lustre/obdclass/lu_object.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * Lustre Object.
   5  *
   6  *  Copyright (C) 2006 Cluster File Systems, Inc.
   7  *   Author: Nikita Danilov <nikita@clusterfs.com>
   8  *
   9  *   This file is part of the Lustre file system, http://www.lustre.org
  10  *   Lustre is a trademark of Cluster File Systems, Inc.
  11  *
  12  *   You may have signed or agreed to another license before downloading
  13  *   this software.  If so, you are bound by the terms and conditions
  14  *   of that agreement, and the following does not apply to you.  See the
  15  *   LICENSE file included with this distribution for more information.
  16  *
  17  *   If you did not agree to a different license, then this copy of Lustre
  18  *   is open source software; you can redistribute it and/or modify it
  19  *   under the terms of version 2 of the GNU General Public License as
  20  *   published by the Free Software Foundation.
  21  *
  22  *   In either case, Lustre is distributed in the hope that it will be
  23  *   useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  24  *   of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25  *   license text for more details.
  26  *
  27  * These are the only exported functions, they provide some generic
  28  * infrastructure for managing object devices
  29  */
  30
  31 #define DEBUG_SUBSYSTEM S_CLASS
  32 #ifndef EXPORT_SYMTAB
  33 # define EXPORT_SYMTAB
  34 #endif
  35
  36 #include <linux/seq_file.h>
  37 #include <linux/module.h>
  38 #include <obd_support.h>
  39 #include <lustre_disk.h>
  40 #include <lustre_fid.h>
  41 #include <lu_object.h>
  42 #include <libcfs/list.h>
  43
  44 static void lu_object_free(const struct lu_context *ctx, struct lu_object *o);
  45
  46 /*
  47  * Decrease reference counter on object. If last reference is freed, return
  48  * object to the cache, unless lu_object_is_dying(o) holds. In the latter
  49  * case, free object immediately.
  50  */
  51 void lu_object_put(const struct lu_context *ctxt, struct lu_object *o)
  52 {
  53         struct lu_object_header *top;
  54         struct lu_site          *site;
  55         struct lu_object        *orig;
  56         int                      kill_it;
  57
  58         top = o->lo_header;
  59         site = o->lo_dev->ld_site;
  60         orig = o;
  61         kill_it = 0;
  62         spin_lock(&site->ls_guard);
  63         if (-- top->loh_ref == 0) {
  64                 /*
  65                  * When last reference is released, iterate over object
  66                  * layers, and notify them that object is no longer busy.
  67                  */
  68                 list_for_each_entry(o, &top->loh_layers, lo_linkage) {
  69                         if (o->lo_ops->loo_object_release != NULL)
  70                                 o->lo_ops->loo_object_release(ctxt, o);
  71                 }
  72                 -- site->ls_busy;
  73                 if (lu_object_is_dying(top)) {
  74                         /*
  75                          * If object is dying (will not be cached), removed it
  76                          * from hash table and LRU.
  77                          *
  78                          * This is done with hash table and LRU lists
  79                          * locked. As the only way to acquire first reference
  80                          * to previously unreferenced object is through
  81                          * hash-table lookup (lu_object_find()), or LRU
  82                          * scanning (lu_site_purge()), that are done under
  83                          * hash-table and LRU lock, no race with concurrent
  84                          * object lookup is possible and we can safely destroy
  85                          * object below.
  86                          */
  87                         hlist_del_init(&top->loh_hash);
  88                         list_del_init(&top->loh_lru);
  89                         kill_it = 1;
  90                 }
  91         }
  92         spin_unlock(&site->ls_guard);
  93         if (kill_it)
  94                 /*
  95                  * Object was already removed from hash and lru above, can
  96                  * kill it.
  97                  */
  98                 lu_object_free(ctxt, orig);
  99 }
 100 EXPORT_SYMBOL(lu_object_put);
 101
 102 /*
 103  * Allocate new object.
 104  *
 105  * This follows object creation protocol, described in the comment within
 106  * struct lu_device_operations definition.
 107  */
 108 static struct lu_object *lu_object_alloc(const struct lu_context *ctxt,
 109                                          struct lu_site *s,
 110                                          const struct lu_fid *f)
 111 {
 112         struct lu_object *scan;
 113         struct lu_object *top;
 114         int clean;
 115         int result;
 116
 117         /*
 118          * Create top-level object slice. This will also create
 119          * lu_object_header.
 120          */
 121         top = s->ls_top_dev->ld_ops->ldo_object_alloc(ctxt,
 122                                                       NULL, s->ls_top_dev);
 123         if (IS_ERR(top))
 124                 RETURN(top);
 125         s->ls_total ++;
 126         /*
 127          * This is the only place where object fid is assigned. It's constant
 128          * after this point.
 129          */
 130         top->lo_header->loh_fid = *f;
 131         do {
 132                 /*
 133                  * Call ->loo_object_init() repeatedly, until no more new
 134                  * object slices are created.
 135                  */
 136                 clean = 1;
 137                 list_for_each_entry(scan,
 138                                     &top->lo_header->loh_layers, lo_linkage) {
 139                         if (scan->lo_flags & LU_OBJECT_ALLOCATED)
 140                                 continue;
 141                         clean = 0;
 142                         scan->lo_header = top->lo_header;
 143                         result = scan->lo_ops->loo_object_init(ctxt, scan);
 144                         if (result != 0) {
 145                                 lu_object_free(ctxt, top);
 146                                 RETURN(ERR_PTR(result));
 147                         }
 148                         scan->lo_flags |= LU_OBJECT_ALLOCATED;
 149                 }
 150         } while (!clean);
 151         s->ls_stats.s_created ++;
 152         RETURN(top);
 153 }
 154
 155 /*
 156  * Free object.
 157  */
 158 static void lu_object_free(const struct lu_context *ctx, struct lu_object *o)
 159 {
 160         struct list_head splice;
 161         struct lu_object *scan;
 162
 163         /*
 164          * First call ->loo_object_delete() method to release all resources.
 165          */
 166         list_for_each_entry_reverse(scan,
 167                                     &o->lo_header->loh_layers, lo_linkage) {
 168                 if (scan->lo_ops->loo_object_delete != NULL)
 169                         scan->lo_ops->loo_object_delete(ctx, scan);
 170         }
 171         -- o->lo_dev->ld_site->ls_total;
 172         /*
 173          * Then, splice object layers into stand-alone list, and call
 174          * ->loo_object_free() on all layers to free memory. Splice is
 175          * necessary, because lu_object_header is freed together with the
 176          * top-level slice.
 177          */
 178         INIT_LIST_HEAD(&splice);
 179         list_splice_init(&o->lo_header->loh_layers, &splice);
 180         while (!list_empty(&splice)) {
 181                 o = container_of0(splice.next, struct lu_object, lo_linkage);
 182                 list_del_init(&o->lo_linkage);
 183                 LASSERT(o->lo_ops->loo_object_free != NULL);
 184                 o->lo_ops->loo_object_free(ctx, o);
 185         }
 186 }
 187
 188 /*
 189  * Free @nr objects from the cold end of the site LRU list.
 190  */
 191 void lu_site_purge(const struct lu_context *ctx, struct lu_site *s, int nr)
 192 {
 193         struct list_head         dispose;
 194         struct lu_object_header *h;
 195         struct lu_object_header *temp;
 196
 197         INIT_LIST_HEAD(&dispose);
 198         /*
 199          * Under LRU list lock, scan LRU list and move unreferenced objects to
 200          * the dispose list, removing them from LRU and hash table.
 201          */
 202         spin_lock(&s->ls_guard);
 203         list_for_each_entry_safe(h, temp, &s->ls_lru, loh_lru) {
 204                 if (nr-- == 0)
 205                         break;
 206                 if (h->loh_ref > 0)
 207                         continue;
 208                 hlist_del_init(&h->loh_hash);
 209                 list_move(&h->loh_lru, &dispose);
 210         }
 211         spin_unlock(&s->ls_guard);
 212         /*
 213          * Free everything on the dispose list. This is safe against races due
 214          * to the reasons described in lu_object_put().
 215          */
 216         while (!list_empty(&dispose)) {
 217                 h = container_of0(dispose.next,
 218                                  struct lu_object_header, loh_lru);
 219                 list_del_init(&h->loh_lru);
 220                 lu_object_free(ctx, lu_object_top(h));
 221                 s->ls_stats.s_lru_purged ++;
 222         }
 223 }
 224 EXPORT_SYMBOL(lu_site_purge);
 225
 226 /*
 227  * Print human readable representation of the @o to the @f.
 228  */
 229 int lu_object_print(const struct lu_context *ctx,
 230                     struct seq_file *f, const struct lu_object *o)
 231 {
 232         static char ruler[] = "........................................";
 233         struct lu_object_header *top;
 234         int nob;
 235         int depth;
 236
 237         nob = 0;
 238         top = o->lo_header;
 239         list_for_each_entry(o, &top->loh_layers, lo_linkage) {
 240                 depth = o->lo_depth;
 241                 LASSERT(o->lo_ops->loo_object_print != NULL);
 242                 /*
 243                  * print `.' @depth times.
 244                  */
 245                 nob += seq_printf(f, "%*.*s", depth, depth, ruler);
 246                 nob += o->lo_ops->loo_object_print(ctx, f, o);
 247                 nob += seq_printf(f, "\n");
 248         }
 249         return nob;
 250 }
 251 EXPORT_SYMBOL(lu_object_print);
 252
 253 /*
 254  * Check object consistency.
 255  */
 256 int lu_object_invariant(const struct lu_object *o)
 257 {
 258         struct lu_object_header *top;
 259
 260         top = o->lo_header;
 261         list_for_each_entry(o, &top->loh_layers, lo_linkage) {
 262                 if (o->lo_ops->loo_object_invariant != NULL &&
 263                     !o->lo_ops->loo_object_invariant(o))
 264                         return 0;
 265         }
 266         return 1;
 267 }
 268 EXPORT_SYMBOL(lu_object_invariant);
 269
 270 static struct lu_object *htable_lookup(struct lu_site *s,
 271                                        const struct hlist_head *bucket,
 272                                        const struct lu_fid *f)
 273 {
 274         struct lu_object_header *h;
 275         struct hlist_node *scan;
 276
 277         hlist_for_each_entry(h, scan, bucket, loh_hash) {
 278                 s->ls_stats.s_cache_check ++;
 279                 if (lu_fid_eq(&h->loh_fid, f) && !lu_object_is_dying(h)) {
 280                         /* bump reference count... */
 281                         if (h->loh_ref ++ == 0)
 282                                 ++ s->ls_busy;
 283                         /* and move to the head of the LRU */
 284                         list_move_tail(&h->loh_lru, &s->ls_lru);
 285                         s->ls_stats.s_cache_hit ++;
 286                         return lu_object_top(h);
 287                 }
 288         }
 289         s->ls_stats.s_cache_miss ++;
 290         return NULL;
 291 }
 292
 293 static __u32 fid_hash(const struct lu_fid *f)
 294 {
 295         /* all objects with same id and different versions will belong to same
 296          * collisions list. */
 297         return (fid_seq(f) - 1) * LUSTRE_SEQ_MAX_WIDTH + fid_oid(f);
 298 }
 299
 300 /*
 301  * Search cache for an object with the fid @f. If such object is found, return
 302  * it. Otherwise, create new object, insert it into cache and return it. In
 303  * any case, additional reference is acquired on the returned object.
 304  */
 305 struct lu_object *lu_object_find(const struct lu_context *ctxt,
 306                                  struct lu_site *s, const struct lu_fid *f)
 307 {
 308         struct lu_object  *o;
 309         struct lu_object  *shadow;
 310         struct hlist_head *bucket;
 311
 312         /*
 313          * This uses standard index maintenance protocol:
 314          *
 315          *     - search index under lock, and return object if found;
 316          *     - otherwise, unlock index, allocate new object;
 317          *     - lock index and search again;
 318          *     - if nothing is found (usual case), insert newly created
 319          *       object into index;
 320          *     - otherwise (race: other thread inserted object), free
 321          *       object just allocated.
 322          *     - unlock index;
 323          *     - return object.
 324          */
 325
 326         bucket = s->ls_hash + (fid_hash(f) & s->ls_hash_mask);
 327         spin_lock(&s->ls_guard);
 328         o = htable_lookup(s, bucket, f);
 329
 330         spin_unlock(&s->ls_guard);
 331         if (o != NULL)
 332                 return o;
 333         /*
 334          * Allocate new object. This may result in rather complicated
 335          * operations, including fld queries, inode loading, etc.
 336          */
 337         o = lu_object_alloc(ctxt, s, f);
 338         if (IS_ERR(o))
 339                 return o;
 340
 341         LASSERT(lu_fid_eq(lu_object_fid(o), f));
 342
 343         spin_lock(&s->ls_guard);
 344         shadow = htable_lookup(s, bucket, f);
 345         if (shadow == NULL) {
 346                 hlist_add_head(&o->lo_header->loh_hash, bucket);
 347                 list_add_tail(&s->ls_lru, &o->lo_header->loh_lru);
 348                 ++ s->ls_busy;
 349                 shadow = o;
 350                 o = NULL;
 351         } else
 352                 s->ls_stats.s_cache_race ++;
 353         spin_unlock(&s->ls_guard);
 354         if (o != NULL)
 355                 lu_object_free(ctxt, o);
 356         return shadow;
 357 }
 358 EXPORT_SYMBOL(lu_object_find);
 359
 360 enum {
 361         LU_SITE_HTABLE_BITS = 8,
 362         LU_SITE_HTABLE_SIZE = (1 << LU_SITE_HTABLE_BITS),
 363         LU_SITE_HTABLE_MASK = LU_SITE_HTABLE_SIZE - 1
 364 };
 365
 366 /*
 367  * Initialize site @s, with @d as the top level device.
 368  */
 369 int lu_site_init(struct lu_site *s, struct lu_device *top)
 370 {
 371         int result;
 372         ENTRY;
 373
 374         memset(s, 0, sizeof *s);
 375         spin_lock_init(&s->ls_guard);
 376         CFS_INIT_LIST_HEAD(&s->ls_lru);
 377         s->ls_top_dev = top;
 378         top->ld_site = s;
 379         lu_device_get(top);
 380         /*
 381          * XXX nikita: fixed size hash-table.
 382          */
 383         s->ls_hash_mask = LU_SITE_HTABLE_MASK;
 384         OBD_ALLOC(s->ls_hash, LU_SITE_HTABLE_SIZE * sizeof s->ls_hash[0]);
 385         if (s->ls_hash != NULL) {
 386                 int i;
 387                 for (i = 0; i < LU_SITE_HTABLE_SIZE; i++)
 388                         INIT_HLIST_HEAD(&s->ls_hash[i]);
 389                 result = 0;
 390         } else {
 391                 result = -ENOMEM;
 392         }
 393
 394         RETURN(result);
 395 }
 396 EXPORT_SYMBOL(lu_site_init);
 397
 398 /*
 399  * Finalize @s and release its resources.
 400  */
 401 void lu_site_fini(struct lu_site *s)
 402 {
 403         LASSERT(list_empty(&s->ls_lru));
 404         LASSERT(s->ls_total == 0);
 405         LASSERT(s->ls_busy == 0);
 406
 407         if (s->ls_hash != NULL) {
 408                 int i;
 409                 for (i = 0; i < LU_SITE_HTABLE_SIZE; i++)
 410                         LASSERT(hlist_empty(&s->ls_hash[i]));
 411                 OBD_FREE(s->ls_hash,
 412                          LU_SITE_HTABLE_SIZE * sizeof s->ls_hash[0]);
 413                 s->ls_hash = NULL;
 414        }
 415        if (s->ls_top_dev != NULL) {
 416                s->ls_top_dev->ld_site = NULL;
 417                lu_device_put(s->ls_top_dev);
 418                s->ls_top_dev = NULL;
 419        }
 420  }
 421 EXPORT_SYMBOL(lu_site_fini);
 422
 423 /*
 424  * Acquire additional reference on device @d
 425  */
 426 void lu_device_get(struct lu_device *d)
 427 {
 428         atomic_inc(&d->ld_ref);
 429 }
 430 EXPORT_SYMBOL(lu_device_get);
 431
 432 /*
 433  * Release reference on device @d.
 434  */
 435 void lu_device_put(struct lu_device *d)
 436 {
 437         atomic_dec(&d->ld_ref);
 438 }
 439 EXPORT_SYMBOL(lu_device_put);
 440
 441 /*
 442  * Initialize device @d of type @t.
 443  */
 444 int lu_device_init(struct lu_device *d, struct lu_device_type *t)
 445 {
 446         memset(d, 0, sizeof *d);
 447         atomic_set(&d->ld_ref, 0);
 448         d->ld_type = t;
 449         return 0;
 450 }
 451 EXPORT_SYMBOL(lu_device_init);
 452
 453 /*
 454  * Finalize device @d.
 455  */
 456 void lu_device_fini(struct lu_device *d)
 457 {
 458         LASSERT(atomic_read(&d->ld_ref) == 0);
 459 }
 460 EXPORT_SYMBOL(lu_device_fini);
 461
 462 /*
 463  * Initialize object @o that is part of compound object @h and was created by
 464  * device @d.
 465  */
 466 int lu_object_init(struct lu_object *o,
 467                    struct lu_object_header *h, struct lu_device *d)
 468 {
 469         memset(o, 0, sizeof *o);
 470         o->lo_header = h;
 471         o->lo_dev    = d;
 472         lu_device_get(d);
 473         CFS_INIT_LIST_HEAD(&o->lo_linkage);
 474         return 0;
 475 }
 476 EXPORT_SYMBOL(lu_object_init);
 477
 478 /*
 479  * Finalize object and release its resources.
 480  */
 481 void lu_object_fini(struct lu_object *o)
 482 {
 483         LASSERT(list_empty(&o->lo_linkage));
 484
 485         if (o->lo_dev != NULL) {
 486                 lu_device_put(o->lo_dev);
 487                 o->lo_dev = NULL;
 488         }
 489 }
 490 EXPORT_SYMBOL(lu_object_fini);
 491
 492 /*
 493  * Add object @o as first layer of compound object @h
 494  *
 495  * This is typically called by the ->ldo_object_alloc() method of top-level
 496  * device.
 497  */
 498 void lu_object_add_top(struct lu_object_header *h, struct lu_object *o)
 499 {
 500         list_move(&o->lo_linkage, &h->loh_layers);
 501 }
 502 EXPORT_SYMBOL(lu_object_add_top);
 503
 504 /*
 505  * Add object @o as a layer of compound object, going after @before.1
 506  *
 507  * This is typically called by the ->ldo_object_alloc() method of
 508  * @before->lo_dev.
 509  */
 510 void lu_object_add(struct lu_object *before, struct lu_object *o)
 511 {
 512         list_move(&o->lo_linkage, &before->lo_linkage);
 513 }
 514 EXPORT_SYMBOL(lu_object_add);
 515
 516 /*
 517  * Initialize compound object.
 518  */
 519 int lu_object_header_init(struct lu_object_header *h)
 520 {
 521         memset(h, 0, sizeof *h);
 522         h->loh_ref = 1;
 523         INIT_HLIST_NODE(&h->loh_hash);
 524         CFS_INIT_LIST_HEAD(&h->loh_lru);
 525         CFS_INIT_LIST_HEAD(&h->loh_layers);
 526         return 0;
 527 }
 528 EXPORT_SYMBOL(lu_object_header_init);
 529
 530 /*
 531  * Finalize compound object.
 532  */
 533 void lu_object_header_fini(struct lu_object_header *h)
 534 {
 535         LASSERT(list_empty(&h->loh_layers));
 536         LASSERT(list_empty(&h->loh_lru));
 537         LASSERT(hlist_unhashed(&h->loh_hash));
 538 }
 539 EXPORT_SYMBOL(lu_object_header_fini);
 540
 541 /*
 542  * Given a compound object, find its slice, corresponding to the device type
 543  * @dtype.
 544  */
 545 struct lu_object *lu_object_locate(struct lu_object_header *h,
 546                                    struct lu_device_type *dtype)
 547 {
 548         struct lu_object *o;
 549
 550         list_for_each_entry(o, &h->loh_layers, lo_linkage) {
 551                 if (o->lo_dev->ld_type == dtype)
 552                         return o;
 553         }
 554         return NULL;
 555 }
 556 EXPORT_SYMBOL(lu_object_locate);
 557
 558 enum {
 559         /*
 560          * Maximal number of tld slots.
 561          */
 562         LU_CONTEXT_KEY_NR = 16
 563 };
 564
 565 static struct lu_context_key *lu_keys[LU_CONTEXT_KEY_NR] = { NULL, };
 566
 567 static spinlock_t lu_keys_guard = SPIN_LOCK_UNLOCKED;
 568
 569 /*
 570  * Register new key.
 571  */
 572 int lu_context_key_register(struct lu_context_key *key)
 573 {
 574         int result;
 575         int i;
 576
 577         LASSERT(key->lct_init != NULL);
 578         LASSERT(key->lct_fini != NULL);
 579         LASSERT(key->lct_tags != 0);
 580
 581         result = -ENFILE;
 582         spin_lock(&lu_keys_guard);
 583         for (i = 0; i < ARRAY_SIZE(lu_keys); ++i) {
 584                 if (lu_keys[i] == NULL) {
 585                         key->lct_index = i;
 586                         key->lct_used = 1;
 587                         lu_keys[i] = key;
 588                         result = 0;
 589                         break;
 590                 }
 591         }
 592         spin_unlock(&lu_keys_guard);
 593         return result;
 594 }
 595 EXPORT_SYMBOL(lu_context_key_register);
 596
 597 /*
 598  * Deregister key.
 599  */
 600 void lu_context_key_degister(struct lu_context_key *key)
 601 {
 602         LASSERT(key->lct_used >= 1);
 603         LASSERT(0 <= key->lct_index && key->lct_index < ARRAY_SIZE(lu_keys));
 604
 605         if (key->lct_used > 1)
 606                 CERROR("key has instances.\n");
 607         spin_lock(&lu_keys_guard);
 608         lu_keys[key->lct_index] = NULL;
 609         spin_unlock(&lu_keys_guard);
 610 }
 611 EXPORT_SYMBOL(lu_context_key_degister);
 612
 613 /*
 614  * Return value associated with key @key in context @ctx.
 615  */
 616 void *lu_context_key_get(const struct lu_context *ctx,
 617                          struct lu_context_key *key)
 618 {
 619         LASSERT(0 <= key->lct_index && key->lct_index < ARRAY_SIZE(lu_keys));
 620         return ctx->lc_value[key->lct_index];
 621 }
 622 EXPORT_SYMBOL(lu_context_key_get);
 623
 624 static void keys_fini(struct lu_context *ctx)
 625 {
 626         int i;
 627
 628         if (ctx->lc_value != NULL) {
 629                 for (i = 0; i < ARRAY_SIZE(lu_keys); ++i) {
 630                         if (ctx->lc_value[i] != NULL) {
 631                                 struct lu_context_key *key;
 632
 633                                 key = lu_keys[i];
 634                                 LASSERT(key != NULL);
 635                                 LASSERT(key->lct_fini != NULL);
 636                                 LASSERT(key->lct_used > 1);
 637
 638                                 key->lct_fini(ctx, key, ctx->lc_value[i]);
 639                                 key->lct_used--;
 640                                 ctx->lc_value[i] = NULL;
 641                         }
 642                 }
 643                 OBD_FREE(ctx->lc_value,
 644                          ARRAY_SIZE(lu_keys) * sizeof ctx->lc_value[0]);
 645                 ctx->lc_value = NULL;
 646         }
 647 }
 648
 649 static int keys_init(struct lu_context *ctx)
 650 {
 651         int i;
 652         int result;
 653
 654         OBD_ALLOC(ctx->lc_value, ARRAY_SIZE(lu_keys) * sizeof ctx->lc_value[0]);
 655         if (ctx->lc_value != NULL) {
 656                 for (i = 0; i < ARRAY_SIZE(lu_keys); ++i) {
 657                         struct lu_context_key *key;
 658
 659                         key = lu_keys[i];
 660                         if (key != NULL && key->lct_tags & ctx->lc_tags) {
 661                                 void *value;
 662
 663                                 LASSERT(key->lct_init != NULL);
 664                                 LASSERT(key->lct_index == i);
 665
 666                                 value = key->lct_init(ctx, key);
 667                                 if (IS_ERR(value)) {
 668                                         keys_fini(ctx);
 669                                         return PTR_ERR(value);
 670                                 }
 671                                 key->lct_used++;
 672                                 ctx->lc_value[i] = value;
 673                         }
 674                 }
 675                 result = 0;
 676         } else
 677                 result = -ENOMEM;
 678         return result;
 679 }
 680
 681 /*
 682  * Initialize context data-structure. Create values for all keys.
 683  */
 684 int lu_context_init(struct lu_context *ctx, __u32 tags)
 685 {
 686         memset(ctx, 0, sizeof *ctx);
 687         ctx->lc_tags = tags;
 688         keys_init(ctx);
 689         return 0;
 690 }
 691 EXPORT_SYMBOL(lu_context_init);
 692
 693 /*
 694  * Finalize context data-structure. Destroy key values.
 695  */
 696 void lu_context_fini(struct lu_context *ctx)
 697 {
 698         keys_fini(ctx);
 699 }
 700 EXPORT_SYMBOL(lu_context_fini);
 701
 702 /*
 703  * Called before entering context.
 704  */
 705 void lu_context_enter(struct lu_context *ctx)
 706 {
 707 }
 708 EXPORT_SYMBOL(lu_context_enter);
 709
 710 /*
 711  * Called after exiting from @ctx
 712  */
 713 void lu_context_exit(struct lu_context *ctx)
 714 {
 715 }
 716 EXPORT_SYMBOL(lu_context_exit);