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_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_name);
 131
 132         spin_lock(&lockres->l_lock);
 133
 134         lksb = &(lockres->l_lksb);
 135         if (lksb->status != DLM_NORMAL) {
 136                 mlog(ML_ERROR, "lksb status value of %u on lockres %s\n",
 137                      lksb->status, lockres->l_name);
 138                 spin_unlock(&lockres->l_lock);
 139                 return;
 140         }
 141
 142         mlog_bug_on_msg(lockres->l_requested == LKM_IVMODE,
 143                         "Lockres %s, requested ivmode. flags 0x%x\n",
 144                         lockres->l_name, lockres->l_flags);
 145
 146         /* we're downconverting. */
 147         if (lockres->l_requested < lockres->l_level) {
 148                 if (lockres->l_requested <=
 149                     user_highest_compat_lock_level(lockres->l_blocking)) {
 150                         lockres->l_blocking = LKM_NLMODE;
 151                         lockres->l_flags &= ~USER_LOCK_BLOCKED;
 152                 }
 153         }
 154
 155         lockres->l_level = lockres->l_requested;
 156         lockres->l_requested = LKM_IVMODE;
 157         lockres->l_flags |= USER_LOCK_ATTACHED;
 158         lockres->l_flags &= ~USER_LOCK_BUSY;
 159
 160         spin_unlock(&lockres->l_lock);
 161
 162         wake_up(&lockres->l_event);
 163 }
 164
 165 static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
 166 {
 167         struct inode *inode;
 168         inode = user_dlm_inode_from_user_lockres(lockres);
 169         if (!igrab(inode))
 170                 BUG();
 171 }
 172
 173 static void user_dlm_unblock_lock(void *opaque);
 174
 175 static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
 176 {
 177         if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
 178                 user_dlm_grab_inode_ref(lockres);
 179
 180                 INIT_WORK(&lockres->l_work, user_dlm_unblock_lock,
 181                           lockres);
 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_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_name);
 235
 236         if (status != DLM_NORMAL)
 237                 mlog(ML_ERROR, "Dlm returns status %d\n", status);
 238
 239         spin_lock(&lockres->l_lock);
 240         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN)
 241                 lockres->l_level = LKM_IVMODE;
 242         else {
 243                 lockres->l_requested = LKM_IVMODE; /* cancel an
 244                                                     * upconvert
 245                                                     * request. */
 246                 lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 247                 /* we want the unblock thread to look at it again
 248                  * now. */
 249                 __user_dlm_queue_lockres(lockres);
 250         }
 251
 252         lockres->l_flags &= ~USER_LOCK_BUSY;
 253         spin_unlock(&lockres->l_lock);
 254
 255         wake_up(&lockres->l_event);
 256 }
 257
 258 static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
 259 {
 260         struct inode *inode;
 261         inode = user_dlm_inode_from_user_lockres(lockres);
 262         iput(inode);
 263 }
 264
 265 static void user_dlm_unblock_lock(void *opaque)
 266 {
 267         int new_level, status;
 268         struct user_lock_res *lockres = (struct user_lock_res *) opaque;
 269         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 270
 271         mlog(0, "processing lockres %s\n", lockres->l_name);
 272
 273         spin_lock(&lockres->l_lock);
 274
 275         mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
 276                         "Lockres %s, flags 0x%x\n",
 277                         lockres->l_name, lockres->l_flags);
 278
 279         /* notice that we don't clear USER_LOCK_BLOCKED here. If it's
 280          * set, we want user_ast clear it. */
 281         lockres->l_flags &= ~USER_LOCK_QUEUED;
 282
 283         /* It's valid to get here and no longer be blocked - if we get
 284          * several basts in a row, we might be queued by the first
 285          * one, the unblock thread might run and clear the queued
 286          * flag, and finally we might get another bast which re-queues
 287          * us before our ast for the downconvert is called. */
 288         if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
 289                 mlog(0, "Lockres %s, flags 0x%x: queued but not blocking\n",
 290                         lockres->l_name, lockres->l_flags);
 291                 spin_unlock(&lockres->l_lock);
 292                 goto drop_ref;
 293         }
 294
 295         if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
 296                 mlog(0, "lock is in teardown so we do nothing\n");
 297                 spin_unlock(&lockres->l_lock);
 298                 goto drop_ref;
 299         }
 300
 301         if (lockres->l_flags & USER_LOCK_BUSY) {
 302                 mlog(0, "BUSY flag detected...\n");
 303                 if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
 304                         spin_unlock(&lockres->l_lock);
 305                         goto drop_ref;
 306                 }
 307
 308                 lockres->l_flags |= USER_LOCK_IN_CANCEL;
 309                 spin_unlock(&lockres->l_lock);
 310
 311                 status = dlmunlock(dlm,
 312                                    &lockres->l_lksb,
 313                                    LKM_CANCEL,
 314                                    user_unlock_ast,
 315                                    lockres);
 316                 if (status == DLM_CANCELGRANT) {
 317                         /* If we got this, then the ast was fired
 318                          * before we could cancel. We cleanup our
 319                          * state, and restart the function. */
 320                         spin_lock(&lockres->l_lock);
 321                         lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
 322                         spin_unlock(&lockres->l_lock);
 323                 } else if (status != DLM_NORMAL)
 324                         user_log_dlm_error("dlmunlock", status, lockres);
 325                 goto drop_ref;
 326         }
 327
 328         /* If there are still incompat holders, we can exit safely
 329          * without worrying about re-queueing this lock as that will
 330          * happen on the last call to user_cluster_unlock. */
 331         if ((lockres->l_blocking == LKM_EXMODE)
 332             && (lockres->l_ex_holders || lockres->l_ro_holders)) {
 333                 spin_unlock(&lockres->l_lock);
 334                 mlog(0, "can't downconvert for ex: ro = %u, ex = %u\n",
 335                         lockres->l_ro_holders, lockres->l_ex_holders);
 336                 goto drop_ref;
 337         }
 338
 339         if ((lockres->l_blocking == LKM_PRMODE)
 340             && lockres->l_ex_holders) {
 341                 spin_unlock(&lockres->l_lock);
 342                 mlog(0, "can't downconvert for pr: ex = %u\n",
 343                         lockres->l_ex_holders);
 344                 goto drop_ref;
 345         }
 346
 347         /* yay, we can downconvert now. */
 348         new_level = user_highest_compat_lock_level(lockres->l_blocking);
 349         lockres->l_requested = new_level;
 350         lockres->l_flags |= USER_LOCK_BUSY;
 351         mlog(0, "Downconvert lock from %d to %d\n",
 352                 lockres->l_level, new_level);
 353         spin_unlock(&lockres->l_lock);
 354
 355         /* need lock downconvert request now... */
 356         status = dlmlock(dlm,
 357                          new_level,
 358                          &lockres->l_lksb,
 359                          LKM_CONVERT|LKM_VALBLK,
 360                          lockres->l_name,
 361                          user_ast,
 362                          lockres,
 363                          user_bast);
 364         if (status != DLM_NORMAL) {
 365                 user_log_dlm_error("dlmlock", status, lockres);
 366                 user_recover_from_dlm_error(lockres);
 367         }
 368
 369 drop_ref:
 370         user_dlm_drop_inode_ref(lockres);
 371 }
 372
 373 static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
 374                                         int level)
 375 {
 376         switch(level) {
 377         case LKM_EXMODE:
 378                 lockres->l_ex_holders++;
 379                 break;
 380         case LKM_PRMODE:
 381                 lockres->l_ro_holders++;
 382                 break;
 383         default:
 384                 BUG();
 385         }
 386 }
 387
 388 /* predict what lock level we'll be dropping down to on behalf
 389  * of another node, and return true if the currently wanted
 390  * level will be compatible with it. */
 391 static inline int
 392 user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
 393                                   int wanted)
 394 {
 395         BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));
 396
 397         return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
 398 }
 399
 400 int user_dlm_cluster_lock(struct user_lock_res *lockres,
 401                           int level,
 402                           int lkm_flags)
 403 {
 404         int status, local_flags;
 405         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 406
 407         if (level != LKM_EXMODE &&
 408             level != LKM_PRMODE) {
 409                 mlog(ML_ERROR, "lockres %s: invalid request!\n",
 410                      lockres->l_name);
 411                 status = -EINVAL;
 412                 goto bail;
 413         }
 414
 415         mlog(0, "lockres %s: asking for %s lock, passed flags = 0x%x\n",
 416                 lockres->l_name,
 417                 (level == LKM_EXMODE) ? "LKM_EXMODE" : "LKM_PRMODE",
 418                 lkm_flags);
 419
 420 again:
 421         if (signal_pending(current)) {
 422                 status = -ERESTARTSYS;
 423                 goto bail;
 424         }
 425
 426         spin_lock(&lockres->l_lock);
 427
 428         /* We only compare against the currently granted level
 429          * here. If the lock is blocked waiting on a downconvert,
 430          * we'll get caught below. */
 431         if ((lockres->l_flags & USER_LOCK_BUSY) &&
 432             (level > lockres->l_level)) {
 433                 /* is someone sitting in dlm_lock? If so, wait on
 434                  * them. */
 435                 spin_unlock(&lockres->l_lock);
 436
 437                 user_wait_on_busy_lock(lockres);
 438                 goto again;
 439         }
 440
 441         if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
 442             (!user_may_continue_on_blocked_lock(lockres, level))) {
 443                 /* is the lock is currently blocked on behalf of
 444                  * another node */
 445                 spin_unlock(&lockres->l_lock);
 446
 447                 user_wait_on_blocked_lock(lockres);
 448                 goto again;
 449         }
 450
 451         if (level > lockres->l_level) {
 452                 local_flags = lkm_flags | LKM_VALBLK;
 453                 if (lockres->l_level != LKM_IVMODE)
 454                         local_flags |= LKM_CONVERT;
 455
 456                 lockres->l_requested = level;
 457                 lockres->l_flags |= USER_LOCK_BUSY;
 458                 spin_unlock(&lockres->l_lock);
 459
 460                 BUG_ON(level == LKM_IVMODE);
 461                 BUG_ON(level == LKM_NLMODE);
 462
 463                 mlog(0, "lock %s, get lock from %d to level = %d\n",
 464                         lockres->l_name, lockres->l_level, level);
 465
 466                 /* call dlm_lock to upgrade lock now */
 467                 status = dlmlock(dlm,
 468                                  level,
 469                                  &lockres->l_lksb,
 470                                  local_flags,
 471                                  lockres->l_name,
 472                                  user_ast,
 473                                  lockres,
 474                                  user_bast);
 475                 if (status != DLM_NORMAL) {
 476                         if ((lkm_flags & LKM_NOQUEUE) &&
 477                             (status == DLM_NOTQUEUED))
 478                                 status = -EAGAIN;
 479                         else {
 480                                 user_log_dlm_error("dlmlock", status, lockres);
 481                                 status = -EINVAL;
 482                         }
 483                         user_recover_from_dlm_error(lockres);
 484                         goto bail;
 485                 }
 486
 487                 mlog(0, "lock %s, successfull return from dlmlock\n",
 488                         lockres->l_name);
 489
 490                 user_wait_on_busy_lock(lockres);
 491                 goto again;
 492         }
 493
 494         user_dlm_inc_holders(lockres, level);
 495         spin_unlock(&lockres->l_lock);
 496
 497         mlog(0, "lockres %s: Got %s lock!\n", lockres->l_name,
 498                 (level == LKM_EXMODE) ? "LKM_EXMODE" : "LKM_PRMODE");
 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", lockres->l_name);
 528                 return;
 529         }
 530
 531         mlog(0, "lockres %s: dropping %s lock\n", lockres->l_name,
 532                 (level == LKM_EXMODE) ? "LKM_EXMODE" : "LKM_PRMODE");
 533
 534         spin_lock(&lockres->l_lock);
 535         user_dlm_dec_holders(lockres, level);
 536         __user_dlm_cond_queue_lockres(lockres);
 537         spin_unlock(&lockres->l_lock);
 538 }
 539
 540 void user_dlm_write_lvb(struct inode *inode,
 541                         const char *val,
 542                         unsigned int len)
 543 {
 544         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 545         char *lvb = lockres->l_lksb.lvb;
 546
 547         BUG_ON(len > DLM_LVB_LEN);
 548
 549         spin_lock(&lockres->l_lock);
 550
 551         BUG_ON(lockres->l_level < LKM_EXMODE);
 552         memcpy(lvb, val, len);
 553
 554         spin_unlock(&lockres->l_lock);
 555 }
 556
 557 void user_dlm_read_lvb(struct inode *inode,
 558                        char *val,
 559                        unsigned int len)
 560 {
 561         struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 562         char *lvb = lockres->l_lksb.lvb;
 563
 564         BUG_ON(len > DLM_LVB_LEN);
 565
 566         spin_lock(&lockres->l_lock);
 567
 568         BUG_ON(lockres->l_level < LKM_PRMODE);
 569         memcpy(val, lvb, len);
 570
 571         spin_unlock(&lockres->l_lock);
 572 }
 573
 574 void user_dlm_lock_res_init(struct user_lock_res *lockres,
 575                             struct dentry *dentry)
 576 {
 577         memset(lockres, 0, sizeof(*lockres));
 578
 579         spin_lock_init(&lockres->l_lock);
 580         init_waitqueue_head(&lockres->l_event);
 581         lockres->l_level = LKM_IVMODE;
 582         lockres->l_requested = LKM_IVMODE;
 583         lockres->l_blocking = LKM_IVMODE;
 584
 585         /* should have been checked before getting here. */
 586         BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);
 587
 588         memcpy(lockres->l_name,
 589                dentry->d_name.name,
 590                dentry->d_name.len);
 591 }
 592
 593 int user_dlm_destroy_lock(struct user_lock_res *lockres)
 594 {
 595         int status = -EBUSY;
 596         struct dlm_ctxt *dlm = dlm_ctxt_from_user_lockres(lockres);
 597
 598         mlog(0, "asked to destroy %s\n", lockres->l_name);
 599
 600         spin_lock(&lockres->l_lock);
 601         while (lockres->l_flags & USER_LOCK_BUSY) {
 602                 spin_unlock(&lockres->l_lock);
 603
 604                 mlog(0, "lock %s is busy\n", lockres->l_name);
 605
 606                 user_wait_on_busy_lock(lockres);
 607
 608                 spin_lock(&lockres->l_lock);
 609         }
 610
 611         if (lockres->l_ro_holders || lockres->l_ex_holders) {
 612                 spin_unlock(&lockres->l_lock);
 613                 mlog(0, "lock %s has holders\n", lockres->l_name);
 614                 goto bail;
 615         }
 616
 617         status = 0;
 618         if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
 619                 spin_unlock(&lockres->l_lock);
 620                 mlog(0, "lock %s is not attached\n", lockres->l_name);
 621                 goto bail;
 622         }
 623
 624         lockres->l_flags &= ~USER_LOCK_ATTACHED;
 625         lockres->l_flags |= USER_LOCK_BUSY;
 626         lockres->l_flags |= USER_LOCK_IN_TEARDOWN;
 627         spin_unlock(&lockres->l_lock);
 628
 629         mlog(0, "unlocking lockres %s\n", lockres->l_name);
 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_KERNEL);
 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 }