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.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 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie);
  50
  51 /*
  52  * The list of blocked locks to retry
  53  */
  54 static LIST_HEAD(nlm_blocked);
  55 static DEFINE_SPINLOCK(nlm_blocked_lock);
  56
  57 /*
  58  * Insert a blocked lock into the global list
  59  */
  60 static void
  61 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
  62 {
  63         struct nlm_block *b;
  64         struct list_head *pos;
  65
  66         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
  67         if (list_empty(&block->b_list)) {
  68                 kref_get(&block->b_count);
  69         } else {
  70                 list_del_init(&block->b_list);
  71         }
  72
  73         pos = &nlm_blocked;
  74         if (when != NLM_NEVER) {
  75                 if ((when += jiffies) == NLM_NEVER)
  76                         when ++;
  77                 list_for_each(pos, &nlm_blocked) {
  78                         b = list_entry(pos, struct nlm_block, b_list);
  79                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
  80                                 break;
  81                 }
  82                 /* On normal exit from the loop, pos == &nlm_blocked,
  83                  * so we will be adding to the end of the list - good
  84                  */
  85         }
  86
  87         list_add_tail(&block->b_list, pos);
  88         block->b_when = when;
  89 }
  90
  91 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
  92 {
  93         spin_lock(&nlm_blocked_lock);
  94         nlmsvc_insert_block_locked(block, when);
  95         spin_unlock(&nlm_blocked_lock);
  96 }
  97
  98 /*
  99  * Remove a block from the global list
 100  */
 101 static inline void
 102 nlmsvc_remove_block(struct nlm_block *block)
 103 {
 104         if (!list_empty(&block->b_list)) {
 105                 spin_lock(&nlm_blocked_lock);
 106                 list_del_init(&block->b_list);
 107                 spin_unlock(&nlm_blocked_lock);
 108                 nlmsvc_release_block(block);
 109         }
 110 }
 111
 112 /*
 113  * Find a block for a given lock
 114  */
 115 static struct nlm_block *
 116 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 117 {
 118         struct nlm_block        *block;
 119         struct file_lock        *fl;
 120
 121         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
 122                                 file, lock->fl.fl_pid,
 123                                 (long long)lock->fl.fl_start,
 124                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
 125         list_for_each_entry(block, &nlm_blocked, b_list) {
 126                 fl = &block->b_call->a_args.lock.fl;
 127                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
 128                                 block->b_file, fl->fl_pid,
 129                                 (long long)fl->fl_start,
 130                                 (long long)fl->fl_end, fl->fl_type,
 131                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
 132                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
 133                         kref_get(&block->b_count);
 134                         return block;
 135                 }
 136         }
 137
 138         return NULL;
 139 }
 140
 141 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 142 {
 143         if (a->len != b->len)
 144                 return 0;
 145         if (memcmp(a->data, b->data, a->len))
 146                 return 0;
 147         return 1;
 148 }
 149
 150 /*
 151  * Find a block with a given NLM cookie.
 152  */
 153 static inline struct nlm_block *
 154 nlmsvc_find_block(struct nlm_cookie *cookie)
 155 {
 156         struct nlm_block *block;
 157
 158         list_for_each_entry(block, &nlm_blocked, b_list) {
 159                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
 160                         goto found;
 161         }
 162
 163         return NULL;
 164
 165 found:
 166         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
 167         kref_get(&block->b_count);
 168         return block;
 169 }
 170
 171 /*
 172  * Create a block and initialize it.
 173  *
 174  * Note: we explicitly set the cookie of the grant reply to that of
 175  * the blocked lock request. The spec explicitly mentions that the client
 176  * should _not_ rely on the callback containing the same cookie as the
 177  * request, but (as I found out later) that's because some implementations
 178  * do just this. Never mind the standards comittees, they support our
 179  * logging industries.
 180  *
 181  * 10 years later: I hope we can safely ignore these old and broken
 182  * clients by now. Let's fix this so we can uniquely identify an incoming
 183  * GRANTED_RES message by cookie, without having to rely on the client's IP
 184  * address. --okir
 185  */
 186 static struct nlm_block *
 187 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
 188                     struct nlm_file *file, struct nlm_lock *lock,
 189                     struct nlm_cookie *cookie)
 190 {
 191         struct nlm_block        *block;
 192         struct nlm_rqst         *call = NULL;
 193
 194         nlm_get_host(host);
 195         call = nlm_alloc_call(host);
 196         if (call == NULL)
 197                 return NULL;
 198
 199         /* Allocate memory for block, and initialize arguments */
 200         block = kzalloc(sizeof(*block), GFP_KERNEL);
 201         if (block == NULL)
 202                 goto failed;
 203         kref_init(&block->b_count);
 204         INIT_LIST_HEAD(&block->b_list);
 205         INIT_LIST_HEAD(&block->b_flist);
 206
 207         if (!nlmsvc_setgrantargs(call, lock))
 208                 goto failed_free;
 209
 210         /* Set notifier function for VFS, and init args */
 211         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 212         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 213         nlmclnt_next_cookie(&call->a_args.cookie);
 214
 215         dprintk("lockd: created block %p...\n", block);
 216
 217         /* Create and initialize the block */
 218         block->b_daemon = rqstp->rq_server;
 219         block->b_host   = host;
 220         block->b_file   = file;
 221         block->b_fl = NULL;
 222         file->f_count++;
 223
 224         /* Add to file's list of blocks */
 225         list_add(&block->b_flist, &file->f_blocks);
 226
 227         /* Set up RPC arguments for callback */
 228         block->b_call = call;
 229         call->a_flags   = RPC_TASK_ASYNC;
 230         call->a_block = block;
 231
 232         return block;
 233
 234 failed_free:
 235         kfree(block);
 236 failed:
 237         nlmsvc_release_call(call);
 238         return NULL;
 239 }
 240
 241 /*
 242  * Delete a block.
 243  * It is the caller's responsibility to check whether the file
 244  * can be closed hereafter.
 245  */
 246 static int nlmsvc_unlink_block(struct nlm_block *block)
 247 {
 248         int status;
 249         dprintk("lockd: unlinking block %p...\n", block);
 250
 251         /* Remove block from list */
 252         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
 253         nlmsvc_remove_block(block);
 254         return status;
 255 }
 256
 257 static void nlmsvc_free_block(struct kref *kref)
 258 {
 259         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 260         struct nlm_file         *file = block->b_file;
 261
 262         dprintk("lockd: freeing block %p...\n", block);
 263
 264         /* Remove block from file's list of blocks */
 265         mutex_lock(&file->f_mutex);
 266         list_del_init(&block->b_flist);
 267         mutex_unlock(&file->f_mutex);
 268
 269         nlmsvc_freegrantargs(block->b_call);
 270         nlmsvc_release_call(block->b_call);
 271         nlm_release_file(block->b_file);
 272         kfree(block->b_fl);
 273         kfree(block);
 274 }
 275
 276 static void nlmsvc_release_block(struct nlm_block *block)
 277 {
 278         if (block != NULL)
 279                 kref_put(&block->b_count, nlmsvc_free_block);
 280 }
 281
 282 /*
 283  * Loop over all blocks and delete blocks held by
 284  * a matching host.
 285  */
 286 void nlmsvc_traverse_blocks(struct nlm_host *host,
 287                         struct nlm_file *file,
 288                         nlm_host_match_fn_t match)
 289 {
 290         struct nlm_block *block, *next;
 291
 292 restart:
 293         mutex_lock(&file->f_mutex);
 294         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 295                 if (!match(block->b_host, host))
 296                         continue;
 297                 /* Do not destroy blocks that are not on
 298                  * the global retry list - why? */
 299                 if (list_empty(&block->b_list))
 300                         continue;
 301                 kref_get(&block->b_count);
 302                 mutex_unlock(&file->f_mutex);
 303                 nlmsvc_unlink_block(block);
 304                 nlmsvc_release_block(block);
 305                 goto restart;
 306         }
 307         mutex_unlock(&file->f_mutex);
 308 }
 309
 310 /*
 311  * Initialize arguments for GRANTED call. The nlm_rqst structure
 312  * has been cleared already.
 313  */
 314 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 315 {
 316         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 317         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 318         call->a_args.lock.caller = utsname()->nodename;
 319         call->a_args.lock.oh.len = lock->oh.len;
 320
 321         /* set default data area */
 322         call->a_args.lock.oh.data = call->a_owner;
 323         call->a_args.lock.svid = lock->fl.fl_pid;
 324
 325         if (lock->oh.len > NLMCLNT_OHSIZE) {
 326                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 327                 if (!data)
 328                         return 0;
 329                 call->a_args.lock.oh.data = (u8 *) data;
 330         }
 331
 332         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 333         return 1;
 334 }
 335
 336 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 337 {
 338         if (call->a_args.lock.oh.data != call->a_owner)
 339                 kfree(call->a_args.lock.oh.data);
 340
 341         locks_release_private(&call->a_args.lock.fl);
 342 }
 343
 344 /*
 345  * Deferred lock request handling for non-blocking lock
 346  */
 347 static __be32
 348 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 349 {
 350         __be32 status = nlm_lck_denied_nolocks;
 351
 352         block->b_flags |= B_QUEUED;
 353
 354         nlmsvc_insert_block(block, NLM_TIMEOUT);
 355
 356         block->b_cache_req = &rqstp->rq_chandle;
 357         if (rqstp->rq_chandle.defer) {
 358                 block->b_deferred_req =
 359                         rqstp->rq_chandle.defer(block->b_cache_req);
 360                 if (block->b_deferred_req != NULL)
 361                         status = nlm_drop_reply;
 362         }
 363         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 364                 block, block->b_flags, ntohl(status));
 365
 366         return status;
 367 }
 368
 369 /*
 370  * Attempt to establish a lock, and if it can't be granted, block it
 371  * if required.
 372  */
 373 __be32
 374 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 375             struct nlm_host *host, struct nlm_lock *lock, int wait,
 376             struct nlm_cookie *cookie, int reclaim)
 377 {
 378         struct nlm_block        *block = NULL;
 379         int                     error;
 380         __be32                  ret;
 381
 382         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 383                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 384                                 file->f_file->f_path.dentry->d_inode->i_ino,
 385                                 lock->fl.fl_type, lock->fl.fl_pid,
 386                                 (long long)lock->fl.fl_start,
 387                                 (long long)lock->fl.fl_end,
 388                                 wait);
 389
 390         /* Lock file against concurrent access */
 391         mutex_lock(&file->f_mutex);
 392         /* Get existing block (in case client is busy-waiting)
 393          * or create new block
 394          */
 395         block = nlmsvc_lookup_block(file, lock);
 396         if (block == NULL) {
 397                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 398                 ret = nlm_lck_denied_nolocks;
 399                 if (block == NULL)
 400                         goto out;
 401                 lock = &block->b_call->a_args.lock;
 402         } else
 403                 lock->fl.fl_flags &= ~FL_SLEEP;
 404
 405         if (block->b_flags & B_QUEUED) {
 406                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
 407                                                         block, block->b_flags);
 408                 if (block->b_granted) {
 409                         nlmsvc_unlink_block(block);
 410                         ret = nlm_granted;
 411                         goto out;
 412                 }
 413                 if (block->b_flags & B_TIMED_OUT) {
 414                         nlmsvc_unlink_block(block);
 415                         ret = nlm_lck_denied;
 416                         goto out;
 417                 }
 418                 ret = nlm_drop_reply;
 419                 goto out;
 420         }
 421
 422         if (locks_in_grace() && !reclaim) {
 423                 ret = nlm_lck_denied_grace_period;
 424                 goto out;
 425         }
 426         if (reclaim && !locks_in_grace()) {
 427                 ret = nlm_lck_denied_grace_period;
 428                 goto out;
 429         }
 430
 431         if (!wait)
 432                 lock->fl.fl_flags &= ~FL_SLEEP;
 433         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 434         lock->fl.fl_flags &= ~FL_SLEEP;
 435
 436         dprintk("lockd: vfs_lock_file returned %d\n", error);
 437         switch (error) {
 438                 case 0:
 439                         ret = nlm_granted;
 440                         goto out;
 441                 case -EAGAIN:
 442                         /*
 443                          * If this is a blocking request for an
 444                          * already pending lock request then we need
 445                          * to put it back on lockd's block list
 446                          */
 447                         if (wait)
 448                                 break;
 449                         ret = nlm_lck_denied;
 450                         goto out;
 451                 case FILE_LOCK_DEFERRED:
 452                         if (wait)
 453                                 break;
 454                         /* Filesystem lock operation is in progress
 455                            Add it to the queue waiting for callback */
 456                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
 457                         goto out;
 458                 case -EDEADLK:
 459                         ret = nlm_deadlock;
 460                         goto out;
 461                 default:                        /* includes ENOLCK */
 462                         ret = nlm_lck_denied_nolocks;
 463                         goto out;
 464         }
 465
 466         ret = nlm_lck_blocked;
 467
 468         /* Append to list of blocked */
 469         nlmsvc_insert_block(block, NLM_NEVER);
 470 out:
 471         mutex_unlock(&file->f_mutex);
 472         nlmsvc_release_block(block);
 473         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 474         return ret;
 475 }
 476
 477 /*
 478  * Test for presence of a conflicting lock.
 479  */
 480 __be32
 481 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 482                 struct nlm_host *host, struct nlm_lock *lock,
 483                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
 484 {
 485         struct nlm_block        *block = NULL;
 486         int                     error;
 487         __be32                  ret;
 488
 489         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 490                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 491                                 file->f_file->f_path.dentry->d_inode->i_ino,
 492                                 lock->fl.fl_type,
 493                                 (long long)lock->fl.fl_start,
 494                                 (long long)lock->fl.fl_end);
 495
 496         /* Get existing block (in case client is busy-waiting) */
 497         block = nlmsvc_lookup_block(file, lock);
 498
 499         if (block == NULL) {
 500                 struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
 501
 502                 if (conf == NULL)
 503                         return nlm_granted;
 504                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 505                 if (block == NULL) {
 506                         kfree(conf);
 507                         return nlm_granted;
 508                 }
 509                 block->b_fl = conf;
 510         }
 511         if (block->b_flags & B_QUEUED) {
 512                 dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
 513                         block, block->b_flags, block->b_fl);
 514                 if (block->b_flags & B_TIMED_OUT) {
 515                         nlmsvc_unlink_block(block);
 516                         ret = nlm_lck_denied;
 517                         goto out;
 518                 }
 519                 if (block->b_flags & B_GOT_CALLBACK) {
 520                         nlmsvc_unlink_block(block);
 521                         if (block->b_fl != NULL
 522                                         && block->b_fl->fl_type != F_UNLCK) {
 523                                 lock->fl = *block->b_fl;
 524                                 goto conf_lock;
 525                         } else {
 526                                 ret = nlm_granted;
 527                                 goto out;
 528                         }
 529                 }
 530                 ret = nlm_drop_reply;
 531                 goto out;
 532         }
 533
 534         if (locks_in_grace()) {
 535                 ret = nlm_lck_denied_grace_period;
 536                 goto out;
 537         }
 538         error = vfs_test_lock(file->f_file, &lock->fl);
 539         if (error == FILE_LOCK_DEFERRED) {
 540                 ret = nlmsvc_defer_lock_rqst(rqstp, block);
 541                 goto out;
 542         }
 543         if (error) {
 544                 ret = nlm_lck_denied_nolocks;
 545                 goto out;
 546         }
 547         if (lock->fl.fl_type == F_UNLCK) {
 548                 ret = nlm_granted;
 549                 goto out;
 550         }
 551
 552 conf_lock:
 553         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 554                 lock->fl.fl_type, (long long)lock->fl.fl_start,
 555                 (long long)lock->fl.fl_end);
 556         conflock->caller = "somehost";  /* FIXME */
 557         conflock->len = strlen(conflock->caller);
 558         conflock->oh.len = 0;           /* don't return OH info */
 559         conflock->svid = lock->fl.fl_pid;
 560         conflock->fl.fl_type = lock->fl.fl_type;
 561         conflock->fl.fl_start = lock->fl.fl_start;
 562         conflock->fl.fl_end = lock->fl.fl_end;
 563         ret = nlm_lck_denied;
 564 out:
 565         if (block)
 566                 nlmsvc_release_block(block);
 567         return ret;
 568 }
 569
 570 /*
 571  * Remove a lock.
 572  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 573  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 574  * afterwards. In this case the block will still be there, and hence
 575  * must be removed.
 576  */
 577 __be32
 578 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
 579 {
 580         int     error;
 581
 582         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 583                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 584                                 file->f_file->f_path.dentry->d_inode->i_ino,
 585                                 lock->fl.fl_pid,
 586                                 (long long)lock->fl.fl_start,
 587                                 (long long)lock->fl.fl_end);
 588
 589         /* First, cancel any lock that might be there */
 590         nlmsvc_cancel_blocked(file, lock);
 591
 592         lock->fl.fl_type = F_UNLCK;
 593         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 594
 595         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 596 }
 597
 598 /*
 599  * Cancel a previously blocked request.
 600  *
 601  * A cancel request always overrides any grant that may currently
 602  * be in progress.
 603  * The calling procedure must check whether the file can be closed.
 604  */
 605 __be32
 606 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
 607 {
 608         struct nlm_block        *block;
 609         int status = 0;
 610
 611         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 612                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 613                                 file->f_file->f_path.dentry->d_inode->i_ino,
 614                                 lock->fl.fl_pid,
 615                                 (long long)lock->fl.fl_start,
 616                                 (long long)lock->fl.fl_end);
 617
 618         if (locks_in_grace())
 619                 return nlm_lck_denied_grace_period;
 620
 621         mutex_lock(&file->f_mutex);
 622         block = nlmsvc_lookup_block(file, lock);
 623         mutex_unlock(&file->f_mutex);
 624         if (block != NULL) {
 625                 vfs_cancel_lock(block->b_file->f_file,
 626                                 &block->b_call->a_args.lock.fl);
 627                 status = nlmsvc_unlink_block(block);
 628                 nlmsvc_release_block(block);
 629         }
 630         return status ? nlm_lck_denied : nlm_granted;
 631 }
 632
 633 /*
 634  * This is a callback from the filesystem for VFS file lock requests.
 635  * It will be used if lm_grant is defined and the filesystem can not
 636  * respond to the request immediately.
 637  * For GETLK request it will copy the reply to the nlm_block.
 638  * For SETLK or SETLKW request it will get the local posix lock.
 639  * In all cases it will move the block to the head of nlm_blocked q where
 640  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
 641  * deferred rpc for GETLK and SETLK.
 642  */
 643 static void
 644 nlmsvc_update_deferred_block(struct nlm_block *block, struct file_lock *conf,
 645                              int result)
 646 {
 647         block->b_flags |= B_GOT_CALLBACK;
 648         if (result == 0)
 649                 block->b_granted = 1;
 650         else
 651                 block->b_flags |= B_TIMED_OUT;
 652         if (conf) {
 653                 if (block->b_fl)
 654                         __locks_copy_lock(block->b_fl, conf);
 655         }
 656 }
 657
 658 static int nlmsvc_grant_deferred(struct file_lock *fl, struct file_lock *conf,
 659                                         int result)
 660 {
 661         struct nlm_block *block;
 662         int rc = -ENOENT;
 663
 664         spin_lock(&nlm_blocked_lock);
 665         list_for_each_entry(block, &nlm_blocked, b_list) {
 666                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 667                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
 668                                                         block, block->b_flags);
 669                         if (block->b_flags & B_QUEUED) {
 670                                 if (block->b_flags & B_TIMED_OUT) {
 671                                         rc = -ENOLCK;
 672                                         break;
 673                                 }
 674                                 nlmsvc_update_deferred_block(block, conf, result);
 675                         } else if (result == 0)
 676                                 block->b_granted = 1;
 677
 678                         nlmsvc_insert_block_locked(block, 0);
 679                         svc_wake_up(block->b_daemon);
 680                         rc = 0;
 681                         break;
 682                 }
 683         }
 684         spin_unlock(&nlm_blocked_lock);
 685         if (rc == -ENOENT)
 686                 printk(KERN_WARNING "lockd: grant for unknown block\n");
 687         return rc;
 688 }
 689
 690 /*
 691  * Unblock a blocked lock request. This is a callback invoked from the
 692  * VFS layer when a lock on which we blocked is removed.
 693  *
 694  * This function doesn't grant the blocked lock instantly, but rather moves
 695  * the block to the head of nlm_blocked where it can be picked up by lockd.
 696  */
 697 static void
 698 nlmsvc_notify_blocked(struct file_lock *fl)
 699 {
 700         struct nlm_block        *block;
 701
 702         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 703         spin_lock(&nlm_blocked_lock);
 704         list_for_each_entry(block, &nlm_blocked, b_list) {
 705                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 706                         nlmsvc_insert_block_locked(block, 0);
 707                         spin_unlock(&nlm_blocked_lock);
 708                         svc_wake_up(block->b_daemon);
 709                         return;
 710                 }
 711         }
 712         spin_unlock(&nlm_blocked_lock);
 713         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 714 }
 715
 716 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 717 {
 718         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 719 }
 720
 721 const struct lock_manager_operations nlmsvc_lock_operations = {
 722         .lm_compare_owner = nlmsvc_same_owner,
 723         .lm_notify = nlmsvc_notify_blocked,
 724         .lm_grant = nlmsvc_grant_deferred,
 725 };
 726
 727 /*
 728  * Try to claim a lock that was previously blocked.
 729  *
 730  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 731  * RPC thread when notifying the client. This seems like overkill...
 732  * Here's why:
 733  *  -   we don't want to use a synchronous RPC thread, otherwise
 734  *      we might find ourselves hanging on a dead portmapper.
 735  *  -   Some lockd implementations (e.g. HP) don't react to
 736  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 737  */
 738 static void
 739 nlmsvc_grant_blocked(struct nlm_block *block)
 740 {
 741         struct nlm_file         *file = block->b_file;
 742         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 743         int                     error;
 744
 745         dprintk("lockd: grant blocked lock %p\n", block);
 746
 747         kref_get(&block->b_count);
 748
 749         /* Unlink block request from list */
 750         nlmsvc_unlink_block(block);
 751
 752         /* If b_granted is true this means we've been here before.
 753          * Just retry the grant callback, possibly refreshing the RPC
 754          * binding */
 755         if (block->b_granted) {
 756                 nlm_rebind_host(block->b_host);
 757                 goto callback;
 758         }
 759
 760         /* Try the lock operation again */
 761         lock->fl.fl_flags |= FL_SLEEP;
 762         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 763         lock->fl.fl_flags &= ~FL_SLEEP;
 764
 765         switch (error) {
 766         case 0:
 767                 break;
 768         case FILE_LOCK_DEFERRED:
 769                 dprintk("lockd: lock still blocked error %d\n", error);
 770                 nlmsvc_insert_block(block, NLM_NEVER);
 771                 nlmsvc_release_block(block);
 772                 return;
 773         default:
 774                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 775                                 -error, __func__);
 776                 nlmsvc_insert_block(block, 10 * HZ);
 777                 nlmsvc_release_block(block);
 778                 return;
 779         }
 780
 781 callback:
 782         /* Lock was granted by VFS. */
 783         dprintk("lockd: GRANTing blocked lock.\n");
 784         block->b_granted = 1;
 785
 786         /* keep block on the list, but don't reattempt until the RPC
 787          * completes or the submission fails
 788          */
 789         nlmsvc_insert_block(block, NLM_NEVER);
 790
 791         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
 792          * will queue up a new one if this one times out
 793          */
 794         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
 795                                 &nlmsvc_grant_ops);
 796
 797         /* RPC submission failed, wait a bit and retry */
 798         if (error < 0)
 799                 nlmsvc_insert_block(block, 10 * HZ);
 800 }
 801
 802 /*
 803  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 804  * RPC call has succeeded or timed out.
 805  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 806  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 807  * chain once more in order to have it removed by lockd itself (which can
 808  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 809  */
 810 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 811 {
 812         struct nlm_rqst         *call = data;
 813         struct nlm_block        *block = call->a_block;
 814         unsigned long           timeout;
 815
 816         dprintk("lockd: GRANT_MSG RPC callback\n");
 817
 818         spin_lock(&nlm_blocked_lock);
 819         /* if the block is not on a list at this point then it has
 820          * been invalidated. Don't try to requeue it.
 821          *
 822          * FIXME: it's possible that the block is removed from the list
 823          * after this check but before the nlmsvc_insert_block. In that
 824          * case it will be added back. Perhaps we need better locking
 825          * for nlm_blocked?
 826          */
 827         if (list_empty(&block->b_list))
 828                 goto out;
 829
 830         /* Technically, we should down the file semaphore here. Since we
 831          * move the block towards the head of the queue only, no harm
 832          * can be done, though. */
 833         if (task->tk_status < 0) {
 834                 /* RPC error: Re-insert for retransmission */
 835                 timeout = 10 * HZ;
 836         } else {
 837                 /* Call was successful, now wait for client callback */
 838                 timeout = 60 * HZ;
 839         }
 840         nlmsvc_insert_block_locked(block, timeout);
 841         svc_wake_up(block->b_daemon);
 842 out:
 843         spin_unlock(&nlm_blocked_lock);
 844 }
 845
 846 /*
 847  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
 848  * .rpc_release rpc_call_op
 849  */
 850 static void nlmsvc_grant_release(void *data)
 851 {
 852         struct nlm_rqst         *call = data;
 853         nlmsvc_release_block(call->a_block);
 854 }
 855
 856 static const struct rpc_call_ops nlmsvc_grant_ops = {
 857         .rpc_call_done = nlmsvc_grant_callback,
 858         .rpc_release = nlmsvc_grant_release,
 859 };
 860
 861 /*
 862  * We received a GRANT_RES callback. Try to find the corresponding
 863  * block.
 864  */
 865 void
 866 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 867 {
 868         struct nlm_block        *block;
 869
 870         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 871                 *(unsigned int *)(cookie->data), status);
 872         if (!(block = nlmsvc_find_block(cookie)))
 873                 return;
 874
 875         if (block) {
 876                 if (status == nlm_lck_denied_grace_period) {
 877                         /* Try again in a couple of seconds */
 878                         nlmsvc_insert_block(block, 10 * HZ);
 879                 } else {
 880                         /* Lock is now held by client, or has been rejected.
 881                          * In both cases, the block should be removed. */
 882                         nlmsvc_unlink_block(block);
 883                 }
 884         }
 885         nlmsvc_release_block(block);
 886 }
 887
 888 /* Helper function to handle retry of a deferred block.
 889  * If it is a blocking lock, call grant_blocked.
 890  * For a non-blocking lock or test lock, revisit the request.
 891  */
 892 static void
 893 retry_deferred_block(struct nlm_block *block)
 894 {
 895         if (!(block->b_flags & B_GOT_CALLBACK))
 896                 block->b_flags |= B_TIMED_OUT;
 897         nlmsvc_insert_block(block, NLM_TIMEOUT);
 898         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
 899         if (block->b_deferred_req) {
 900                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
 901                 block->b_deferred_req = NULL;
 902         }
 903 }
 904
 905 /*
 906  * Retry all blocked locks that have been notified. This is where lockd
 907  * picks up locks that can be granted, or grant notifications that must
 908  * be retransmitted.
 909  */
 910 unsigned long
 911 nlmsvc_retry_blocked(void)
 912 {
 913         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
 914         struct nlm_block *block;
 915
 916         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
 917                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 918
 919                 if (block->b_when == NLM_NEVER)
 920                         break;
 921                 if (time_after(block->b_when, jiffies)) {
 922                         timeout = block->b_when - jiffies;
 923                         break;
 924                 }
 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         }
 935
 936         return timeout;
 937 }
 938
 939 #ifdef RPC_DEBUG
 940 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
 941 {
 942         /*
 943          * We can get away with a static buffer because we're only
 944          * called with BKL held.
 945          */
 946         static char buf[2*NLM_MAXCOOKIELEN+1];
 947         unsigned int i, len = sizeof(buf);
 948         char *p = buf;
 949
 950         len--;  /* allow for trailing \0 */
 951         if (len < 3)
 952                 return "???";
 953         for (i = 0 ; i < cookie->len ; i++) {
 954                 if (len < 2) {
 955                         strcpy(p-3, "...");
 956                         break;
 957                 }
 958                 sprintf(p, "%02x", cookie->data[i]);
 959                 p += 2;
 960                 len -= 2;
 961         }
 962         *p = '\0';
 963
 964         return buf;
 965 }
 966 #endif