fs/lockd/svclock.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/lockd/svclock.c
   4  *
   5  * Handling of server-side locks, mostly of the blocked variety.
   6  * This is the ugliest part of lockd because we tread on very thin ice.
   7  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
   8  * IMNSHO introducing the grant callback into the NLM protocol was one
   9  * of the worst ideas Sun ever had. Except maybe for the idea of doing
  10  * NFS file locking at all.
  11  *
  12  * I'm trying hard to avoid race conditions by protecting most accesses
  13  * to a file's list of blocked locks through a semaphore. The global
  14  * list of blocked locks is not protected in this fashion however.
  15  * Therefore, some functions (such as the RPC callback for the async grant
  16  * call) move blocked locks towards the head of the list *while some other
  17  * process might be traversing it*. This should not be a problem in
  18  * practice, because this will only cause functions traversing the list
  19  * to visit some blocks twice.
  20  *
  21  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  22  */
  23
  24 #include <linux/types.h>
  25 #include <linux/slab.h>
  26 #include <linux/errno.h>
  27 #include <linux/kernel.h>
  28 #include <linux/sched.h>
  29 #include <linux/sunrpc/clnt.h>
  30 #include <linux/sunrpc/svc_xprt.h>
  31 #include <linux/lockd/nlm.h>
  32 #include <linux/lockd/lockd.h>
  33 #include <linux/kthread.h>
  34 #include <linux/exportfs.h>
  35
  36 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
  37
  38 #ifdef CONFIG_LOCKD_V4
  39 #define nlm_deadlock    nlm4_deadlock
  40 #else
  41 #define nlm_deadlock    nlm_lck_denied
  42 #endif
  43
  44 static void nlmsvc_release_block(struct nlm_block *block);
  45 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
  46 static void     nlmsvc_remove_block(struct nlm_block *block);
  47
  48 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
  49 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
  50 static const struct rpc_call_ops nlmsvc_grant_ops;
  51
  52 /*
  53  * The list of blocked locks to retry
  54  */
  55 static LIST_HEAD(nlm_blocked);
  56 static DEFINE_SPINLOCK(nlm_blocked_lock);
  57
  58 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  59 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
  60 {
  61         /*
  62          * We can get away with a static buffer because this is only called
  63          * from lockd, which is single-threaded.
  64          */
  65         static char buf[2*NLM_MAXCOOKIELEN+1];
  66         unsigned int i, len = sizeof(buf);
  67         char *p = buf;
  68
  69         len--;  /* allow for trailing \0 */
  70         if (len < 3)
  71                 return "???";
  72         for (i = 0 ; i < cookie->len ; i++) {
  73                 if (len < 2) {
  74                         strcpy(p-3, "...");
  75                         break;
  76                 }
  77                 sprintf(p, "%02x", cookie->data[i]);
  78                 p += 2;
  79                 len -= 2;
  80         }
  81         *p = '\0';
  82
  83         return buf;
  84 }
  85 #endif
  86
  87 /*
  88  * Insert a blocked lock into the global list
  89  */
  90 static void
  91 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
  92 {
  93         struct nlm_block *b;
  94         struct list_head *pos;
  95
  96         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
  97         if (list_empty(&block->b_list)) {
  98                 kref_get(&block->b_count);
  99         } else {
 100                 list_del_init(&block->b_list);
 101         }
 102
 103         pos = &nlm_blocked;
 104         if (when != NLM_NEVER) {
 105                 if ((when += jiffies) == NLM_NEVER)
 106                         when ++;
 107                 list_for_each(pos, &nlm_blocked) {
 108                         b = list_entry(pos, struct nlm_block, b_list);
 109                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
 110                                 break;
 111                 }
 112                 /* On normal exit from the loop, pos == &nlm_blocked,
 113                  * so we will be adding to the end of the list - good
 114                  */
 115         }
 116
 117         list_add_tail(&block->b_list, pos);
 118         block->b_when = when;
 119 }
 120
 121 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
 122 {
 123         spin_lock(&nlm_blocked_lock);
 124         nlmsvc_insert_block_locked(block, when);
 125         spin_unlock(&nlm_blocked_lock);
 126 }
 127
 128 /*
 129  * Remove a block from the global list
 130  */
 131 static inline void
 132 nlmsvc_remove_block(struct nlm_block *block)
 133 {
 134         if (!list_empty(&block->b_list)) {
 135                 spin_lock(&nlm_blocked_lock);
 136                 list_del_init(&block->b_list);
 137                 spin_unlock(&nlm_blocked_lock);
 138                 nlmsvc_release_block(block);
 139         }
 140 }
 141
 142 /*
 143  * Find a block for a given lock
 144  */
 145 static struct nlm_block *
 146 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 147 {
 148         struct nlm_block        *block;
 149         struct file_lock        *fl;
 150
 151         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
 152                                 file, lock->fl.fl_pid,
 153                                 (long long)lock->fl.fl_start,
 154                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
 155         list_for_each_entry(block, &nlm_blocked, b_list) {
 156                 fl = &block->b_call->a_args.lock.fl;
 157                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
 158                                 block->b_file, fl->fl_pid,
 159                                 (long long)fl->fl_start,
 160                                 (long long)fl->fl_end, fl->fl_type,
 161                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
 162                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
 163                         kref_get(&block->b_count);
 164                         return block;
 165                 }
 166         }
 167
 168         return NULL;
 169 }
 170
 171 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 172 {
 173         if (a->len != b->len)
 174                 return 0;
 175         if (memcmp(a->data, b->data, a->len))
 176                 return 0;
 177         return 1;
 178 }
 179
 180 /*
 181  * Find a block with a given NLM cookie.
 182  */
 183 static inline struct nlm_block *
 184 nlmsvc_find_block(struct nlm_cookie *cookie)
 185 {
 186         struct nlm_block *block;
 187
 188         list_for_each_entry(block, &nlm_blocked, b_list) {
 189                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
 190                         goto found;
 191         }
 192
 193         return NULL;
 194
 195 found:
 196         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
 197         kref_get(&block->b_count);
 198         return block;
 199 }
 200
 201 /*
 202  * Create a block and initialize it.
 203  *
 204  * Note: we explicitly set the cookie of the grant reply to that of
 205  * the blocked lock request. The spec explicitly mentions that the client
 206  * should _not_ rely on the callback containing the same cookie as the
 207  * request, but (as I found out later) that's because some implementations
 208  * do just this. Never mind the standards comittees, they support our
 209  * logging industries.
 210  *
 211  * 10 years later: I hope we can safely ignore these old and broken
 212  * clients by now. Let's fix this so we can uniquely identify an incoming
 213  * GRANTED_RES message by cookie, without having to rely on the client's IP
 214  * address. --okir
 215  */
 216 static struct nlm_block *
 217 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
 218                     struct nlm_file *file, struct nlm_lock *lock,
 219                     struct nlm_cookie *cookie)
 220 {
 221         struct nlm_block        *block;
 222         struct nlm_rqst         *call = NULL;
 223
 224         call = nlm_alloc_call(host);
 225         if (call == NULL)
 226                 return NULL;
 227
 228         /* Allocate memory for block, and initialize arguments */
 229         block = kzalloc(sizeof(*block), GFP_KERNEL);
 230         if (block == NULL)
 231                 goto failed;
 232         kref_init(&block->b_count);
 233         INIT_LIST_HEAD(&block->b_list);
 234         INIT_LIST_HEAD(&block->b_flist);
 235
 236         if (!nlmsvc_setgrantargs(call, lock))
 237                 goto failed_free;
 238
 239         /* Set notifier function for VFS, and init args */
 240         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 241         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 242         nlmclnt_next_cookie(&call->a_args.cookie);
 243
 244         dprintk("lockd: created block %p...\n", block);
 245
 246         /* Create and initialize the block */
 247         block->b_daemon = rqstp->rq_server;
 248         block->b_host   = host;
 249         block->b_file   = file;
 250         file->f_count++;
 251
 252         /* Add to file's list of blocks */
 253         list_add(&block->b_flist, &file->f_blocks);
 254
 255         /* Set up RPC arguments for callback */
 256         block->b_call = call;
 257         call->a_flags   = RPC_TASK_ASYNC;
 258         call->a_block = block;
 259
 260         return block;
 261
 262 failed_free:
 263         kfree(block);
 264 failed:
 265         nlmsvc_release_call(call);
 266         return NULL;
 267 }
 268
 269 /*
 270  * Delete a block.
 271  * It is the caller's responsibility to check whether the file
 272  * can be closed hereafter.
 273  */
 274 static int nlmsvc_unlink_block(struct nlm_block *block)
 275 {
 276         int status;
 277         dprintk("lockd: unlinking block %p...\n", block);
 278
 279         /* Remove block from list */
 280         status = locks_delete_block(&block->b_call->a_args.lock.fl);
 281         nlmsvc_remove_block(block);
 282         return status;
 283 }
 284
 285 static void nlmsvc_free_block(struct kref *kref)
 286 {
 287         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 288         struct nlm_file         *file = block->b_file;
 289
 290         dprintk("lockd: freeing block %p...\n", block);
 291
 292         /* Remove block from file's list of blocks */
 293         list_del_init(&block->b_flist);
 294         mutex_unlock(&file->f_mutex);
 295
 296         nlmsvc_freegrantargs(block->b_call);
 297         nlmsvc_release_call(block->b_call);
 298         nlm_release_file(block->b_file);
 299         kfree(block);
 300 }
 301
 302 static void nlmsvc_release_block(struct nlm_block *block)
 303 {
 304         if (block != NULL)
 305                 kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
 306 }
 307
 308 /*
 309  * Loop over all blocks and delete blocks held by
 310  * a matching host.
 311  */
 312 void nlmsvc_traverse_blocks(struct nlm_host *host,
 313                         struct nlm_file *file,
 314                         nlm_host_match_fn_t match)
 315 {
 316         struct nlm_block *block, *next;
 317
 318 restart:
 319         mutex_lock(&file->f_mutex);
 320         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 321                 if (!match(block->b_host, host))
 322                         continue;
 323                 /* Do not destroy blocks that are not on
 324                  * the global retry list - why? */
 325                 if (list_empty(&block->b_list))
 326                         continue;
 327                 kref_get(&block->b_count);
 328                 mutex_unlock(&file->f_mutex);
 329                 nlmsvc_unlink_block(block);
 330                 nlmsvc_release_block(block);
 331                 goto restart;
 332         }
 333         mutex_unlock(&file->f_mutex);
 334 }
 335
 336 static struct nlm_lockowner *
 337 nlmsvc_get_lockowner(struct nlm_lockowner *lockowner)
 338 {
 339         refcount_inc(&lockowner->count);
 340         return lockowner;
 341 }
 342
 343 static void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
 344 {
 345         if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
 346                 return;
 347         list_del(&lockowner->list);
 348         spin_unlock(&lockowner->host->h_lock);
 349         nlmsvc_release_host(lockowner->host);
 350         kfree(lockowner);
 351 }
 352
 353 static struct nlm_lockowner *__nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
 354 {
 355         struct nlm_lockowner *lockowner;
 356         list_for_each_entry(lockowner, &host->h_lockowners, list) {
 357                 if (lockowner->pid != pid)
 358                         continue;
 359                 return nlmsvc_get_lockowner(lockowner);
 360         }
 361         return NULL;
 362 }
 363
 364 static struct nlm_lockowner *nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
 365 {
 366         struct nlm_lockowner *res, *new = NULL;
 367
 368         spin_lock(&host->h_lock);
 369         res = __nlmsvc_find_lockowner(host, pid);
 370
 371         if (res == NULL) {
 372                 spin_unlock(&host->h_lock);
 373                 new = kmalloc(sizeof(*res), GFP_KERNEL);
 374                 spin_lock(&host->h_lock);
 375                 res = __nlmsvc_find_lockowner(host, pid);
 376                 if (res == NULL && new != NULL) {
 377                         res = new;
 378                         /* fs/locks.c will manage the refcount through lock_ops */
 379                         refcount_set(&new->count, 1);
 380                         new->pid = pid;
 381                         new->host = nlm_get_host(host);
 382                         list_add(&new->list, &host->h_lockowners);
 383                         new = NULL;
 384                 }
 385         }
 386
 387         spin_unlock(&host->h_lock);
 388         kfree(new);
 389         return res;
 390 }
 391
 392 void
 393 nlmsvc_release_lockowner(struct nlm_lock *lock)
 394 {
 395         if (lock->fl.fl_owner)
 396                 nlmsvc_put_lockowner(lock->fl.fl_owner);
 397 }
 398
 399 void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host,
 400                                                 pid_t pid)
 401 {
 402         fl->fl_owner = nlmsvc_find_lockowner(host, pid);
 403 }
 404
 405 /*
 406  * Initialize arguments for GRANTED call. The nlm_rqst structure
 407  * has been cleared already.
 408  */
 409 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 410 {
 411         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 412         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 413         call->a_args.lock.caller = utsname()->nodename;
 414         call->a_args.lock.oh.len = lock->oh.len;
 415
 416         /* set default data area */
 417         call->a_args.lock.oh.data = call->a_owner;
 418         call->a_args.lock.svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
 419
 420         if (lock->oh.len > NLMCLNT_OHSIZE) {
 421                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 422                 if (!data)
 423                         return 0;
 424                 call->a_args.lock.oh.data = (u8 *) data;
 425         }
 426
 427         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 428         return 1;
 429 }
 430
 431 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 432 {
 433         if (call->a_args.lock.oh.data != call->a_owner)
 434                 kfree(call->a_args.lock.oh.data);
 435
 436         locks_release_private(&call->a_args.lock.fl);
 437 }
 438
 439 /*
 440  * Deferred lock request handling for non-blocking lock
 441  */
 442 static __be32
 443 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 444 {
 445         __be32 status = nlm_lck_denied_nolocks;
 446
 447         block->b_flags |= B_QUEUED;
 448
 449         nlmsvc_insert_block(block, NLM_TIMEOUT);
 450
 451         block->b_cache_req = &rqstp->rq_chandle;
 452         if (rqstp->rq_chandle.defer) {
 453                 block->b_deferred_req =
 454                         rqstp->rq_chandle.defer(block->b_cache_req);
 455                 if (block->b_deferred_req != NULL)
 456                         status = nlm_drop_reply;
 457         }
 458         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 459                 block, block->b_flags, ntohl(status));
 460
 461         return status;
 462 }
 463
 464 /*
 465  * Attempt to establish a lock, and if it can't be granted, block it
 466  * if required.
 467  */
 468 __be32
 469 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 470             struct nlm_host *host, struct nlm_lock *lock, int wait,
 471             struct nlm_cookie *cookie, int reclaim)
 472 {
 473 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 474         struct inode            *inode = nlmsvc_file_inode(file);
 475 #endif
 476         struct nlm_block        *block = NULL;
 477         int                     error;
 478         int                     mode;
 479         int                     async_block = 0;
 480         __be32                  ret;
 481
 482         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 483                                 inode->i_sb->s_id, inode->i_ino,
 484                                 lock->fl.fl_type, lock->fl.fl_pid,
 485                                 (long long)lock->fl.fl_start,
 486                                 (long long)lock->fl.fl_end,
 487                                 wait);
 488
 489         if (nlmsvc_file_file(file)->f_op->lock) {
 490                 async_block = wait;
 491                 wait = 0;
 492         }
 493
 494         /* Lock file against concurrent access */
 495         mutex_lock(&file->f_mutex);
 496         /* Get existing block (in case client is busy-waiting)
 497          * or create new block
 498          */
 499         block = nlmsvc_lookup_block(file, lock);
 500         if (block == NULL) {
 501                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 502                 ret = nlm_lck_denied_nolocks;
 503                 if (block == NULL)
 504                         goto out;
 505                 lock = &block->b_call->a_args.lock;
 506         } else
 507                 lock->fl.fl_flags &= ~FL_SLEEP;
 508
 509         if (block->b_flags & B_QUEUED) {
 510                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
 511                                                         block, block->b_flags);
 512                 if (block->b_granted) {
 513                         nlmsvc_unlink_block(block);
 514                         ret = nlm_granted;
 515                         goto out;
 516                 }
 517                 if (block->b_flags & B_TIMED_OUT) {
 518                         nlmsvc_unlink_block(block);
 519                         ret = nlm_lck_denied;
 520                         goto out;
 521                 }
 522                 ret = nlm_drop_reply;
 523                 goto out;
 524         }
 525
 526         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
 527                 ret = nlm_lck_denied_grace_period;
 528                 goto out;
 529         }
 530         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
 531                 ret = nlm_lck_denied_grace_period;
 532                 goto out;
 533         }
 534
 535         if (!wait)
 536                 lock->fl.fl_flags &= ~FL_SLEEP;
 537         mode = lock_to_openmode(&lock->fl);
 538         error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
 539         lock->fl.fl_flags &= ~FL_SLEEP;
 540
 541         dprintk("lockd: vfs_lock_file returned %d\n", error);
 542         switch (error) {
 543                 case 0:
 544                         ret = nlm_granted;
 545                         goto out;
 546                 case -EAGAIN:
 547                         /*
 548                          * If this is a blocking request for an
 549                          * already pending lock request then we need
 550                          * to put it back on lockd's block list
 551                          */
 552                         if (wait)
 553                                 break;
 554                         ret = async_block ? nlm_lck_blocked : nlm_lck_denied;
 555                         goto out;
 556                 case FILE_LOCK_DEFERRED:
 557                         if (wait)
 558                                 break;
 559                         /* Filesystem lock operation is in progress
 560                            Add it to the queue waiting for callback */
 561                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
 562                         goto out;
 563                 case -EDEADLK:
 564                         ret = nlm_deadlock;
 565                         goto out;
 566                 default:                        /* includes ENOLCK */
 567                         ret = nlm_lck_denied_nolocks;
 568                         goto out;
 569         }
 570
 571         ret = nlm_lck_blocked;
 572
 573         /* Append to list of blocked */
 574         nlmsvc_insert_block(block, NLM_NEVER);
 575 out:
 576         mutex_unlock(&file->f_mutex);
 577         nlmsvc_release_block(block);
 578         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 579         return ret;
 580 }
 581
 582 /*
 583  * Test for presence of a conflicting lock.
 584  */
 585 __be32
 586 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 587                 struct nlm_host *host, struct nlm_lock *lock,
 588                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
 589 {
 590         int                     error;
 591         int                     mode;
 592         __be32                  ret;
 593         struct nlm_lockowner    *test_owner;
 594
 595         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 596                                 nlmsvc_file_inode(file)->i_sb->s_id,
 597                                 nlmsvc_file_inode(file)->i_ino,
 598                                 lock->fl.fl_type,
 599                                 (long long)lock->fl.fl_start,
 600                                 (long long)lock->fl.fl_end);
 601
 602         if (locks_in_grace(SVC_NET(rqstp))) {
 603                 ret = nlm_lck_denied_grace_period;
 604                 goto out;
 605         }
 606
 607         /* If there's a conflicting lock, remember to clean up the test lock */
 608         test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
 609
 610         mode = lock_to_openmode(&lock->fl);
 611         error = vfs_test_lock(file->f_file[mode], &lock->fl);
 612         if (error) {
 613                 /* We can't currently deal with deferred test requests */
 614                 if (error == FILE_LOCK_DEFERRED)
 615                         WARN_ON_ONCE(1);
 616
 617                 ret = nlm_lck_denied_nolocks;
 618                 goto out;
 619         }
 620
 621         if (lock->fl.fl_type == F_UNLCK) {
 622                 ret = nlm_granted;
 623                 goto out;
 624         }
 625
 626         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 627                 lock->fl.fl_type, (long long)lock->fl.fl_start,
 628                 (long long)lock->fl.fl_end);
 629         conflock->caller = "somehost";  /* FIXME */
 630         conflock->len = strlen(conflock->caller);
 631         conflock->oh.len = 0;           /* don't return OH info */
 632         conflock->svid = lock->fl.fl_pid;
 633         conflock->fl.fl_type = lock->fl.fl_type;
 634         conflock->fl.fl_start = lock->fl.fl_start;
 635         conflock->fl.fl_end = lock->fl.fl_end;
 636         locks_release_private(&lock->fl);
 637
 638         /* Clean up the test lock */
 639         lock->fl.fl_owner = NULL;
 640         nlmsvc_put_lockowner(test_owner);
 641
 642         ret = nlm_lck_denied;
 643 out:
 644         return ret;
 645 }
 646
 647 /*
 648  * Remove a lock.
 649  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 650  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 651  * afterwards. In this case the block will still be there, and hence
 652  * must be removed.
 653  */
 654 __be32
 655 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 656 {
 657         int     error = 0;
 658
 659         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 660                                 nlmsvc_file_inode(file)->i_sb->s_id,
 661                                 nlmsvc_file_inode(file)->i_ino,
 662                                 lock->fl.fl_pid,
 663                                 (long long)lock->fl.fl_start,
 664                                 (long long)lock->fl.fl_end);
 665
 666         /* First, cancel any lock that might be there */
 667         nlmsvc_cancel_blocked(net, file, lock);
 668
 669         lock->fl.fl_type = F_UNLCK;
 670         if (file->f_file[O_RDONLY])
 671                 error = vfs_lock_file(file->f_file[O_RDONLY], F_SETLK,
 672                                         &lock->fl, NULL);
 673         if (file->f_file[O_WRONLY])
 674                 error = vfs_lock_file(file->f_file[O_WRONLY], F_SETLK,
 675                                         &lock->fl, NULL);
 676
 677         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 678 }
 679
 680 /*
 681  * Cancel a previously blocked request.
 682  *
 683  * A cancel request always overrides any grant that may currently
 684  * be in progress.
 685  * The calling procedure must check whether the file can be closed.
 686  */
 687 __be32
 688 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 689 {
 690         struct nlm_block        *block;
 691         int status = 0;
 692         int mode;
 693
 694         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 695                                 nlmsvc_file_inode(file)->i_sb->s_id,
 696                                 nlmsvc_file_inode(file)->i_ino,
 697                                 lock->fl.fl_pid,
 698                                 (long long)lock->fl.fl_start,
 699                                 (long long)lock->fl.fl_end);
 700
 701         if (locks_in_grace(net))
 702                 return nlm_lck_denied_grace_period;
 703
 704         mutex_lock(&file->f_mutex);
 705         block = nlmsvc_lookup_block(file, lock);
 706         mutex_unlock(&file->f_mutex);
 707         if (block != NULL) {
 708                 mode = lock_to_openmode(&lock->fl);
 709                 vfs_cancel_lock(block->b_file->f_file[mode],
 710                                 &block->b_call->a_args.lock.fl);
 711                 status = nlmsvc_unlink_block(block);
 712                 nlmsvc_release_block(block);
 713         }
 714         return status ? nlm_lck_denied : nlm_granted;
 715 }
 716
 717 /*
 718  * This is a callback from the filesystem for VFS file lock requests.
 719  * It will be used if lm_grant is defined and the filesystem can not
 720  * respond to the request immediately.
 721  * For SETLK or SETLKW request it will get the local posix lock.
 722  * In all cases it will move the block to the head of nlm_blocked q where
 723  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
 724  * deferred rpc for GETLK and SETLK.
 725  */
 726 static void
 727 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
 728 {
 729         block->b_flags |= B_GOT_CALLBACK;
 730         if (result == 0)
 731                 block->b_granted = 1;
 732         else
 733                 block->b_flags |= B_TIMED_OUT;
 734 }
 735
 736 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
 737 {
 738         struct nlm_block *block;
 739         int rc = -ENOENT;
 740
 741         spin_lock(&nlm_blocked_lock);
 742         list_for_each_entry(block, &nlm_blocked, b_list) {
 743                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 744                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
 745                                                         block, block->b_flags);
 746                         if (block->b_flags & B_QUEUED) {
 747                                 if (block->b_flags & B_TIMED_OUT) {
 748                                         rc = -ENOLCK;
 749                                         break;
 750                                 }
 751                                 nlmsvc_update_deferred_block(block, result);
 752                         } else if (result == 0)
 753                                 block->b_granted = 1;
 754
 755                         nlmsvc_insert_block_locked(block, 0);
 756                         svc_wake_up(block->b_daemon);
 757                         rc = 0;
 758                         break;
 759                 }
 760         }
 761         spin_unlock(&nlm_blocked_lock);
 762         if (rc == -ENOENT)
 763                 printk(KERN_WARNING "lockd: grant for unknown block\n");
 764         return rc;
 765 }
 766
 767 /*
 768  * Unblock a blocked lock request. This is a callback invoked from the
 769  * VFS layer when a lock on which we blocked is removed.
 770  *
 771  * This function doesn't grant the blocked lock instantly, but rather moves
 772  * the block to the head of nlm_blocked where it can be picked up by lockd.
 773  */
 774 static void
 775 nlmsvc_notify_blocked(struct file_lock *fl)
 776 {
 777         struct nlm_block        *block;
 778
 779         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 780         spin_lock(&nlm_blocked_lock);
 781         list_for_each_entry(block, &nlm_blocked, b_list) {
 782                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 783                         nlmsvc_insert_block_locked(block, 0);
 784                         spin_unlock(&nlm_blocked_lock);
 785                         svc_wake_up(block->b_daemon);
 786                         return;
 787                 }
 788         }
 789         spin_unlock(&nlm_blocked_lock);
 790         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 791 }
 792
 793 static fl_owner_t nlmsvc_get_owner(fl_owner_t owner)
 794 {
 795         return nlmsvc_get_lockowner(owner);
 796 }
 797
 798 static void nlmsvc_put_owner(fl_owner_t owner)
 799 {
 800         nlmsvc_put_lockowner(owner);
 801 }
 802
 803 const struct lock_manager_operations nlmsvc_lock_operations = {
 804         .lm_notify = nlmsvc_notify_blocked,
 805         .lm_grant = nlmsvc_grant_deferred,
 806         .lm_get_owner = nlmsvc_get_owner,
 807         .lm_put_owner = nlmsvc_put_owner,
 808 };
 809
 810 /*
 811  * Try to claim a lock that was previously blocked.
 812  *
 813  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 814  * RPC thread when notifying the client. This seems like overkill...
 815  * Here's why:
 816  *  -   we don't want to use a synchronous RPC thread, otherwise
 817  *      we might find ourselves hanging on a dead portmapper.
 818  *  -   Some lockd implementations (e.g. HP) don't react to
 819  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 820  */
 821 static void
 822 nlmsvc_grant_blocked(struct nlm_block *block)
 823 {
 824         struct nlm_file         *file = block->b_file;
 825         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 826         int                     mode;
 827         int                     error;
 828         loff_t                  fl_start, fl_end;
 829
 830         dprintk("lockd: grant blocked lock %p\n", block);
 831
 832         kref_get(&block->b_count);
 833
 834         /* Unlink block request from list */
 835         nlmsvc_unlink_block(block);
 836
 837         /* If b_granted is true this means we've been here before.
 838          * Just retry the grant callback, possibly refreshing the RPC
 839          * binding */
 840         if (block->b_granted) {
 841                 nlm_rebind_host(block->b_host);
 842                 goto callback;
 843         }
 844
 845         /* Try the lock operation again */
 846         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
 847          * them unchanged for the GRANT_MSG
 848          */
 849         lock->fl.fl_flags |= FL_SLEEP;
 850         fl_start = lock->fl.fl_start;
 851         fl_end = lock->fl.fl_end;
 852         mode = lock_to_openmode(&lock->fl);
 853         error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
 854         lock->fl.fl_flags &= ~FL_SLEEP;
 855         lock->fl.fl_start = fl_start;
 856         lock->fl.fl_end = fl_end;
 857
 858         switch (error) {
 859         case 0:
 860                 break;
 861         case FILE_LOCK_DEFERRED:
 862                 dprintk("lockd: lock still blocked error %d\n", error);
 863                 nlmsvc_insert_block(block, NLM_NEVER);
 864                 nlmsvc_release_block(block);
 865                 return;
 866         default:
 867                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 868                                 -error, __func__);
 869                 nlmsvc_insert_block(block, 10 * HZ);
 870                 nlmsvc_release_block(block);
 871                 return;
 872         }
 873
 874 callback:
 875         /* Lock was granted by VFS. */
 876         dprintk("lockd: GRANTing blocked lock.\n");
 877         block->b_granted = 1;
 878
 879         /* keep block on the list, but don't reattempt until the RPC
 880          * completes or the submission fails
 881          */
 882         nlmsvc_insert_block(block, NLM_NEVER);
 883
 884         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
 885          * will queue up a new one if this one times out
 886          */
 887         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
 888                                 &nlmsvc_grant_ops);
 889
 890         /* RPC submission failed, wait a bit and retry */
 891         if (error < 0)
 892                 nlmsvc_insert_block(block, 10 * HZ);
 893 }
 894
 895 /*
 896  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 897  * RPC call has succeeded or timed out.
 898  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 899  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 900  * chain once more in order to have it removed by lockd itself (which can
 901  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 902  */
 903 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 904 {
 905         struct nlm_rqst         *call = data;
 906         struct nlm_block        *block = call->a_block;
 907         unsigned long           timeout;
 908
 909         dprintk("lockd: GRANT_MSG RPC callback\n");
 910
 911         spin_lock(&nlm_blocked_lock);
 912         /* if the block is not on a list at this point then it has
 913          * been invalidated. Don't try to requeue it.
 914          *
 915          * FIXME: it's possible that the block is removed from the list
 916          * after this check but before the nlmsvc_insert_block. In that
 917          * case it will be added back. Perhaps we need better locking
 918          * for nlm_blocked?
 919          */
 920         if (list_empty(&block->b_list))
 921                 goto out;
 922
 923         /* Technically, we should down the file semaphore here. Since we
 924          * move the block towards the head of the queue only, no harm
 925          * can be done, though. */
 926         if (task->tk_status < 0) {
 927                 /* RPC error: Re-insert for retransmission */
 928                 timeout = 10 * HZ;
 929         } else {
 930                 /* Call was successful, now wait for client callback */
 931                 timeout = 60 * HZ;
 932         }
 933         nlmsvc_insert_block_locked(block, timeout);
 934         svc_wake_up(block->b_daemon);
 935 out:
 936         spin_unlock(&nlm_blocked_lock);
 937 }
 938
 939 /*
 940  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
 941  * .rpc_release rpc_call_op
 942  */
 943 static void nlmsvc_grant_release(void *data)
 944 {
 945         struct nlm_rqst         *call = data;
 946         nlmsvc_release_block(call->a_block);
 947 }
 948
 949 static const struct rpc_call_ops nlmsvc_grant_ops = {
 950         .rpc_call_done = nlmsvc_grant_callback,
 951         .rpc_release = nlmsvc_grant_release,
 952 };
 953
 954 /*
 955  * We received a GRANT_RES callback. Try to find the corresponding
 956  * block.
 957  */
 958 void
 959 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 960 {
 961         struct nlm_block        *block;
 962
 963         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 964                 *(unsigned int *)(cookie->data), status);
 965         if (!(block = nlmsvc_find_block(cookie)))
 966                 return;
 967
 968         if (status == nlm_lck_denied_grace_period) {
 969                 /* Try again in a couple of seconds */
 970                 nlmsvc_insert_block(block, 10 * HZ);
 971         } else {
 972                 /*
 973                  * Lock is now held by client, or has been rejected.
 974                  * In both cases, the block should be removed.
 975                  */
 976                 nlmsvc_unlink_block(block);
 977         }
 978         nlmsvc_release_block(block);
 979 }
 980
 981 /* Helper function to handle retry of a deferred block.
 982  * If it is a blocking lock, call grant_blocked.
 983  * For a non-blocking lock or test lock, revisit the request.
 984  */
 985 static void
 986 retry_deferred_block(struct nlm_block *block)
 987 {
 988         if (!(block->b_flags & B_GOT_CALLBACK))
 989                 block->b_flags |= B_TIMED_OUT;
 990         nlmsvc_insert_block(block, NLM_TIMEOUT);
 991         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
 992         if (block->b_deferred_req) {
 993                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
 994                 block->b_deferred_req = NULL;
 995         }
 996 }
 997
 998 /*
 999  * Retry all blocked locks that have been notified. This is where lockd
1000  * picks up locks that can be granted, or grant notifications that must
1001  * be retransmitted.
1002  */
1003 unsigned long
1004 nlmsvc_retry_blocked(void)
1005 {
1006         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
1007         struct nlm_block *block;
1008
1009         spin_lock(&nlm_blocked_lock);
1010         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
1011                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
1012
1013                 if (block->b_when == NLM_NEVER)
1014                         break;
1015                 if (time_after(block->b_when, jiffies)) {
1016                         timeout = block->b_when - jiffies;
1017                         break;
1018                 }
1019                 spin_unlock(&nlm_blocked_lock);
1020
1021                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
1022                         block, block->b_when);
1023                 if (block->b_flags & B_QUEUED) {
1024                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
1025                                 block, block->b_granted, block->b_flags);
1026                         retry_deferred_block(block);
1027                 } else
1028                         nlmsvc_grant_blocked(block);
1029                 spin_lock(&nlm_blocked_lock);
1030         }
1031         spin_unlock(&nlm_blocked_lock);
1032
1033         return timeout;
1034 }