git.oblomov.eu Git - linux-2.6/blob - fs/gfs2/locking/dlm/lock.c

   1 /*
   2  * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   3  * Copyright (C) 2004-2005 Red Hat, Inc.  All rights reserved.
   4  *
   5  * This copyrighted material is made available to anyone wishing to use,
   6  * modify, copy, or redistribute it subject to the terms and conditions
   7  * of the GNU General Public License version 2.
   8  */
   9
  10 #include "lock_dlm.h"
  11
  12 static char junk_lvb[GDLM_LVB_SIZE];
  13
  14
  15 /* convert dlm lock-mode to gfs lock-state */
  16
  17 static s16 gdlm_make_lmstate(s16 dlmmode)
  18 {
  19         switch (dlmmode) {
  20         case DLM_LOCK_IV:
  21         case DLM_LOCK_NL:
  22                 return LM_ST_UNLOCKED;
  23         case DLM_LOCK_EX:
  24                 return LM_ST_EXCLUSIVE;
  25         case DLM_LOCK_CW:
  26                 return LM_ST_DEFERRED;
  27         case DLM_LOCK_PR:
  28                 return LM_ST_SHARED;
  29         }
  30         gdlm_assert(0, "unknown DLM mode %d", dlmmode);
  31         return -1;
  32 }
  33
  34 /* A lock placed on this queue is re-submitted to DLM as soon as the lock_dlm
  35    thread gets to it. */
  36
  37 static void queue_submit(struct gdlm_lock *lp)
  38 {
  39         struct gdlm_ls *ls = lp->ls;
  40
  41         spin_lock(&ls->async_lock);
  42         list_add_tail(&lp->delay_list, &ls->submit);
  43         spin_unlock(&ls->async_lock);
  44         wake_up(&ls->thread_wait);
  45 }
  46
  47 static void wake_up_ast(struct gdlm_lock *lp)
  48 {
  49         clear_bit(LFL_AST_WAIT, &lp->flags);
  50         smp_mb__after_clear_bit();
  51         wake_up_bit(&lp->flags, LFL_AST_WAIT);
  52 }
  53
  54 static void gdlm_delete_lp(struct gdlm_lock *lp)
  55 {
  56         struct gdlm_ls *ls = lp->ls;
  57
  58         spin_lock(&ls->async_lock);
  59         if (!list_empty(&lp->delay_list))
  60                 list_del_init(&lp->delay_list);
  61         ls->all_locks_count--;
  62         spin_unlock(&ls->async_lock);
  63
  64         kfree(lp);
  65 }
  66
  67 static void gdlm_queue_delayed(struct gdlm_lock *lp)
  68 {
  69         struct gdlm_ls *ls = lp->ls;
  70
  71         spin_lock(&ls->async_lock);
  72         list_add_tail(&lp->delay_list, &ls->delayed);
  73         spin_unlock(&ls->async_lock);
  74 }
  75
  76 static void process_complete(struct gdlm_lock *lp)
  77 {
  78         struct gdlm_ls *ls = lp->ls;
  79         struct lm_async_cb acb;
  80
  81         memset(&acb, 0, sizeof(acb));
  82
  83         if (lp->lksb.sb_status == -DLM_ECANCEL) {
  84                 log_info("complete dlm cancel %x,%llx flags %lx",
  85                          lp->lockname.ln_type,
  86                          (unsigned long long)lp->lockname.ln_number,
  87                          lp->flags);
  88
  89                 lp->req = lp->cur;
  90                 acb.lc_ret |= LM_OUT_CANCELED;
  91                 if (lp->cur == DLM_LOCK_IV)
  92                         lp->lksb.sb_lkid = 0;
  93                 goto out;
  94         }
  95
  96         if (test_and_clear_bit(LFL_DLM_UNLOCK, &lp->flags)) {
  97                 if (lp->lksb.sb_status != -DLM_EUNLOCK) {
  98                         log_info("unlock sb_status %d %x,%llx flags %lx",
  99                                  lp->lksb.sb_status, lp->lockname.ln_type,
 100                                  (unsigned long long)lp->lockname.ln_number,
 101                                  lp->flags);
 102                         return;
 103                 }
 104
 105                 lp->cur = DLM_LOCK_IV;
 106                 lp->req = DLM_LOCK_IV;
 107                 lp->lksb.sb_lkid = 0;
 108
 109                 if (test_and_clear_bit(LFL_UNLOCK_DELETE, &lp->flags)) {
 110                         gdlm_delete_lp(lp);
 111                         return;
 112                 }
 113                 goto out;
 114         }
 115
 116         if (lp->lksb.sb_flags & DLM_SBF_VALNOTVALID)
 117                 memset(lp->lksb.sb_lvbptr, 0, GDLM_LVB_SIZE);
 118
 119         if (lp->lksb.sb_flags & DLM_SBF_ALTMODE) {
 120                 if (lp->req == DLM_LOCK_PR)
 121                         lp->req = DLM_LOCK_CW;
 122                 else if (lp->req == DLM_LOCK_CW)
 123                         lp->req = DLM_LOCK_PR;
 124         }
 125
 126         /*
 127          * A canceled lock request.  The lock was just taken off the delayed
 128          * list and was never even submitted to dlm.
 129          */
 130
 131         if (test_and_clear_bit(LFL_CANCEL, &lp->flags)) {
 132                 log_info("complete internal cancel %x,%llx",
 133                          lp->lockname.ln_type,
 134                          (unsigned long long)lp->lockname.ln_number);
 135                 lp->req = lp->cur;
 136                 acb.lc_ret |= LM_OUT_CANCELED;
 137                 goto out;
 138         }
 139
 140         /*
 141          * An error occured.
 142          */
 143
 144         if (lp->lksb.sb_status) {
 145                 /* a "normal" error */
 146                 if ((lp->lksb.sb_status == -EAGAIN) &&
 147                     (lp->lkf & DLM_LKF_NOQUEUE)) {
 148                         lp->req = lp->cur;
 149                         if (lp->cur == DLM_LOCK_IV)
 150                                 lp->lksb.sb_lkid = 0;
 151                         goto out;
 152                 }
 153
 154                 /* this could only happen with cancels I think */
 155                 log_info("ast sb_status %d %x,%llx flags %lx",
 156                          lp->lksb.sb_status, lp->lockname.ln_type,
 157                          (unsigned long long)lp->lockname.ln_number,
 158                          lp->flags);
 159                 return;
 160         }
 161
 162         /*
 163          * This is an AST for an EX->EX conversion for sync_lvb from GFS.
 164          */
 165
 166         if (test_and_clear_bit(LFL_SYNC_LVB, &lp->flags)) {
 167                 wake_up_ast(lp);
 168                 return;
 169         }
 170
 171         /*
 172          * A lock has been demoted to NL because it initially completed during
 173          * BLOCK_LOCKS.  Now it must be requested in the originally requested
 174          * mode.
 175          */
 176
 177         if (test_and_clear_bit(LFL_REREQUEST, &lp->flags)) {
 178                 gdlm_assert(lp->req == DLM_LOCK_NL, "%x,%llx",
 179                             lp->lockname.ln_type,
 180                             (unsigned long long)lp->lockname.ln_number);
 181                 gdlm_assert(lp->prev_req > DLM_LOCK_NL, "%x,%llx",
 182                             lp->lockname.ln_type,
 183                             (unsigned long long)lp->lockname.ln_number);
 184
 185                 lp->cur = DLM_LOCK_NL;
 186                 lp->req = lp->prev_req;
 187                 lp->prev_req = DLM_LOCK_IV;
 188                 lp->lkf &= ~DLM_LKF_CONVDEADLK;
 189
 190                 set_bit(LFL_NOCACHE, &lp->flags);
 191
 192                 if (test_bit(DFL_BLOCK_LOCKS, &ls->flags) &&
 193                     !test_bit(LFL_NOBLOCK, &lp->flags))
 194                         gdlm_queue_delayed(lp);
 195                 else
 196                         queue_submit(lp);
 197                 return;
 198         }
 199
 200         /*
 201          * A request is granted during dlm recovery.  It may be granted
 202          * because the locks of a failed node were cleared.  In that case,
 203          * there may be inconsistent data beneath this lock and we must wait
 204          * for recovery to complete to use it.  When gfs recovery is done this
 205          * granted lock will be converted to NL and then reacquired in this
 206          * granted state.
 207          */
 208
 209         if (test_bit(DFL_BLOCK_LOCKS, &ls->flags) &&
 210             !test_bit(LFL_NOBLOCK, &lp->flags) &&
 211             lp->req != DLM_LOCK_NL) {
 212
 213                 lp->cur = lp->req;
 214                 lp->prev_req = lp->req;
 215                 lp->req = DLM_LOCK_NL;
 216                 lp->lkf |= DLM_LKF_CONVERT;
 217                 lp->lkf &= ~DLM_LKF_CONVDEADLK;
 218
 219                 log_debug("rereq %x,%llx id %x %d,%d",
 220                           lp->lockname.ln_type,
 221                           (unsigned long long)lp->lockname.ln_number,
 222                           lp->lksb.sb_lkid, lp->cur, lp->req);
 223
 224                 set_bit(LFL_REREQUEST, &lp->flags);
 225                 queue_submit(lp);
 226                 return;
 227         }
 228
 229         /*
 230          * DLM demoted the lock to NL before it was granted so GFS must be
 231          * told it cannot cache data for this lock.
 232          */
 233
 234         if (lp->lksb.sb_flags & DLM_SBF_DEMOTED)
 235                 set_bit(LFL_NOCACHE, &lp->flags);
 236
 237 out:
 238         /*
 239          * This is an internal lock_dlm lock
 240          */
 241
 242         if (test_bit(LFL_INLOCK, &lp->flags)) {
 243                 clear_bit(LFL_NOBLOCK, &lp->flags);
 244                 lp->cur = lp->req;
 245                 wake_up_ast(lp);
 246                 return;
 247         }
 248
 249         /*
 250          * Normal completion of a lock request.  Tell GFS it now has the lock.
 251          */
 252
 253         clear_bit(LFL_NOBLOCK, &lp->flags);
 254         lp->cur = lp->req;
 255
 256         acb.lc_name = lp->lockname;
 257         acb.lc_ret |= gdlm_make_lmstate(lp->cur);
 258
 259         ls->fscb(ls->sdp, LM_CB_ASYNC, &acb);
 260 }
 261
 262 static void gdlm_ast(void *astarg)
 263 {
 264         struct gdlm_lock *lp = astarg;
 265         clear_bit(LFL_ACTIVE, &lp->flags);
 266         process_complete(lp);
 267 }
 268
 269 static void process_blocking(struct gdlm_lock *lp, int bast_mode)
 270 {
 271         struct gdlm_ls *ls = lp->ls;
 272         unsigned int cb = 0;
 273
 274         switch (gdlm_make_lmstate(bast_mode)) {
 275         case LM_ST_EXCLUSIVE:
 276                 cb = LM_CB_NEED_E;
 277                 break;
 278         case LM_ST_DEFERRED:
 279                 cb = LM_CB_NEED_D;
 280                 break;
 281         case LM_ST_SHARED:
 282                 cb = LM_CB_NEED_S;
 283                 break;
 284         default:
 285                 gdlm_assert(0, "unknown bast mode %u", bast_mode);
 286         }
 287
 288         ls->fscb(ls->sdp, cb, &lp->lockname);
 289 }
 290
 291
 292 static void gdlm_bast(void *astarg, int mode)
 293 {
 294         struct gdlm_lock *lp = astarg;
 295
 296         if (!mode) {
 297                 printk(KERN_INFO "lock_dlm: bast mode zero %x,%llx\n",
 298                         lp->lockname.ln_type,
 299                         (unsigned long long)lp->lockname.ln_number);
 300                 return;
 301         }
 302
 303         process_blocking(lp, mode);
 304 }
 305
 306 /* convert gfs lock-state to dlm lock-mode */
 307
 308 static s16 make_mode(s16 lmstate)
 309 {
 310         switch (lmstate) {
 311         case LM_ST_UNLOCKED:
 312                 return DLM_LOCK_NL;
 313         case LM_ST_EXCLUSIVE:
 314                 return DLM_LOCK_EX;
 315         case LM_ST_DEFERRED:
 316                 return DLM_LOCK_CW;
 317         case LM_ST_SHARED:
 318                 return DLM_LOCK_PR;
 319         }
 320         gdlm_assert(0, "unknown LM state %d", lmstate);
 321         return -1;
 322 }
 323
 324
 325 /* verify agreement with GFS on the current lock state, NB: DLM_LOCK_NL and
 326    DLM_LOCK_IV are both considered LM_ST_UNLOCKED by GFS. */
 327
 328 static void check_cur_state(struct gdlm_lock *lp, unsigned int cur_state)
 329 {
 330         s16 cur = make_mode(cur_state);
 331         if (lp->cur != DLM_LOCK_IV)
 332                 gdlm_assert(lp->cur == cur, "%d, %d", lp->cur, cur);
 333 }
 334
 335 static inline unsigned int make_flags(struct gdlm_lock *lp,
 336                                       unsigned int gfs_flags,
 337                                       s16 cur, s16 req)
 338 {
 339         unsigned int lkf = 0;
 340
 341         if (gfs_flags & LM_FLAG_TRY)
 342                 lkf |= DLM_LKF_NOQUEUE;
 343
 344         if (gfs_flags & LM_FLAG_TRY_1CB) {
 345                 lkf |= DLM_LKF_NOQUEUE;
 346                 lkf |= DLM_LKF_NOQUEUEBAST;
 347         }
 348
 349         if (gfs_flags & LM_FLAG_PRIORITY) {
 350                 lkf |= DLM_LKF_NOORDER;
 351                 lkf |= DLM_LKF_HEADQUE;
 352         }
 353
 354         if (gfs_flags & LM_FLAG_ANY) {
 355                 if (req == DLM_LOCK_PR)
 356                         lkf |= DLM_LKF_ALTCW;
 357                 else if (req == DLM_LOCK_CW)
 358                         lkf |= DLM_LKF_ALTPR;
 359         }
 360
 361         if (lp->lksb.sb_lkid != 0) {
 362                 lkf |= DLM_LKF_CONVERT;
 363         }
 364
 365         if (lp->lvb)
 366                 lkf |= DLM_LKF_VALBLK;
 367
 368         return lkf;
 369 }
 370
 371 /* make_strname - convert GFS lock numbers to a string */
 372
 373 static inline void make_strname(const struct lm_lockname *lockname,
 374                                 struct gdlm_strname *str)
 375 {
 376         sprintf(str->name, "%8x%16llx", lockname->ln_type,
 377                 (unsigned long long)lockname->ln_number);
 378         str->namelen = GDLM_STRNAME_BYTES;
 379 }
 380
 381 static int gdlm_create_lp(struct gdlm_ls *ls, struct lm_lockname *name,
 382                           struct gdlm_lock **lpp)
 383 {
 384         struct gdlm_lock *lp;
 385
 386         lp = kzalloc(sizeof(struct gdlm_lock), GFP_NOFS);
 387         if (!lp)
 388                 return -ENOMEM;
 389
 390         lp->lockname = *name;
 391         make_strname(name, &lp->strname);
 392         lp->ls = ls;
 393         lp->cur = DLM_LOCK_IV;
 394         INIT_LIST_HEAD(&lp->delay_list);
 395
 396         spin_lock(&ls->async_lock);
 397         ls->all_locks_count++;
 398         spin_unlock(&ls->async_lock);
 399
 400         *lpp = lp;
 401         return 0;
 402 }
 403
 404 int gdlm_get_lock(void *lockspace, struct lm_lockname *name,
 405                   void **lockp)
 406 {
 407         struct gdlm_lock *lp;
 408         int error;
 409
 410         error = gdlm_create_lp(lockspace, name, &lp);
 411
 412         *lockp = lp;
 413         return error;
 414 }
 415
 416 void gdlm_put_lock(void *lock)
 417 {
 418         gdlm_delete_lp(lock);
 419 }
 420
 421 unsigned int gdlm_do_lock(struct gdlm_lock *lp)
 422 {
 423         struct gdlm_ls *ls = lp->ls;
 424         int error, bast = 1;
 425
 426         /*
 427          * When recovery is in progress, delay lock requests for submission
 428          * once recovery is done.  Requests for recovery (NOEXP) and unlocks
 429          * can pass.
 430          */
 431
 432         if (test_bit(DFL_BLOCK_LOCKS, &ls->flags) &&
 433             !test_bit(LFL_NOBLOCK, &lp->flags) && lp->req != DLM_LOCK_NL) {
 434                 gdlm_queue_delayed(lp);
 435                 return LM_OUT_ASYNC;
 436         }
 437
 438         /*
 439          * Submit the actual lock request.
 440          */
 441
 442         if (test_bit(LFL_NOBAST, &lp->flags))
 443                 bast = 0;
 444
 445         set_bit(LFL_ACTIVE, &lp->flags);
 446
 447         log_debug("lk %x,%llx id %x %d,%d %x", lp->lockname.ln_type,
 448                   (unsigned long long)lp->lockname.ln_number, lp->lksb.sb_lkid,
 449                   lp->cur, lp->req, lp->lkf);
 450
 451         error = dlm_lock(ls->dlm_lockspace, lp->req, &lp->lksb, lp->lkf,
 452                          lp->strname.name, lp->strname.namelen, 0, gdlm_ast,
 453                          lp, bast ? gdlm_bast : NULL);
 454
 455         if ((error == -EAGAIN) && (lp->lkf & DLM_LKF_NOQUEUE)) {
 456                 lp->lksb.sb_status = -EAGAIN;
 457                 gdlm_ast(lp);
 458                 error = 0;
 459         }
 460
 461         if (error) {
 462                 log_error("%s: gdlm_lock %x,%llx err=%d cur=%d req=%d lkf=%x "
 463                           "flags=%lx", ls->fsname, lp->lockname.ln_type,
 464                           (unsigned long long)lp->lockname.ln_number, error,
 465                           lp->cur, lp->req, lp->lkf, lp->flags);
 466                 return LM_OUT_ERROR;
 467         }
 468         return LM_OUT_ASYNC;
 469 }
 470
 471 static unsigned int gdlm_do_unlock(struct gdlm_lock *lp)
 472 {
 473         struct gdlm_ls *ls = lp->ls;
 474         unsigned int lkf = 0;
 475         int error;
 476
 477         set_bit(LFL_DLM_UNLOCK, &lp->flags);
 478         set_bit(LFL_ACTIVE, &lp->flags);
 479
 480         if (lp->lvb)
 481                 lkf = DLM_LKF_VALBLK;
 482
 483         log_debug("un %x,%llx %x %d %x", lp->lockname.ln_type,
 484                   (unsigned long long)lp->lockname.ln_number,
 485                   lp->lksb.sb_lkid, lp->cur, lkf);
 486
 487         error = dlm_unlock(ls->dlm_lockspace, lp->lksb.sb_lkid, lkf, NULL, lp);
 488
 489         if (error) {
 490                 log_error("%s: gdlm_unlock %x,%llx err=%d cur=%d req=%d lkf=%x "
 491                           "flags=%lx", ls->fsname, lp->lockname.ln_type,
 492                           (unsigned long long)lp->lockname.ln_number, error,
 493                           lp->cur, lp->req, lp->lkf, lp->flags);
 494                 return LM_OUT_ERROR;
 495         }
 496         return LM_OUT_ASYNC;
 497 }
 498
 499 unsigned int gdlm_lock(void *lock, unsigned int cur_state,
 500                        unsigned int req_state, unsigned int flags)
 501 {
 502         struct gdlm_lock *lp = lock;
 503
 504         if (req_state == LM_ST_UNLOCKED)
 505                 return gdlm_unlock(lock, cur_state);
 506
 507         if (req_state == LM_ST_UNLOCKED)
 508                 return gdlm_unlock(lock, cur_state);
 509
 510         clear_bit(LFL_DLM_CANCEL, &lp->flags);
 511         if (flags & LM_FLAG_NOEXP)
 512                 set_bit(LFL_NOBLOCK, &lp->flags);
 513
 514         check_cur_state(lp, cur_state);
 515         lp->req = make_mode(req_state);
 516         lp->lkf = make_flags(lp, flags, lp->cur, lp->req);
 517
 518         return gdlm_do_lock(lp);
 519 }
 520
 521 unsigned int gdlm_unlock(void *lock, unsigned int cur_state)
 522 {
 523         struct gdlm_lock *lp = lock;
 524
 525         clear_bit(LFL_DLM_CANCEL, &lp->flags);
 526         if (lp->cur == DLM_LOCK_IV)
 527                 return 0;
 528         return gdlm_do_unlock(lp);
 529 }
 530
 531 void gdlm_cancel(void *lock)
 532 {
 533         struct gdlm_lock *lp = lock;
 534         struct gdlm_ls *ls = lp->ls;
 535         int error, delay_list = 0;
 536
 537         if (test_bit(LFL_DLM_CANCEL, &lp->flags))
 538                 return;
 539
 540         log_info("gdlm_cancel %x,%llx flags %lx", lp->lockname.ln_type,
 541                  (unsigned long long)lp->lockname.ln_number, lp->flags);
 542
 543         spin_lock(&ls->async_lock);
 544         if (!list_empty(&lp->delay_list)) {
 545                 list_del_init(&lp->delay_list);
 546                 delay_list = 1;
 547         }
 548         spin_unlock(&ls->async_lock);
 549
 550         if (delay_list) {
 551                 set_bit(LFL_CANCEL, &lp->flags);
 552                 set_bit(LFL_ACTIVE, &lp->flags);
 553                 gdlm_ast(lp);
 554                 return;
 555         }
 556
 557         if (!test_bit(LFL_ACTIVE, &lp->flags) ||
 558             test_bit(LFL_DLM_UNLOCK, &lp->flags)) {
 559                 log_info("gdlm_cancel skip %x,%llx flags %lx",
 560                          lp->lockname.ln_type,
 561                          (unsigned long long)lp->lockname.ln_number, lp->flags);
 562                 return;
 563         }
 564
 565         /* the lock is blocked in the dlm */
 566
 567         set_bit(LFL_DLM_CANCEL, &lp->flags);
 568         set_bit(LFL_ACTIVE, &lp->flags);
 569
 570         error = dlm_unlock(ls->dlm_lockspace, lp->lksb.sb_lkid, DLM_LKF_CANCEL,
 571                            NULL, lp);
 572
 573         log_info("gdlm_cancel rv %d %x,%llx flags %lx", error,
 574                  lp->lockname.ln_type,
 575                  (unsigned long long)lp->lockname.ln_number, lp->flags);
 576
 577         if (error == -EBUSY)
 578                 clear_bit(LFL_DLM_CANCEL, &lp->flags);
 579 }
 580
 581 static int gdlm_add_lvb(struct gdlm_lock *lp)
 582 {
 583         char *lvb;
 584
 585         lvb = kzalloc(GDLM_LVB_SIZE, GFP_NOFS);
 586         if (!lvb)
 587                 return -ENOMEM;
 588
 589         lp->lksb.sb_lvbptr = lvb;
 590         lp->lvb = lvb;
 591         return 0;
 592 }
 593
 594 static void gdlm_del_lvb(struct gdlm_lock *lp)
 595 {
 596         kfree(lp->lvb);
 597         lp->lvb = NULL;
 598         lp->lksb.sb_lvbptr = NULL;
 599 }
 600
 601 static int gdlm_ast_wait(void *word)
 602 {
 603         schedule();
 604         return 0;
 605 }
 606
 607 /* This can do a synchronous dlm request (requiring a lock_dlm thread to get
 608    the completion) because gfs won't call hold_lvb() during a callback (from
 609    the context of a lock_dlm thread). */
 610
 611 static int hold_null_lock(struct gdlm_lock *lp)
 612 {
 613         struct gdlm_lock *lpn = NULL;
 614         int error;
 615
 616         if (lp->hold_null) {
 617                 printk(KERN_INFO "lock_dlm: lvb already held\n");
 618                 return 0;
 619         }
 620
 621         error = gdlm_create_lp(lp->ls, &lp->lockname, &lpn);
 622         if (error)
 623                 goto out;
 624
 625         lpn->lksb.sb_lvbptr = junk_lvb;
 626         lpn->lvb = junk_lvb;
 627
 628         lpn->req = DLM_LOCK_NL;
 629         lpn->lkf = DLM_LKF_VALBLK | DLM_LKF_EXPEDITE;
 630         set_bit(LFL_NOBAST, &lpn->flags);
 631         set_bit(LFL_INLOCK, &lpn->flags);
 632         set_bit(LFL_AST_WAIT, &lpn->flags);
 633
 634         gdlm_do_lock(lpn);
 635         wait_on_bit(&lpn->flags, LFL_AST_WAIT, gdlm_ast_wait, TASK_UNINTERRUPTIBLE);
 636         error = lpn->lksb.sb_status;
 637         if (error) {
 638                 printk(KERN_INFO "lock_dlm: hold_null_lock dlm error %d\n",
 639                        error);
 640                 gdlm_delete_lp(lpn);
 641                 lpn = NULL;
 642         }
 643 out:
 644         lp->hold_null = lpn;
 645         return error;
 646 }
 647
 648 /* This cannot do a synchronous dlm request (requiring a lock_dlm thread to get
 649    the completion) because gfs may call unhold_lvb() during a callback (from
 650    the context of a lock_dlm thread) which could cause a deadlock since the
 651    other lock_dlm thread could be engaged in recovery. */
 652
 653 static void unhold_null_lock(struct gdlm_lock *lp)
 654 {
 655         struct gdlm_lock *lpn = lp->hold_null;
 656
 657         gdlm_assert(lpn, "%x,%llx", lp->lockname.ln_type,
 658                     (unsigned long long)lp->lockname.ln_number);
 659         lpn->lksb.sb_lvbptr = NULL;
 660         lpn->lvb = NULL;
 661         set_bit(LFL_UNLOCK_DELETE, &lpn->flags);
 662         gdlm_do_unlock(lpn);
 663         lp->hold_null = NULL;
 664 }
 665
 666 /* Acquire a NL lock because gfs requires the value block to remain
 667    intact on the resource while the lvb is "held" even if it's holding no locks
 668    on the resource. */
 669
 670 int gdlm_hold_lvb(void *lock, char **lvbp)
 671 {
 672         struct gdlm_lock *lp = lock;
 673         int error;
 674
 675         error = gdlm_add_lvb(lp);
 676         if (error)
 677                 return error;
 678
 679         *lvbp = lp->lvb;
 680
 681         error = hold_null_lock(lp);
 682         if (error)
 683                 gdlm_del_lvb(lp);
 684
 685         return error;
 686 }
 687
 688 void gdlm_unhold_lvb(void *lock, char *lvb)
 689 {
 690         struct gdlm_lock *lp = lock;
 691
 692         unhold_null_lock(lp);
 693         gdlm_del_lvb(lp);
 694 }
 695
 696 void gdlm_submit_delayed(struct gdlm_ls *ls)
 697 {
 698         struct gdlm_lock *lp, *safe;
 699
 700         spin_lock(&ls->async_lock);
 701         list_for_each_entry_safe(lp, safe, &ls->delayed, delay_list) {
 702                 list_del_init(&lp->delay_list);
 703                 list_add_tail(&lp->delay_list, &ls->submit);
 704         }
 705         spin_unlock(&ls->async_lock);
 706         wake_up(&ls->thread_wait);
 707 }
 708