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