lttng_trace_chunk_create_subdirectory(
 680                 struct lttng_trace_chunk *chunk,
 681                 const char *path)
 682 {
 683         int ret;
 684         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 685
 686         DBG("Creating trace chunk subdirectory \"%s\"", path);
 687         pthread_mutex_lock(&chunk->lock);
 688         if (!chunk->credentials.is_set) {
 689                 /*
 690                  * Fatal error, credentials must be set before a
 691                  * directory is created.
 692                  */
 693                 ERR("Credentials of trace chunk are unset: refusing to create subdirectory \"%s\"",
 694                                 path);
 695                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 696                 goto end;
 697         }
 698         if (!chunk->mode.is_set ||
 699                         chunk->mode.value != TRACE_CHUNK_MODE_OWNER) {
 700                 ERR("Attempted to create trace chunk subdirectory \"%s\" through a non-owner chunk",
 701                                 path);
 702                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_OPERATION;
 703                 goto end;
 704         }
 705         if (!chunk->chunk_directory.is_set) {
 706                 ERR("Attempted to create trace chunk subdirectory \"%s\" before setting the chunk output directory",
 707                                 path);
 708                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 709                 goto end;
 710         }
 711         if (*path == '/') {
 712                 ERR("Refusing to create absolute trace chunk directory \"%s\"",
 713                                 path);
 714                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
 715                 goto end;
 716         }
 717         ret = lttng_directory_handle_create_subdirectory_recursive_as_user(
 718                         &chunk->chunk_directory.value, path,
 719                         DIR_CREATION_MODE,
 720                         chunk->credentials.value.use_current_user ?
 721                                         NULL : &chunk->credentials.value.user);
 722         if (ret) {
 723                 PERROR("Failed to create trace chunk subdirectory \"%s\"",
 724                                 path);
 725                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 726                 goto end;
 727         }
 728         ret = add_top_level_directory_unique(chunk, path);
 729         if (ret) {
 730                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 731                 goto end;
 732         }
 733 end:
 734         pthread_mutex_unlock(&chunk->lock);
 735         return status;
 736 }
 737
 738 LTTNG_HIDDEN
 739 enum lttng_trace_chunk_status lttng_trace_chunk_open_file(
 740                 struct lttng_trace_chunk *chunk, const char *file_path,
 741                 int flags, mode_t mode, int *out_fd)
 742 {
 743         int ret;
 744         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 745
 746         DBG("Opening trace chunk file \"%s\"", file_path);
 747         pthread_mutex_lock(&chunk->lock);
 748         if (!chunk->credentials.is_set) {
 749                 /*
 750                  * Fatal error, credentials must be set before a
 751                  * file is created.
 752                  */
 753                 ERR("Credentials of trace chunk are unset: refusing to open file \"%s\"",
 754                                 file_path);
 755                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 756                 goto end;
 757         }
 758         if (!chunk->chunk_directory.is_set) {
 759                 ERR("Attempted to open trace chunk file \"%s\" before setting the chunk output directory",
 760                                 file_path);
 761                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 762                 goto end;
 763         }
 764         ret = lttng_directory_handle_open_file_as_user(
 765                         &chunk->chunk_directory.value, file_path, flags, mode,
 766                         chunk->credentials.value.use_current_user ?
 767                                         NULL : &chunk->credentials.value.user);
 768         if (ret < 0) {
 769                 ERR("Failed to open file relative to trace chunk file_path = \"%s\", flags = %d, mode = %d",
 770                                 file_path, flags, (int) mode);
 771                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 772                 goto end;
 773         }
 774         *out_fd = ret;
 775 end:
 776         pthread_mutex_unlock(&chunk->lock);
 777         return status;
 778 }
 779
 780 LTTNG_HIDDEN
 781 int lttng_trace_chunk_unlink_file(struct lttng_trace_chunk *chunk,
 782                 const char *file_path)
 783 {
 784         int ret;
 785         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 786
 787         DBG("Unlinking trace chunk file \"%s\"", file_path);
 788         pthread_mutex_lock(&chunk->lock);
 789         if (!chunk->credentials.is_set) {
 790                 /*
 791                  * Fatal error, credentials must be set before a
 792                  * directory is created.
 793                  */
 794                 ERR("Credentials of trace chunk are unset: refusing to unlink file \"%s\"",
 795                                 file_path);
 796                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 797                 goto end;
 798         }
 799         if (!chunk->chunk_directory.is_set) {
 800                 ERR("Attempted to unlink trace chunk file \"%s\" before setting the chunk output directory",
 801                                 file_path);
 802                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 803                 goto end;
 804         }
 805         ret = lttng_directory_handle_unlink_file_as_user(
 806                         &chunk->chunk_directory.value, file_path,
 807                         chunk->credentials.value.use_current_user ?
 808                                         NULL : &chunk->credentials.value.user);
 809         if (ret < 0) {
 810                 status = LTTNG_TRACE_CHUNK_STATUS_ERROR;
 811                 goto end;
 812         }
 813 end:
 814         pthread_mutex_unlock(&chunk->lock);
 815         return status;
 816 }
 817
 818 static
 819 void lttng_trace_chunk_move_to_completed(struct lttng_trace_chunk *trace_chunk)
 820 {
 821         int ret;
 822         char *directory_to_rename = NULL;
 823         bool free_directory_to_rename = false;
 824         char *archived_chunk_name = NULL;
 825         const uint64_t chunk_id = LTTNG_OPTIONAL_GET(trace_chunk->id);
 826         const time_t creation_timestamp =
 827                         LTTNG_OPTIONAL_GET(trace_chunk->timestamp_creation);
 828         const time_t close_timestamp =
 829                         LTTNG_OPTIONAL_GET(trace_chunk->timestamp_close);
 830         LTTNG_OPTIONAL(struct lttng_directory_handle) archived_chunks_directory = {};
 831
 832         if (!trace_chunk->mode.is_set ||
 833                         trace_chunk->mode.value != TRACE_CHUNK_MODE_OWNER ||
 834                         !trace_chunk->session_output_directory.is_set) {
 835                 /*
 836                  * This command doesn't need to run if the output is remote
 837                  * or if the trace chunk is not owned by this process.
 838                  */
 839                 goto end;
 840         }
 841
 842         assert(trace_chunk->mode.value == TRACE_CHUNK_MODE_OWNER);
 843         assert(!trace_chunk->name_overriden);
 844
 845         /*
 846          * The fist trace chunk of a session is directly output to the
 847          * session's output folder. In this case, the top level directories
 848          * must be moved to a temporary folder before that temporary directory
 849          * is renamed to match the chunk's name.
 850          */
 851         if (chunk_id == 0) {
 852                 struct lttng_directory_handle temporary_rename_directory;
 853                 size_t i, count = lttng_dynamic_pointer_array_get_count(
 854                                 &trace_chunk->top_level_directories);
 855
 856                 ret = lttng_directory_handle_create_subdirectory_as_user(
 857                                 &trace_chunk->session_output_directory.value,
 858                                 DEFAULT_TEMPORARY_CHUNK_RENAME_DIRECTORY,
 859                                 DIR_CREATION_MODE,
 860                                 !trace_chunk->credentials.value.use_current_user ?
 861                                         &trace_chunk->credentials.value.user : NULL);
 862                 if (ret) {
 863                         PERROR("Failed to create temporary trace chunk rename directory \"%s\"",
 864                                         DEFAULT_TEMPORARY_CHUNK_RENAME_DIRECTORY);
 865                 }
 866
 867                 ret = lttng_directory_handle_init_from_handle(&temporary_rename_directory,
 868                                 DEFAULT_TEMPORARY_CHUNK_RENAME_DIRECTORY,
 869                                 &trace_chunk->session_output_directory.value);
 870                 if (ret) {
 871                         ERR("Failed to get handle to temporary trace chunk rename directory");
 872                         goto end;
 873                 }
 874
 875                 for (i = 0; i < count; i++) {
 876                         const char *top_level_name =
 877                                         lttng_dynamic_pointer_array_get_pointer(
 878                                                 &trace_chunk->top_level_directories, i);
 879
 880                         ret = lttng_directory_handle_rename_as_user(
 881                                         &trace_chunk->session_output_directory.value,
 882                                         top_level_name,
 883                                         &temporary_rename_directory,
 884                                         top_level_name,
 885                                         LTTNG_OPTIONAL_GET(trace_chunk->credentials).use_current_user ?
 886                                                 NULL :
 887                                                 &trace_chunk->credentials.value.user);
 888                         if (ret) {
 889                                 PERROR("Failed to move \"%s\" to temporary trace chunk rename directory",
 890                                                 top_level_name);
 891                                 lttng_directory_handle_fini(
 892                                                 &temporary_rename_directory);
 893                                 goto end;
 894                         }
 895                 }
 896                 lttng_directory_handle_fini(&temporary_rename_directory);
 897                 directory_to_rename = DEFAULT_TEMPORARY_CHUNK_RENAME_DIRECTORY;
 898                 free_directory_to_rename = false;
 899         } else {
 900                 directory_to_rename = generate_chunk_name(chunk_id,
 901                                 creation_timestamp, NULL);
 902                 if (!directory_to_rename) {
 903                         ERR("Failed to generate initial trace chunk name while renaming trace chunk");
 904                 }
 905                 free_directory_to_rename = true;
 906         }
 907
 908         archived_chunk_name = generate_chunk_name(chunk_id, creation_timestamp,
 909                         &close_timestamp);
 910         if (!archived_chunk_name) {
 911                 ERR("Failed to generate archived trace chunk name while renaming trace chunk");
 912                 goto end;
 913         }
 914
 915         ret = lttng_directory_handle_create_subdirectory_as_user(
 916                         &trace_chunk->session_output_directory.value,
 917                         DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY,
 918                         DIR_CREATION_MODE,
 919                         !trace_chunk->credentials.value.use_current_user ?
 920                                         &trace_chunk->credentials.value.user :
 921                                         NULL);
 922         if (ret) {
 923                 PERROR("Failed to create \"" DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY
 924                                 "\" directory for archived trace chunks");
 925                 goto end;
 926         }
 927
 928         ret = lttng_directory_handle_init_from_handle(
 929                         &archived_chunks_directory.value,
 930                         DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY,
 931                         &trace_chunk->session_output_directory.value);
 932         if (ret) {
 933                 PERROR("Failed to get handle to archived trace chunks directory");
 934                 goto end;
 935         }
 936         archived_chunks_directory.is_set = true;
 937
 938         ret = lttng_directory_handle_rename_as_user(
 939                         &trace_chunk->session_output_directory.value,
 940                         directory_to_rename,
 941                         &archived_chunks_directory.value,
 942                         archived_chunk_name,
 943                         LTTNG_OPTIONAL_GET(trace_chunk->credentials).use_current_user ?
 944                                 NULL :
 945                                 &trace_chunk->credentials.value.user);
 946         if (ret) {
 947                 PERROR("Failed to rename folder \"%s\" to \"%s\"",
 948                                 directory_to_rename, archived_chunk_name);
 949         }
 950
 951 end:
 952         if (archived_chunks_directory.is_set) {
 953                 lttng_directory_handle_fini(&archived_chunks_directory.value);
 954         }
 955         free(archived_chunk_name);
 956         if (free_directory_to_rename) {
 957                 free(directory_to_rename);
 958         }
 959 }
 960
 961 LTTNG_HIDDEN
 962 enum lttng_trace_chunk_status lttng_trace_chunk_get_close_command(
 963                 struct lttng_trace_chunk *chunk,
 964                 enum lttng_trace_chunk_command_type *command_type)
 965 {
 966         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 967
 968         pthread_mutex_lock(&chunk->lock);
 969         if (chunk->close_command.is_set) {
 970                 *command_type = chunk->close_command.value;
 971                 status = LTTNG_TRACE_CHUNK_STATUS_OK;
 972         } else {
 973                 status = LTTNG_TRACE_CHUNK_STATUS_NONE;
 974         }
 975         pthread_mutex_unlock(&chunk->lock);
 976         return status;
 977 }
 978
 979 LTTNG_HIDDEN
 980 enum lttng_trace_chunk_status lttng_trace_chunk_set_close_command(
 981                 struct lttng_trace_chunk *chunk,
 982                 enum lttng_trace_chunk_command_type close_command)
 983 {
 984         enum lttng_trace_chunk_status status = LTTNG_TRACE_CHUNK_STATUS_OK;
 985
 986         if (close_command < LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED ||
 987                         close_command >= LTTNG_TRACE_CHUNK_COMMAND_TYPE_MAX) {
 988                 status = LTTNG_TRACE_CHUNK_STATUS_INVALID_ARGUMENT;
 989                 goto end_unlock;
 990         }
 991
 992         pthread_mutex_lock(&chunk->lock);
 993         if (chunk->close_command.is_set) {
 994                 DBG("Overriding trace chunk close command from \"%s\" to \"%s\"",
 995                                 close_command_names[chunk->close_command.value],
 996                                 close_command_names[close_command]);
 997         } else {
 998                 DBG("Setting trace chunk close command to \"%s\"",
 999                                 close_command_names[close_command]);
1000         }
1001         LTTNG_OPTIONAL_SET(&chunk->close_command, close_command);
1002         pthread_mutex_unlock(&chunk->lock);
1003 end_unlock:
1004         return status;
1005 }
1006
1007 LTTNG_HIDDEN
1008 const char *lttng_trace_chunk_command_type_get_name(
1009                 enum lttng_trace_chunk_command_type command)
1010 {
1011         switch (command) {
1012         case LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED:
1013                 return "move to completed trace chunk folder";
1014         default:
1015                 abort();
1016         }
1017 }
1018
1019 LTTNG_HIDDEN
1020 bool lttng_trace_chunk_get(struct lttng_trace_chunk *chunk)
1021 {
1022         return urcu_ref_get_unless_zero(&chunk->ref);
1023 }
1024
1025 static
1026 void free_lttng_trace_chunk_registry_element(struct rcu_head *node)
1027 {
1028         struct lttng_trace_chunk_registry_element *element =
1029                         container_of(node, typeof(*element), rcu_node);
1030
1031         lttng_trace_chunk_fini(&element->chunk);
1032         free(element);
1033 }
1034
1035 static
1036 void lttng_trace_chunk_release(struct urcu_ref *ref)
1037 {
1038         struct lttng_trace_chunk *chunk = container_of(ref, typeof(*chunk),
1039                         ref);
1040
1041         if (chunk->close_command.is_set) {
1042                 close_command_funcs[chunk->close_command.value](chunk);
1043         }
1044
1045         if (chunk->in_registry_element) {
1046                 struct lttng_trace_chunk_registry_element *element;
1047
1048                 element = container_of(chunk, typeof(*element), chunk);
1049                 if (element->registry) {
1050                         rcu_read_lock();
1051                         cds_lfht_del(element->registry->ht,
1052                                         &element->trace_chunk_registry_ht_node);
1053                         rcu_read_unlock();
1054                         call_rcu(&element->rcu_node,
1055                                         free_lttng_trace_chunk_registry_element);
1056                 } else {
1057                         /* Never published, can be free'd immediately. */
1058                         free_lttng_trace_chunk_registry_element(
1059                                         &element->rcu_node);
1060                 }
1061         } else {
1062                 /* Not RCU-protected, free immediately. */
1063                 lttng_trace_chunk_fini(chunk);
1064                 free(chunk);
1065         }
1066 }
1067
1068 LTTNG_HIDDEN
1069 void lttng_trace_chunk_put(struct lttng_trace_chunk *chunk)
1070 {
1071         if (!chunk) {
1072                 return;
1073         }
1074         assert(chunk->ref.refcount);
1075         urcu_ref_put(&chunk->ref, lttng_trace_chunk_release);
1076 }
1077
1078 LTTNG_HIDDEN
1079 struct lttng_trace_chunk_registry *lttng_trace_chunk_registry_create(void)
1080 {
1081         struct lttng_trace_chunk_registry *registry;
1082
1083         registry = zmalloc(sizeof(*registry));
1084         if (!registry) {
1085                 goto end;
1086         }
1087
1088         registry->ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
1089                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
1090         if (!registry->ht) {
1091                 goto error;
1092         }
1093 end:
1094         return registry;
1095 error:
1096         lttng_trace_chunk_registry_destroy(registry);
1097         goto end;
1098 }
1099
1100 LTTNG_HIDDEN
1101 void lttng_trace_chunk_registry_destroy(
1102                 struct lttng_trace_chunk_registry *registry)
1103 {
1104         if (!registry) {
1105                 return;
1106         }
1107         if (registry->ht) {
1108                 int ret = cds_lfht_destroy(registry->ht, NULL);
1109                 assert(!ret);
1110         }
1111         free(registry);
1112 }
1113
1114 static
1115 struct lttng_trace_chunk_registry_element *
1116 lttng_trace_chunk_registry_element_create_from_chunk(
1117                 struct lttng_trace_chunk *chunk, uint64_t session_id)
1118 {
1119         struct lttng_trace_chunk_registry_element *element =
1120                         zmalloc(sizeof(*element));
1121
1122         if (!element) {
1123                 goto end;
1124         }
1125         cds_lfht_node_init(&element->trace_chunk_registry_ht_node);
1126         element->session_id = session_id;
1127
1128         element->chunk = *chunk;
1129         lttng_trace_chunk_init(&element->chunk);
1130         if (chunk->session_output_directory.is_set) {
1131                 element->chunk.session_output_directory.value =
1132                                 lttng_directory_handle_move(
1133                                         &chunk->session_output_directory.value);
1134         }
1135         if (chunk->chunk_directory.is_set) {
1136                 element->chunk.chunk_directory.value =
1137                                 lttng_directory_handle_move(
1138                                         &chunk->chunk_directory.value);
1139         }
1140         /*
1141          * The original chunk becomes invalid; the name attribute is transferred
1142          * to the new chunk instance.
1143          */
1144         chunk->name = NULL;
1145         element->chunk.in_registry_element = true;
1146 end:
1147         return element;
1148 }
1149
1150 LTTNG_HIDDEN
1151 struct lttng_trace_chunk *
1152 lttng_trace_chunk_registry_publish_chunk(
1153                 struct lttng_trace_chunk_registry *registry,
1154                 uint64_t session_id, struct lttng_trace_chunk *chunk)
1155 {
1156         struct lttng_trace_chunk_registry_element *element;
1157         unsigned long element_hash;
1158
1159         pthread_mutex_lock(&chunk->lock);
1160         element = lttng_trace_chunk_registry_element_create_from_chunk(chunk,
1161                         session_id);
1162         pthread_mutex_unlock(&chunk->lock);
1163         if (!element) {
1164                 goto end;
1165         }
1166         /*
1167          * chunk is now invalid, the only valid operation is a 'put' from the
1168          * caller.
1169          */
1170         chunk = NULL;
1171         element_hash = lttng_trace_chunk_registry_element_hash(element);
1172
1173         rcu_read_lock();
1174         while (1) {
1175                 struct cds_lfht_node *published_node;
1176                 struct lttng_trace_chunk *published_chunk;
1177                 struct lttng_trace_chunk_registry_element *published_element;
1178
1179                 published_node = cds_lfht_add_unique(registry->ht,
1180                                 element_hash,
1181                                 lttng_trace_chunk_registry_element_match,
1182                                 element,
1183                                 &element->trace_chunk_registry_ht_node);
1184                 if (published_node == &element->trace_chunk_registry_ht_node) {
1185                         /* Successfully published the new element. */
1186                         element->registry = registry;
1187                         /* Acquire a reference for the caller. */
1188                         if (lttng_trace_chunk_get(&element->chunk)) {
1189                                 break;
1190                         } else {
1191                                 /*
1192                                  * Another thread concurrently unpublished the
1193                                  * trace chunk. This is currently unexpected.
1194                                  *
1195                                  * Re-attempt to publish.
1196                                  */
1197                                 ERR("Attemp to publish a trace chunk to the chunk registry raced with a trace chunk deletion");
1198                                 continue;
1199                         }
1200                 }
1201
1202                 /*
1203                  * An equivalent trace chunk was published before this trace
1204                  * chunk. Attempt to acquire a reference to the one that was
1205                  * already published and release the reference to the copy we
1206                  * created if successful.
1207                  */
1208                 published_element = container_of(published_node,
1209                                 typeof(*published_element),
1210                                 trace_chunk_registry_ht_node);
1211                 published_chunk = &published_element->chunk;
1212                 if (lttng_trace_chunk_get(published_chunk)) {
1213                         lttng_trace_chunk_put(&element->chunk);
1214                         element = published_element;
1215                         break;
1216                 }
1217                 /*
1218                  * A reference to the previously published trace chunk could not
1219                  * be acquired. Hence, retry to publish our copy of the trace
1220                  * chunk.
1221                  */
1222         }
1223         rcu_read_unlock();
1224 end:
1225         return element ? &element->chunk : NULL;
1226 }
1227
1228 /*
1229  * Note that the caller must be registered as an RCU thread.
1230  * However, it does not need to hold the RCU read lock. The RCU read lock is
1231  * acquired to perform the look-up in the registry's hash table and held until
1232  * after a reference to the "found" trace chunk is acquired.
1233  *
1234  * IOW, holding a reference guarantees the existence of the object for the
1235  * caller.
1236  */
1237 static
1238 struct lttng_trace_chunk *_lttng_trace_chunk_registry_find_chunk(
1239                 const struct lttng_trace_chunk_registry *registry,
1240                 uint64_t session_id, uint64_t *chunk_id)
1241 {
1242         const struct lttng_trace_chunk_registry_element target_element = {
1243                 .chunk.id.is_set = !!chunk_id,
1244                 .chunk.id.value = chunk_id ? *chunk_id : 0,
1245                 .session_id = session_id,
1246         };
1247         const unsigned long element_hash =
1248                         lttng_trace_chunk_registry_element_hash(
1249                                 &target_element);
1250         struct cds_lfht_node *published_node;
1251         struct lttng_trace_chunk_registry_element *published_element;
1252         struct lttng_trace_chunk *published_chunk = NULL;
1253         struct cds_lfht_iter iter;
1254
1255         rcu_read_lock();
1256         cds_lfht_lookup(registry->ht,
1257                         element_hash,
1258                         lttng_trace_chunk_registry_element_match,
1259                         &target_element,
1260                         &iter);
1261         published_node = cds_lfht_iter_get_node(&iter);
1262         if (!published_node) {
1263                 goto end;
1264         }
1265
1266         published_element = container_of(published_node,
1267                         typeof(*published_element),
1268                         trace_chunk_registry_ht_node);
1269         if (lttng_trace_chunk_get(&published_element->chunk)) {
1270                 published_chunk = &published_element->chunk;
1271         }
1272 end:
1273         rcu_read_unlock();
1274         return published_chunk;
1275 }
1276
1277 LTTNG_HIDDEN
1278 struct lttng_trace_chunk *
1279 lttng_trace_chunk_registry_find_chunk(
1280                 const struct lttng_trace_chunk_registry *registry,
1281                 uint64_t session_id, uint64_t chunk_id)
1282 {
1283         return _lttng_trace_chunk_registry_find_chunk(registry,
1284                         session_id, &chunk_id);
1285 }
1286
1287 LTTNG_HIDDEN
1288 struct lttng_trace_chunk *
1289 lttng_trace_chunk_registry_find_anonymous_chunk(
1290                 const struct lttng_trace_chunk_registry *registry,
1291                 uint64_t session_id)
1292 {
1293         return _lttng_trace_chunk_registry_find_chunk(registry,
1294                         session_id, NULL);
1295 }