kernel/fs/ocfs2/dlmfs/userdlm.c

   1 /* -*- mode: c; c-basic-offset: 8; -*-
   2  * vim: noexpandtab sw=8 ts=8 sts=0:
   3  *
   4  * userdlm.c
   5  *
   6  * Code which implements the kernel side of a minimal userspace
   7  * interface to our DLM.
   8  *
   9  * Many of the functions here are pared down versions of dlmglue.c
  10  * functions.
  11  *
  12  * Copyright (C) 2003, 2004 Oracle.  All rights reserved.
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public
  16  * License as published by the Free Software Foundation; either
  17  * version 2 of the License, or (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22  * General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public
  25  * License along with this program; if not, write to the
  26  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  27  * Boston, MA 021110-1307, USA.
  28  */
  29
  30 #include <linux/signal.h>
  31
  32 #include <linux/module.h>
  33 #include <linux/fs.h>
  34 #include <linux/types.h>
  35 #include <linux/crc32.h>
  36
  37 #include "ocfs2_lockingver.h"
  38 #include "stackglue.h"
  39 #include "userdlm.h"
  40
  41 #define MLOG_MASK_PREFIX ML_DLMFS
  42 #include "cluster/masklog.h"
  43
  44
  45 static inline struct user_lock_res *user_lksb_to_lock_res(struct ocfs2_dlm_lksb *lksb)
  46 {
  47         return container_of(lksb, struct user_lock_res, l_lksb);
  48 }
  49
  50 static inline int user_check_wait_flag(struct user_lock_res *lockres,
  51                                        int flag)
  52 {
  53         int ret;
  54
  55         spin_lock(&lockres->l_lock);
  56         ret = lockres->l_flags & flag;
  57         spin_unlock(&lockres->l_lock);
  58
  59         return ret;
  60 }
  61
  62 static inline void user_wait_on_busy_lock(struct user_lock_res *lockres)
  63
  64 {
  65         wait_event(lockres->l_event,
  66                    !user_check_wait_flag(lockres, USER_LOCK_BUSY));
  67 }
  68
  69 static inline void user_wait_on_blocked_lock(struct user_lock_res *lockres)
  70
  71 {
  72         wait_event(lockres->l_event,
  73                    !user_check_wait_flag(lockres, USER_LOCK_BLOCKED));
  74 }
  75
  76 /* I heart container_of... */
  77 static inline struct ocfs2_cluster_connection *
  78 cluster_connection_from_user_lockres(struct user_lock_res *lockres)
  79 {
  80         struct dlmfs_inode_private *ip;
  81
  82         ip = container_of(lockres,
  83                           struct dlmfs_inode_private,
  84                           ip_lockres);
  85         return ip->ip_conn;
  86 }
  87
  88 static struct inode *
  89 user_dlm_inode_from_user_lockres(struct user_lock_res *lockres)
  90 {
  91         struct dlmfs_inode_private *ip;
  92
  93         ip = container_of(lockres,
  94                           struct dlmfs_inode_private,
  95                           ip_lockres);
  96         return &ip->ip_vfs_inode;
  97 }
  98
  99 static inline void user_recover_from_dlm_error(struct user_lock_res *lockres)
 100 {
 101         spin_lock(&lockres->l_lock);
 102         lockres->l_flags &= ~USER_LOCK_BUSY;
 103         spin_unlock(&lockres->l_lock);
 104 }
 105
 106 #define user_log_dlm_error(_func, _stat, _lockres) do {                 \
 107         mlog(ML_ERROR, "Dlm error %d while calling %s on "              \
 108                 "resource %.*s\n", _stat, _func,                        \
 109                 _lockres->l_namelen, _lockres->l_name);                 \
 110 } while (0)
 111
 112 /* WARNING: This function lives in a world where the only three lock
 113  * levels are EX, PR, and NL. It *will* have to be adjusted when more
 114  * lock types are added. */
 115 static inline int user_highest_compat_lock_level(int level)
 116 {
 117         int new_level = DLM_LOCK_EX;
 118
 119         if (level == DLM_LOCK_EX)
 120                 new_level = DLM_LOCK_NL;
 121         else if (level == DLM_LOCK_PR)
 122                 new_level = DLM_LOCK_PR;
 123         return new_level;
 124 }
 125
 126 static void user_ast(struct ocfs2_dlm_lksb *lksb)
 127 {
 128         struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
 129         int status;
 130
 131         mlog(ML_BASTS, "AST fired for lockres %.*s, level %d => %d\n",
 132              lockres->l_namelen, lockres->l_name, lockres->l_level,
 133              lockres->l_requested);
 134
 135         spin_lock(&lockres->l_lock);
 136
 137         status = ocfs2_dlm_lock_status(&lockres->l_lksb);
 138         if (status) {
 139                 mlog(ML_ERROR, "lksb status value of %u on lockres %.*s\n",
 140                      status, lockres->l_namelen, lockres->l_name);
 141                 spin_unlock(&lockres->l_lock);
 142                 return;
 143         }
 144
 145         mlog_bug_on_msg(lockres->l_requested == DLM_LOCK_IV,
 146                         "Lockres %.*s, requested ivmode. flags 0x%x\n",
 147                         lockres->l_namelen, lockres->l_name, lockres->l_flags);
 148
 149         /* we're downconverting. */
 150         if (lockres->l_requested < lockres->l_level) {
 151                 if (lockres->l_requested <=
 152                     user_highest_compat_lock_level(lockres->l_blocking)) {
 153                         lockres->l_blocking = DLM_LOCK_NL;
 154                         lockres->l_flags &= ~USER_LOCK_BLOCKED;
 155                 }
 156         }
 157
 158         lockres->l_level = lockres->l_requested;
 159         lockres->l_requested = DLM_LOCK_IV;
 160         lockres->l_flags |= USER_LOCK_ATTACHED;
 161         lockres->l_flags &= ~USER_LOCK_BUSY;
 162
 163         spin_unlock(&lockres->l_lock);
 164
 165         wake_up(&lockres->l_event);
 166 }
 167
 168 static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
 169 {
 170         struct inode *inode;
 171         inode = user_dlm_inode_from_user_lockres(lockres);
 172         if (!igrab(inode))
 173                 BUG();
 174 }
 175
 176 static void user_dlm_unblock_lock(struct work_struct *work);
 177
 178 static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
 179 {
 180         if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
 181                 user_dlm_grab_inode_ref(lockres);
 182
 183                 INIT_WORK(&lockres->l_work, user_dlm_unblock_lock);
 184
 185                 queue_work(user_dlm_worker, &lockres->l_work);
 186                 lockres->l_flags |= USER_LOCK_QUEUED;
 187         }
 188 }
 189
 190 static void __user_dlm_cond_queue_lockres(struct user_lock_res *lockres)
 191 {
 192         int queue = 0;
 193
 194         if (!(lockres->l_flags & USER_LOCK_BLOCKED))
 195                 return;
 196
 197         switch (lockres->l_blocking) {
 198         case DLM_LOCK_EX:
 199                 if (!lockres->l_ex_holders && !lockres->l_ro_holders)
 200                         queue = 1;
 201                 break;
 202         case DLM_LOCK_PR:
 203                 if (!lockres->l_ex_holders)
 204                         queue = 1;
 205                 break;
 206         default:
 207                 BUG();
 208         }
 209
 210         if (queue)
 211                 __user_dlm_queue_lockres(lockres);
 212 }
 213
 214 static void user_bast(struct ocfs2_dlm_lksb *lksb, int level)
 215 {
 216         struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
 217
 218         mlog(ML_BASTS, "BAST fired for lockres %.*s, blocking %d, level %d\n",
 219              lockres->l_namelen, lockres->l_name, level, lockres->l_level);
 220
 221         spin_lock(&lockres->l_lock);
 222         lockres->l_flags |= USER_LOCK_BLOCKED;
 223         if (level > lockres->l_blocking)
 224                 lockres->l_blocking = level;
 225
 226         __user_dlm_queue_lockres(lockres);
 227         spin_unlock(&lockres->l_lock);
 228
 229         wake_up(&lockres->l_event);
 230 }
 231
 232 static void user_unlock_ast(struct ocfs2_dlm_lksb *lksb, int status)
 233 {
 234         struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
 235
 236         mlog(ML_BASTS, "UNLOCK AST fired for lockres %.*s, flags 0x%x\n",
 237              lockres->l_namelen, lockres->l_name, lockres->l_flags);
 238
 239         if (status)
 240                 mlog(ML_ERROR, "dlm returns status %d\n", status);
 241
 242         spin_lock(&lockres->l_lock);
 243         /* The teardown flag gets set early during the unlock process,
 244          * so test the cancel flag to make sure that this ast isn't
 245          * for a concurrent cancel. */
 246         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN
 247             && !(lockres->l_flags & USER_LOCK_IN_CANCEL)) {
 248                 lockres->l_level = DLM_LOCK_IV;
 249         } else if (status == DLM_CANCELGRANT) {
 250                 /* We tried to cancel a convert request, but it was
 251                  * already granted. Don't clear the busy flag - the
 252                  * ast should've done this already. */
 253                 BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
 254                 lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 255                 goto out_noclear;
 256         } else {
 257                 BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
 258                 /* Cancel succeeded, we want to re-queue */
 259                 lockres->l_requested = DLM_LOCK_IV; /* cancel an
 260                                                     * upconvert
 261                                                     * request. */
 262                 lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 263                 /* we want the unblock thread to look at it again
 264                  * now. */
 265                 if (lockres->l_flags & USER_LOCK_BLOCKED)
 266                         __user_dlm_queue_lockres(lockres);
 267         }
 268
 269         lockres->l_flags &= ~USER_LOCK_BUSY;
 270 out_noclear:
 271         spin_unlock(&lockres->l_lock);
 272
 273         wake_up(&lockres->l_event);
 274 }
 275
 276 /*
 277  * This is the userdlmfs locking protocol version.
 278  *
 279  * See fs/ocfs2/dlmglue.c for more details on locking versions.
 280  */
 281 static struct ocfs2_locking_protocol user_dlm_lproto = {
 282         .lp_max_version = {
 283                 .pv_major = OCFS2_LOCKING_PROTOCOL_MAJOR,
 284                 .pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
 285         },
 286         .lp_lock_ast            = user_ast,
 287         .lp_blocking_ast        = user_bast,
 288         .lp_unlock_ast          = user_unlock_ast,
 289 };
 290
 291 static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
 292 {
 293         struct inode *inode;
 294         inode = user_dlm_inode_from_user_lockres(lockres);
 295         iput(inode);
 296 }
 297
 298 static void user_dlm_unblock_lock(struct work_struct *work)
 299 {
 300         int new_level, status;
 301         struct user_lock_res *lockres =
 302                 container_of(work, struct user_lock_res, l_work);
 303         struct ocfs2_cluster_connection *conn =
 304                 cluster_connection_from_user_lockres(lockres);
 305
 306         mlog(0, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);
 307
 308         spin_lock(&lockres->l_lock);
 309
 310         mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
 311                         "Lockres %.*s, flags 0x%x\n",
 312                         lockres->l_namelen, lockres->l_name, lockres->l_flags);
 313
 314         /* notice that we don't clear USER_LOCK_BLOCKED here. If it's
 315          * set, we want user_ast clear it. */
 316         lockres->l_flags &= ~USER_LOCK_QUEUED;
 317
 318         /* It's valid to get here and no longer be blocked - if we get
 319          * several basts in a row, we might be queued by the first
 320          * one, the unblock thread might run and clear the queued
 321          * flag, and finally we might get another bast which re-queues
 322          * us before our ast for the downconvert is called. */
 323         if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
 324                 mlog(ML_BASTS, "lockres %.*s USER_LOCK_BLOCKED\n",
 325                      lockres->l_namelen, lockres->l_name);
 326                 spin_unlock(&lockres->l_lock);
 327                 goto drop_ref;
 328         }
 329
 330         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
 331                 mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_TEARDOWN\n",
 332                      lockres->l_namelen, lockres->l_name);
 333                 spin_unlock(&lockres->l_lock);
 334                 goto drop_ref;
 335         }
 336
 337         if (lockres->l_flags & USER_LOCK_BUSY) {
 338                 if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
 339                         mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_CANCEL\n",
 340                              lockres->l_namelen, lockres->l_name);
 341                         spin_unlock(&lockres->l_lock);
 342                         goto drop_ref;
 343                 }
 344
 345                 lockres->l_flags |= USER_LOCK_IN_CANCEL;
 346                 spin_unlock(&lockres->l_lock);
 347
 348                 status = ocfs2_dlm_unlock(conn, &lockres->l_lksb,
 349                                           DLM_LKF_CANCEL);
 350                 if (status)
 351                         user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
 352                 goto drop_ref;
 353         }
 354
 355         /* If there are still incompat holders, we can exit safely
 356          * without worrying about re-queueing this lock as that will
 357          * happen on the last call to user_cluster_unlock. */
 358         if ((lockres->l_blocking == DLM_LOCK_EX)
 359             && (lockres->l_ex_holders || lockres->l_ro_holders)) {
 360                 spin_unlock(&lockres->l_lock);
 361                 mlog(ML_BASTS, "lockres %.*s, EX/PR Holders %u,%u\n",
 362                      lockres->l_namelen, lockres->l_name,
 363                      lockres->l_ex_holders, lockres->l_ro_holders);
 364                 goto drop_ref;
 365         }
 366
 367         if ((lockres->l_blocking == DLM_LOCK_PR)
 368             && lockres->l_ex_holders) {
 369                 spin_unlock(&lockres->l_lock);
 370                 mlog(ML_BASTS, "lockres %.*s, EX Holders %u\n",
 371                      lockres->l_namelen, lockres->l_name,
 372                      lockres->l_ex_holders);
 373                 goto drop_ref;
 374         }
 375
 376         /* yay, we can downconvert now. */
 377         new_level = user_highest_compat_lock_level(lockres->l_blocking);
 378         lockres->l_requested = new_level;
 379         lockres->l_flags |= USER_LOCK_BUSY;
 380         mlog(ML_BASTS, "lockres %.*s, downconvert %d => %d\n",
 381              lockres->l_namelen, lockres->l_name, lockres->l_level, new_level);
 382         spin_unlock(&lockres->l_lock);
 383
 384         /* need lock downconvert request now... */
 385         status = ocfs2_dlm_lock(conn, new_level, &lockres->l_lksb,
 386                                 DLM_LKF_CONVERT|DLM_LKF_VALBLK,
 387                                 lockres->l_name,
 388                                 lockres->l_namelen);
 389         if (status) {
 390                 user_log_dlm_error("ocfs2_dlm_lock", status, lockres);
 391                 user_recover_from_dlm_error(lockres);
 392         }
 393
 394 drop_ref:
 395         user_dlm_drop_inode_ref(lockres);
 396 }
 397
 398 static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
 399                                         int level)
 400 {
 401         switch(level) {
 402         case DLM_LOCK_EX:
 403                 lockres->l_ex_holders++;
 404                 break;
 405         case DLM_LOCK_PR:
 406                 lockres->l_ro_holders++;
 407                 break;
 408         default:
 409                 BUG();
 410         }
 411 }
 412
 413 /* predict what lock level we'll be dropping down to on behalf
 414  * of another node, and return true if the currently wanted
 415  * level will be compatible with it. */
 416 static inline int
 417 user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
 418                                   int wanted)
 419 {
 420         BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));
 421
 422         return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
 423 }
 424
 425 int user_dlm_cluster_lock(struct user_lock_res *lockres,
 426                           int level,
 427                           int lkm_flags)
 428 {
 429         int status, local_flags;
 430         struct ocfs2_cluster_connection *conn =
 431                 cluster_connection_from_user_lockres(lockres);
 432
 433         if (level != DLM_LOCK_EX &&
 434             level != DLM_LOCK_PR) {
 435                 mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
 436                      lockres->l_namelen, lockres->l_name);
 437                 status = -EINVAL;
 438                 goto bail;
 439         }
 440
 441         mlog(ML_BASTS, "lockres %.*s, level %d, flags = 0x%x\n",
 442              lockres->l_namelen, lockres->l_name, level, lkm_flags);
 443
 444 again:
 445         if (signal_pending(current)) {
 446                 status = -ERESTARTSYS;
 447                 goto bail;
 448         }
 449
 450         spin_lock(&lockres->l_lock);
 451
 452         /* We only compare against the currently granted level
 453          * here. If the lock is blocked waiting on a downconvert,
 454          * we'll get caught below. */
 455         if ((lockres->l_flags & USER_LOCK_BUSY) &&
 456             (level > lockres->l_level)) {
 457                 /* is someone sitting in dlm_lock? If so, wait on
 458                  * them. */
 459                 spin_unlock(&lockres->l_lock);
 460
 461                 user_wait_on_busy_lock(lockres);
 462                 goto again;
 463         }
 464
 465         if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
 466             (!user_may_continue_on_blocked_lock(lockres, level))) {
 467                 /* is the lock is currently blocked on behalf of
 468                  * another node */
 469                 spin_unlock(&lockres->l_lock);
 470
 471                 user_wait_on_blocked_lock(lockres);
 472                 goto again;
 473         }
 474
 475         if (level > lockres->l_level) {
 476                 local_flags = lkm_flags | DLM_LKF_VALBLK;
 477                 if (lockres->l_level != DLM_LOCK_IV)
 478                         local_flags |= DLM_LKF_CONVERT;
 479
 480                 lockres->l_requested = level;
 481                 lockres->l_flags |= USER_LOCK_BUSY;
 482                 spin_unlock(&lockres->l_lock);
 483
 484                 BUG_ON(level == DLM_LOCK_IV);
 485                 BUG_ON(level == DLM_LOCK_NL);
 486
 487                 /* call dlm_lock to upgrade lock now */
 488                 status = ocfs2_dlm_lock(conn, level, &lockres->l_lksb,
 489                                         local_flags, lockres->l_name,
 490                                         lockres->l_namelen);
 491                 if (status) {
 492                         if ((lkm_flags & DLM_LKF_NOQUEUE) &&
 493                             (status != -EAGAIN))
 494                                 user_log_dlm_error("ocfs2_dlm_lock",
 495                                                    status, lockres);
 496                         user_recover_from_dlm_error(lockres);
 497                         goto bail;
 498                 }
 499
 500                 user_wait_on_busy_lock(lockres);
 501                 goto again;
 502         }
 503
 504         user_dlm_inc_holders(lockres, level);
 505         spin_unlock(&lockres->l_lock);
 506
 507         status = 0;
 508 bail:
 509         return status;
 510 }
 511
 512 static inline void user_dlm_dec_holders(struct user_lock_res *lockres,
 513                                         int level)
 514 {
 515         switch(level) {
 516         case DLM_LOCK_EX:
 517                 BUG_ON(!lockres->l_ex_holders);
 518                 lockres->l_ex_holders--;
 519                 break;
 520         case DLM_LOCK_PR:
 521                 BUG_ON(!lockres->l_ro_holders);
 522                 lockres->l_ro_holders--;
 523                 break;
 524         default:
 525                 BUG();
 526         }
 527 }
 528
 529 void user_dlm_cluster_unlock(struct user_lock_res *lockres,
 530                              int level)
 531 {
 532         if (level != DLM_LOCK_EX &&
 533             level != DLM_LOCK_PR) {
 534                 mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
 535                      lockres->l_namelen, lockres->l_name);
 536                 return;
 537         }
 538
 539         spin_lock(&lockres->l_lock);
 540         user_dlm_dec_holders(lockres, level);
 541         __user_dlm_cond_queue_lockres(lockres);
 542         spin_unlock(&lockres->l_lock);
 543 }
 544
 545 void user_dlm_write_lvb(struct inode *inode,
 546                         const char *val,
 547                         unsigned int len)
 548 {
 549         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 550         char *lvb;
 551
 552         BUG_ON(len > DLM_LVB_LEN);
 553
 554         spin_lock(&lockres->l_lock);
 555
 556         BUG_ON(lockres->l_level < DLM_LOCK_EX);
 557         lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
 558         memcpy(lvb, val, len);
 559
 560         spin_unlock(&lockres->l_lock);
 561 }
 562
 563 ssize_t user_dlm_read_lvb(struct inode *inode,
 564                           char *val,
 565                           unsigned int len)
 566 {
 567         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 568         char *lvb;
 569         ssize_t ret = len;
 570
 571         BUG_ON(len > DLM_LVB_LEN);
 572
 573         spin_lock(&lockres->l_lock);
 574
 575         BUG_ON(lockres->l_level < DLM_LOCK_PR);
 576         if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)) {
 577                 lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
 578                 memcpy(val, lvb, len);
 579         } else
 580                 ret = 0;
 581
 582         spin_unlock(&lockres->l_lock);
 583         return ret;
 584 }
 585
 586 void user_dlm_lock_res_init(struct user_lock_res *lockres,
 587                             struct dentry *dentry)
 588 {
 589         memset(lockres, 0, sizeof(*lockres));
 590
 591         spin_lock_init(&lockres->l_lock);
 592         init_waitqueue_head(&lockres->l_event);
 593         lockres->l_level = DLM_LOCK_IV;
 594         lockres->l_requested = DLM_LOCK_IV;
 595         lockres->l_blocking = DLM_LOCK_IV;
 596
 597         /* should have been checked before getting here. */
 598         BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);
 599
 600         memcpy(lockres->l_name,
 601                dentry->d_name.name,
 602                dentry->d_name.len);
 603         lockres->l_namelen = dentry->d_name.len;
 604 }
 605
 606 int user_dlm_destroy_lock(struct user_lock_res *lockres)
 607 {
 608         int status = -EBUSY;
 609         struct ocfs2_cluster_connection *conn =
 610                 cluster_connection_from_user_lockres(lockres);
 611
 612         mlog(ML_BASTS, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);
 613
 614         spin_lock(&lockres->l_lock);
 615         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
 616                 spin_unlock(&lockres->l_lock);
 617                 return 0;
 618         }
 619
 620         lockres->l_flags |= USER_LOCK_IN_TEARDOWN;
 621
 622         while (lockres->l_flags & USER_LOCK_BUSY) {
 623                 spin_unlock(&lockres->l_lock);
 624
 625                 user_wait_on_busy_lock(lockres);
 626
 627                 spin_lock(&lockres->l_lock);
 628         }
 629
 630         if (lockres->l_ro_holders || lockres->l_ex_holders) {
 631                 spin_unlock(&lockres->l_lock);
 632                 goto bail;
 633         }
 634
 635         status = 0;
 636         if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
 637                 spin_unlock(&lockres->l_lock);
 638                 goto bail;
 639         }
 640
 641         lockres->l_flags &= ~USER_LOCK_ATTACHED;
 642         lockres->l_flags |= USER_LOCK_BUSY;
 643         spin_unlock(&lockres->l_lock);
 644
 645         status = ocfs2_dlm_unlock(conn, &lockres->l_lksb, DLM_LKF_VALBLK);
 646         if (status) {
 647                 user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
 648                 goto bail;
 649         }
 650
 651         user_wait_on_busy_lock(lockres);
 652
 653         status = 0;
 654 bail:
 655         return status;
 656 }
 657
 658 static void user_dlm_recovery_handler_noop(int node_num,
 659                                            void *recovery_data)
 660 {
 661         /* We ignore recovery events */
 662         return;
 663 }
 664
 665 void user_dlm_set_locking_protocol(void)
 666 {
 667         ocfs2_stack_glue_set_max_proto_version(&user_dlm_lproto.lp_max_version);
 668 }
 669
 670 struct ocfs2_cluster_connection *user_dlm_register(struct qstr *name)
 671 {
 672         int rc;
 673         struct ocfs2_cluster_connection *conn;
 674
 675         rc = ocfs2_cluster_connect_agnostic(name->name, name->len,
 676                                             &user_dlm_lproto,
 677                                             user_dlm_recovery_handler_noop,
 678                                             NULL, &conn);
 679         if (rc)
 680                 mlog_errno(rc);
 681
 682         return rc ? ERR_PTR(rc) : conn;
 683 }
 684
 685 void user_dlm_unregister(struct ocfs2_cluster_connection *conn)
 686 {
 687         ocfs2_cluster_disconnect(conn, 0);
 688 }