kernel/drivers/staging/lustre/lustre/lov/lov_lock.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   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 version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  19  *
  20  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  21  * CA 95054 USA or visit www.sun.com if you need additional information or
  22  * have any questions.
  23  *
  24  * GPL HEADER END
  25  */
  26 /*
  27  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  28  * Use is subject to license terms.
  29  *
  30  * Copyright (c) 2011, 2012, Intel Corporation.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * Implementation of cl_lock for LOV layer.
  37  *
  38  *   Author: Nikita Danilov <nikita.danilov@sun.com>
  39  */
  40
  41 #define DEBUG_SUBSYSTEM S_LOV
  42
  43 #include "lov_cl_internal.h"
  44
  45 /** \addtogroup lov
  46  *  @{
  47  */
  48
  49 static struct cl_lock_closure *lov_closure_get(const struct lu_env *env,
  50                                                struct cl_lock *parent);
  51
  52 static int lov_lock_unuse(const struct lu_env *env,
  53                           const struct cl_lock_slice *slice);
  54 /*****************************************************************************
  55  *
  56  * Lov lock operations.
  57  *
  58  */
  59
  60 static struct lov_sublock_env *lov_sublock_env_get(const struct lu_env *env,
  61                                                    struct cl_lock *parent,
  62                                                    struct lov_lock_sub *lls)
  63 {
  64         struct lov_sublock_env *subenv;
  65         struct lov_io     *lio    = lov_env_io(env);
  66         struct cl_io       *io     = lio->lis_cl.cis_io;
  67         struct lov_io_sub      *sub;
  68
  69         subenv = &lov_env_session(env)->ls_subenv;
  70
  71         /*
  72          * FIXME: We tend to use the subio's env & io to call the sublock
  73          * lock operations because osc lock sometimes stores some control
  74          * variables in thread's IO information(Now only lockless information).
  75          * However, if the lock's host(object) is different from the object
  76          * for current IO, we have no way to get the subenv and subio because
  77          * they are not initialized at all. As a temp fix, in this case,
  78          * we still borrow the parent's env to call sublock operations.
  79          */
  80         if (!io || !cl_object_same(io->ci_obj, parent->cll_descr.cld_obj)) {
  81                 subenv->lse_env = env;
  82                 subenv->lse_io  = io;
  83                 subenv->lse_sub = NULL;
  84         } else {
  85                 sub = lov_sub_get(env, lio, lls->sub_stripe);
  86                 if (!IS_ERR(sub)) {
  87                         subenv->lse_env = sub->sub_env;
  88                         subenv->lse_io  = sub->sub_io;
  89                         subenv->lse_sub = sub;
  90                 } else {
  91                         subenv = (void *)sub;
  92                 }
  93         }
  94         return subenv;
  95 }
  96
  97 static void lov_sublock_env_put(struct lov_sublock_env *subenv)
  98 {
  99         if (subenv && subenv->lse_sub)
 100                 lov_sub_put(subenv->lse_sub);
 101 }
 102
 103 static void lov_sublock_adopt(const struct lu_env *env, struct lov_lock *lck,
 104                               struct cl_lock *sublock, int idx,
 105                               struct lov_lock_link *link)
 106 {
 107         struct lovsub_lock *lsl;
 108         struct cl_lock     *parent = lck->lls_cl.cls_lock;
 109         int              rc;
 110
 111         LASSERT(cl_lock_is_mutexed(parent));
 112         LASSERT(cl_lock_is_mutexed(sublock));
 113
 114         lsl = cl2sub_lock(sublock);
 115         /*
 116          * check that sub-lock doesn't have lock link to this top-lock.
 117          */
 118         LASSERT(lov_lock_link_find(env, lck, lsl) == NULL);
 119         LASSERT(idx < lck->lls_nr);
 120
 121         lck->lls_sub[idx].sub_lock = lsl;
 122         lck->lls_nr_filled++;
 123         LASSERT(lck->lls_nr_filled <= lck->lls_nr);
 124         list_add_tail(&link->lll_list, &lsl->lss_parents);
 125         link->lll_idx = idx;
 126         link->lll_super = lck;
 127         cl_lock_get(parent);
 128         lu_ref_add(&parent->cll_reference, "lov-child", sublock);
 129         lck->lls_sub[idx].sub_flags |= LSF_HELD;
 130         cl_lock_user_add(env, sublock);
 131
 132         rc = lov_sublock_modify(env, lck, lsl, &sublock->cll_descr, idx);
 133         LASSERT(rc == 0); /* there is no way this can fail, currently */
 134 }
 135
 136 static struct cl_lock *lov_sublock_alloc(const struct lu_env *env,
 137                                          const struct cl_io *io,
 138                                          struct lov_lock *lck,
 139                                          int idx, struct lov_lock_link **out)
 140 {
 141         struct cl_lock       *sublock;
 142         struct cl_lock       *parent;
 143         struct lov_lock_link *link;
 144
 145         LASSERT(idx < lck->lls_nr);
 146
 147         link = kmem_cache_alloc(lov_lock_link_kmem, GFP_NOFS | __GFP_ZERO);
 148         if (link != NULL) {
 149                 struct lov_sublock_env *subenv;
 150                 struct lov_lock_sub  *lls;
 151                 struct cl_lock_descr *descr;
 152
 153                 parent = lck->lls_cl.cls_lock;
 154                 lls    = &lck->lls_sub[idx];
 155                 descr  = &lls->sub_got;
 156
 157                 subenv = lov_sublock_env_get(env, parent, lls);
 158                 if (!IS_ERR(subenv)) {
 159                         /* CAVEAT: Don't try to add a field in lov_lock_sub
 160                          * to remember the subio. This is because lock is able
 161                          * to be cached, but this is not true for IO. This
 162                          * further means a sublock might be referenced in
 163                          * different io context. -jay */
 164
 165                         sublock = cl_lock_hold(subenv->lse_env, subenv->lse_io,
 166                                                descr, "lov-parent", parent);
 167                         lov_sublock_env_put(subenv);
 168                 } else {
 169                         /* error occurs. */
 170                         sublock = (void *)subenv;
 171                 }
 172
 173                 if (!IS_ERR(sublock))
 174                         *out = link;
 175                 else
 176                         kmem_cache_free(lov_lock_link_kmem, link);
 177         } else
 178                 sublock = ERR_PTR(-ENOMEM);
 179         return sublock;
 180 }
 181
 182 static void lov_sublock_unlock(const struct lu_env *env,
 183                                struct lovsub_lock *lsl,
 184                                struct cl_lock_closure *closure,
 185                                struct lov_sublock_env *subenv)
 186 {
 187         lov_sublock_env_put(subenv);
 188         lsl->lss_active = NULL;
 189         cl_lock_disclosure(env, closure);
 190 }
 191
 192 static int lov_sublock_lock(const struct lu_env *env,
 193                             struct lov_lock *lck,
 194                             struct lov_lock_sub *lls,
 195                             struct cl_lock_closure *closure,
 196                             struct lov_sublock_env **lsep)
 197 {
 198         struct lovsub_lock *sublock;
 199         struct cl_lock     *child;
 200         int              result = 0;
 201
 202         LASSERT(list_empty(&closure->clc_list));
 203
 204         sublock = lls->sub_lock;
 205         child = sublock->lss_cl.cls_lock;
 206         result = cl_lock_closure_build(env, child, closure);
 207         if (result == 0) {
 208                 struct cl_lock *parent = closure->clc_origin;
 209
 210                 LASSERT(cl_lock_is_mutexed(child));
 211                 sublock->lss_active = parent;
 212
 213                 if (unlikely((child->cll_state == CLS_FREEING) ||
 214                              (child->cll_flags & CLF_CANCELLED))) {
 215                         struct lov_lock_link *link;
 216                         /*
 217                          * we could race with lock deletion which temporarily
 218                          * put the lock in freeing state, bug 19080.
 219                          */
 220                         LASSERT(!(lls->sub_flags & LSF_HELD));
 221
 222                         link = lov_lock_link_find(env, lck, sublock);
 223                         LASSERT(link != NULL);
 224                         lov_lock_unlink(env, link, sublock);
 225                         lov_sublock_unlock(env, sublock, closure, NULL);
 226                         lck->lls_cancel_race = 1;
 227                         result = CLO_REPEAT;
 228                 } else if (lsep) {
 229                         struct lov_sublock_env *subenv;
 230
 231                         subenv = lov_sublock_env_get(env, parent, lls);
 232                         if (IS_ERR(subenv)) {
 233                                 lov_sublock_unlock(env, sublock,
 234                                                    closure, NULL);
 235                                 result = PTR_ERR(subenv);
 236                         } else {
 237                                 *lsep = subenv;
 238                         }
 239                 }
 240         }
 241         return result;
 242 }
 243
 244 /**
 245  * Updates the result of a top-lock operation from a result of sub-lock
 246  * sub-operations. Top-operations like lov_lock_{enqueue,use,unuse}() iterate
 247  * over sub-locks and lov_subresult() is used to calculate return value of a
 248  * top-operation. To this end, possible return values of sub-operations are
 249  * ordered as
 250  *
 251  *     - 0                success
 252  *     - CLO_WAIT          wait for event
 253  *     - CLO_REPEAT      repeat top-operation
 254  *     - -ne            fundamental error
 255  *
 256  * Top-level return code can only go down through this list. CLO_REPEAT
 257  * overwrites CLO_WAIT, because lock mutex was released and sleeping condition
 258  * has to be rechecked by the upper layer.
 259  */
 260 static int lov_subresult(int result, int rc)
 261 {
 262         int result_rank;
 263         int rc_rank;
 264
 265         LASSERTF(result <= 0 || result == CLO_REPEAT || result == CLO_WAIT,
 266                  "result = %d", result);
 267         LASSERTF(rc <= 0 || rc == CLO_REPEAT || rc == CLO_WAIT,
 268                  "rc = %d\n", rc);
 269         CLASSERT(CLO_WAIT < CLO_REPEAT);
 270
 271         /* calculate ranks in the ordering above */
 272         result_rank = result < 0 ? 1 + CLO_REPEAT : result;
 273         rc_rank = rc < 0 ? 1 + CLO_REPEAT : rc;
 274
 275         if (result_rank < rc_rank)
 276                 result = rc;
 277         return result;
 278 }
 279
 280 /**
 281  * Creates sub-locks for a given lov_lock for the first time.
 282  *
 283  * Goes through all sub-objects of top-object, and creates sub-locks on every
 284  * sub-object intersecting with top-lock extent. This is complicated by the
 285  * fact that top-lock (that is being created) can be accessed concurrently
 286  * through already created sub-locks (possibly shared with other top-locks).
 287  */
 288 static int lov_lock_sub_init(const struct lu_env *env,
 289                              struct lov_lock *lck, const struct cl_io *io)
 290 {
 291         int result = 0;
 292         int i;
 293         int nr;
 294         u64 start;
 295         u64 end;
 296         u64 file_start;
 297         u64 file_end;
 298
 299         struct lov_object       *loo    = cl2lov(lck->lls_cl.cls_obj);
 300         struct lov_layout_raid0 *r0     = lov_r0(loo);
 301         struct cl_lock    *parent = lck->lls_cl.cls_lock;
 302
 303         lck->lls_orig = parent->cll_descr;
 304         file_start = cl_offset(lov2cl(loo), parent->cll_descr.cld_start);
 305         file_end   = cl_offset(lov2cl(loo), parent->cll_descr.cld_end + 1) - 1;
 306
 307         for (i = 0, nr = 0; i < r0->lo_nr; i++) {
 308                 /*
 309                  * XXX for wide striping smarter algorithm is desirable,
 310                  * breaking out of the loop, early.
 311                  */
 312                 if (likely(r0->lo_sub[i] != NULL) &&
 313                     lov_stripe_intersects(loo->lo_lsm, i,
 314                                           file_start, file_end, &start, &end))
 315                         nr++;
 316         }
 317         LASSERT(nr > 0);
 318         lck->lls_sub = libcfs_kvzalloc(nr * sizeof(lck->lls_sub[0]), GFP_NOFS);
 319         if (lck->lls_sub == NULL)
 320                 return -ENOMEM;
 321
 322         lck->lls_nr = nr;
 323         /*
 324          * First, fill in sub-lock descriptions in
 325          * lck->lls_sub[].sub_descr. They are used by lov_sublock_alloc()
 326          * (called below in this function, and by lov_lock_enqueue()) to
 327          * create sub-locks. At this moment, no other thread can access
 328          * top-lock.
 329          */
 330         for (i = 0, nr = 0; i < r0->lo_nr; ++i) {
 331                 if (likely(r0->lo_sub[i] != NULL) &&
 332                     lov_stripe_intersects(loo->lo_lsm, i,
 333                                           file_start, file_end, &start, &end)) {
 334                         struct cl_lock_descr *descr;
 335
 336                         descr = &lck->lls_sub[nr].sub_descr;
 337
 338                         LASSERT(descr->cld_obj == NULL);
 339                         descr->cld_obj   = lovsub2cl(r0->lo_sub[i]);
 340                         descr->cld_start = cl_index(descr->cld_obj, start);
 341                         descr->cld_end   = cl_index(descr->cld_obj, end);
 342                         descr->cld_mode  = parent->cll_descr.cld_mode;
 343                         descr->cld_gid   = parent->cll_descr.cld_gid;
 344                         descr->cld_enq_flags   = parent->cll_descr.cld_enq_flags;
 345                         /* XXX has no effect */
 346                         lck->lls_sub[nr].sub_got = *descr;
 347                         lck->lls_sub[nr].sub_stripe = i;
 348                         nr++;
 349                 }
 350         }
 351         LASSERT(nr == lck->lls_nr);
 352
 353         /*
 354          * Some sub-locks can be missing at this point. This is not a problem,
 355          * because enqueue will create them anyway. Main duty of this function
 356          * is to fill in sub-lock descriptions in a race free manner.
 357          */
 358         return result;
 359 }
 360
 361 static int lov_sublock_release(const struct lu_env *env, struct lov_lock *lck,
 362                                int i, int deluser, int rc)
 363 {
 364         struct cl_lock *parent = lck->lls_cl.cls_lock;
 365
 366         LASSERT(cl_lock_is_mutexed(parent));
 367
 368         if (lck->lls_sub[i].sub_flags & LSF_HELD) {
 369                 struct cl_lock    *sublock;
 370                 int dying;
 371
 372                 LASSERT(lck->lls_sub[i].sub_lock != NULL);
 373                 sublock = lck->lls_sub[i].sub_lock->lss_cl.cls_lock;
 374                 LASSERT(cl_lock_is_mutexed(sublock));
 375
 376                 lck->lls_sub[i].sub_flags &= ~LSF_HELD;
 377                 if (deluser)
 378                         cl_lock_user_del(env, sublock);
 379                 /*
 380                  * If the last hold is released, and cancellation is pending
 381                  * for a sub-lock, release parent mutex, to avoid keeping it
 382                  * while sub-lock is being paged out.
 383                  */
 384                 dying = (sublock->cll_descr.cld_mode == CLM_PHANTOM ||
 385                          sublock->cll_descr.cld_mode == CLM_GROUP ||
 386                          (sublock->cll_flags & (CLF_CANCELPEND|CLF_DOOMED))) &&
 387                         sublock->cll_holds == 1;
 388                 if (dying)
 389                         cl_lock_mutex_put(env, parent);
 390                 cl_lock_unhold(env, sublock, "lov-parent", parent);
 391                 if (dying) {
 392                         cl_lock_mutex_get(env, parent);
 393                         rc = lov_subresult(rc, CLO_REPEAT);
 394                 }
 395                 /*
 396                  * From now on lck->lls_sub[i].sub_lock is a "weak" pointer,
 397                  * not backed by a reference on a
 398                  * sub-lock. lovsub_lock_delete() will clear
 399                  * lck->lls_sub[i].sub_lock under semaphores, just before
 400                  * sub-lock is destroyed.
 401                  */
 402         }
 403         return rc;
 404 }
 405
 406 static void lov_sublock_hold(const struct lu_env *env, struct lov_lock *lck,
 407                              int i)
 408 {
 409         struct cl_lock *parent = lck->lls_cl.cls_lock;
 410
 411         LASSERT(cl_lock_is_mutexed(parent));
 412
 413         if (!(lck->lls_sub[i].sub_flags & LSF_HELD)) {
 414                 struct cl_lock *sublock;
 415
 416                 LASSERT(lck->lls_sub[i].sub_lock != NULL);
 417                 sublock = lck->lls_sub[i].sub_lock->lss_cl.cls_lock;
 418                 LASSERT(cl_lock_is_mutexed(sublock));
 419                 LASSERT(sublock->cll_state != CLS_FREEING);
 420
 421                 lck->lls_sub[i].sub_flags |= LSF_HELD;
 422
 423                 cl_lock_get_trust(sublock);
 424                 cl_lock_hold_add(env, sublock, "lov-parent", parent);
 425                 cl_lock_user_add(env, sublock);
 426                 cl_lock_put(env, sublock);
 427         }
 428 }
 429
 430 static void lov_lock_fini(const struct lu_env *env,
 431                           struct cl_lock_slice *slice)
 432 {
 433         struct lov_lock *lck;
 434         int i;
 435
 436         lck = cl2lov_lock(slice);
 437         LASSERT(lck->lls_nr_filled == 0);
 438         if (lck->lls_sub != NULL) {
 439                 for (i = 0; i < lck->lls_nr; ++i)
 440                         /*
 441                          * No sub-locks exists at this point, as sub-lock has
 442                          * a reference on its parent.
 443                          */
 444                         LASSERT(lck->lls_sub[i].sub_lock == NULL);
 445                 kvfree(lck->lls_sub);
 446         }
 447         kmem_cache_free(lov_lock_kmem, lck);
 448 }
 449
 450 static int lov_lock_enqueue_wait(const struct lu_env *env,
 451                                  struct lov_lock *lck,
 452                                  struct cl_lock *sublock)
 453 {
 454         struct cl_lock *lock = lck->lls_cl.cls_lock;
 455         int          result;
 456
 457         LASSERT(cl_lock_is_mutexed(lock));
 458
 459         cl_lock_mutex_put(env, lock);
 460         result = cl_lock_enqueue_wait(env, sublock, 0);
 461         cl_lock_mutex_get(env, lock);
 462         return result ?: CLO_REPEAT;
 463 }
 464
 465 /**
 466  * Tries to advance a state machine of a given sub-lock toward enqueuing of
 467  * the top-lock.
 468  *
 469  * \retval 0 if state-transition can proceed
 470  * \retval -ve otherwise.
 471  */
 472 static int lov_lock_enqueue_one(const struct lu_env *env, struct lov_lock *lck,
 473                                 struct cl_lock *sublock,
 474                                 struct cl_io *io, __u32 enqflags, int last)
 475 {
 476         int result;
 477
 478         /* first, try to enqueue a sub-lock ... */
 479         result = cl_enqueue_try(env, sublock, io, enqflags);
 480         if ((sublock->cll_state == CLS_ENQUEUED) && !(enqflags & CEF_AGL)) {
 481                 /* if it is enqueued, try to `wait' on it---maybe it's already
 482                  * granted */
 483                 result = cl_wait_try(env, sublock);
 484                 if (result == CLO_REENQUEUED)
 485                         result = CLO_WAIT;
 486         }
 487         /*
 488          * If CEF_ASYNC flag is set, then all sub-locks can be enqueued in
 489          * parallel, otherwise---enqueue has to wait until sub-lock is granted
 490          * before proceeding to the next one.
 491          */
 492         if ((result == CLO_WAIT) && (sublock->cll_state <= CLS_HELD) &&
 493             (enqflags & CEF_ASYNC) && (!last || (enqflags & CEF_AGL)))
 494                 result = 0;
 495         return result;
 496 }
 497
 498 /**
 499  * Helper function for lov_lock_enqueue() that creates missing sub-lock.
 500  */
 501 static int lov_sublock_fill(const struct lu_env *env, struct cl_lock *parent,
 502                             struct cl_io *io, struct lov_lock *lck, int idx)
 503 {
 504         struct lov_lock_link *link = NULL;
 505         struct cl_lock       *sublock;
 506         int                result;
 507
 508         LASSERT(parent->cll_depth == 1);
 509         cl_lock_mutex_put(env, parent);
 510         sublock = lov_sublock_alloc(env, io, lck, idx, &link);
 511         if (!IS_ERR(sublock))
 512                 cl_lock_mutex_get(env, sublock);
 513         cl_lock_mutex_get(env, parent);
 514
 515         if (!IS_ERR(sublock)) {
 516                 cl_lock_get_trust(sublock);
 517                 if (parent->cll_state == CLS_QUEUING &&
 518                     lck->lls_sub[idx].sub_lock == NULL) {
 519                         lov_sublock_adopt(env, lck, sublock, idx, link);
 520                 } else {
 521                         kmem_cache_free(lov_lock_link_kmem, link);
 522                         /* other thread allocated sub-lock, or enqueue is no
 523                          * longer going on */
 524                         cl_lock_mutex_put(env, parent);
 525                         cl_lock_unhold(env, sublock, "lov-parent", parent);
 526                         cl_lock_mutex_get(env, parent);
 527                 }
 528                 cl_lock_mutex_put(env, sublock);
 529                 cl_lock_put(env, sublock);
 530                 result = CLO_REPEAT;
 531         } else
 532                 result = PTR_ERR(sublock);
 533         return result;
 534 }
 535
 536 /**
 537  * Implementation of cl_lock_operations::clo_enqueue() for lov layer. This
 538  * function is rather subtle, as it enqueues top-lock (i.e., advances top-lock
 539  * state machine from CLS_QUEUING to CLS_ENQUEUED states) by juggling sub-lock
 540  * state machines in the face of sub-locks sharing (by multiple top-locks),
 541  * and concurrent sub-lock cancellations.
 542  */
 543 static int lov_lock_enqueue(const struct lu_env *env,
 544                             const struct cl_lock_slice *slice,
 545                             struct cl_io *io, __u32 enqflags)
 546 {
 547         struct cl_lock   *lock    = slice->cls_lock;
 548         struct lov_lock *lck     = cl2lov_lock(slice);
 549         struct cl_lock_closure *closure = lov_closure_get(env, lock);
 550         int i;
 551         int result;
 552         enum cl_lock_state minstate;
 553
 554         for (result = 0, minstate = CLS_FREEING, i = 0; i < lck->lls_nr; ++i) {
 555                 int rc;
 556                 struct lovsub_lock     *sub;
 557                 struct lov_lock_sub    *lls;
 558                 struct cl_lock   *sublock;
 559                 struct lov_sublock_env *subenv;
 560
 561                 if (lock->cll_state != CLS_QUEUING) {
 562                         /*
 563                          * Lock might have left QUEUING state if previous
 564                          * iteration released its mutex. Stop enqueing in this
 565                          * case and let the upper layer to decide what to do.
 566                          */
 567                         LASSERT(i > 0 && result != 0);
 568                         break;
 569                 }
 570
 571                 lls = &lck->lls_sub[i];
 572                 sub = lls->sub_lock;
 573                 /*
 574                  * Sub-lock might have been canceled, while top-lock was
 575                  * cached.
 576                  */
 577                 if (sub == NULL) {
 578                         result = lov_sublock_fill(env, lock, io, lck, i);
 579                         /* lov_sublock_fill() released @lock mutex,
 580                          * restart. */
 581                         break;
 582                 }
 583                 sublock = sub->lss_cl.cls_lock;
 584                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 585                 if (rc == 0) {
 586                         lov_sublock_hold(env, lck, i);
 587                         rc = lov_lock_enqueue_one(subenv->lse_env, lck, sublock,
 588                                                   subenv->lse_io, enqflags,
 589                                                   i == lck->lls_nr - 1);
 590                         minstate = min(minstate, sublock->cll_state);
 591                         if (rc == CLO_WAIT) {
 592                                 switch (sublock->cll_state) {
 593                                 case CLS_QUEUING:
 594                                         /* take recursive mutex, the lock is
 595                                          * released in lov_lock_enqueue_wait.
 596                                          */
 597                                         cl_lock_mutex_get(env, sublock);
 598                                         lov_sublock_unlock(env, sub, closure,
 599                                                            subenv);
 600                                         rc = lov_lock_enqueue_wait(env, lck,
 601                                                                    sublock);
 602                                         break;
 603                                 case CLS_CACHED:
 604                                         cl_lock_get(sublock);
 605                                         /* take recursive mutex of sublock */
 606                                         cl_lock_mutex_get(env, sublock);
 607                                         /* need to release all locks in closure
 608                                          * otherwise it may deadlock. LU-2683.*/
 609                                         lov_sublock_unlock(env, sub, closure,
 610                                                            subenv);
 611                                         /* sublock and parent are held. */
 612                                         rc = lov_sublock_release(env, lck, i,
 613                                                                  1, rc);
 614                                         cl_lock_mutex_put(env, sublock);
 615                                         cl_lock_put(env, sublock);
 616                                         break;
 617                                 default:
 618                                         lov_sublock_unlock(env, sub, closure,
 619                                                            subenv);
 620                                         break;
 621                                 }
 622                         } else {
 623                                 LASSERT(sublock->cll_conflict == NULL);
 624                                 lov_sublock_unlock(env, sub, closure, subenv);
 625                         }
 626                 }
 627                 result = lov_subresult(result, rc);
 628                 if (result != 0)
 629                         break;
 630         }
 631         cl_lock_closure_fini(closure);
 632         return result ?: minstate >= CLS_ENQUEUED ? 0 : CLO_WAIT;
 633 }
 634
 635 static int lov_lock_unuse(const struct lu_env *env,
 636                           const struct cl_lock_slice *slice)
 637 {
 638         struct lov_lock *lck     = cl2lov_lock(slice);
 639         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 640         int i;
 641         int result;
 642
 643         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 644                 int rc;
 645                 struct lovsub_lock     *sub;
 646                 struct cl_lock   *sublock;
 647                 struct lov_lock_sub    *lls;
 648                 struct lov_sublock_env *subenv;
 649
 650                 /* top-lock state cannot change concurrently, because single
 651                  * thread (one that released the last hold) carries unlocking
 652                  * to the completion. */
 653                 LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 654                 lls = &lck->lls_sub[i];
 655                 sub = lls->sub_lock;
 656                 if (sub == NULL)
 657                         continue;
 658
 659                 sublock = sub->lss_cl.cls_lock;
 660                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 661                 if (rc == 0) {
 662                         if (lls->sub_flags & LSF_HELD) {
 663                                 LASSERT(sublock->cll_state == CLS_HELD ||
 664                                         sublock->cll_state == CLS_ENQUEUED);
 665                                 rc = cl_unuse_try(subenv->lse_env, sublock);
 666                                 rc = lov_sublock_release(env, lck, i, 0, rc);
 667                         }
 668                         lov_sublock_unlock(env, sub, closure, subenv);
 669                 }
 670                 result = lov_subresult(result, rc);
 671         }
 672
 673         if (result == 0 && lck->lls_cancel_race) {
 674                 lck->lls_cancel_race = 0;
 675                 result = -ESTALE;
 676         }
 677         cl_lock_closure_fini(closure);
 678         return result;
 679 }
 680
 681 static void lov_lock_cancel(const struct lu_env *env,
 682                            const struct cl_lock_slice *slice)
 683 {
 684         struct lov_lock *lck     = cl2lov_lock(slice);
 685         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 686         int i;
 687         int result;
 688
 689         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 690                 int rc;
 691                 struct lovsub_lock     *sub;
 692                 struct cl_lock   *sublock;
 693                 struct lov_lock_sub    *lls;
 694                 struct lov_sublock_env *subenv;
 695
 696                 /* top-lock state cannot change concurrently, because single
 697                  * thread (one that released the last hold) carries unlocking
 698                  * to the completion. */
 699                 lls = &lck->lls_sub[i];
 700                 sub = lls->sub_lock;
 701                 if (sub == NULL)
 702                         continue;
 703
 704                 sublock = sub->lss_cl.cls_lock;
 705                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 706                 if (rc == 0) {
 707                         if (!(lls->sub_flags & LSF_HELD)) {
 708                                 lov_sublock_unlock(env, sub, closure, subenv);
 709                                 continue;
 710                         }
 711
 712                         switch (sublock->cll_state) {
 713                         case CLS_HELD:
 714                                 rc = cl_unuse_try(subenv->lse_env, sublock);
 715                                 lov_sublock_release(env, lck, i, 0, 0);
 716                                 break;
 717                         default:
 718                                 lov_sublock_release(env, lck, i, 1, 0);
 719                                 break;
 720                         }
 721                         lov_sublock_unlock(env, sub, closure, subenv);
 722                 }
 723
 724                 if (rc == CLO_REPEAT) {
 725                         --i;
 726                         continue;
 727                 }
 728
 729                 result = lov_subresult(result, rc);
 730         }
 731
 732         if (result)
 733                 CL_LOCK_DEBUG(D_ERROR, env, slice->cls_lock,
 734                               "lov_lock_cancel fails with %d.\n", result);
 735
 736         cl_lock_closure_fini(closure);
 737 }
 738
 739 static int lov_lock_wait(const struct lu_env *env,
 740                          const struct cl_lock_slice *slice)
 741 {
 742         struct lov_lock *lck     = cl2lov_lock(slice);
 743         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 744         enum cl_lock_state      minstate;
 745         int                  reenqueued;
 746         int                  result;
 747         int                  i;
 748
 749 again:
 750         for (result = 0, minstate = CLS_FREEING, i = 0, reenqueued = 0;
 751              i < lck->lls_nr; ++i) {
 752                 int rc;
 753                 struct lovsub_lock     *sub;
 754                 struct cl_lock   *sublock;
 755                 struct lov_lock_sub    *lls;
 756                 struct lov_sublock_env *subenv;
 757
 758                 lls = &lck->lls_sub[i];
 759                 sub = lls->sub_lock;
 760                 LASSERT(sub != NULL);
 761                 sublock = sub->lss_cl.cls_lock;
 762                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 763                 if (rc == 0) {
 764                         LASSERT(sublock->cll_state >= CLS_ENQUEUED);
 765                         if (sublock->cll_state < CLS_HELD)
 766                                 rc = cl_wait_try(env, sublock);
 767
 768                         minstate = min(minstate, sublock->cll_state);
 769                         lov_sublock_unlock(env, sub, closure, subenv);
 770                 }
 771                 if (rc == CLO_REENQUEUED) {
 772                         reenqueued++;
 773                         rc = 0;
 774                 }
 775                 result = lov_subresult(result, rc);
 776                 if (result != 0)
 777                         break;
 778         }
 779         /* Each sublock only can be reenqueued once, so will not loop for
 780          * ever. */
 781         if (result == 0 && reenqueued != 0)
 782                 goto again;
 783         cl_lock_closure_fini(closure);
 784         return result ?: minstate >= CLS_HELD ? 0 : CLO_WAIT;
 785 }
 786
 787 static int lov_lock_use(const struct lu_env *env,
 788                         const struct cl_lock_slice *slice)
 789 {
 790         struct lov_lock *lck     = cl2lov_lock(slice);
 791         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 792         int                  result;
 793         int                  i;
 794
 795         LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 796
 797         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 798                 int rc;
 799                 struct lovsub_lock     *sub;
 800                 struct cl_lock   *sublock;
 801                 struct lov_lock_sub    *lls;
 802                 struct lov_sublock_env *subenv;
 803
 804                 LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 805
 806                 lls = &lck->lls_sub[i];
 807                 sub = lls->sub_lock;
 808                 if (sub == NULL) {
 809                         /*
 810                          * Sub-lock might have been canceled, while top-lock was
 811                          * cached.
 812                          */
 813                         result = -ESTALE;
 814                         break;
 815                 }
 816
 817                 sublock = sub->lss_cl.cls_lock;
 818                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 819                 if (rc == 0) {
 820                         LASSERT(sublock->cll_state != CLS_FREEING);
 821                         lov_sublock_hold(env, lck, i);
 822                         if (sublock->cll_state == CLS_CACHED) {
 823                                 rc = cl_use_try(subenv->lse_env, sublock, 0);
 824                                 if (rc != 0)
 825                                         rc = lov_sublock_release(env, lck,
 826                                                                  i, 1, rc);
 827                         } else if (sublock->cll_state == CLS_NEW) {
 828                                 /* Sub-lock might have been canceled, while
 829                                  * top-lock was cached. */
 830                                 result = -ESTALE;
 831                                 lov_sublock_release(env, lck, i, 1, result);
 832                         }
 833                         lov_sublock_unlock(env, sub, closure, subenv);
 834                 }
 835                 result = lov_subresult(result, rc);
 836                 if (result != 0)
 837                         break;
 838         }
 839
 840         if (lck->lls_cancel_race) {
 841                 /*
 842                  * If there is unlocking happened at the same time, then
 843                  * sublock_lock state should be FREEING, and lov_sublock_lock
 844                  * should return CLO_REPEAT. In this case, it should return
 845                  * ESTALE, and up layer should reset the lock state to be NEW.
 846                  */
 847                 lck->lls_cancel_race = 0;
 848                 LASSERT(result != 0);
 849                 result = -ESTALE;
 850         }
 851         cl_lock_closure_fini(closure);
 852         return result;
 853 }
 854
 855 #if 0
 856 static int lock_lock_multi_match()
 857 {
 858         struct cl_lock    *lock    = slice->cls_lock;
 859         struct cl_lock_descr    *subneed = &lov_env_info(env)->lti_ldescr;
 860         struct lov_object       *loo     = cl2lov(lov->lls_cl.cls_obj);
 861         struct lov_layout_raid0 *r0      = lov_r0(loo);
 862         struct lov_lock_sub     *sub;
 863         struct cl_object        *subobj;
 864         u64  fstart;
 865         u64  fend;
 866         u64  start;
 867         u64  end;
 868         int i;
 869
 870         fstart = cl_offset(need->cld_obj, need->cld_start);
 871         fend   = cl_offset(need->cld_obj, need->cld_end + 1) - 1;
 872         subneed->cld_mode = need->cld_mode;
 873         cl_lock_mutex_get(env, lock);
 874         for (i = 0; i < lov->lls_nr; ++i) {
 875                 sub = &lov->lls_sub[i];
 876                 if (sub->sub_lock == NULL)
 877                         continue;
 878                 subobj = sub->sub_descr.cld_obj;
 879                 if (!lov_stripe_intersects(loo->lo_lsm, sub->sub_stripe,
 880                                            fstart, fend, &start, &end))
 881                         continue;
 882                 subneed->cld_start = cl_index(subobj, start);
 883                 subneed->cld_end   = cl_index(subobj, end);
 884                 subneed->cld_obj   = subobj;
 885                 if (!cl_lock_ext_match(&sub->sub_got, subneed)) {
 886                         result = 0;
 887                         break;
 888                 }
 889         }
 890         cl_lock_mutex_put(env, lock);
 891 }
 892 #endif
 893
 894 /**
 895  * Check if the extent region \a descr is covered by \a child against the
 896  * specific \a stripe.
 897  */
 898 static int lov_lock_stripe_is_matching(const struct lu_env *env,
 899                                        struct lov_object *lov, int stripe,
 900                                        const struct cl_lock_descr *child,
 901                                        const struct cl_lock_descr *descr)
 902 {
 903         struct lov_stripe_md *lsm = lov->lo_lsm;
 904         u64 start;
 905         u64 end;
 906         int result;
 907
 908         if (lov_r0(lov)->lo_nr == 1)
 909                 return cl_lock_ext_match(child, descr);
 910
 911         /*
 912          * For a multi-stripes object:
 913          * - make sure the descr only covers child's stripe, and
 914          * - check if extent is matching.
 915          */
 916         start = cl_offset(&lov->lo_cl, descr->cld_start);
 917         end   = cl_offset(&lov->lo_cl, descr->cld_end + 1) - 1;
 918         result = 0;
 919         /* glimpse should work on the object with LOV EA hole. */
 920         if (end - start <= lsm->lsm_stripe_size) {
 921                 int idx;
 922
 923                 idx = lov_stripe_number(lsm, start);
 924                 if (idx == stripe ||
 925                     unlikely(lov_r0(lov)->lo_sub[idx] == NULL)) {
 926                         idx = lov_stripe_number(lsm, end);
 927                         if (idx == stripe ||
 928                             unlikely(lov_r0(lov)->lo_sub[idx] == NULL))
 929                                 result = 1;
 930                 }
 931         }
 932
 933         if (result != 0) {
 934                 struct cl_lock_descr *subd = &lov_env_info(env)->lti_ldescr;
 935                 u64 sub_start;
 936                 u64 sub_end;
 937
 938                 subd->cld_obj  = NULL;   /* don't need sub object at all */
 939                 subd->cld_mode = descr->cld_mode;
 940                 subd->cld_gid  = descr->cld_gid;
 941                 result = lov_stripe_intersects(lsm, stripe, start, end,
 942                                                &sub_start, &sub_end);
 943                 LASSERT(result);
 944                 subd->cld_start = cl_index(child->cld_obj, sub_start);
 945                 subd->cld_end   = cl_index(child->cld_obj, sub_end);
 946                 result = cl_lock_ext_match(child, subd);
 947         }
 948         return result;
 949 }
 950
 951 /**
 952  * An implementation of cl_lock_operations::clo_fits_into() method.
 953  *
 954  * Checks whether a lock (given by \a slice) is suitable for \a
 955  * io. Multi-stripe locks can be used only for "quick" io, like truncate, or
 956  * O_APPEND write.
 957  *
 958  * \see ccc_lock_fits_into().
 959  */
 960 static int lov_lock_fits_into(const struct lu_env *env,
 961                               const struct cl_lock_slice *slice,
 962                               const struct cl_lock_descr *need,
 963                               const struct cl_io *io)
 964 {
 965         struct lov_lock   *lov = cl2lov_lock(slice);
 966         struct lov_object *obj = cl2lov(slice->cls_obj);
 967         int result;
 968
 969         LASSERT(cl_object_same(need->cld_obj, slice->cls_obj));
 970         LASSERT(lov->lls_nr > 0);
 971
 972         /* for top lock, it's necessary to match enq flags otherwise it will
 973          * run into problem if a sublock is missing and reenqueue. */
 974         if (need->cld_enq_flags != lov->lls_orig.cld_enq_flags)
 975                 return 0;
 976
 977         if (need->cld_mode == CLM_GROUP)
 978                 /*
 979                  * always allow to match group lock.
 980                  */
 981                 result = cl_lock_ext_match(&lov->lls_orig, need);
 982         else if (lov->lls_nr == 1) {
 983                 struct cl_lock_descr *got = &lov->lls_sub[0].sub_got;
 984
 985                 result = lov_lock_stripe_is_matching(env,
 986                                                      cl2lov(slice->cls_obj),
 987                                                      lov->lls_sub[0].sub_stripe,
 988                                                      got, need);
 989         } else if (io->ci_type != CIT_SETATTR && io->ci_type != CIT_MISC &&
 990                    !cl_io_is_append(io) && need->cld_mode != CLM_PHANTOM)
 991                 /*
 992                  * Multi-stripe locks are only suitable for `quick' IO and for
 993                  * glimpse.
 994                  */
 995                 result = 0;
 996         else
 997                 /*
 998                  * Most general case: multi-stripe existing lock, and
 999                  * (potentially) multi-stripe @need lock. Check that @need is
1000                  * covered by @lov's sub-locks.
1001                  *
1002                  * For now, ignore lock expansions made by the server, and
1003                  * match against original lock extent.
1004                  */
1005                 result = cl_lock_ext_match(&lov->lls_orig, need);
1006         CDEBUG(D_DLMTRACE, DDESCR"/"DDESCR" %d %d/%d: %d\n",
1007                PDESCR(&lov->lls_orig), PDESCR(&lov->lls_sub[0].sub_got),
1008                lov->lls_sub[0].sub_stripe, lov->lls_nr, lov_r0(obj)->lo_nr,
1009                result);
1010         return result;
1011 }
1012
1013 void lov_lock_unlink(const struct lu_env *env,
1014                      struct lov_lock_link *link, struct lovsub_lock *sub)
1015 {
1016         struct lov_lock *lck    = link->lll_super;
1017         struct cl_lock  *parent = lck->lls_cl.cls_lock;
1018
1019         LASSERT(cl_lock_is_mutexed(parent));
1020         LASSERT(cl_lock_is_mutexed(sub->lss_cl.cls_lock));
1021
1022         list_del_init(&link->lll_list);
1023         LASSERT(lck->lls_sub[link->lll_idx].sub_lock == sub);
1024         /* yank this sub-lock from parent's array */
1025         lck->lls_sub[link->lll_idx].sub_lock = NULL;
1026         LASSERT(lck->lls_nr_filled > 0);
1027         lck->lls_nr_filled--;
1028         lu_ref_del(&parent->cll_reference, "lov-child", sub->lss_cl.cls_lock);
1029         cl_lock_put(env, parent);
1030         kmem_cache_free(lov_lock_link_kmem, link);
1031 }
1032
1033 struct lov_lock_link *lov_lock_link_find(const struct lu_env *env,
1034                                          struct lov_lock *lck,
1035                                          struct lovsub_lock *sub)
1036 {
1037         struct lov_lock_link *scan;
1038
1039         LASSERT(cl_lock_is_mutexed(sub->lss_cl.cls_lock));
1040
1041         list_for_each_entry(scan, &sub->lss_parents, lll_list) {
1042                 if (scan->lll_super == lck)
1043                         return scan;
1044         }
1045         return NULL;
1046 }
1047
1048 /**
1049  * An implementation of cl_lock_operations::clo_delete() method. This is
1050  * invoked for "top-to-bottom" delete, when lock destruction starts from the
1051  * top-lock, e.g., as a result of inode destruction.
1052  *
1053  * Unlinks top-lock from all its sub-locks. Sub-locks are not deleted there:
1054  * this is done separately elsewhere:
1055  *
1056  *     - for inode destruction, lov_object_delete() calls cl_object_kill() for
1057  *       each sub-object, purging its locks;
1058  *
1059  *     - in other cases (e.g., a fatal error with a top-lock) sub-locks are
1060  *       left in the cache.
1061  */
1062 static void lov_lock_delete(const struct lu_env *env,
1063                             const struct cl_lock_slice *slice)
1064 {
1065         struct lov_lock *lck     = cl2lov_lock(slice);
1066         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
1067         struct lov_lock_link   *link;
1068         int                  rc;
1069         int                  i;
1070
1071         LASSERT(slice->cls_lock->cll_state == CLS_FREEING);
1072
1073         for (i = 0; i < lck->lls_nr; ++i) {
1074                 struct lov_lock_sub *lls = &lck->lls_sub[i];
1075                 struct lovsub_lock  *lsl = lls->sub_lock;
1076
1077                 if (lsl == NULL) /* already removed */
1078                         continue;
1079
1080                 rc = lov_sublock_lock(env, lck, lls, closure, NULL);
1081                 if (rc == CLO_REPEAT) {
1082                         --i;
1083                         continue;
1084                 }
1085
1086                 LASSERT(rc == 0);
1087                 LASSERT(lsl->lss_cl.cls_lock->cll_state < CLS_FREEING);
1088
1089                 if (lls->sub_flags & LSF_HELD)
1090                         lov_sublock_release(env, lck, i, 1, 0);
1091
1092                 link = lov_lock_link_find(env, lck, lsl);
1093                 LASSERT(link != NULL);
1094                 lov_lock_unlink(env, link, lsl);
1095                 LASSERT(lck->lls_sub[i].sub_lock == NULL);
1096
1097                 lov_sublock_unlock(env, lsl, closure, NULL);
1098         }
1099
1100         cl_lock_closure_fini(closure);
1101 }
1102
1103 static int lov_lock_print(const struct lu_env *env, void *cookie,
1104                           lu_printer_t p, const struct cl_lock_slice *slice)
1105 {
1106         struct lov_lock *lck = cl2lov_lock(slice);
1107         int           i;
1108
1109         (*p)(env, cookie, "%d\n", lck->lls_nr);
1110         for (i = 0; i < lck->lls_nr; ++i) {
1111                 struct lov_lock_sub *sub;
1112
1113                 sub = &lck->lls_sub[i];
1114                 (*p)(env, cookie, "    %d %x: ", i, sub->sub_flags);
1115                 if (sub->sub_lock != NULL)
1116                         cl_lock_print(env, cookie, p,
1117                                       sub->sub_lock->lss_cl.cls_lock);
1118                 else
1119                         (*p)(env, cookie, "---\n");
1120         }
1121         return 0;
1122 }
1123
1124 static const struct cl_lock_operations lov_lock_ops = {
1125         .clo_fini      = lov_lock_fini,
1126         .clo_enqueue   = lov_lock_enqueue,
1127         .clo_wait      = lov_lock_wait,
1128         .clo_use       = lov_lock_use,
1129         .clo_unuse     = lov_lock_unuse,
1130         .clo_cancel    = lov_lock_cancel,
1131         .clo_fits_into = lov_lock_fits_into,
1132         .clo_delete    = lov_lock_delete,
1133         .clo_print     = lov_lock_print
1134 };
1135
1136 int lov_lock_init_raid0(const struct lu_env *env, struct cl_object *obj,
1137                         struct cl_lock *lock, const struct cl_io *io)
1138 {
1139         struct lov_lock *lck;
1140         int result;
1141
1142         lck = kmem_cache_alloc(lov_lock_kmem, GFP_NOFS | __GFP_ZERO);
1143         if (lck != NULL) {
1144                 cl_lock_slice_add(lock, &lck->lls_cl, obj, &lov_lock_ops);
1145                 result = lov_lock_sub_init(env, lck, io);
1146         } else
1147                 result = -ENOMEM;
1148         return result;
1149 }
1150
1151 static void lov_empty_lock_fini(const struct lu_env *env,
1152                                 struct cl_lock_slice *slice)
1153 {
1154         struct lov_lock *lck = cl2lov_lock(slice);
1155
1156         kmem_cache_free(lov_lock_kmem, lck);
1157 }
1158
1159 static int lov_empty_lock_print(const struct lu_env *env, void *cookie,
1160                         lu_printer_t p, const struct cl_lock_slice *slice)
1161 {
1162         (*p)(env, cookie, "empty\n");
1163         return 0;
1164 }
1165
1166 /* XXX: more methods will be added later. */
1167 static const struct cl_lock_operations lov_empty_lock_ops = {
1168         .clo_fini  = lov_empty_lock_fini,
1169         .clo_print = lov_empty_lock_print
1170 };
1171
1172 int lov_lock_init_empty(const struct lu_env *env, struct cl_object *obj,
1173                 struct cl_lock *lock, const struct cl_io *io)
1174 {
1175         struct lov_lock *lck;
1176         int result = -ENOMEM;
1177
1178         lck = kmem_cache_alloc(lov_lock_kmem, GFP_NOFS | __GFP_ZERO);
1179         if (lck != NULL) {
1180                 cl_lock_slice_add(lock, &lck->lls_cl, obj, &lov_empty_lock_ops);
1181                 lck->lls_orig = lock->cll_descr;
1182                 result = 0;
1183         }
1184         return result;
1185 }
1186
1187 static struct cl_lock_closure *lov_closure_get(const struct lu_env *env,
1188                                                struct cl_lock *parent)
1189 {
1190         struct cl_lock_closure *closure;
1191
1192         closure = &lov_env_info(env)->lti_closure;
1193         LASSERT(list_empty(&closure->clc_list));
1194         cl_lock_closure_init(env, closure, parent, 1);
1195         return closure;
1196 }
1197
1198 /** @} lov */