fs/ocfs2/dlm/dlmthread.c

   1 /* -*- mode: c; c-basic-offset: 8; -*-
   2  * vim: noexpandtab sw=8 ts=8 sts=0:
   3  *
   4  * dlmthread.c
   5  *
   6  * standalone DLM module
   7  *
   8  * Copyright (C) 2004 Oracle.  All rights reserved.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2 of the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public
  21  * License along with this program; if not, write to the
  22  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23  * Boston, MA 021110-1307, USA.
  24  *
  25  */
  26
  27
  28 #include <linux/module.h>
  29 #include <linux/fs.h>
  30 #include <linux/types.h>
  31 #include <linux/slab.h>
  32 #include <linux/highmem.h>
  33 #include <linux/utsname.h>
  34 #include <linux/init.h>
  35 #include <linux/sysctl.h>
  36 #include <linux/random.h>
  37 #include <linux/blkdev.h>
  38 #include <linux/socket.h>
  39 #include <linux/inet.h>
  40 #include <linux/timer.h>
  41 #include <linux/kthread.h>
  42 #include <linux/delay.h>
  43
  44
  45 #include "cluster/heartbeat.h"
  46 #include "cluster/nodemanager.h"
  47 #include "cluster/tcp.h"
  48
  49 #include "dlmapi.h"
  50 #include "dlmcommon.h"
  51 #include "dlmdomain.h"
  52
  53 #define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_THREAD)
  54 #include "cluster/masklog.h"
  55
  56 static int dlm_thread(void *data);
  57 static void dlm_flush_asts(struct dlm_ctxt *dlm);
  58
  59 #define dlm_lock_is_remote(dlm, lock)     ((lock)->ml.node != (dlm)->node_num)
  60
  61 /* will exit holding res->spinlock, but may drop in function */
  62 /* waits until flags are cleared on res->state */
  63 void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags)
  64 {
  65         DECLARE_WAITQUEUE(wait, current);
  66
  67         assert_spin_locked(&res->spinlock);
  68
  69         add_wait_queue(&res->wq, &wait);
  70 repeat:
  71         set_current_state(TASK_UNINTERRUPTIBLE);
  72         if (res->state & flags) {
  73                 spin_unlock(&res->spinlock);
  74                 schedule();
  75                 spin_lock(&res->spinlock);
  76                 goto repeat;
  77         }
  78         remove_wait_queue(&res->wq, &wait);
  79         current->state = TASK_RUNNING;
  80 }
  81
  82 int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
  83 {
  84         if (list_empty(&res->granted) &&
  85             list_empty(&res->converting) &&
  86             list_empty(&res->blocked))
  87                 return 0;
  88         return 1;
  89 }
  90
  91 /* "unused": the lockres has no locks, is not on the dirty list,
  92  * has no inflight locks (in the gap between mastery and acquiring
  93  * the first lock), and has no bits in its refmap.
  94  * truly ready to be freed. */
  95 int __dlm_lockres_unused(struct dlm_lock_resource *res)
  96 {
  97         if (!__dlm_lockres_has_locks(res) &&
  98             list_empty(&res->dirty)) {
  99                 /* try not to scan the bitmap unless the first two
 100                  * conditions are already true */
 101                 int bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
 102                 if (bit >= O2NM_MAX_NODES) {
 103                         /* since the bit for dlm->node_num is not
 104                          * set, inflight_locks better be zero */
 105                         BUG_ON(res->inflight_locks != 0);
 106                         return 1;
 107                 }
 108         }
 109         return 0;
 110 }
 111
 112
 113 /* Call whenever you may have added or deleted something from one of
 114  * the lockres queue's. This will figure out whether it belongs on the
 115  * unused list or not and does the appropriate thing. */
 116 void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
 117                               struct dlm_lock_resource *res)
 118 {
 119         mlog_entry("%.*s\n", res->lockname.len, res->lockname.name);
 120
 121         assert_spin_locked(&dlm->spinlock);
 122         assert_spin_locked(&res->spinlock);
 123
 124         if (__dlm_lockres_unused(res)){
 125                 if (list_empty(&res->purge)) {
 126                         mlog(0, "putting lockres %.*s:%p onto purge list\n",
 127                              res->lockname.len, res->lockname.name, res);
 128
 129                         res->last_used = jiffies;
 130                         dlm_lockres_get(res);
 131                         list_add_tail(&res->purge, &dlm->purge_list);
 132                         dlm->purge_count++;
 133                 }
 134         } else if (!list_empty(&res->purge)) {
 135                 mlog(0, "removing lockres %.*s:%p from purge list, owner=%u\n",
 136                      res->lockname.len, res->lockname.name, res, res->owner);
 137
 138                 list_del_init(&res->purge);
 139                 dlm_lockres_put(res);
 140                 dlm->purge_count--;
 141         }
 142 }
 143
 144 void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
 145                             struct dlm_lock_resource *res)
 146 {
 147         mlog_entry("%.*s\n", res->lockname.len, res->lockname.name);
 148         spin_lock(&dlm->spinlock);
 149         spin_lock(&res->spinlock);
 150
 151         __dlm_lockres_calc_usage(dlm, res);
 152
 153         spin_unlock(&res->spinlock);
 154         spin_unlock(&dlm->spinlock);
 155 }
 156
 157 int dlm_purge_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 158 {
 159         int master;
 160         int ret = 0;
 161
 162         spin_lock(&res->spinlock);
 163         if (!__dlm_lockres_unused(res)) {
 164                 spin_unlock(&res->spinlock);
 165                 mlog(0, "%s:%.*s: tried to purge but not unused\n",
 166                      dlm->name, res->lockname.len, res->lockname.name);
 167                 return -ENOTEMPTY;
 168         }
 169         master = (res->owner == dlm->node_num);
 170         if (!master)
 171                 res->state |= DLM_LOCK_RES_DROPPING_REF;
 172         spin_unlock(&res->spinlock);
 173
 174         mlog(0, "purging lockres %.*s, master = %d\n", res->lockname.len,
 175              res->lockname.name, master);
 176
 177         if (!master) {
 178                 /* drop spinlock to do messaging, retake below */
 179                 spin_unlock(&dlm->spinlock);
 180                 /* clear our bit from the master's refmap, ignore errors */
 181                 ret = dlm_drop_lockres_ref(dlm, res);
 182                 if (ret < 0) {
 183                         mlog_errno(ret);
 184                         if (!dlm_is_host_down(ret))
 185                                 BUG();
 186                 }
 187                 mlog(0, "%s:%.*s: dlm_deref_lockres returned %d\n",
 188                      dlm->name, res->lockname.len, res->lockname.name, ret);
 189                 spin_lock(&dlm->spinlock);
 190         }
 191
 192         if (!list_empty(&res->purge)) {
 193                 mlog(0, "removing lockres %.*s:%p from purgelist, "
 194                      "master = %d\n", res->lockname.len, res->lockname.name,
 195                      res, master);
 196                 list_del_init(&res->purge);
 197                 dlm_lockres_put(res);
 198                 dlm->purge_count--;
 199         }
 200         __dlm_unhash_lockres(res);
 201
 202         /* lockres is not in the hash now.  drop the flag and wake up
 203          * any processes waiting in dlm_get_lock_resource. */
 204         if (!master) {
 205                 spin_lock(&res->spinlock);
 206                 res->state &= ~DLM_LOCK_RES_DROPPING_REF;
 207                 spin_unlock(&res->spinlock);
 208                 wake_up(&res->wq);
 209         }
 210         return 0;
 211 }
 212
 213 static void dlm_run_purge_list(struct dlm_ctxt *dlm,
 214                                int purge_now)
 215 {
 216         unsigned int run_max, unused;
 217         unsigned long purge_jiffies;
 218         struct dlm_lock_resource *lockres;
 219
 220         spin_lock(&dlm->spinlock);
 221         run_max = dlm->purge_count;
 222
 223         while(run_max && !list_empty(&dlm->purge_list)) {
 224                 run_max--;
 225
 226                 lockres = list_entry(dlm->purge_list.next,
 227                                      struct dlm_lock_resource, purge);
 228
 229                 /* Status of the lockres *might* change so double
 230                  * check. If the lockres is unused, holding the dlm
 231                  * spinlock will prevent people from getting and more
 232                  * refs on it -- there's no need to keep the lockres
 233                  * spinlock. */
 234                 spin_lock(&lockres->spinlock);
 235                 unused = __dlm_lockres_unused(lockres);
 236                 spin_unlock(&lockres->spinlock);
 237
 238                 if (!unused)
 239                         continue;
 240
 241                 purge_jiffies = lockres->last_used +
 242                         msecs_to_jiffies(DLM_PURGE_INTERVAL_MS);
 243
 244                 /* Make sure that we want to be processing this guy at
 245                  * this time. */
 246                 if (!purge_now && time_after(purge_jiffies, jiffies)) {
 247                         /* Since resources are added to the purge list
 248                          * in tail order, we can stop at the first
 249                          * unpurgable resource -- anyone added after
 250                          * him will have a greater last_used value */
 251                         break;
 252                 }
 253
 254                 mlog(0, "removing lockres %.*s:%p from purgelist\n",
 255                      lockres->lockname.len, lockres->lockname.name, lockres);
 256                 list_del_init(&lockres->purge);
 257                 dlm_lockres_put(lockres);
 258                 dlm->purge_count--;
 259
 260                 /* This may drop and reacquire the dlm spinlock if it
 261                  * has to do migration. */
 262                 mlog(0, "calling dlm_purge_lockres!\n");
 263                 if (dlm_purge_lockres(dlm, lockres))
 264                         BUG();
 265                 mlog(0, "DONE calling dlm_purge_lockres!\n");
 266
 267                 /* Avoid adding any scheduling latencies */
 268                 cond_resched_lock(&dlm->spinlock);
 269         }
 270
 271         spin_unlock(&dlm->spinlock);
 272 }
 273
 274 static void dlm_shuffle_lists(struct dlm_ctxt *dlm,
 275                               struct dlm_lock_resource *res)
 276 {
 277         struct dlm_lock *lock, *target;
 278         struct list_head *iter;
 279         struct list_head *head;
 280         int can_grant = 1;
 281
 282         //mlog(0, "res->lockname.len=%d\n", res->lockname.len);
 283         //mlog(0, "res->lockname.name=%p\n", res->lockname.name);
 284         //mlog(0, "shuffle res %.*s\n", res->lockname.len,
 285         //        res->lockname.name);
 286
 287         /* because this function is called with the lockres
 288          * spinlock, and because we know that it is not migrating/
 289          * recovering/in-progress, it is fine to reserve asts and
 290          * basts right before queueing them all throughout */
 291         assert_spin_locked(&res->spinlock);
 292         BUG_ON((res->state & (DLM_LOCK_RES_MIGRATING|
 293                               DLM_LOCK_RES_RECOVERING|
 294                               DLM_LOCK_RES_IN_PROGRESS)));
 295
 296 converting:
 297         if (list_empty(&res->converting))
 298                 goto blocked;
 299         mlog(0, "res %.*s has locks on a convert queue\n", res->lockname.len,
 300              res->lockname.name);
 301
 302         target = list_entry(res->converting.next, struct dlm_lock, list);
 303         if (target->ml.convert_type == LKM_IVMODE) {
 304                 mlog(ML_ERROR, "%.*s: converting a lock with no "
 305                      "convert_type!\n", res->lockname.len, res->lockname.name);
 306                 BUG();
 307         }
 308         head = &res->granted;
 309         list_for_each(iter, head) {
 310                 lock = list_entry(iter, struct dlm_lock, list);
 311                 if (lock==target)
 312                         continue;
 313                 if (!dlm_lock_compatible(lock->ml.type,
 314                                          target->ml.convert_type)) {
 315                         can_grant = 0;
 316                         /* queue the BAST if not already */
 317                         if (lock->ml.highest_blocked == LKM_IVMODE) {
 318                                 __dlm_lockres_reserve_ast(res);
 319                                 dlm_queue_bast(dlm, lock);
 320                         }
 321                         /* update the highest_blocked if needed */
 322                         if (lock->ml.highest_blocked < target->ml.convert_type)
 323                                 lock->ml.highest_blocked =
 324                                         target->ml.convert_type;
 325                 }
 326         }
 327         head = &res->converting;
 328         list_for_each(iter, head) {
 329                 lock = list_entry(iter, struct dlm_lock, list);
 330                 if (lock==target)
 331                         continue;
 332                 if (!dlm_lock_compatible(lock->ml.type,
 333                                          target->ml.convert_type)) {
 334                         can_grant = 0;
 335                         if (lock->ml.highest_blocked == LKM_IVMODE) {
 336                                 __dlm_lockres_reserve_ast(res);
 337                                 dlm_queue_bast(dlm, lock);
 338                         }
 339                         if (lock->ml.highest_blocked < target->ml.convert_type)
 340                                 lock->ml.highest_blocked =
 341                                         target->ml.convert_type;
 342                 }
 343         }
 344
 345         /* we can convert the lock */
 346         if (can_grant) {
 347                 spin_lock(&target->spinlock);
 348                 BUG_ON(target->ml.highest_blocked != LKM_IVMODE);
 349
 350                 mlog(0, "calling ast for converting lock: %.*s, have: %d, "
 351                      "granting: %d, node: %u\n", res->lockname.len,
 352                      res->lockname.name, target->ml.type,
 353                      target->ml.convert_type, target->ml.node);
 354
 355                 target->ml.type = target->ml.convert_type;
 356                 target->ml.convert_type = LKM_IVMODE;
 357                 list_move_tail(&target->list, &res->granted);
 358
 359                 BUG_ON(!target->lksb);
 360                 target->lksb->status = DLM_NORMAL;
 361
 362                 spin_unlock(&target->spinlock);
 363
 364                 __dlm_lockres_reserve_ast(res);
 365                 dlm_queue_ast(dlm, target);
 366                 /* go back and check for more */
 367                 goto converting;
 368         }
 369
 370 blocked:
 371         if (list_empty(&res->blocked))
 372                 goto leave;
 373         target = list_entry(res->blocked.next, struct dlm_lock, list);
 374
 375         head = &res->granted;
 376         list_for_each(iter, head) {
 377                 lock = list_entry(iter, struct dlm_lock, list);
 378                 if (lock==target)
 379                         continue;
 380                 if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
 381                         can_grant = 0;
 382                         if (lock->ml.highest_blocked == LKM_IVMODE) {
 383                                 __dlm_lockres_reserve_ast(res);
 384                                 dlm_queue_bast(dlm, lock);
 385                         }
 386                         if (lock->ml.highest_blocked < target->ml.type)
 387                                 lock->ml.highest_blocked = target->ml.type;
 388                 }
 389         }
 390
 391         head = &res->converting;
 392         list_for_each(iter, head) {
 393                 lock = list_entry(iter, struct dlm_lock, list);
 394                 if (lock==target)
 395                         continue;
 396                 if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
 397                         can_grant = 0;
 398                         if (lock->ml.highest_blocked == LKM_IVMODE) {
 399                                 __dlm_lockres_reserve_ast(res);
 400                                 dlm_queue_bast(dlm, lock);
 401                         }
 402                         if (lock->ml.highest_blocked < target->ml.type)
 403                                 lock->ml.highest_blocked = target->ml.type;
 404                 }
 405         }
 406
 407         /* we can grant the blocked lock (only
 408          * possible if converting list empty) */
 409         if (can_grant) {
 410                 spin_lock(&target->spinlock);
 411                 BUG_ON(target->ml.highest_blocked != LKM_IVMODE);
 412
 413                 mlog(0, "calling ast for blocked lock: %.*s, granting: %d, "
 414                      "node: %u\n", res->lockname.len, res->lockname.name,
 415                      target->ml.type, target->ml.node);
 416
 417                 // target->ml.type is already correct
 418                 list_move_tail(&target->list, &res->granted);
 419
 420                 BUG_ON(!target->lksb);
 421                 target->lksb->status = DLM_NORMAL;
 422
 423                 spin_unlock(&target->spinlock);
 424
 425                 __dlm_lockres_reserve_ast(res);
 426                 dlm_queue_ast(dlm, target);
 427                 /* go back and check for more */
 428                 goto converting;
 429         }
 430
 431 leave:
 432         return;
 433 }
 434
 435 /* must have NO locks when calling this with res !=NULL * */
 436 void dlm_kick_thread(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 437 {
 438         mlog_entry("dlm=%p, res=%p\n", dlm, res);
 439         if (res) {
 440                 spin_lock(&dlm->spinlock);
 441                 spin_lock(&res->spinlock);
 442                 __dlm_dirty_lockres(dlm, res);
 443                 spin_unlock(&res->spinlock);
 444                 spin_unlock(&dlm->spinlock);
 445         }
 446         wake_up(&dlm->dlm_thread_wq);
 447 }
 448
 449 void __dlm_dirty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 450 {
 451         mlog_entry("dlm=%p, res=%p\n", dlm, res);
 452
 453         assert_spin_locked(&dlm->spinlock);
 454         assert_spin_locked(&res->spinlock);
 455
 456         /* don't shuffle secondary queues */
 457         if ((res->owner == dlm->node_num) &&
 458             !(res->state & DLM_LOCK_RES_DIRTY)) {
 459                 /* ref for dirty_list */
 460                 dlm_lockres_get(res);
 461                 list_add_tail(&res->dirty, &dlm->dirty_list);
 462                 res->state |= DLM_LOCK_RES_DIRTY;
 463         }
 464 }
 465
 466
 467 /* Launch the NM thread for the mounted volume */
 468 int dlm_launch_thread(struct dlm_ctxt *dlm)
 469 {
 470         mlog(0, "starting dlm thread...\n");
 471
 472         dlm->dlm_thread_task = kthread_run(dlm_thread, dlm, "dlm_thread");
 473         if (IS_ERR(dlm->dlm_thread_task)) {
 474                 mlog_errno(PTR_ERR(dlm->dlm_thread_task));
 475                 dlm->dlm_thread_task = NULL;
 476                 return -EINVAL;
 477         }
 478
 479         return 0;
 480 }
 481
 482 void dlm_complete_thread(struct dlm_ctxt *dlm)
 483 {
 484         if (dlm->dlm_thread_task) {
 485                 mlog(ML_KTHREAD, "waiting for dlm thread to exit\n");
 486                 kthread_stop(dlm->dlm_thread_task);
 487                 dlm->dlm_thread_task = NULL;
 488         }
 489 }
 490
 491 static int dlm_dirty_list_empty(struct dlm_ctxt *dlm)
 492 {
 493         int empty;
 494
 495         spin_lock(&dlm->spinlock);
 496         empty = list_empty(&dlm->dirty_list);
 497         spin_unlock(&dlm->spinlock);
 498
 499         return empty;
 500 }
 501
 502 static void dlm_flush_asts(struct dlm_ctxt *dlm)
 503 {
 504         int ret;
 505         struct dlm_lock *lock;
 506         struct dlm_lock_resource *res;
 507         u8 hi;
 508
 509         spin_lock(&dlm->ast_lock);
 510         while (!list_empty(&dlm->pending_asts)) {
 511                 lock = list_entry(dlm->pending_asts.next,
 512                                   struct dlm_lock, ast_list);
 513                 /* get an extra ref on lock */
 514                 dlm_lock_get(lock);
 515                 res = lock->lockres;
 516                 mlog(0, "delivering an ast for this lockres\n");
 517
 518                 BUG_ON(!lock->ast_pending);
 519
 520                 /* remove from list (including ref) */
 521                 list_del_init(&lock->ast_list);
 522                 dlm_lock_put(lock);
 523                 spin_unlock(&dlm->ast_lock);
 524
 525                 if (lock->ml.node != dlm->node_num) {
 526                         ret = dlm_do_remote_ast(dlm, res, lock);
 527                         if (ret < 0)
 528                                 mlog_errno(ret);
 529                 } else
 530                         dlm_do_local_ast(dlm, res, lock);
 531
 532                 spin_lock(&dlm->ast_lock);
 533
 534                 /* possible that another ast was queued while
 535                  * we were delivering the last one */
 536                 if (!list_empty(&lock->ast_list)) {
 537                         mlog(0, "aha another ast got queued while "
 538                              "we were finishing the last one.  will "
 539                              "keep the ast_pending flag set.\n");
 540                 } else
 541                         lock->ast_pending = 0;
 542
 543                 /* drop the extra ref.
 544                  * this may drop it completely. */
 545                 dlm_lock_put(lock);
 546                 dlm_lockres_release_ast(dlm, res);
 547         }
 548
 549         while (!list_empty(&dlm->pending_basts)) {
 550                 lock = list_entry(dlm->pending_basts.next,
 551                                   struct dlm_lock, bast_list);
 552                 /* get an extra ref on lock */
 553                 dlm_lock_get(lock);
 554                 res = lock->lockres;
 555
 556                 BUG_ON(!lock->bast_pending);
 557
 558                 /* get the highest blocked lock, and reset */
 559                 spin_lock(&lock->spinlock);
 560                 BUG_ON(lock->ml.highest_blocked <= LKM_IVMODE);
 561                 hi = lock->ml.highest_blocked;
 562                 lock->ml.highest_blocked = LKM_IVMODE;
 563                 spin_unlock(&lock->spinlock);
 564
 565                 /* remove from list (including ref) */
 566                 list_del_init(&lock->bast_list);
 567                 dlm_lock_put(lock);
 568                 spin_unlock(&dlm->ast_lock);
 569
 570                 mlog(0, "delivering a bast for this lockres "
 571                      "(blocked = %d\n", hi);
 572
 573                 if (lock->ml.node != dlm->node_num) {
 574                         ret = dlm_send_proxy_bast(dlm, res, lock, hi);
 575                         if (ret < 0)
 576                                 mlog_errno(ret);
 577                 } else
 578                         dlm_do_local_bast(dlm, res, lock, hi);
 579
 580                 spin_lock(&dlm->ast_lock);
 581
 582                 /* possible that another bast was queued while
 583                  * we were delivering the last one */
 584                 if (!list_empty(&lock->bast_list)) {
 585                         mlog(0, "aha another bast got queued while "
 586                              "we were finishing the last one.  will "
 587                              "keep the bast_pending flag set.\n");
 588                 } else
 589                         lock->bast_pending = 0;
 590
 591                 /* drop the extra ref.
 592                  * this may drop it completely. */
 593                 dlm_lock_put(lock);
 594                 dlm_lockres_release_ast(dlm, res);
 595         }
 596         wake_up(&dlm->ast_wq);
 597         spin_unlock(&dlm->ast_lock);
 598 }
 599
 600
 601 #define DLM_THREAD_TIMEOUT_MS (4 * 1000)
 602 #define DLM_THREAD_MAX_DIRTY  100
 603 #define DLM_THREAD_MAX_ASTS   10
 604
 605 static int dlm_thread(void *data)
 606 {
 607         struct dlm_lock_resource *res;
 608         struct dlm_ctxt *dlm = data;
 609         unsigned long timeout = msecs_to_jiffies(DLM_THREAD_TIMEOUT_MS);
 610
 611         mlog(0, "dlm thread running for %s...\n", dlm->name);
 612
 613         while (!kthread_should_stop()) {
 614                 int n = DLM_THREAD_MAX_DIRTY;
 615
 616                 /* dlm_shutting_down is very point-in-time, but that
 617                  * doesn't matter as we'll just loop back around if we
 618                  * get false on the leading edge of a state
 619                  * transition. */
 620                 dlm_run_purge_list(dlm, dlm_shutting_down(dlm));
 621
 622                 /* We really don't want to hold dlm->spinlock while
 623                  * calling dlm_shuffle_lists on each lockres that
 624                  * needs to have its queues adjusted and AST/BASTs
 625                  * run.  So let's pull each entry off the dirty_list
 626                  * and drop dlm->spinlock ASAP.  Once off the list,
 627                  * res->spinlock needs to be taken again to protect
 628                  * the queues while calling dlm_shuffle_lists.  */
 629                 spin_lock(&dlm->spinlock);
 630                 while (!list_empty(&dlm->dirty_list)) {
 631                         int delay = 0;
 632                         res = list_entry(dlm->dirty_list.next,
 633                                          struct dlm_lock_resource, dirty);
 634
 635                         /* peel a lockres off, remove it from the list,
 636                          * unset the dirty flag and drop the dlm lock */
 637                         BUG_ON(!res);
 638                         dlm_lockres_get(res);
 639
 640                         spin_lock(&res->spinlock);
 641                         res->state &= ~DLM_LOCK_RES_DIRTY;
 642                         list_del_init(&res->dirty);
 643                         spin_unlock(&res->spinlock);
 644                         spin_unlock(&dlm->spinlock);
 645                         /* Drop dirty_list ref */
 646                         dlm_lockres_put(res);
 647
 648                         /* lockres can be re-dirtied/re-added to the
 649                          * dirty_list in this gap, but that is ok */
 650
 651                         spin_lock(&res->spinlock);
 652                         if (res->owner != dlm->node_num) {
 653                                 __dlm_print_one_lock_resource(res);
 654                                 mlog(ML_ERROR, "inprog:%s, mig:%s, reco:%s, dirty:%s\n",
 655                                      res->state & DLM_LOCK_RES_IN_PROGRESS ? "yes" : "no",
 656                                      res->state & DLM_LOCK_RES_MIGRATING ? "yes" : "no",
 657                                      res->state & DLM_LOCK_RES_RECOVERING ? "yes" : "no",
 658                                      res->state & DLM_LOCK_RES_DIRTY ? "yes" : "no");
 659                         }
 660                         BUG_ON(res->owner != dlm->node_num);
 661
 662                         /* it is now ok to move lockreses in these states
 663                          * to the dirty list, assuming that they will only be
 664                          * dirty for a short while. */
 665                         if (res->state & (DLM_LOCK_RES_IN_PROGRESS |
 666                                           DLM_LOCK_RES_MIGRATING |
 667                                           DLM_LOCK_RES_RECOVERING)) {
 668                                 /* move it to the tail and keep going */
 669                                 spin_unlock(&res->spinlock);
 670                                 mlog(0, "delaying list shuffling for in-"
 671                                      "progress lockres %.*s, state=%d\n",
 672                                      res->lockname.len, res->lockname.name,
 673                                      res->state);
 674                                 delay = 1;
 675                                 goto in_progress;
 676                         }
 677
 678                         /* at this point the lockres is not migrating/
 679                          * recovering/in-progress.  we have the lockres
 680                          * spinlock and do NOT have the dlm lock.
 681                          * safe to reserve/queue asts and run the lists. */
 682
 683                         mlog(0, "calling dlm_shuffle_lists with dlm=%s, "
 684                              "res=%.*s\n", dlm->name,
 685                              res->lockname.len, res->lockname.name);
 686
 687                         /* called while holding lockres lock */
 688                         dlm_shuffle_lists(dlm, res);
 689                         spin_unlock(&res->spinlock);
 690
 691                         dlm_lockres_calc_usage(dlm, res);
 692
 693 in_progress:
 694
 695                         spin_lock(&dlm->spinlock);
 696                         /* if the lock was in-progress, stick
 697                          * it on the back of the list */
 698                         if (delay) {
 699                                 /* ref for dirty_list */
 700                                 dlm_lockres_get(res);
 701                                 spin_lock(&res->spinlock);
 702                                 list_add_tail(&res->dirty, &dlm->dirty_list);
 703                                 res->state |= DLM_LOCK_RES_DIRTY;
 704                                 spin_unlock(&res->spinlock);
 705                         }
 706                         dlm_lockres_put(res);
 707
 708                         /* unlikely, but we may need to give time to
 709                          * other tasks */
 710                         if (!--n) {
 711                                 mlog(0, "throttling dlm_thread\n");
 712                                 break;
 713                         }
 714                 }
 715
 716                 spin_unlock(&dlm->spinlock);
 717                 dlm_flush_asts(dlm);
 718
 719                 /* yield and continue right away if there is more work to do */
 720                 if (!n) {
 721                         cond_resched();
 722                         continue;
 723                 }
 724
 725                 wait_event_interruptible_timeout(dlm->dlm_thread_wq,
 726                                                  !dlm_dirty_list_empty(dlm) ||
 727                                                  kthread_should_stop(),
 728                                                  timeout);
 729         }
 730
 731         mlog(0, "quitting DLM thread\n");
 732         return 0;
 733 }