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, 2013, 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 infomation(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         ENTRY;
 114
 115         lsl = cl2sub_lock(sublock);
 116         /*
 117          * check that sub-lock doesn't have lock link to this top-lock.
 118          */
 119         LASSERT(lov_lock_link_find(env, lck, lsl) == NULL);
 120         LASSERT(idx < lck->lls_nr);
 121
 122         lck->lls_sub[idx].sub_lock = lsl;
 123         lck->lls_nr_filled++;
 124         LASSERT(lck->lls_nr_filled <= lck->lls_nr);
 125         cfs_list_add_tail(&link->lll_list, &lsl->lss_parents);
 126         link->lll_idx = idx;
 127         link->lll_super = lck;
 128         cl_lock_get(parent);
 129         lu_ref_add(&parent->cll_reference, "lov-child", sublock);
 130         lck->lls_sub[idx].sub_flags |= LSF_HELD;
 131         cl_lock_user_add(env, sublock);
 132
 133         rc = lov_sublock_modify(env, lck, lsl, &sublock->cll_descr, idx);
 134         LASSERT(rc == 0); /* there is no way this can fail, currently */
 135         EXIT;
 136 }
 137
 138 static struct cl_lock *lov_sublock_alloc(const struct lu_env *env,
 139                                          const struct cl_io *io,
 140                                          struct lov_lock *lck,
 141                                          int idx, struct lov_lock_link **out)
 142 {
 143         struct cl_lock       *sublock;
 144         struct cl_lock       *parent;
 145         struct lov_lock_link *link;
 146
 147         LASSERT(idx < lck->lls_nr);
 148         ENTRY;
 149
 150         OBD_SLAB_ALLOC_PTR_GFP(link, lov_lock_link_kmem, __GFP_IO);
 151         if (link != NULL) {
 152                 struct lov_sublock_env *subenv;
 153                 struct lov_lock_sub  *lls;
 154                 struct cl_lock_descr *descr;
 155
 156                 parent = lck->lls_cl.cls_lock;
 157                 lls    = &lck->lls_sub[idx];
 158                 descr  = &lls->sub_got;
 159
 160                 subenv = lov_sublock_env_get(env, parent, lls);
 161                 if (!IS_ERR(subenv)) {
 162                         /* CAVEAT: Don't try to add a field in lov_lock_sub
 163                          * to remember the subio. This is because lock is able
 164                          * to be cached, but this is not true for IO. This
 165                          * further means a sublock might be referenced in
 166                          * different io context. -jay */
 167
 168                         sublock = cl_lock_hold(subenv->lse_env, subenv->lse_io,
 169                                                descr, "lov-parent", parent);
 170                         lov_sublock_env_put(subenv);
 171                 } else {
 172                         /* error occurs. */
 173                         sublock = (void*)subenv;
 174                 }
 175
 176                 if (!IS_ERR(sublock))
 177                         *out = link;
 178                 else
 179                         OBD_SLAB_FREE_PTR(link, lov_lock_link_kmem);
 180         } else
 181                 sublock = ERR_PTR(-ENOMEM);
 182         RETURN(sublock);
 183 }
 184
 185 static void lov_sublock_unlock(const struct lu_env *env,
 186                                struct lovsub_lock *lsl,
 187                                struct cl_lock_closure *closure,
 188                                struct lov_sublock_env *subenv)
 189 {
 190         ENTRY;
 191         lov_sublock_env_put(subenv);
 192         lsl->lss_active = NULL;
 193         cl_lock_disclosure(env, closure);
 194         EXIT;
 195 }
 196
 197 static int lov_sublock_lock(const struct lu_env *env,
 198                             struct lov_lock *lck,
 199                             struct lov_lock_sub *lls,
 200                             struct cl_lock_closure *closure,
 201                             struct lov_sublock_env **lsep)
 202 {
 203         struct lovsub_lock *sublock;
 204         struct cl_lock     *child;
 205         int                 result = 0;
 206         ENTRY;
 207
 208         LASSERT(cfs_list_empty(&closure->clc_list));
 209
 210         sublock = lls->sub_lock;
 211         child = sublock->lss_cl.cls_lock;
 212         result = cl_lock_closure_build(env, child, closure);
 213         if (result == 0) {
 214                 struct cl_lock *parent = closure->clc_origin;
 215
 216                 LASSERT(cl_lock_is_mutexed(child));
 217                 sublock->lss_active = parent;
 218
 219                 if (unlikely((child->cll_state == CLS_FREEING) ||
 220                              (child->cll_flags & CLF_CANCELLED))) {
 221                         struct lov_lock_link *link;
 222                         /*
 223                          * we could race with lock deletion which temporarily
 224                          * put the lock in freeing state, bug 19080.
 225                          */
 226                         LASSERT(!(lls->sub_flags & LSF_HELD));
 227
 228                         link = lov_lock_link_find(env, lck, sublock);
 229                         LASSERT(link != NULL);
 230                         lov_lock_unlink(env, link, sublock);
 231                         lov_sublock_unlock(env, sublock, closure, NULL);
 232                         lck->lls_cancel_race = 1;
 233                         result = CLO_REPEAT;
 234                 } else if (lsep) {
 235                         struct lov_sublock_env *subenv;
 236                         subenv = lov_sublock_env_get(env, parent, lls);
 237                         if (IS_ERR(subenv)) {
 238                                 lov_sublock_unlock(env, sublock,
 239                                                    closure, NULL);
 240                                 result = PTR_ERR(subenv);
 241                         } else {
 242                                 *lsep = subenv;
 243                         }
 244                 }
 245         }
 246         RETURN(result);
 247 }
 248
 249 /**
 250  * Updates the result of a top-lock operation from a result of sub-lock
 251  * sub-operations. Top-operations like lov_lock_{enqueue,use,unuse}() iterate
 252  * over sub-locks and lov_subresult() is used to calculate return value of a
 253  * top-operation. To this end, possible return values of sub-operations are
 254  * ordered as
 255  *
 256  *     - 0                  success
 257  *     - CLO_WAIT           wait for event
 258  *     - CLO_REPEAT         repeat top-operation
 259  *     - -ne                fundamental error
 260  *
 261  * Top-level return code can only go down through this list. CLO_REPEAT
 262  * overwrites CLO_WAIT, because lock mutex was released and sleeping condition
 263  * has to be rechecked by the upper layer.
 264  */
 265 static int lov_subresult(int result, int rc)
 266 {
 267         int result_rank;
 268         int rc_rank;
 269
 270         ENTRY;
 271
 272         LASSERTF(result <= 0 || result == CLO_REPEAT || result == CLO_WAIT,
 273                  "result = %d", result);
 274         LASSERTF(rc <= 0 || rc == CLO_REPEAT || rc == CLO_WAIT,
 275                  "rc = %d\n", rc);
 276         CLASSERT(CLO_WAIT < CLO_REPEAT);
 277
 278         /* calculate ranks in the ordering above */
 279         result_rank = result < 0 ? 1 + CLO_REPEAT : result;
 280         rc_rank = rc < 0 ? 1 + CLO_REPEAT : rc;
 281
 282         if (result_rank < rc_rank)
 283                 result = rc;
 284         RETURN(result);
 285 }
 286
 287 /**
 288  * Creates sub-locks for a given lov_lock for the first time.
 289  *
 290  * Goes through all sub-objects of top-object, and creates sub-locks on every
 291  * sub-object intersecting with top-lock extent. This is complicated by the
 292  * fact that top-lock (that is being created) can be accessed concurrently
 293  * through already created sub-locks (possibly shared with other top-locks).
 294  */
 295 static int lov_lock_sub_init(const struct lu_env *env,
 296                              struct lov_lock *lck, const struct cl_io *io)
 297 {
 298         int result = 0;
 299         int i;
 300         int nr;
 301         obd_off start;
 302         obd_off end;
 303         obd_off file_start;
 304         obd_off file_end;
 305
 306         struct lov_object       *loo    = cl2lov(lck->lls_cl.cls_obj);
 307         struct lov_layout_raid0 *r0     = lov_r0(loo);
 308         struct cl_lock          *parent = lck->lls_cl.cls_lock;
 309
 310         ENTRY;
 311
 312         lck->lls_orig = parent->cll_descr;
 313         file_start = cl_offset(lov2cl(loo), parent->cll_descr.cld_start);
 314         file_end   = cl_offset(lov2cl(loo), parent->cll_descr.cld_end + 1) - 1;
 315
 316         for (i = 0, nr = 0; i < r0->lo_nr; i++) {
 317                 /*
 318                  * XXX for wide striping smarter algorithm is desirable,
 319                  * breaking out of the loop, early.
 320                  */
 321                 if (lov_stripe_intersects(loo->lo_lsm, i,
 322                                           file_start, file_end, &start, &end))
 323                         nr++;
 324         }
 325         LASSERT(nr > 0);
 326         OBD_ALLOC_LARGE(lck->lls_sub, nr * sizeof lck->lls_sub[0]);
 327         if (lck->lls_sub == NULL)
 328                 RETURN(-ENOMEM);
 329
 330         lck->lls_nr = nr;
 331         /*
 332          * First, fill in sub-lock descriptions in
 333          * lck->lls_sub[].sub_descr. They are used by lov_sublock_alloc()
 334          * (called below in this function, and by lov_lock_enqueue()) to
 335          * create sub-locks. At this moment, no other thread can access
 336          * top-lock.
 337          */
 338         for (i = 0, nr = 0; i < r0->lo_nr; ++i) {
 339                 if (lov_stripe_intersects(loo->lo_lsm, i,
 340                                           file_start, file_end, &start, &end)) {
 341                         struct cl_lock_descr *descr;
 342
 343                         descr = &lck->lls_sub[nr].sub_descr;
 344
 345                         LASSERT(descr->cld_obj == NULL);
 346                         descr->cld_obj   = lovsub2cl(r0->lo_sub[i]);
 347                         descr->cld_start = cl_index(descr->cld_obj, start);
 348                         descr->cld_end   = cl_index(descr->cld_obj, end);
 349                         descr->cld_mode  = parent->cll_descr.cld_mode;
 350                         descr->cld_gid   = parent->cll_descr.cld_gid;
 351                         descr->cld_enq_flags   = parent->cll_descr.cld_enq_flags;
 352                         /* XXX has no effect */
 353                         lck->lls_sub[nr].sub_got = *descr;
 354                         lck->lls_sub[nr].sub_stripe = i;
 355                         nr++;
 356                 }
 357         }
 358         LASSERT(nr == lck->lls_nr);
 359         /*
 360          * Then, create sub-locks. Once at least one sub-lock was created,
 361          * top-lock can be reached by other threads.
 362          */
 363         for (i = 0; i < lck->lls_nr; ++i) {
 364                 struct cl_lock       *sublock;
 365                 struct lov_lock_link *link;
 366
 367                 if (lck->lls_sub[i].sub_lock == NULL) {
 368                         sublock = lov_sublock_alloc(env, io, lck, i, &link);
 369                         if (IS_ERR(sublock)) {
 370                                 result = PTR_ERR(sublock);
 371                                 break;
 372                         }
 373                         cl_lock_get_trust(sublock);
 374                         cl_lock_mutex_get(env, sublock);
 375                         cl_lock_mutex_get(env, parent);
 376                         /*
 377                          * recheck under mutex that sub-lock wasn't created
 378                          * concurrently, and that top-lock is still alive.
 379                          */
 380                         if (lck->lls_sub[i].sub_lock == NULL &&
 381                             parent->cll_state < CLS_FREEING) {
 382                                 lov_sublock_adopt(env, lck, sublock, i, link);
 383                                 cl_lock_mutex_put(env, parent);
 384                         } else {
 385                                 OBD_SLAB_FREE_PTR(link, lov_lock_link_kmem);
 386                                 cl_lock_mutex_put(env, parent);
 387                                 cl_lock_unhold(env, sublock,
 388                                                "lov-parent", parent);
 389                         }
 390                         cl_lock_mutex_put(env, sublock);
 391                         cl_lock_put(env, sublock);
 392                 }
 393         }
 394         /*
 395          * Some sub-locks can be missing at this point. This is not a problem,
 396          * because enqueue will create them anyway. Main duty of this function
 397          * is to fill in sub-lock descriptions in a race free manner.
 398          */
 399         RETURN(result);
 400 }
 401
 402 static int lov_sublock_release(const struct lu_env *env, struct lov_lock *lck,
 403                                int i, int deluser, int rc)
 404 {
 405         struct cl_lock *parent = lck->lls_cl.cls_lock;
 406
 407         LASSERT(cl_lock_is_mutexed(parent));
 408         ENTRY;
 409
 410         if (lck->lls_sub[i].sub_flags & LSF_HELD) {
 411                 struct cl_lock    *sublock;
 412                 int dying;
 413
 414                 LASSERT(lck->lls_sub[i].sub_lock != NULL);
 415                 sublock = lck->lls_sub[i].sub_lock->lss_cl.cls_lock;
 416                 LASSERT(cl_lock_is_mutexed(sublock));
 417
 418                 lck->lls_sub[i].sub_flags &= ~LSF_HELD;
 419                 if (deluser)
 420                         cl_lock_user_del(env, sublock);
 421                 /*
 422                  * If the last hold is released, and cancellation is pending
 423                  * for a sub-lock, release parent mutex, to avoid keeping it
 424                  * while sub-lock is being paged out.
 425                  */
 426                 dying = (sublock->cll_descr.cld_mode == CLM_PHANTOM ||
 427                          sublock->cll_descr.cld_mode == CLM_GROUP ||
 428                          (sublock->cll_flags & (CLF_CANCELPEND|CLF_DOOMED))) &&
 429                         sublock->cll_holds == 1;
 430                 if (dying)
 431                         cl_lock_mutex_put(env, parent);
 432                 cl_lock_unhold(env, sublock, "lov-parent", parent);
 433                 if (dying) {
 434                         cl_lock_mutex_get(env, parent);
 435                         rc = lov_subresult(rc, CLO_REPEAT);
 436                 }
 437                 /*
 438                  * From now on lck->lls_sub[i].sub_lock is a "weak" pointer,
 439                  * not backed by a reference on a
 440                  * sub-lock. lovsub_lock_delete() will clear
 441                  * lck->lls_sub[i].sub_lock under semaphores, just before
 442                  * sub-lock is destroyed.
 443                  */
 444         }
 445         RETURN(rc);
 446 }
 447
 448 static void lov_sublock_hold(const struct lu_env *env, struct lov_lock *lck,
 449                              int i)
 450 {
 451         struct cl_lock *parent = lck->lls_cl.cls_lock;
 452
 453         LASSERT(cl_lock_is_mutexed(parent));
 454         ENTRY;
 455
 456         if (!(lck->lls_sub[i].sub_flags & LSF_HELD)) {
 457                 struct cl_lock *sublock;
 458
 459                 LASSERT(lck->lls_sub[i].sub_lock != NULL);
 460                 sublock = lck->lls_sub[i].sub_lock->lss_cl.cls_lock;
 461                 LASSERT(cl_lock_is_mutexed(sublock));
 462                 LASSERT(sublock->cll_state != CLS_FREEING);
 463
 464                 lck->lls_sub[i].sub_flags |= LSF_HELD;
 465
 466                 cl_lock_get_trust(sublock);
 467                 cl_lock_hold_add(env, sublock, "lov-parent", parent);
 468                 cl_lock_user_add(env, sublock);
 469                 cl_lock_put(env, sublock);
 470         }
 471         EXIT;
 472 }
 473
 474 static void lov_lock_fini(const struct lu_env *env,
 475                           struct cl_lock_slice *slice)
 476 {
 477         struct lov_lock *lck;
 478         int i;
 479
 480         ENTRY;
 481         lck = cl2lov_lock(slice);
 482         LASSERT(lck->lls_nr_filled == 0);
 483         if (lck->lls_sub != NULL) {
 484                 for (i = 0; i < lck->lls_nr; ++i)
 485                         /*
 486                          * No sub-locks exists at this point, as sub-lock has
 487                          * a reference on its parent.
 488                          */
 489                         LASSERT(lck->lls_sub[i].sub_lock == NULL);
 490                 OBD_FREE_LARGE(lck->lls_sub,
 491                                lck->lls_nr * sizeof lck->lls_sub[0]);
 492         }
 493         OBD_SLAB_FREE_PTR(lck, lov_lock_kmem);
 494         EXIT;
 495 }
 496
 497 static int lov_lock_enqueue_wait(const struct lu_env *env,
 498                                  struct lov_lock *lck,
 499                                  struct cl_lock *sublock)
 500 {
 501         struct cl_lock *lock = lck->lls_cl.cls_lock;
 502         int             result;
 503         ENTRY;
 504
 505         LASSERT(cl_lock_is_mutexed(lock));
 506
 507         cl_lock_mutex_put(env, lock);
 508         result = cl_lock_enqueue_wait(env, sublock, 0);
 509         cl_lock_mutex_get(env, lock);
 510         RETURN(result ?: CLO_REPEAT);
 511 }
 512
 513 /**
 514  * Tries to advance a state machine of a given sub-lock toward enqueuing of
 515  * the top-lock.
 516  *
 517  * \retval 0 if state-transition can proceed
 518  * \retval -ve otherwise.
 519  */
 520 static int lov_lock_enqueue_one(const struct lu_env *env, struct lov_lock *lck,
 521                                 struct cl_lock *sublock,
 522                                 struct cl_io *io, __u32 enqflags, int last)
 523 {
 524         int result;
 525         ENTRY;
 526
 527         /* first, try to enqueue a sub-lock ... */
 528         result = cl_enqueue_try(env, sublock, io, enqflags);
 529         if ((sublock->cll_state == CLS_ENQUEUED) && !(enqflags & CEF_AGL)) {
 530                 /* if it is enqueued, try to `wait' on it---maybe it's already
 531                  * granted */
 532                 result = cl_wait_try(env, sublock);
 533                 if (result == CLO_REENQUEUED)
 534                         result = CLO_WAIT;
 535         }
 536         /*
 537          * If CEF_ASYNC flag is set, then all sub-locks can be enqueued in
 538          * parallel, otherwise---enqueue has to wait until sub-lock is granted
 539          * before proceeding to the next one.
 540          */
 541         if ((result == CLO_WAIT) && (sublock->cll_state <= CLS_HELD) &&
 542             (enqflags & CEF_ASYNC) && (!last || (enqflags & CEF_AGL)))
 543                 result = 0;
 544         RETURN(result);
 545 }
 546
 547 /**
 548  * Helper function for lov_lock_enqueue() that creates missing sub-lock.
 549  */
 550 static int lov_sublock_fill(const struct lu_env *env, struct cl_lock *parent,
 551                             struct cl_io *io, struct lov_lock *lck, int idx)
 552 {
 553         struct lov_lock_link *link;
 554         struct cl_lock       *sublock;
 555         int                   result;
 556
 557         LASSERT(parent->cll_depth == 1);
 558         cl_lock_mutex_put(env, parent);
 559         sublock = lov_sublock_alloc(env, io, lck, idx, &link);
 560         if (!IS_ERR(sublock))
 561                 cl_lock_mutex_get(env, sublock);
 562         cl_lock_mutex_get(env, parent);
 563
 564         if (!IS_ERR(sublock)) {
 565                 cl_lock_get_trust(sublock);
 566                 if (parent->cll_state == CLS_QUEUING &&
 567                     lck->lls_sub[idx].sub_lock == NULL) {
 568                         lov_sublock_adopt(env, lck, sublock, idx, link);
 569                 } else {
 570                         OBD_SLAB_FREE_PTR(link, lov_lock_link_kmem);
 571                         /* other thread allocated sub-lock, or enqueue is no
 572                          * longer going on */
 573                         cl_lock_mutex_put(env, parent);
 574                         cl_lock_unhold(env, sublock, "lov-parent", parent);
 575                         cl_lock_mutex_get(env, parent);
 576                 }
 577                 cl_lock_mutex_put(env, sublock);
 578                 cl_lock_put(env, sublock);
 579                 result = CLO_REPEAT;
 580         } else
 581                 result = PTR_ERR(sublock);
 582         return result;
 583 }
 584
 585 /**
 586  * Implementation of cl_lock_operations::clo_enqueue() for lov layer. This
 587  * function is rather subtle, as it enqueues top-lock (i.e., advances top-lock
 588  * state machine from CLS_QUEUING to CLS_ENQUEUED states) by juggling sub-lock
 589  * state machines in the face of sub-locks sharing (by multiple top-locks),
 590  * and concurrent sub-lock cancellations.
 591  */
 592 static int lov_lock_enqueue(const struct lu_env *env,
 593                             const struct cl_lock_slice *slice,
 594                             struct cl_io *io, __u32 enqflags)
 595 {
 596         struct cl_lock         *lock    = slice->cls_lock;
 597         struct lov_lock        *lck     = cl2lov_lock(slice);
 598         struct cl_lock_closure *closure = lov_closure_get(env, lock);
 599         int i;
 600         int result;
 601         enum cl_lock_state minstate;
 602
 603         ENTRY;
 604
 605         for (result = 0, minstate = CLS_FREEING, i = 0; i < lck->lls_nr; ++i) {
 606                 int rc;
 607                 struct lovsub_lock     *sub;
 608                 struct lov_lock_sub    *lls;
 609                 struct cl_lock         *sublock;
 610                 struct lov_sublock_env *subenv;
 611
 612                 if (lock->cll_state != CLS_QUEUING) {
 613                         /*
 614                          * Lock might have left QUEUING state if previous
 615                          * iteration released its mutex. Stop enqueing in this
 616                          * case and let the upper layer to decide what to do.
 617                          */
 618                         LASSERT(i > 0 && result != 0);
 619                         break;
 620                 }
 621
 622                 lls = &lck->lls_sub[i];
 623                 sub = lls->sub_lock;
 624                 /*
 625                  * Sub-lock might have been canceled, while top-lock was
 626                  * cached.
 627                  */
 628                 if (sub == NULL) {
 629                         result = lov_sublock_fill(env, lock, io, lck, i);
 630                         /* lov_sublock_fill() released @lock mutex,
 631                          * restart. */
 632                         break;
 633                 }
 634                 sublock = sub->lss_cl.cls_lock;
 635                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 636                 if (rc == 0) {
 637                         lov_sublock_hold(env, lck, i);
 638                         rc = lov_lock_enqueue_one(subenv->lse_env, lck, sublock,
 639                                                   subenv->lse_io, enqflags,
 640                                                   i == lck->lls_nr - 1);
 641                         minstate = min(minstate, sublock->cll_state);
 642                         if (rc == CLO_WAIT) {
 643                                 switch (sublock->cll_state) {
 644                                 case CLS_QUEUING:
 645                                         /* take recursive mutex, the lock is
 646                                          * released in lov_lock_enqueue_wait.
 647                                          */
 648                                         cl_lock_mutex_get(env, sublock);
 649                                         lov_sublock_unlock(env, sub, closure,
 650                                                            subenv);
 651                                         rc = lov_lock_enqueue_wait(env, lck,
 652                                                                    sublock);
 653                                         break;
 654                                 case CLS_CACHED:
 655                                         cl_lock_get(sublock);
 656                                         /* take recursive mutex of sublock */
 657                                         cl_lock_mutex_get(env, sublock);
 658                                         /* need to release all locks in closure
 659                                          * otherwise it may deadlock. LU-2683.*/
 660                                         lov_sublock_unlock(env, sub, closure,
 661                                                            subenv);
 662                                         /* sublock and parent are held. */
 663                                         rc = lov_sublock_release(env, lck, i,
 664                                                                  1, rc);
 665                                         cl_lock_mutex_put(env, sublock);
 666                                         cl_lock_put(env, sublock);
 667                                         break;
 668                                 default:
 669                                         lov_sublock_unlock(env, sub, closure,
 670                                                            subenv);
 671                                         break;
 672                                 }
 673                         } else {
 674                                 LASSERT(sublock->cll_conflict == NULL);
 675                                 lov_sublock_unlock(env, sub, closure, subenv);
 676                         }
 677                 }
 678                 result = lov_subresult(result, rc);
 679                 if (result != 0)
 680                         break;
 681         }
 682         cl_lock_closure_fini(closure);
 683         RETURN(result ?: minstate >= CLS_ENQUEUED ? 0 : CLO_WAIT);
 684 }
 685
 686 static int lov_lock_unuse(const struct lu_env *env,
 687                           const struct cl_lock_slice *slice)
 688 {
 689         struct lov_lock        *lck     = cl2lov_lock(slice);
 690         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 691         int i;
 692         int result;
 693
 694         ENTRY;
 695
 696         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 697                 int rc;
 698                 struct lovsub_lock     *sub;
 699                 struct cl_lock         *sublock;
 700                 struct lov_lock_sub    *lls;
 701                 struct lov_sublock_env *subenv;
 702
 703                 /* top-lock state cannot change concurrently, because single
 704                  * thread (one that released the last hold) carries unlocking
 705                  * to the completion. */
 706                 LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 707                 lls = &lck->lls_sub[i];
 708                 sub = lls->sub_lock;
 709                 if (sub == NULL)
 710                         continue;
 711
 712                 sublock = sub->lss_cl.cls_lock;
 713                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 714                 if (rc == 0) {
 715                         if (lls->sub_flags & LSF_HELD) {
 716                                 LASSERT(sublock->cll_state == CLS_HELD ||
 717                                         sublock->cll_state == CLS_ENQUEUED);
 718                                 rc = cl_unuse_try(subenv->lse_env, sublock);
 719                                 rc = lov_sublock_release(env, lck, i, 0, rc);
 720                         }
 721                         lov_sublock_unlock(env, sub, closure, subenv);
 722                 }
 723                 result = lov_subresult(result, rc);
 724         }
 725
 726         if (result == 0 && lck->lls_cancel_race) {
 727                 lck->lls_cancel_race = 0;
 728                 result = -ESTALE;
 729         }
 730         cl_lock_closure_fini(closure);
 731         RETURN(result);
 732 }
 733
 734
 735 static void lov_lock_cancel(const struct lu_env *env,
 736                            const struct cl_lock_slice *slice)
 737 {
 738         struct lov_lock        *lck     = cl2lov_lock(slice);
 739         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 740         int i;
 741         int result;
 742
 743         ENTRY;
 744
 745         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 746                 int rc;
 747                 struct lovsub_lock     *sub;
 748                 struct cl_lock         *sublock;
 749                 struct lov_lock_sub    *lls;
 750                 struct lov_sublock_env *subenv;
 751
 752                 /* top-lock state cannot change concurrently, because single
 753                  * thread (one that released the last hold) carries unlocking
 754                  * to the completion. */
 755                 lls = &lck->lls_sub[i];
 756                 sub = lls->sub_lock;
 757                 if (sub == NULL)
 758                         continue;
 759
 760                 sublock = sub->lss_cl.cls_lock;
 761                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 762                 if (rc == 0) {
 763                         if (!(lls->sub_flags & LSF_HELD)) {
 764                                 lov_sublock_unlock(env, sub, closure, subenv);
 765                                 continue;
 766                         }
 767
 768                         switch(sublock->cll_state) {
 769                         case CLS_HELD:
 770                                 rc = cl_unuse_try(subenv->lse_env, sublock);
 771                                 lov_sublock_release(env, lck, i, 0, 0);
 772                                 break;
 773                         default:
 774                                 lov_sublock_release(env, lck, i, 1, 0);
 775                                 break;
 776                         }
 777                         lov_sublock_unlock(env, sub, closure, subenv);
 778                 }
 779
 780                 if (rc == CLO_REPEAT) {
 781                         --i;
 782                         continue;
 783                 }
 784
 785                 result = lov_subresult(result, rc);
 786         }
 787
 788         if (result)
 789                 CL_LOCK_DEBUG(D_ERROR, env, slice->cls_lock,
 790                               "lov_lock_cancel fails with %d.\n", result);
 791
 792         cl_lock_closure_fini(closure);
 793 }
 794
 795 static int lov_lock_wait(const struct lu_env *env,
 796                          const struct cl_lock_slice *slice)
 797 {
 798         struct lov_lock        *lck     = cl2lov_lock(slice);
 799         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 800         enum cl_lock_state      minstate;
 801         int                     reenqueued;
 802         int                     result;
 803         int                     i;
 804
 805         ENTRY;
 806
 807 again:
 808         for (result = 0, minstate = CLS_FREEING, i = 0, reenqueued = 0;
 809              i < lck->lls_nr; ++i) {
 810                 int rc;
 811                 struct lovsub_lock     *sub;
 812                 struct cl_lock         *sublock;
 813                 struct lov_lock_sub    *lls;
 814                 struct lov_sublock_env *subenv;
 815
 816                 lls = &lck->lls_sub[i];
 817                 sub = lls->sub_lock;
 818                 LASSERT(sub != NULL);
 819                 sublock = sub->lss_cl.cls_lock;
 820                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 821                 if (rc == 0) {
 822                         LASSERT(sublock->cll_state >= CLS_ENQUEUED);
 823                         if (sublock->cll_state < CLS_HELD)
 824                                 rc = cl_wait_try(env, sublock);
 825
 826                         minstate = min(minstate, sublock->cll_state);
 827                         lov_sublock_unlock(env, sub, closure, subenv);
 828                 }
 829                 if (rc == CLO_REENQUEUED) {
 830                         reenqueued++;
 831                         rc = 0;
 832                 }
 833                 result = lov_subresult(result, rc);
 834                 if (result != 0)
 835                         break;
 836         }
 837         /* Each sublock only can be reenqueued once, so will not loop for
 838          * ever. */
 839         if (result == 0 && reenqueued != 0)
 840                 goto again;
 841         cl_lock_closure_fini(closure);
 842         RETURN(result ?: minstate >= CLS_HELD ? 0 : CLO_WAIT);
 843 }
 844
 845 static int lov_lock_use(const struct lu_env *env,
 846                         const struct cl_lock_slice *slice)
 847 {
 848         struct lov_lock        *lck     = cl2lov_lock(slice);
 849         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
 850         int                     result;
 851         int                     i;
 852
 853         LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 854         ENTRY;
 855
 856         for (result = 0, i = 0; i < lck->lls_nr; ++i) {
 857                 int rc;
 858                 struct lovsub_lock     *sub;
 859                 struct cl_lock         *sublock;
 860                 struct lov_lock_sub    *lls;
 861                 struct lov_sublock_env *subenv;
 862
 863                 LASSERT(slice->cls_lock->cll_state == CLS_INTRANSIT);
 864
 865                 lls = &lck->lls_sub[i];
 866                 sub = lls->sub_lock;
 867                 if (sub == NULL) {
 868                         /*
 869                          * Sub-lock might have been canceled, while top-lock was
 870                          * cached.
 871                          */
 872                         result = -ESTALE;
 873                         break;
 874                 }
 875
 876                 sublock = sub->lss_cl.cls_lock;
 877                 rc = lov_sublock_lock(env, lck, lls, closure, &subenv);
 878                 if (rc == 0) {
 879                         LASSERT(sublock->cll_state != CLS_FREEING);
 880                         lov_sublock_hold(env, lck, i);
 881                         if (sublock->cll_state == CLS_CACHED) {
 882                                 rc = cl_use_try(subenv->lse_env, sublock, 0);
 883                                 if (rc != 0)
 884                                         rc = lov_sublock_release(env, lck,
 885                                                                  i, 1, rc);
 886                         } else if (sublock->cll_state == CLS_NEW) {
 887                                 /* Sub-lock might have been canceled, while
 888                                  * top-lock was cached. */
 889                                 result = -ESTALE;
 890                                 lov_sublock_release(env, lck, i, 1, result);
 891                         }
 892                         lov_sublock_unlock(env, sub, closure, subenv);
 893                 }
 894                 result = lov_subresult(result, rc);
 895                 if (result != 0)
 896                         break;
 897         }
 898
 899         if (lck->lls_cancel_race) {
 900                 /*
 901                  * If there is unlocking happened at the same time, then
 902                  * sublock_lock state should be FREEING, and lov_sublock_lock
 903                  * should return CLO_REPEAT. In this case, it should return
 904                  * ESTALE, and up layer should reset the lock state to be NEW.
 905                  */
 906                 lck->lls_cancel_race = 0;
 907                 LASSERT(result != 0);
 908                 result = -ESTALE;
 909         }
 910         cl_lock_closure_fini(closure);
 911         RETURN(result);
 912 }
 913
 914 #if 0
 915 static int lock_lock_multi_match()
 916 {
 917         struct cl_lock          *lock    = slice->cls_lock;
 918         struct cl_lock_descr    *subneed = &lov_env_info(env)->lti_ldescr;
 919         struct lov_object       *loo     = cl2lov(lov->lls_cl.cls_obj);
 920         struct lov_layout_raid0 *r0      = lov_r0(loo);
 921         struct lov_lock_sub     *sub;
 922         struct cl_object        *subobj;
 923         obd_off  fstart;
 924         obd_off  fend;
 925         obd_off  start;
 926         obd_off  end;
 927         int i;
 928
 929         fstart = cl_offset(need->cld_obj, need->cld_start);
 930         fend   = cl_offset(need->cld_obj, need->cld_end + 1) - 1;
 931         subneed->cld_mode = need->cld_mode;
 932         cl_lock_mutex_get(env, lock);
 933         for (i = 0; i < lov->lls_nr; ++i) {
 934                 sub = &lov->lls_sub[i];
 935                 if (sub->sub_lock == NULL)
 936                         continue;
 937                 subobj = sub->sub_descr.cld_obj;
 938                 if (!lov_stripe_intersects(loo->lo_lsm, sub->sub_stripe,
 939                                            fstart, fend, &start, &end))
 940                         continue;
 941                 subneed->cld_start = cl_index(subobj, start);
 942                 subneed->cld_end   = cl_index(subobj, end);
 943                 subneed->cld_obj   = subobj;
 944                 if (!cl_lock_ext_match(&sub->sub_got, subneed)) {
 945                         result = 0;
 946                         break;
 947                 }
 948         }
 949         cl_lock_mutex_put(env, lock);
 950 }
 951 #endif
 952
 953 /**
 954  * Check if the extent region \a descr is covered by \a child against the
 955  * specific \a stripe.
 956  */
 957 static int lov_lock_stripe_is_matching(const struct lu_env *env,
 958                                        struct lov_object *lov, int stripe,
 959                                        const struct cl_lock_descr *child,
 960                                        const struct cl_lock_descr *descr)
 961 {
 962         struct lov_stripe_md *lsm = lov->lo_lsm;
 963         obd_off start;
 964         obd_off end;
 965         int result;
 966
 967         if (lov_r0(lov)->lo_nr == 1)
 968                 return cl_lock_ext_match(child, descr);
 969
 970         /*
 971          * For a multi-stripes object:
 972          * - make sure the descr only covers child's stripe, and
 973          * - check if extent is matching.
 974          */
 975         start = cl_offset(&lov->lo_cl, descr->cld_start);
 976         end   = cl_offset(&lov->lo_cl, descr->cld_end + 1) - 1;
 977         result = end - start <= lsm->lsm_stripe_size &&
 978                  stripe == lov_stripe_number(lsm, start) &&
 979                  stripe == lov_stripe_number(lsm, end);
 980         if (result) {
 981                 struct cl_lock_descr *subd = &lov_env_info(env)->lti_ldescr;
 982                 obd_off sub_start;
 983                 obd_off sub_end;
 984
 985                 subd->cld_obj  = NULL;   /* don't need sub object at all */
 986                 subd->cld_mode = descr->cld_mode;
 987                 subd->cld_gid  = descr->cld_gid;
 988                 result = lov_stripe_intersects(lsm, stripe, start, end,
 989                                                &sub_start, &sub_end);
 990                 LASSERT(result);
 991                 subd->cld_start = cl_index(child->cld_obj, sub_start);
 992                 subd->cld_end   = cl_index(child->cld_obj, sub_end);
 993                 result = cl_lock_ext_match(child, subd);
 994         }
 995         return result;
 996 }
 997
 998 /**
 999  * An implementation of cl_lock_operations::clo_fits_into() method.
1000  *
1001  * Checks whether a lock (given by \a slice) is suitable for \a
1002  * io. Multi-stripe locks can be used only for "quick" io, like truncate, or
1003  * O_APPEND write.
1004  *
1005  * \see ccc_lock_fits_into().
1006  */
1007 static int lov_lock_fits_into(const struct lu_env *env,
1008                               const struct cl_lock_slice *slice,
1009                               const struct cl_lock_descr *need,
1010                               const struct cl_io *io)
1011 {
1012         struct lov_lock   *lov = cl2lov_lock(slice);
1013         struct lov_object *obj = cl2lov(slice->cls_obj);
1014         int result;
1015
1016         LASSERT(cl_object_same(need->cld_obj, slice->cls_obj));
1017         LASSERT(lov->lls_nr > 0);
1018
1019         ENTRY;
1020
1021         /* for top lock, it's necessary to match enq flags otherwise it will
1022          * run into problem if a sublock is missing and reenqueue. */
1023         if (need->cld_enq_flags != lov->lls_orig.cld_enq_flags)
1024                 return 0;
1025
1026         if (lov->lls_ever_canceled)
1027                 return 0;
1028
1029         if (need->cld_mode == CLM_GROUP)
1030                 /*
1031                  * always allow to match group lock.
1032                  */
1033                 result = cl_lock_ext_match(&lov->lls_orig, need);
1034         else if (lov->lls_nr == 1) {
1035                 struct cl_lock_descr *got = &lov->lls_sub[0].sub_got;
1036                 result = lov_lock_stripe_is_matching(env,
1037                                                      cl2lov(slice->cls_obj),
1038                                                      lov->lls_sub[0].sub_stripe,
1039                                                      got, need);
1040         } else if (io->ci_type != CIT_SETATTR && io->ci_type != CIT_MISC &&
1041                    !cl_io_is_append(io) && need->cld_mode != CLM_PHANTOM)
1042                 /*
1043                  * Multi-stripe locks are only suitable for `quick' IO and for
1044                  * glimpse.
1045                  */
1046                 result = 0;
1047         else
1048                 /*
1049                  * Most general case: multi-stripe existing lock, and
1050                  * (potentially) multi-stripe @need lock. Check that @need is
1051                  * covered by @lov's sub-locks.
1052                  *
1053                  * For now, ignore lock expansions made by the server, and
1054                  * match against original lock extent.
1055                  */
1056                 result = cl_lock_ext_match(&lov->lls_orig, need);
1057         CDEBUG(D_DLMTRACE, DDESCR"/"DDESCR" %d %d/%d: %d\n",
1058                PDESCR(&lov->lls_orig), PDESCR(&lov->lls_sub[0].sub_got),
1059                lov->lls_sub[0].sub_stripe, lov->lls_nr, lov_r0(obj)->lo_nr,
1060                result);
1061         RETURN(result);
1062 }
1063
1064 void lov_lock_unlink(const struct lu_env *env,
1065                      struct lov_lock_link *link, struct lovsub_lock *sub)
1066 {
1067         struct lov_lock *lck    = link->lll_super;
1068         struct cl_lock  *parent = lck->lls_cl.cls_lock;
1069
1070         LASSERT(cl_lock_is_mutexed(parent));
1071         LASSERT(cl_lock_is_mutexed(sub->lss_cl.cls_lock));
1072         ENTRY;
1073
1074         cfs_list_del_init(&link->lll_list);
1075         LASSERT(lck->lls_sub[link->lll_idx].sub_lock == sub);
1076         /* yank this sub-lock from parent's array */
1077         lck->lls_sub[link->lll_idx].sub_lock = NULL;
1078         LASSERT(lck->lls_nr_filled > 0);
1079         lck->lls_nr_filled--;
1080         lu_ref_del(&parent->cll_reference, "lov-child", sub->lss_cl.cls_lock);
1081         cl_lock_put(env, parent);
1082         OBD_SLAB_FREE_PTR(link, lov_lock_link_kmem);
1083         EXIT;
1084 }
1085
1086 struct lov_lock_link *lov_lock_link_find(const struct lu_env *env,
1087                                          struct lov_lock *lck,
1088                                          struct lovsub_lock *sub)
1089 {
1090         struct lov_lock_link *scan;
1091
1092         LASSERT(cl_lock_is_mutexed(sub->lss_cl.cls_lock));
1093         ENTRY;
1094
1095         cfs_list_for_each_entry(scan, &sub->lss_parents, lll_list) {
1096                 if (scan->lll_super == lck)
1097                         RETURN(scan);
1098         }
1099         RETURN(NULL);
1100 }
1101
1102 /**
1103  * An implementation of cl_lock_operations::clo_delete() method. This is
1104  * invoked for "top-to-bottom" delete, when lock destruction starts from the
1105  * top-lock, e.g., as a result of inode destruction.
1106  *
1107  * Unlinks top-lock from all its sub-locks. Sub-locks are not deleted there:
1108  * this is done separately elsewhere:
1109  *
1110  *     - for inode destruction, lov_object_delete() calls cl_object_kill() for
1111  *       each sub-object, purging its locks;
1112  *
1113  *     - in other cases (e.g., a fatal error with a top-lock) sub-locks are
1114  *       left in the cache.
1115  */
1116 static void lov_lock_delete(const struct lu_env *env,
1117                             const struct cl_lock_slice *slice)
1118 {
1119         struct lov_lock        *lck     = cl2lov_lock(slice);
1120         struct cl_lock_closure *closure = lov_closure_get(env, slice->cls_lock);
1121         struct lov_lock_link   *link;
1122         int                     rc;
1123         int                     i;
1124
1125         LASSERT(slice->cls_lock->cll_state == CLS_FREEING);
1126         ENTRY;
1127
1128         for (i = 0; i < lck->lls_nr; ++i) {
1129                 struct lov_lock_sub *lls = &lck->lls_sub[i];
1130                 struct lovsub_lock  *lsl = lls->sub_lock;
1131
1132                 if (lsl == NULL) /* already removed */
1133                         continue;
1134
1135                 rc = lov_sublock_lock(env, lck, lls, closure, NULL);
1136                 if (rc == CLO_REPEAT) {
1137                         --i;
1138                         continue;
1139                 }
1140
1141                 LASSERT(rc == 0);
1142                 LASSERT(lsl->lss_cl.cls_lock->cll_state < CLS_FREEING);
1143
1144                 if (lls->sub_flags & LSF_HELD)
1145                         lov_sublock_release(env, lck, i, 1, 0);
1146
1147                 link = lov_lock_link_find(env, lck, lsl);
1148                 LASSERT(link != NULL);
1149                 lov_lock_unlink(env, link, lsl);
1150                 LASSERT(lck->lls_sub[i].sub_lock == NULL);
1151
1152                 lov_sublock_unlock(env, lsl, closure, NULL);
1153         }
1154
1155         cl_lock_closure_fini(closure);
1156         EXIT;
1157 }
1158
1159 static int lov_lock_print(const struct lu_env *env, void *cookie,
1160                           lu_printer_t p, const struct cl_lock_slice *slice)
1161 {
1162         struct lov_lock *lck = cl2lov_lock(slice);
1163         int              i;
1164
1165         (*p)(env, cookie, "%d\n", lck->lls_nr);
1166         for (i = 0; i < lck->lls_nr; ++i) {
1167                 struct lov_lock_sub *sub;
1168
1169                 sub = &lck->lls_sub[i];
1170                 (*p)(env, cookie, "    %d %x: ", i, sub->sub_flags);
1171                 if (sub->sub_lock != NULL)
1172                         cl_lock_print(env, cookie, p,
1173                                       sub->sub_lock->lss_cl.cls_lock);
1174                 else
1175                         (*p)(env, cookie, "---\n");
1176         }
1177         return 0;
1178 }
1179
1180 static const struct cl_lock_operations lov_lock_ops = {
1181         .clo_fini      = lov_lock_fini,
1182         .clo_enqueue   = lov_lock_enqueue,
1183         .clo_wait      = lov_lock_wait,
1184         .clo_use       = lov_lock_use,
1185         .clo_unuse     = lov_lock_unuse,
1186         .clo_cancel    = lov_lock_cancel,
1187         .clo_fits_into = lov_lock_fits_into,
1188         .clo_delete    = lov_lock_delete,
1189         .clo_print     = lov_lock_print
1190 };
1191
1192 int lov_lock_init_raid0(const struct lu_env *env, struct cl_object *obj,
1193                         struct cl_lock *lock, const struct cl_io *io)
1194 {
1195         struct lov_lock *lck;
1196         int result;
1197
1198         ENTRY;
1199         OBD_SLAB_ALLOC_PTR_GFP(lck, lov_lock_kmem, __GFP_IO);
1200         if (lck != NULL) {
1201                 cl_lock_slice_add(lock, &lck->lls_cl, obj, &lov_lock_ops);
1202                 result = lov_lock_sub_init(env, lck, io);
1203         } else
1204                 result = -ENOMEM;
1205         RETURN(result);
1206 }
1207
1208 static void lov_empty_lock_fini(const struct lu_env *env,
1209                                 struct cl_lock_slice *slice)
1210 {
1211         struct lov_lock *lck = cl2lov_lock(slice);
1212         OBD_SLAB_FREE_PTR(lck, lov_lock_kmem);
1213 }
1214
1215 static int lov_empty_lock_print(const struct lu_env *env, void *cookie,
1216                         lu_printer_t p, const struct cl_lock_slice *slice)
1217 {
1218         (*p)(env, cookie, "empty\n");
1219         return 0;
1220 }
1221
1222 /* XXX: more methods will be added later. */
1223 static const struct cl_lock_operations lov_empty_lock_ops = {
1224         .clo_fini  = lov_empty_lock_fini,
1225         .clo_print = lov_empty_lock_print
1226 };
1227
1228 int lov_lock_init_empty(const struct lu_env *env, struct cl_object *obj,
1229                 struct cl_lock *lock, const struct cl_io *io)
1230 {
1231         struct lov_lock *lck;
1232         int result = -ENOMEM;
1233
1234         ENTRY;
1235         OBD_SLAB_ALLOC_PTR_GFP(lck, lov_lock_kmem, __GFP_IO);
1236         if (lck != NULL) {
1237                 cl_lock_slice_add(lock, &lck->lls_cl, obj, &lov_empty_lock_ops);
1238                 lck->lls_orig = lock->cll_descr;
1239                 result = 0;
1240         }
1241         RETURN(result);
1242 }
1243
1244 static struct cl_lock_closure *lov_closure_get(const struct lu_env *env,
1245                                                struct cl_lock *parent)
1246 {
1247         struct cl_lock_closure *closure;
1248
1249         closure = &lov_env_info(env)->lti_closure;
1250         LASSERT(cfs_list_empty(&closure->clc_list));
1251         cl_lock_closure_init(env, closure, parent, 1);
1252         return closure;
1253 }
1254
1255
1256 /** @} lov */