fs/ocfs2/dlm/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
  38 #include "cluster/nodemanager.h"
  39 #include "cluster/heartbeat.h"
  40 #include "cluster/tcp.h"
  41
  42 #include "dlmapi.h"
  43
  44 #include "userdlm.h"
  45
  46 #define MLOG_MASK_PREFIX ML_DLMFS
  47 #include "cluster/masklog.h"
  48
  49 static inline int user_check_wait_flag(struct user_lock_res *lockres,
  50                                        int flag)
  51 {
  52         int ret;
  53
  54         spin_lock(&lockres->l_lock);
  55         ret = lockres->l_flags & flag;
  56         spin_unlock(&lockres->l_lock);
  57
  58         return ret;
  59 }
  60
  61 static inline void user_wait_on_busy_lock(struct user_lock_res *lockres)
  62
  63 {
  64         wait_event(lockres->l_event,
  65                    !user_check_wait_flag(lockres, USER_LOCK_BUSY));
  66 }
  67
  68 static inline void user_wait_on_blocked_lock(struct user_lock_res *lockres)
  69
  70 {
  71         wait_event(lockres->l_event,
  72                    !user_check_wait_flag(lockres, USER_LOCK_BLOCKED));
  73 }
  74
  75 /* I heart container_of... */
  76 static inline struct dlm_ctxt *
  77 dlm_ctxt_from_user_lockres(struct user_lock_res *lockres)
  78 {
  79         struct dlmfs_inode_private *ip;
  80
  81         ip = container_of(lockres,
  82                           struct dlmfs_inode_private,
  83                           ip_lockres);
  84         return ip->ip_dlm;
  85 }
  86
  87 static struct inode *
  88 user_dlm_inode_from_user_lockres(struct user_lock_res *lockres)
  89 {
  90         struct dlmfs_inode_private *ip;
  91
  92         ip = container_of(lockres,
  93                           struct dlmfs_inode_private,
  94                           ip_lockres);
  95         return &ip->ip_vfs_inode;
  96 }
  97
  98 static inline void user_recover_from_dlm_error(struct user_lock_res *lockres)
  99 {
 100         spin_lock(&lockres->l_lock);
 101         lockres->l_flags &= ~USER_LOCK_BUSY;
 102         spin_unlock(&lockres->l_lock);
 103 }
 104
 105 #define user_log_dlm_error(_func, _stat, _lockres) do {                 \
 106         mlog(ML_ERROR, "Dlm error \"%s\" while calling %s on "          \
 107                 "resource %.*s: %s\n", dlm_errname(_stat), _func,       \
 108                 _lockres->l_namelen, _lockres->l_name, dlm_errmsg(_stat)); \
 109 } while (0)
 110
 111 /* WARNING: This function lives in a world where the only three lock
 112  * levels are EX, PR, and NL. It *will* have to be adjusted when more
 113  * lock types are added. */
 114 static inline int user_highest_compat_lock_level(int level)
 115 {
 116         int new_level = LKM_EXMODE;
 117
 118         if (level == LKM_EXMODE)
 119                 new_level = LKM_NLMODE;
 120         else if (level == LKM_PRMODE)
 121                 new_level = LKM_PRMODE;
 122         return new_level;
 123 }
 124
 125 static void user_ast(void *opaque)
 126 {
 127         struct user_lock_res *lockres = opaque;
 128         struct dlm_lockstatus *lksb;
 129
 130         mlog(0, "AST fired for lockres %.*s\n", lockres->l_namelen,
 131              lockres->l_name);
 132
 133         spin_lock(&lockres->l_lock);
 134
 135         lksb = &(lockres->l_lksb);
 136         if (lksb->status != DLM_NORMAL) {
 137                 mlog(ML_ERROR, "lksb status value of %u on lockres %.*s\n",
 138                      lksb->status, lockres->l_namelen, lockres->l_name);
 139                 spin_unlock(&lockres->l_lock);
 140                 return;
 141         }
 142
 143         mlog_bug_on_msg(lockres->l_requested == LKM_IVMODE,
 144                         "Lockres %.*s, requested ivmode. flags 0x%x\n",
 145                         lockres->l_namelen, lockres->l_name, lockres->l_flags);
 146
 147         /* we're downconverting. */
 148         if (lockres->l_requested < lockres->l_level) {
 149                 if (lockres->l_requested <=
 150                     user_highest_compat_lock_level(lockres->l_blocking)) {
 151                         lockres->l_blocking = LKM_NLMODE;
 152                         lockres->l_flags &= ~USER_LOCK_BLOCKED;
 153                 }
 154         }
 155
 156         lockres->l_level = lockres->l_requested;
 157         lockres->l_requested = LKM_IVMODE;
 158         lockres->l_flags |= USER_LOCK_ATTACHED;
 159         lockres->l_flags &= ~USER_LOCK_BUSY;
 160
 161         spin_unlock(&lockres->l_lock);
 162
 163         wake_up(&lockres->l_event);
 164 }
 165
 166 static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
 167 {
 168         struct inode *inode;
 169         inode = user_dlm_inode_from_user_lockres(lockres);
 170         if (!igrab(inode))
 171                 BUG();
 172 }
 173
 174 static void user_dlm_unblock_lock(struct work_struct *work);
 175
 176 static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
 177 {
 178         if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
 179                 user_dlm_grab_inode_ref(lockres);
 180
 181                 INIT_WORK(&lockres->l_work, user_dlm_unblock_lock);
 182
 183                 queue_work(user_dlm_worker, &lockres->l_work);
 184                 lockres->l_flags |= USER_LOCK_QUEUED;
 185         }
 186 }
 187
 188 static void __user_dlm_cond_queue_lockres(struct user_lock_res *lockres)
 189 {
 190         int queue = 0;
 191
 192         if (!(lockres->l_flags & USER_LOCK_BLOCKED))
 193                 return;
 194
 195         switch (lockres->l_blocking) {
 196         case LKM_EXMODE:
 197                 if (!lockres->l_ex_holders && !lockres->l_ro_holders)
 198                         queue = 1;
 199                 break;
 200         case LKM_PRMODE:
 201                 if (!lockres->l_ex_holders)
 202                         queue = 1;
 203                 break;
 204         default:
 205                 BUG();
 206         }
 207
 208         if (queue)
 209                 __user_dlm_queue_lockres(lockres);
 210 }
 211
 212 static void user_bast(void *opaque, int level)
 213 {
 214         struct user_lock_res *lockres = opaque;
 215
 216         mlog(0, "Blocking AST fired for lockres %.*s. Blocking level %d\n",
 217              lockres->l_namelen, lockres->l_name, level);
 218
 219         spin_lock(&lockres->l_lock);
 220         lockres->l_flags |= USER_LOCK_BLOCKED;
 221         if (level > lockres->l_blocking)
 222                 lockres->l_blocking = level;
 223
 224         __user_dlm_queue_lockres(lockres);
 225         spin_unlock(&lockres->l_lock);
 226
 227         wake_up(&lockres->l_event);
 228 }
 229
 230 static void user_unlock_ast(void *opaque, enum dlm_status status)
 231 {
 232         struct user_lock_res *lockres = opaque;
 233
 234         mlog(0, "UNLOCK AST called on lock %.*s\n", lockres->l_namelen,
 235              lockres->l_name);
 236
 237         if (status != DLM_NORMAL && status != DLM_CANCELGRANT)
 238                 mlog(ML_ERROR, "Dlm returns status %d\n", status);
 239
 240         spin_lock(&lockres->l_lock);
 241         /* The teardown flag gets set early during the unlock process,
 242          * so test the cancel flag to make sure that this ast isn't
 243          * for a concurrent cancel. */
 244         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN
 245             && !(lockres->l_flags & USER_LOCK_IN_CANCEL)) {
 246                 lockres->l_level = LKM_IVMODE;
 247         } else if (status == DLM_CANCELGRANT) {
 248                 /* We tried to cancel a convert request, but it was
 249                  * already granted. Don't clear the busy flag - the
 250                  * ast should've done this already. */
 251                 BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
 252                 lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 253                 goto out_noclear;
 254         } else {
 255                 BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
 256                 /* Cancel succeeded, we want to re-queue */
 257                 lockres->l_requested = LKM_IVMODE; /* cancel an
 258                                                     * upconvert
 259                                                     * request. */
 260                 lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 261                 /* we want the unblock thread to look at it again
 262                  * now. */
 263                 if (lockres->l_flags & USER_LOCK_BLOCKED)
 264                         __user_dlm_queue_lockres(lockres);
 265         }
 266
 267         lockres->l_flags &= ~USER_LOCK_BUSY;
 268 out_noclear:
 269         spin_unlock(&lockres->l_lock);
 270
 271         wake_up(&lockres->l_event);
 272 }
 273
 274 static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
 275 {
 276         struct inode *inode;
 277         inode = user_dlm_inode_from_user_lockres(lockres);
 278         iput(inode);
 279 }
 280
 281 static void user_dlm_unblock_lock(struct work_struct *work)
 282 {
 283         int new_level, status;
 284         struct user_lock_res *lockres =
 285                 container_of(work, struct user_lock_res, l_work);
 286         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 287
 288         mlog(0, "processing lockres %.*s\n", lockres->l_namelen,
 289              lockres->l_name);
 290
 291         spin_lock(&lockres->l_lock);
 292
 293         mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
 294                         "Lockres %.*s, flags 0x%x\n",
 295                         lockres->l_namelen, lockres->l_name, lockres->l_flags);
 296
 297         /* notice that we don't clear USER_LOCK_BLOCKED here. If it's
 298          * set, we want user_ast clear it. */
 299         lockres->l_flags &= ~USER_LOCK_QUEUED;
 300
 301         /* It's valid to get here and no longer be blocked - if we get
 302          * several basts in a row, we might be queued by the first
 303          * one, the unblock thread might run and clear the queued
 304          * flag, and finally we might get another bast which re-queues
 305          * us before our ast for the downconvert is called. */
 306         if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
 307                 spin_unlock(&lockres->l_lock);
 308                 goto drop_ref;
 309         }
 310
 311         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
 312                 spin_unlock(&lockres->l_lock);
 313                 goto drop_ref;
 314         }
 315
 316         if (lockres->l_flags & USER_LOCK_BUSY) {
 317                 if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
 318                         spin_unlock(&lockres->l_lock);
 319                         goto drop_ref;
 320                 }
 321
 322                 lockres->l_flags |= USER_LOCK_IN_CANCEL;
 323                 spin_unlock(&lockres->l_lock);
 324
 325                 status = dlmunlock(dlm,
 326                                    &lockres->l_lksb,
 327                                    LKM_CANCEL,
 328                                    user_unlock_ast,
 329                                    lockres);
 330                 if (status != DLM_NORMAL)
 331                         user_log_dlm_error("dlmunlock", status, lockres);
 332                 goto drop_ref;
 333         }
 334
 335         /* If there are still incompat holders, we can exit safely
 336          * without worrying about re-queueing this lock as that will
 337          * happen on the last call to user_cluster_unlock. */
 338         if ((lockres->l_blocking == LKM_EXMODE)
 339             && (lockres->l_ex_holders || lockres->l_ro_holders)) {
 340                 spin_unlock(&lockres->l_lock);
 341                 mlog(0, "can't downconvert for ex: ro = %u, ex = %u\n",
 342                         lockres->l_ro_holders, lockres->l_ex_holders);
 343                 goto drop_ref;
 344         }
 345
 346         if ((lockres->l_blocking == LKM_PRMODE)
 347             && lockres->l_ex_holders) {
 348                 spin_unlock(&lockres->l_lock);
 349                 mlog(0, "can't downconvert for pr: ex = %u\n",
 350                         lockres->l_ex_holders);
 351                 goto drop_ref;
 352         }
 353
 354         /* yay, we can downconvert now. */
 355         new_level = user_highest_compat_lock_level(lockres->l_blocking);
 356         lockres->l_requested = new_level;
 357         lockres->l_flags |= USER_LOCK_BUSY;
 358         mlog(0, "Downconvert lock from %d to %d\n",
 359                 lockres->l_level, new_level);
 360         spin_unlock(&lockres->l_lock);
 361
 362         /* need lock downconvert request now... */
 363         status = dlmlock(dlm,
 364                          new_level,
 365                          &lockres->l_lksb,
 366                          LKM_CONVERT|LKM_VALBLK,
 367                          lockres->l_name,
 368                          lockres->l_namelen,
 369                          user_ast,
 370                          lockres,
 371                          user_bast);
 372         if (status != DLM_NORMAL) {
 373                 user_log_dlm_error("dlmlock", status, lockres);
 374                 user_recover_from_dlm_error(lockres);
 375         }
 376
 377 drop_ref:
 378         user_dlm_drop_inode_ref(lockres);
 379 }
 380
 381 static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
 382                                         int level)
 383 {
 384         switch(level) {
 385         case LKM_EXMODE:
 386                 lockres->l_ex_holders++;
 387                 break;
 388         case LKM_PRMODE:
 389                 lockres->l_ro_holders++;
 390                 break;
 391         default:
 392                 BUG();
 393         }
 394 }
 395
 396 /* predict what lock level we'll be dropping down to on behalf
 397  * of another node, and return true if the currently wanted
 398  * level will be compatible with it. */
 399 static inline int
 400 user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
 401                                   int wanted)
 402 {
 403         BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));
 404
 405         return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
 406 }
 407
 408 int user_dlm_cluster_lock(struct user_lock_res *lockres,
 409                           int level,
 410                           int lkm_flags)
 411 {
 412         int status, local_flags;
 413         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 414
 415         if (level != LKM_EXMODE &&
 416             level != LKM_PRMODE) {
 417                 mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
 418                      lockres->l_namelen, lockres->l_name);
 419                 status = -EINVAL;
 420                 goto bail;
 421         }
 422
 423         mlog(0, "lockres %.*s: asking for %s lock, passed flags = 0x%x\n",
 424              lockres->l_namelen, lockres->l_name,
 425              (level == LKM_EXMODE) ? "LKM_EXMODE" : "LKM_PRMODE",
 426              lkm_flags);
 427
 428 again:
 429         if (signal_pending(current)) {
 430                 status = -ERESTARTSYS;
 431                 goto bail;
 432         }
 433
 434         spin_lock(&lockres->l_lock);
 435
 436         /* We only compare against the currently granted level
 437          * here. If the lock is blocked waiting on a downconvert,
 438          * we'll get caught below. */
 439         if ((lockres->l_flags & USER_LOCK_BUSY) &&
 440             (level > lockres->l_level)) {
 441                 /* is someone sitting in dlm_lock? If so, wait on
 442                  * them. */
 443                 spin_unlock(&lockres->l_lock);
 444
 445                 user_wait_on_busy_lock(lockres);
 446                 goto again;
 447         }
 448
 449         if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
 450             (!user_may_continue_on_blocked_lock(lockres, level))) {
 451                 /* is the lock is currently blocked on behalf of
 452                  * another node */
 453                 spin_unlock(&lockres->l_lock);
 454
 455                 user_wait_on_blocked_lock(lockres);
 456                 goto again;
 457         }
 458
 459         if (level > lockres->l_level) {
 460                 local_flags = lkm_flags | LKM_VALBLK;
 461                 if (lockres->l_level != LKM_IVMODE)
 462                         local_flags |= LKM_CONVERT;
 463
 464                 lockres->l_requested = level;
 465                 lockres->l_flags |= USER_LOCK_BUSY;
 466                 spin_unlock(&lockres->l_lock);
 467
 468                 BUG_ON(level == LKM_IVMODE);
 469                 BUG_ON(level == LKM_NLMODE);
 470
 471                 /* call dlm_lock to upgrade lock now */
 472                 status = dlmlock(dlm,
 473                                  level,
 474                                  &lockres->l_lksb,
 475                                  local_flags,
 476                                  lockres->l_name,
 477                                  lockres->l_namelen,
 478                                  user_ast,
 479                                  lockres,
 480                                  user_bast);
 481                 if (status != DLM_NORMAL) {
 482                         if ((lkm_flags & LKM_NOQUEUE) &&
 483                             (status == DLM_NOTQUEUED))
 484                                 status = -EAGAIN;
 485                         else {
 486                                 user_log_dlm_error("dlmlock", status, lockres);
 487                                 status = -EINVAL;
 488                         }
 489                         user_recover_from_dlm_error(lockres);
 490                         goto bail;
 491                 }
 492
 493                 user_wait_on_busy_lock(lockres);
 494                 goto again;
 495         }
 496
 497         user_dlm_inc_holders(lockres, level);
 498         spin_unlock(&lockres->l_lock);
 499
 500         status = 0;
 501 bail:
 502         return status;
 503 }
 504
 505 static inline void user_dlm_dec_holders(struct user_lock_res *lockres,
 506                                         int level)
 507 {
 508         switch(level) {
 509         case LKM_EXMODE:
 510                 BUG_ON(!lockres->l_ex_holders);
 511                 lockres->l_ex_holders--;
 512                 break;
 513         case LKM_PRMODE:
 514                 BUG_ON(!lockres->l_ro_holders);
 515                 lockres->l_ro_holders--;
 516                 break;
 517         default:
 518                 BUG();
 519         }
 520 }
 521
 522 void user_dlm_cluster_unlock(struct user_lock_res *lockres,
 523                              int level)
 524 {
 525         if (level != LKM_EXMODE &&
 526             level != LKM_PRMODE) {
 527                 mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
 528                      lockres->l_namelen, lockres->l_name);
 529                 return;
 530         }
 531
 532         spin_lock(&lockres->l_lock);
 533         user_dlm_dec_holders(lockres, level);
 534         __user_dlm_cond_queue_lockres(lockres);
 535         spin_unlock(&lockres->l_lock);
 536 }
 537
 538 void user_dlm_write_lvb(struct inode *inode,
 539                         const char *val,
 540                         unsigned int len)
 541 {
 542         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 543         char *lvb = lockres->l_lksb.lvb;
 544
 545         BUG_ON(len > DLM_LVB_LEN);
 546
 547         spin_lock(&lockres->l_lock);
 548
 549         BUG_ON(lockres->l_level < LKM_EXMODE);
 550         memcpy(lvb, val, len);
 551
 552         spin_unlock(&lockres->l_lock);
 553 }
 554
 555 void user_dlm_read_lvb(struct inode *inode,
 556                        char *val,
 557                        unsigned int len)
 558 {
 559         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 560         char *lvb = lockres->l_lksb.lvb;
 561
 562         BUG_ON(len > DLM_LVB_LEN);
 563
 564         spin_lock(&lockres->l_lock);
 565
 566         BUG_ON(lockres->l_level < LKM_PRMODE);
 567         memcpy(val, lvb, len);
 568
 569         spin_unlock(&lockres->l_lock);
 570 }
 571
 572 void user_dlm_lock_res_init(struct user_lock_res *lockres,
 573                             struct dentry *dentry)
 574 {
 575         memset(lockres, 0, sizeof(*lockres));
 576
 577         spin_lock_init(&lockres->l_lock);
 578         init_waitqueue_head(&lockres->l_event);
 579         lockres->l_level = LKM_IVMODE;
 580         lockres->l_requested = LKM_IVMODE;
 581         lockres->l_blocking = LKM_IVMODE;
 582
 583         /* should have been checked before getting here. */
 584         BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);
 585
 586         memcpy(lockres->l_name,
 587                dentry->d_name.name,
 588                dentry->d_name.len);
 589         lockres->l_namelen = dentry->d_name.len;
 590 }
 591
 592 int user_dlm_destroy_lock(struct user_lock_res *lockres)
 593 {
 594         int status = -EBUSY;
 595         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 596
 597         mlog(0, "asked to destroy %.*s\n", lockres->l_namelen, lockres->l_name);
 598
 599         spin_lock(&lockres->l_lock);
 600         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
 601                 spin_unlock(&lockres->l_lock);
 602                 return 0;
 603         }
 604
 605         lockres->l_flags |= USER_LOCK_IN_TEARDOWN;
 606
 607         while (lockres->l_flags & USER_LOCK_BUSY) {
 608                 spin_unlock(&lockres->l_lock);
 609
 610                 user_wait_on_busy_lock(lockres);
 611
 612                 spin_lock(&lockres->l_lock);
 613         }
 614
 615         if (lockres->l_ro_holders || lockres->l_ex_holders) {
 616                 spin_unlock(&lockres->l_lock);
 617                 goto bail;
 618         }
 619
 620         status = 0;
 621         if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
 622                 spin_unlock(&lockres->l_lock);
 623                 goto bail;
 624         }
 625
 626         lockres->l_flags &= ~USER_LOCK_ATTACHED;
 627         lockres->l_flags |= USER_LOCK_BUSY;
 628         spin_unlock(&lockres->l_lock);
 629
 630         status = dlmunlock(dlm,
 631                            &lockres->l_lksb,
 632                            LKM_VALBLK,
 633                            user_unlock_ast,
 634                            lockres);
 635         if (status != DLM_NORMAL) {
 636                 user_log_dlm_error("dlmunlock", status, lockres);
 637                 status = -EINVAL;
 638                 goto bail;
 639         }
 640
 641         user_wait_on_busy_lock(lockres);
 642
 643         status = 0;
 644 bail:
 645         return status;
 646 }
 647
 648 struct dlm_ctxt *user_dlm_register_context(struct qstr *name)
 649 {
 650         struct dlm_ctxt *dlm;
 651         u32 dlm_key;
 652         char *domain;
 653
 654         domain = kmalloc(name->len + 1, GFP_NOFS);
 655         if (!domain) {
 656                 mlog_errno(-ENOMEM);
 657                 return ERR_PTR(-ENOMEM);
 658         }
 659
 660         dlm_key = crc32_le(0, name->name, name->len);
 661
 662         snprintf(domain, name->len + 1, "%.*s", name->len, name->name);
 663
 664         dlm = dlm_register_domain(domain, dlm_key);
 665         if (IS_ERR(dlm))
 666                 mlog_errno(PTR_ERR(dlm));
 667
 668         kfree(domain);
 669         return dlm;
 670 }
 671
 672 void user_dlm_unregister_context(struct dlm_ctxt *dlm)
 673 {
 674         dlm_unregister_domain(dlm);
 675 }