kernel/fs/lockd/svclock.c

   1 /*
   2  * linux/fs/lockd/svclock.c
   3  *
   4  * Handling of server-side locks, mostly of the blocked variety.
   5  * This is the ugliest part of lockd because we tread on very thin ice.
   6  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
   7  * IMNSHO introducing the grant callback into the NLM protocol was one
   8  * of the worst ideas Sun ever had. Except maybe for the idea of doing
   9  * NFS file locking at all.
  10  *
  11  * I'm trying hard to avoid race conditions by protecting most accesses
  12  * to a file's list of blocked locks through a semaphore. The global
  13  * list of blocked locks is not protected in this fashion however.
  14  * Therefore, some functions (such as the RPC callback for the async grant
  15  * call) move blocked locks towards the head of the list *while some other
  16  * process might be traversing it*. This should not be a problem in
  17  * practice, because this will only cause functions traversing the list
  18  * to visit some blocks twice.
  19  *
  20  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  21  */
  22
  23 #include <linux/types.h>
  24 #include <linux/slab.h>
  25 #include <linux/errno.h>
  26 #include <linux/kernel.h>
  27 #include <linux/sched.h>
  28 #include <linux/sunrpc/clnt.h>
  29 #include <linux/sunrpc/svc_xprt.h>
  30 #include <linux/lockd/nlm.h>
  31 #include <linux/lockd/lockd.h>
  32 #include <linux/kthread.h>
  33
  34 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
  35
  36 #ifdef CONFIG_LOCKD_V4
  37 #define nlm_deadlock    nlm4_deadlock
  38 #else
  39 #define nlm_deadlock    nlm_lck_denied
  40 #endif
  41
  42 static void nlmsvc_release_block(struct nlm_block *block);
  43 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
  44 static void     nlmsvc_remove_block(struct nlm_block *block);
  45
  46 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
  47 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
  48 static const struct rpc_call_ops nlmsvc_grant_ops;
  49
  50 /*
  51  * The list of blocked locks to retry
  52  */
  53 static LIST_HEAD(nlm_blocked);
  54 static DEFINE_SPINLOCK(nlm_blocked_lock);
  55
  56 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  57 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
  58 {
  59         /*
  60          * We can get away with a static buffer because this is only called
  61          * from lockd, which is single-threaded.
  62          */
  63         static char buf[2*NLM_MAXCOOKIELEN+1];
  64         unsigned int i, len = sizeof(buf);
  65         char *p = buf;
  66
  67         len--;  /* allow for trailing \0 */
  68         if (len < 3)
  69                 return "???";
  70         for (i = 0 ; i < cookie->len ; i++) {
  71                 if (len < 2) {
  72                         strcpy(p-3, "...");
  73                         break;
  74                 }
  75                 sprintf(p, "%02x", cookie->data[i]);
  76                 p += 2;
  77                 len -= 2;
  78         }
  79         *p = '\0';
  80
  81         return buf;
  82 }
  83 #endif
  84
  85 /*
  86  * Insert a blocked lock into the global list
  87  */
  88 static void
  89 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
  90 {
  91         struct nlm_block *b;
  92         struct list_head *pos;
  93
  94         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
  95         if (list_empty(&block->b_list)) {
  96                 kref_get(&block->b_count);
  97         } else {
  98                 list_del_init(&block->b_list);
  99         }
 100
 101         pos = &nlm_blocked;
 102         if (when != NLM_NEVER) {
 103                 if ((when += jiffies) == NLM_NEVER)
 104                         when ++;
 105                 list_for_each(pos, &nlm_blocked) {
 106                         b = list_entry(pos, struct nlm_block, b_list);
 107                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
 108                                 break;
 109                 }
 110                 /* On normal exit from the loop, pos == &nlm_blocked,
 111                  * so we will be adding to the end of the list - good
 112                  */
 113         }
 114
 115         list_add_tail(&block->b_list, pos);
 116         block->b_when = when;
 117 }
 118
 119 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
 120 {
 121         spin_lock(&nlm_blocked_lock);
 122         nlmsvc_insert_block_locked(block, when);
 123         spin_unlock(&nlm_blocked_lock);
 124 }
 125
 126 /*
 127  * Remove a block from the global list
 128  */
 129 static inline void
 130 nlmsvc_remove_block(struct nlm_block *block)
 131 {
 132         if (!list_empty(&block->b_list)) {
 133                 spin_lock(&nlm_blocked_lock);
 134                 list_del_init(&block->b_list);
 135                 spin_unlock(&nlm_blocked_lock);
 136                 nlmsvc_release_block(block);
 137         }
 138 }
 139
 140 /*
 141  * Find a block for a given lock
 142  */
 143 static struct nlm_block *
 144 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 145 {
 146         struct nlm_block        *block;
 147         struct file_lock        *fl;
 148
 149         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
 150                                 file, lock->fl.fl_pid,
 151                                 (long long)lock->fl.fl_start,
 152                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
 153         list_for_each_entry(block, &nlm_blocked, b_list) {
 154                 fl = &block->b_call->a_args.lock.fl;
 155                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
 156                                 block->b_file, fl->fl_pid,
 157                                 (long long)fl->fl_start,
 158                                 (long long)fl->fl_end, fl->fl_type,
 159                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
 160                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
 161                         kref_get(&block->b_count);
 162                         return block;
 163                 }
 164         }
 165
 166         return NULL;
 167 }
 168
 169 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 170 {
 171         if (a->len != b->len)
 172                 return 0;
 173         if (memcmp(a->data, b->data, a->len))
 174                 return 0;
 175         return 1;
 176 }
 177
 178 /*
 179  * Find a block with a given NLM cookie.
 180  */
 181 static inline struct nlm_block *
 182 nlmsvc_find_block(struct nlm_cookie *cookie)
 183 {
 184         struct nlm_block *block;
 185
 186         list_for_each_entry(block, &nlm_blocked, b_list) {
 187                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
 188                         goto found;
 189         }
 190
 191         return NULL;
 192
 193 found:
 194         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
 195         kref_get(&block->b_count);
 196         return block;
 197 }
 198
 199 /*
 200  * Create a block and initialize it.
 201  *
 202  * Note: we explicitly set the cookie of the grant reply to that of
 203  * the blocked lock request. The spec explicitly mentions that the client
 204  * should _not_ rely on the callback containing the same cookie as the
 205  * request, but (as I found out later) that's because some implementations
 206  * do just this. Never mind the standards comittees, they support our
 207  * logging industries.
 208  *
 209  * 10 years later: I hope we can safely ignore these old and broken
 210  * clients by now. Let's fix this so we can uniquely identify an incoming
 211  * GRANTED_RES message by cookie, without having to rely on the client's IP
 212  * address. --okir
 213  */
 214 static struct nlm_block *
 215 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
 216                     struct nlm_file *file, struct nlm_lock *lock,
 217                     struct nlm_cookie *cookie)
 218 {
 219         struct nlm_block        *block;
 220         struct nlm_rqst         *call = NULL;
 221
 222         call = nlm_alloc_call(host);
 223         if (call == NULL)
 224                 return NULL;
 225
 226         /* Allocate memory for block, and initialize arguments */
 227         block = kzalloc(sizeof(*block), GFP_KERNEL);
 228         if (block == NULL)
 229                 goto failed;
 230         kref_init(&block->b_count);
 231         INIT_LIST_HEAD(&block->b_list);
 232         INIT_LIST_HEAD(&block->b_flist);
 233
 234         if (!nlmsvc_setgrantargs(call, lock))
 235                 goto failed_free;
 236
 237         /* Set notifier function for VFS, and init args */
 238         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 239         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 240         nlmclnt_next_cookie(&call->a_args.cookie);
 241
 242         dprintk("lockd: created block %p...\n", block);
 243
 244         /* Create and initialize the block */
 245         block->b_daemon = rqstp->rq_server;
 246         block->b_host   = host;
 247         block->b_file   = file;
 248         file->f_count++;
 249
 250         /* Add to file's list of blocks */
 251         list_add(&block->b_flist, &file->f_blocks);
 252
 253         /* Set up RPC arguments for callback */
 254         block->b_call = call;
 255         call->a_flags   = RPC_TASK_ASYNC;
 256         call->a_block = block;
 257
 258         return block;
 259
 260 failed_free:
 261         kfree(block);
 262 failed:
 263         nlmsvc_release_call(call);
 264         return NULL;
 265 }
 266
 267 /*
 268  * Delete a block.
 269  * It is the caller's responsibility to check whether the file
 270  * can be closed hereafter.
 271  */
 272 static int nlmsvc_unlink_block(struct nlm_block *block)
 273 {
 274         int status;
 275         dprintk("lockd: unlinking block %p...\n", block);
 276
 277         /* Remove block from list */
 278         status = posix_unblock_lock(&block->b_call->a_args.lock.fl);
 279         nlmsvc_remove_block(block);
 280         return status;
 281 }
 282
 283 static void nlmsvc_free_block(struct kref *kref)
 284 {
 285         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 286         struct nlm_file         *file = block->b_file;
 287
 288         dprintk("lockd: freeing block %p...\n", block);
 289
 290         /* Remove block from file's list of blocks */
 291         list_del_init(&block->b_flist);
 292         mutex_unlock(&file->f_mutex);
 293
 294         nlmsvc_freegrantargs(block->b_call);
 295         nlmsvc_release_call(block->b_call);
 296         nlm_release_file(block->b_file);
 297         kfree(block);
 298 }
 299
 300 static void nlmsvc_release_block(struct nlm_block *block)
 301 {
 302         if (block != NULL)
 303                 kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
 304 }
 305
 306 /*
 307  * Loop over all blocks and delete blocks held by
 308  * a matching host.
 309  */
 310 void nlmsvc_traverse_blocks(struct nlm_host *host,
 311                         struct nlm_file *file,
 312                         nlm_host_match_fn_t match)
 313 {
 314         struct nlm_block *block, *next;
 315
 316 restart:
 317         mutex_lock(&file->f_mutex);
 318         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 319                 if (!match(block->b_host, host))
 320                         continue;
 321                 /* Do not destroy blocks that are not on
 322                  * the global retry list - why? */
 323                 if (list_empty(&block->b_list))
 324                         continue;
 325                 kref_get(&block->b_count);
 326                 mutex_unlock(&file->f_mutex);
 327                 nlmsvc_unlink_block(block);
 328                 nlmsvc_release_block(block);
 329                 goto restart;
 330         }
 331         mutex_unlock(&file->f_mutex);
 332 }
 333
 334 /*
 335  * Initialize arguments for GRANTED call. The nlm_rqst structure
 336  * has been cleared already.
 337  */
 338 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 339 {
 340         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 341         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 342         call->a_args.lock.caller = utsname()->nodename;
 343         call->a_args.lock.oh.len = lock->oh.len;
 344
 345         /* set default data area */
 346         call->a_args.lock.oh.data = call->a_owner;
 347         call->a_args.lock.svid = lock->fl.fl_pid;
 348
 349         if (lock->oh.len > NLMCLNT_OHSIZE) {
 350                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 351                 if (!data)
 352                         return 0;
 353                 call->a_args.lock.oh.data = (u8 *) data;
 354         }
 355
 356         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 357         return 1;
 358 }
 359
 360 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 361 {
 362         if (call->a_args.lock.oh.data != call->a_owner)
 363                 kfree(call->a_args.lock.oh.data);
 364
 365         locks_release_private(&call->a_args.lock.fl);
 366 }
 367
 368 /*
 369  * Deferred lock request handling for non-blocking lock
 370  */
 371 static __be32
 372 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 373 {
 374         __be32 status = nlm_lck_denied_nolocks;
 375
 376         block->b_flags |= B_QUEUED;
 377
 378         nlmsvc_insert_block(block, NLM_TIMEOUT);
 379
 380         block->b_cache_req = &rqstp->rq_chandle;
 381         if (rqstp->rq_chandle.defer) {
 382                 block->b_deferred_req =
 383                         rqstp->rq_chandle.defer(block->b_cache_req);
 384                 if (block->b_deferred_req != NULL)
 385                         status = nlm_drop_reply;
 386         }
 387         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 388                 block, block->b_flags, ntohl(status));
 389
 390         return status;
 391 }
 392
 393 /*
 394  * Attempt to establish a lock, and if it can't be granted, block it
 395  * if required.
 396  */
 397 __be32
 398 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 399             struct nlm_host *host, struct nlm_lock *lock, int wait,
 400             struct nlm_cookie *cookie, int reclaim)
 401 {
 402         struct nlm_block        *block = NULL;
 403         int                     error;
 404         __be32                  ret;
 405
 406         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 407                                 file_inode(file->f_file)->i_sb->s_id,
 408                                 file_inode(file->f_file)->i_ino,
 409                                 lock->fl.fl_type, lock->fl.fl_pid,
 410                                 (long long)lock->fl.fl_start,
 411                                 (long long)lock->fl.fl_end,
 412                                 wait);
 413
 414         /* Lock file against concurrent access */
 415         mutex_lock(&file->f_mutex);
 416         /* Get existing block (in case client is busy-waiting)
 417          * or create new block
 418          */
 419         block = nlmsvc_lookup_block(file, lock);
 420         if (block == NULL) {
 421                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 422                 ret = nlm_lck_denied_nolocks;
 423                 if (block == NULL)
 424                         goto out;
 425                 lock = &block->b_call->a_args.lock;
 426         } else
 427                 lock->fl.fl_flags &= ~FL_SLEEP;
 428
 429         if (block->b_flags & B_QUEUED) {
 430                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
 431                                                         block, block->b_flags);
 432                 if (block->b_granted) {
 433                         nlmsvc_unlink_block(block);
 434                         ret = nlm_granted;
 435                         goto out;
 436                 }
 437                 if (block->b_flags & B_TIMED_OUT) {
 438                         nlmsvc_unlink_block(block);
 439                         ret = nlm_lck_denied;
 440                         goto out;
 441                 }
 442                 ret = nlm_drop_reply;
 443                 goto out;
 444         }
 445
 446         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
 447                 ret = nlm_lck_denied_grace_period;
 448                 goto out;
 449         }
 450         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
 451                 ret = nlm_lck_denied_grace_period;
 452                 goto out;
 453         }
 454
 455         if (!wait)
 456                 lock->fl.fl_flags &= ~FL_SLEEP;
 457         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 458         lock->fl.fl_flags &= ~FL_SLEEP;
 459
 460         dprintk("lockd: vfs_lock_file returned %d\n", error);
 461         switch (error) {
 462                 case 0:
 463                         ret = nlm_granted;
 464                         goto out;
 465                 case -EAGAIN:
 466                         /*
 467                          * If this is a blocking request for an
 468                          * already pending lock request then we need
 469                          * to put it back on lockd's block list
 470                          */
 471                         if (wait)
 472                                 break;
 473                         ret = nlm_lck_denied;
 474                         goto out;
 475                 case FILE_LOCK_DEFERRED:
 476                         if (wait)
 477                                 break;
 478                         /* Filesystem lock operation is in progress
 479                            Add it to the queue waiting for callback */
 480                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
 481                         goto out;
 482                 case -EDEADLK:
 483                         ret = nlm_deadlock;
 484                         goto out;
 485                 default:                        /* includes ENOLCK */
 486                         ret = nlm_lck_denied_nolocks;
 487                         goto out;
 488         }
 489
 490         ret = nlm_lck_blocked;
 491
 492         /* Append to list of blocked */
 493         nlmsvc_insert_block(block, NLM_NEVER);
 494 out:
 495         mutex_unlock(&file->f_mutex);
 496         nlmsvc_release_block(block);
 497         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 498         return ret;
 499 }
 500
 501 /*
 502  * Test for presence of a conflicting lock.
 503  */
 504 __be32
 505 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 506                 struct nlm_host *host, struct nlm_lock *lock,
 507                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
 508 {
 509         int                     error;
 510         __be32                  ret;
 511
 512         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 513                                 file_inode(file->f_file)->i_sb->s_id,
 514                                 file_inode(file->f_file)->i_ino,
 515                                 lock->fl.fl_type,
 516                                 (long long)lock->fl.fl_start,
 517                                 (long long)lock->fl.fl_end);
 518
 519         if (locks_in_grace(SVC_NET(rqstp))) {
 520                 ret = nlm_lck_denied_grace_period;
 521                 goto out;
 522         }
 523
 524         error = vfs_test_lock(file->f_file, &lock->fl);
 525         if (error) {
 526                 /* We can't currently deal with deferred test requests */
 527                 if (error == FILE_LOCK_DEFERRED)
 528                         WARN_ON_ONCE(1);
 529
 530                 ret = nlm_lck_denied_nolocks;
 531                 goto out;
 532         }
 533
 534         if (lock->fl.fl_type == F_UNLCK) {
 535                 ret = nlm_granted;
 536                 goto out;
 537         }
 538
 539         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 540                 lock->fl.fl_type, (long long)lock->fl.fl_start,
 541                 (long long)lock->fl.fl_end);
 542         conflock->caller = "somehost";  /* FIXME */
 543         conflock->len = strlen(conflock->caller);
 544         conflock->oh.len = 0;           /* don't return OH info */
 545         conflock->svid = lock->fl.fl_pid;
 546         conflock->fl.fl_type = lock->fl.fl_type;
 547         conflock->fl.fl_start = lock->fl.fl_start;
 548         conflock->fl.fl_end = lock->fl.fl_end;
 549         locks_release_private(&lock->fl);
 550         ret = nlm_lck_denied;
 551 out:
 552         return ret;
 553 }
 554
 555 /*
 556  * Remove a lock.
 557  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 558  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 559  * afterwards. In this case the block will still be there, and hence
 560  * must be removed.
 561  */
 562 __be32
 563 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 564 {
 565         int     error;
 566
 567         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 568                                 file_inode(file->f_file)->i_sb->s_id,
 569                                 file_inode(file->f_file)->i_ino,
 570                                 lock->fl.fl_pid,
 571                                 (long long)lock->fl.fl_start,
 572                                 (long long)lock->fl.fl_end);
 573
 574         /* First, cancel any lock that might be there */
 575         nlmsvc_cancel_blocked(net, file, lock);
 576
 577         lock->fl.fl_type = F_UNLCK;
 578         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 579
 580         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 581 }
 582
 583 /*
 584  * Cancel a previously blocked request.
 585  *
 586  * A cancel request always overrides any grant that may currently
 587  * be in progress.
 588  * The calling procedure must check whether the file can be closed.
 589  */
 590 __be32
 591 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 592 {
 593         struct nlm_block        *block;
 594         int status = 0;
 595
 596         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 597                                 file_inode(file->f_file)->i_sb->s_id,
 598                                 file_inode(file->f_file)->i_ino,
 599                                 lock->fl.fl_pid,
 600                                 (long long)lock->fl.fl_start,
 601                                 (long long)lock->fl.fl_end);
 602
 603         if (locks_in_grace(net))
 604                 return nlm_lck_denied_grace_period;
 605
 606         mutex_lock(&file->f_mutex);
 607         block = nlmsvc_lookup_block(file, lock);
 608         mutex_unlock(&file->f_mutex);
 609         if (block != NULL) {
 610                 vfs_cancel_lock(block->b_file->f_file,
 611                                 &block->b_call->a_args.lock.fl);
 612                 status = nlmsvc_unlink_block(block);
 613                 nlmsvc_release_block(block);
 614         }
 615         return status ? nlm_lck_denied : nlm_granted;
 616 }
 617
 618 /*
 619  * This is a callback from the filesystem for VFS file lock requests.
 620  * It will be used if lm_grant is defined and the filesystem can not
 621  * respond to the request immediately.
 622  * For SETLK or SETLKW request it will get the local posix lock.
 623  * In all cases it will move the block to the head of nlm_blocked q where
 624  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
 625  * deferred rpc for GETLK and SETLK.
 626  */
 627 static void
 628 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
 629 {
 630         block->b_flags |= B_GOT_CALLBACK;
 631         if (result == 0)
 632                 block->b_granted = 1;
 633         else
 634                 block->b_flags |= B_TIMED_OUT;
 635 }
 636
 637 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
 638 {
 639         struct nlm_block *block;
 640         int rc = -ENOENT;
 641
 642         spin_lock(&nlm_blocked_lock);
 643         list_for_each_entry(block, &nlm_blocked, b_list) {
 644                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 645                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
 646                                                         block, block->b_flags);
 647                         if (block->b_flags & B_QUEUED) {
 648                                 if (block->b_flags & B_TIMED_OUT) {
 649                                         rc = -ENOLCK;
 650                                         break;
 651                                 }
 652                                 nlmsvc_update_deferred_block(block, result);
 653                         } else if (result == 0)
 654                                 block->b_granted = 1;
 655
 656                         nlmsvc_insert_block_locked(block, 0);
 657                         svc_wake_up(block->b_daemon);
 658                         rc = 0;
 659                         break;
 660                 }
 661         }
 662         spin_unlock(&nlm_blocked_lock);
 663         if (rc == -ENOENT)
 664                 printk(KERN_WARNING "lockd: grant for unknown block\n");
 665         return rc;
 666 }
 667
 668 /*
 669  * Unblock a blocked lock request. This is a callback invoked from the
 670  * VFS layer when a lock on which we blocked is removed.
 671  *
 672  * This function doesn't grant the blocked lock instantly, but rather moves
 673  * the block to the head of nlm_blocked where it can be picked up by lockd.
 674  */
 675 static void
 676 nlmsvc_notify_blocked(struct file_lock *fl)
 677 {
 678         struct nlm_block        *block;
 679
 680         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 681         spin_lock(&nlm_blocked_lock);
 682         list_for_each_entry(block, &nlm_blocked, b_list) {
 683                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 684                         nlmsvc_insert_block_locked(block, 0);
 685                         spin_unlock(&nlm_blocked_lock);
 686                         svc_wake_up(block->b_daemon);
 687                         return;
 688                 }
 689         }
 690         spin_unlock(&nlm_blocked_lock);
 691         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 692 }
 693
 694 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 695 {
 696         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 697 }
 698
 699 /*
 700  * Since NLM uses two "keys" for tracking locks, we need to hash them down
 701  * to one for the blocked_hash. Here, we're just xor'ing the host address
 702  * with the pid in order to create a key value for picking a hash bucket.
 703  */
 704 static unsigned long
 705 nlmsvc_owner_key(struct file_lock *fl)
 706 {
 707         return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
 708 }
 709
 710 const struct lock_manager_operations nlmsvc_lock_operations = {
 711         .lm_compare_owner = nlmsvc_same_owner,
 712         .lm_owner_key = nlmsvc_owner_key,
 713         .lm_notify = nlmsvc_notify_blocked,
 714         .lm_grant = nlmsvc_grant_deferred,
 715 };
 716
 717 /*
 718  * Try to claim a lock that was previously blocked.
 719  *
 720  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 721  * RPC thread when notifying the client. This seems like overkill...
 722  * Here's why:
 723  *  -   we don't want to use a synchronous RPC thread, otherwise
 724  *      we might find ourselves hanging on a dead portmapper.
 725  *  -   Some lockd implementations (e.g. HP) don't react to
 726  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 727  */
 728 static void
 729 nlmsvc_grant_blocked(struct nlm_block *block)
 730 {
 731         struct nlm_file         *file = block->b_file;
 732         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 733         int                     error;
 734         loff_t                  fl_start, fl_end;
 735
 736         dprintk("lockd: grant blocked lock %p\n", block);
 737
 738         kref_get(&block->b_count);
 739
 740         /* Unlink block request from list */
 741         nlmsvc_unlink_block(block);
 742
 743         /* If b_granted is true this means we've been here before.
 744          * Just retry the grant callback, possibly refreshing the RPC
 745          * binding */
 746         if (block->b_granted) {
 747                 nlm_rebind_host(block->b_host);
 748                 goto callback;
 749         }
 750
 751         /* Try the lock operation again */
 752         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
 753          * them unchanged for the GRANT_MSG
 754          */
 755         lock->fl.fl_flags |= FL_SLEEP;
 756         fl_start = lock->fl.fl_start;
 757         fl_end = lock->fl.fl_end;
 758         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 759         lock->fl.fl_flags &= ~FL_SLEEP;
 760         lock->fl.fl_start = fl_start;
 761         lock->fl.fl_end = fl_end;
 762
 763         switch (error) {
 764         case 0:
 765                 break;
 766         case FILE_LOCK_DEFERRED:
 767                 dprintk("lockd: lock still blocked error %d\n", error);
 768                 nlmsvc_insert_block(block, NLM_NEVER);
 769                 nlmsvc_release_block(block);
 770                 return;
 771         default:
 772                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 773                                 -error, __func__);
 774                 nlmsvc_insert_block(block, 10 * HZ);
 775                 nlmsvc_release_block(block);
 776                 return;
 777         }
 778
 779 callback:
 780         /* Lock was granted by VFS. */
 781         dprintk("lockd: GRANTing blocked lock.\n");
 782         block->b_granted = 1;
 783
 784         /* keep block on the list, but don't reattempt until the RPC
 785          * completes or the submission fails
 786          */
 787         nlmsvc_insert_block(block, NLM_NEVER);
 788
 789         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
 790          * will queue up a new one if this one times out
 791          */
 792         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
 793                                 &nlmsvc_grant_ops);
 794
 795         /* RPC submission failed, wait a bit and retry */
 796         if (error < 0)
 797                 nlmsvc_insert_block(block, 10 * HZ);
 798 }
 799
 800 /*
 801  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 802  * RPC call has succeeded or timed out.
 803  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 804  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 805  * chain once more in order to have it removed by lockd itself (which can
 806  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 807  */
 808 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 809 {
 810         struct nlm_rqst         *call = data;
 811         struct nlm_block        *block = call->a_block;
 812         unsigned long           timeout;
 813
 814         dprintk("lockd: GRANT_MSG RPC callback\n");
 815
 816         spin_lock(&nlm_blocked_lock);
 817         /* if the block is not on a list at this point then it has
 818          * been invalidated. Don't try to requeue it.
 819          *
 820          * FIXME: it's possible that the block is removed from the list
 821          * after this check but before the nlmsvc_insert_block. In that
 822          * case it will be added back. Perhaps we need better locking
 823          * for nlm_blocked?
 824          */
 825         if (list_empty(&block->b_list))
 826                 goto out;
 827
 828         /* Technically, we should down the file semaphore here. Since we
 829          * move the block towards the head of the queue only, no harm
 830          * can be done, though. */
 831         if (task->tk_status < 0) {
 832                 /* RPC error: Re-insert for retransmission */
 833                 timeout = 10 * HZ;
 834         } else {
 835                 /* Call was successful, now wait for client callback */
 836                 timeout = 60 * HZ;
 837         }
 838         nlmsvc_insert_block_locked(block, timeout);
 839         svc_wake_up(block->b_daemon);
 840 out:
 841         spin_unlock(&nlm_blocked_lock);
 842 }
 843
 844 /*
 845  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
 846  * .rpc_release rpc_call_op
 847  */
 848 static void nlmsvc_grant_release(void *data)
 849 {
 850         struct nlm_rqst         *call = data;
 851         nlmsvc_release_block(call->a_block);
 852 }
 853
 854 static const struct rpc_call_ops nlmsvc_grant_ops = {
 855         .rpc_call_done = nlmsvc_grant_callback,
 856         .rpc_release = nlmsvc_grant_release,
 857 };
 858
 859 /*
 860  * We received a GRANT_RES callback. Try to find the corresponding
 861  * block.
 862  */
 863 void
 864 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 865 {
 866         struct nlm_block        *block;
 867
 868         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 869                 *(unsigned int *)(cookie->data), status);
 870         if (!(block = nlmsvc_find_block(cookie)))
 871                 return;
 872
 873         if (block) {
 874                 if (status == nlm_lck_denied_grace_period) {
 875                         /* Try again in a couple of seconds */
 876                         nlmsvc_insert_block(block, 10 * HZ);
 877                 } else {
 878                         /* Lock is now held by client, or has been rejected.
 879                          * In both cases, the block should be removed. */
 880                         nlmsvc_unlink_block(block);
 881                 }
 882         }
 883         nlmsvc_release_block(block);
 884 }
 885
 886 /* Helper function to handle retry of a deferred block.
 887  * If it is a blocking lock, call grant_blocked.
 888  * For a non-blocking lock or test lock, revisit the request.
 889  */
 890 static void
 891 retry_deferred_block(struct nlm_block *block)
 892 {
 893         if (!(block->b_flags & B_GOT_CALLBACK))
 894                 block->b_flags |= B_TIMED_OUT;
 895         nlmsvc_insert_block(block, NLM_TIMEOUT);
 896         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
 897         if (block->b_deferred_req) {
 898                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
 899                 block->b_deferred_req = NULL;
 900         }
 901 }
 902
 903 /*
 904  * Retry all blocked locks that have been notified. This is where lockd
 905  * picks up locks that can be granted, or grant notifications that must
 906  * be retransmitted.
 907  */
 908 unsigned long
 909 nlmsvc_retry_blocked(void)
 910 {
 911         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
 912         struct nlm_block *block;
 913
 914         spin_lock(&nlm_blocked_lock);
 915         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
 916                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 917
 918                 if (block->b_when == NLM_NEVER)
 919                         break;
 920                 if (time_after(block->b_when, jiffies)) {
 921                         timeout = block->b_when - jiffies;
 922                         break;
 923                 }
 924                 spin_unlock(&nlm_blocked_lock);
 925
 926                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
 927                         block, block->b_when);
 928                 if (block->b_flags & B_QUEUED) {
 929                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
 930                                 block, block->b_granted, block->b_flags);
 931                         retry_deferred_block(block);
 932                 } else
 933                         nlmsvc_grant_blocked(block);
 934                 spin_lock(&nlm_blocked_lock);
 935         }
 936         spin_unlock(&nlm_blocked_lock);
 937
 938         return timeout;
 939 }