2 * linux/fs/lockd/svclock.c
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.
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.
20 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
23 #include <linux/config.h>
24 #include <linux/types.h>
25 #include <linux/errno.h>
26 #include <linux/kernel.h>
27 #include <linux/sched.h>
28 #include <linux/smp_lock.h>
29 #include <linux/sunrpc/clnt.h>
30 #include <linux/sunrpc/svc.h>
31 #include <linux/lockd/nlm.h>
32 #include <linux/lockd/lockd.h>
34 #define NLMDBG_FACILITY NLMDBG_SVCLOCK
36 #ifdef CONFIG_LOCKD_V4
37 #define nlm_deadlock nlm4_deadlock
39 #define nlm_deadlock nlm_lck_denied
42 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
43 static int nlmsvc_remove_block(struct nlm_block *block);
45 static const struct rpc_call_ops nlmsvc_grant_ops;
48 * The list of blocked locks to retry
50 static struct nlm_block * nlm_blocked;
53 * Insert a blocked lock into the global list
56 nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
58 struct nlm_block **bp, *b;
60 dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
62 nlmsvc_remove_block(block);
64 if (when != NLM_NEVER) {
65 if ((when += jiffies) == NLM_NEVER)
67 while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER)
70 while ((b = *bp) != 0)
80 * Remove a block from the global list
83 nlmsvc_remove_block(struct nlm_block *block)
85 struct nlm_block **bp, *b;
89 for (bp = &nlm_blocked; (b = *bp) != 0; bp = &b->b_next) {
101 * Find a block for a given lock and optionally remove it from
104 static struct nlm_block *
105 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock, int remove)
107 struct nlm_block **head, *block;
108 struct file_lock *fl;
110 dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
111 file, lock->fl.fl_pid,
112 (long long)lock->fl.fl_start,
113 (long long)lock->fl.fl_end, lock->fl.fl_type);
114 for (head = &nlm_blocked; (block = *head) != 0; head = &block->b_next) {
115 fl = &block->b_call.a_args.lock.fl;
116 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
117 block->b_file, fl->fl_pid,
118 (long long)fl->fl_start,
119 (long long)fl->fl_end, fl->fl_type,
120 nlmdbg_cookie2a(&block->b_call.a_args.cookie));
121 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
123 *head = block->b_next;
133 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
137 if(memcmp(a->data,b->data,a->len))
143 * Find a block with a given NLM cookie.
145 static inline struct nlm_block *
146 nlmsvc_find_block(struct nlm_cookie *cookie, struct sockaddr_in *sin)
148 struct nlm_block *block;
150 for (block = nlm_blocked; block; block = block->b_next) {
151 dprintk("cookie: head of blocked queue %p, block %p\n",
153 if (nlm_cookie_match(&block->b_call.a_args.cookie,cookie)
154 && nlm_cmp_addr(sin, &block->b_host->h_addr))
162 * Create a block and initialize it.
164 * Note: we explicitly set the cookie of the grant reply to that of
165 * the blocked lock request. The spec explicitly mentions that the client
166 * should _not_ rely on the callback containing the same cookie as the
167 * request, but (as I found out later) that's because some implementations
168 * do just this. Never mind the standards comittees, they support our
169 * logging industries.
171 static inline struct nlm_block *
172 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
173 struct nlm_lock *lock, struct nlm_cookie *cookie)
175 struct nlm_block *block;
176 struct nlm_host *host;
177 struct nlm_rqst *call;
179 /* Create host handle for callback */
180 host = nlmclnt_lookup_host(&rqstp->rq_addr,
181 rqstp->rq_prot, rqstp->rq_vers);
185 /* Allocate memory for block, and initialize arguments */
186 if (!(block = (struct nlm_block *) kmalloc(sizeof(*block), GFP_KERNEL)))
188 memset(block, 0, sizeof(*block));
189 locks_init_lock(&block->b_call.a_args.lock.fl);
190 locks_init_lock(&block->b_call.a_res.lock.fl);
192 if (!nlmclnt_setgrantargs(&block->b_call, lock))
195 /* Set notifier function for VFS, and init args */
196 block->b_call.a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
197 block->b_call.a_args.cookie = *cookie; /* see above */
199 dprintk("lockd: created block %p...\n", block);
201 /* Create and initialize the block */
202 block->b_daemon = rqstp->rq_server;
203 block->b_host = host;
204 block->b_file = file;
206 /* Add to file's list of blocks */
207 block->b_fnext = file->f_blocks;
208 file->f_blocks = block;
210 /* Set up RPC arguments for callback */
211 call = &block->b_call;
213 call->a_flags = RPC_TASK_ASYNC;
220 nlm_release_host(host);
225 * Delete a block. If the lock was cancelled or the grant callback
226 * failed, unlock is set to 1.
227 * It is the caller's responsibility to check whether the file
228 * can be closed hereafter.
231 nlmsvc_delete_block(struct nlm_block *block, int unlock)
233 struct file_lock *fl = &block->b_call.a_args.lock.fl;
234 struct nlm_file *file = block->b_file;
235 struct nlm_block **bp;
238 dprintk("lockd: deleting block %p...\n", block);
240 /* Remove block from list */
241 nlmsvc_remove_block(block);
243 status = posix_unblock_lock(file->f_file, fl);
245 /* If the block is in the middle of a GRANT callback,
246 * don't kill it yet. */
247 if (block->b_incall) {
248 nlmsvc_insert_block(block, NLM_NEVER);
253 /* Remove block from file's list of blocks */
254 for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
256 *bp = block->b_fnext;
262 nlm_release_host(block->b_host);
263 nlmclnt_freegrantargs(&block->b_call);
269 * Loop over all blocks and perform the action specified.
270 * (NLM_ACT_CHECK handled by nlmsvc_inspect_file).
273 nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
275 struct nlm_block *block, *next;
276 /* XXX: Will everything get cleaned up if we don't unlock here? */
279 for (block = file->f_blocks; block; block = next) {
280 next = block->b_fnext;
281 if (action == NLM_ACT_MARK)
282 block->b_host->h_inuse = 1;
283 else if (action == NLM_ACT_UNLOCK) {
284 if (host == NULL || host == block->b_host)
285 nlmsvc_delete_block(block, 1);
293 * Attempt to establish a lock, and if it can't be granted, block it
297 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
298 struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
300 struct nlm_block *block;
304 dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
305 file->f_file->f_dentry->d_inode->i_sb->s_id,
306 file->f_file->f_dentry->d_inode->i_ino,
307 lock->fl.fl_type, lock->fl.fl_pid,
308 (long long)lock->fl.fl_start,
309 (long long)lock->fl.fl_end,
313 /* Get existing block (in case client is busy-waiting) */
314 block = nlmsvc_lookup_block(file, lock, 0);
317 /* Lock file against concurrent access */
320 error = posix_lock_file(file->f_file, &lock->fl);
322 dprintk("lockd: posix_lock_file returned %d\n", error);
324 if (error != -EAGAIN) {
326 nlmsvc_delete_block(block, 0);
336 default: /* includes ENOLCK */
337 ret = nlm_lck_denied_nolocks;
343 ret = nlm_lck_denied;
347 /* If we don't have a block, create and initialize it. Then
348 * retry because we may have slept in kmalloc. */
349 /* We have to release f_sema as nlmsvc_create_block may try to
350 * to claim it while doing host garbage collection */
353 dprintk("lockd: blocking on this lock (allocating).\n");
354 if (!(block = nlmsvc_create_block(rqstp, file, lock, cookie)))
355 return nlm_lck_denied_nolocks;
359 /* Append to list of blocked */
360 nlmsvc_insert_block(block, NLM_NEVER);
362 ret = nlm_lck_blocked;
366 dprintk("lockd: nlmsvc_lock returned %u\n", ret);
371 * Test for presence of a conflicting lock.
374 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
375 struct nlm_lock *conflock)
377 dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
378 file->f_file->f_dentry->d_inode->i_sb->s_id,
379 file->f_file->f_dentry->d_inode->i_ino,
381 (long long)lock->fl.fl_start,
382 (long long)lock->fl.fl_end);
384 if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
385 dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
386 conflock->fl.fl_type,
387 (long long)conflock->fl.fl_start,
388 (long long)conflock->fl.fl_end);
389 conflock->caller = "somehost"; /* FIXME */
390 conflock->oh.len = 0; /* don't return OH info */
391 conflock->svid = conflock->fl.fl_pid;
392 return nlm_lck_denied;
400 * This implies a CANCEL call: We send a GRANT_MSG, the client replies
401 * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
402 * afterwards. In this case the block will still be there, and hence
406 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
410 dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
411 file->f_file->f_dentry->d_inode->i_sb->s_id,
412 file->f_file->f_dentry->d_inode->i_ino,
414 (long long)lock->fl.fl_start,
415 (long long)lock->fl.fl_end);
417 /* First, cancel any lock that might be there */
418 nlmsvc_cancel_blocked(file, lock);
420 lock->fl.fl_type = F_UNLCK;
421 error = posix_lock_file(file->f_file, &lock->fl);
423 return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
427 * Cancel a previously blocked request.
429 * A cancel request always overrides any grant that may currently
431 * The calling procedure must check whether the file can be closed.
434 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
436 struct nlm_block *block;
439 dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
440 file->f_file->f_dentry->d_inode->i_sb->s_id,
441 file->f_file->f_dentry->d_inode->i_ino,
443 (long long)lock->fl.fl_start,
444 (long long)lock->fl.fl_end);
447 if ((block = nlmsvc_lookup_block(file, lock, 1)) != NULL)
448 status = nlmsvc_delete_block(block, 1);
450 return status ? nlm_lck_denied : nlm_granted;
454 * Unblock a blocked lock request. This is a callback invoked from the
455 * VFS layer when a lock on which we blocked is removed.
457 * This function doesn't grant the blocked lock instantly, but rather moves
458 * the block to the head of nlm_blocked where it can be picked up by lockd.
461 nlmsvc_notify_blocked(struct file_lock *fl)
463 struct nlm_block **bp, *block;
465 dprintk("lockd: VFS unblock notification for block %p\n", fl);
466 for (bp = &nlm_blocked; (block = *bp) != 0; bp = &block->b_next) {
467 if (nlm_compare_locks(&block->b_call.a_args.lock.fl, fl)) {
468 nlmsvc_insert_block(block, 0);
469 svc_wake_up(block->b_daemon);
474 printk(KERN_WARNING "lockd: notification for unknown block!\n");
477 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
479 return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
482 struct lock_manager_operations nlmsvc_lock_operations = {
483 .fl_compare_owner = nlmsvc_same_owner,
484 .fl_notify = nlmsvc_notify_blocked,
488 * Try to claim a lock that was previously blocked.
490 * Note that we use both the RPC_GRANTED_MSG call _and_ an async
491 * RPC thread when notifying the client. This seems like overkill...
493 * - we don't want to use a synchronous RPC thread, otherwise
494 * we might find ourselves hanging on a dead portmapper.
495 * - Some lockd implementations (e.g. HP) don't react to
496 * RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
499 nlmsvc_grant_blocked(struct nlm_block *block)
501 struct nlm_file *file = block->b_file;
502 struct nlm_lock *lock = &block->b_call.a_args.lock;
505 dprintk("lockd: grant blocked lock %p\n", block);
507 /* First thing is lock the file */
510 /* Unlink block request from list */
511 nlmsvc_remove_block(block);
513 /* If b_granted is true this means we've been here before.
514 * Just retry the grant callback, possibly refreshing the RPC
516 if (block->b_granted) {
517 nlm_rebind_host(block->b_host);
521 /* Try the lock operation again */
522 error = posix_lock_file(file->f_file, &lock->fl);
527 dprintk("lockd: lock still blocked\n");
528 nlmsvc_insert_block(block, NLM_NEVER);
531 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
532 -error, __FUNCTION__);
533 nlmsvc_insert_block(block, 10 * HZ);
538 /* Lock was granted by VFS. */
539 dprintk("lockd: GRANTing blocked lock.\n");
540 block->b_granted = 1;
543 /* Schedule next grant callback in 30 seconds */
544 nlmsvc_insert_block(block, 30 * HZ);
546 /* Call the client */
547 nlm_get_host(block->b_call.a_host);
548 if (nlmsvc_async_call(&block->b_call, NLMPROC_GRANTED_MSG,
549 &nlmsvc_grant_ops) < 0)
550 nlm_release_host(block->b_call.a_host);
556 * This is the callback from the RPC layer when the NLM_GRANTED_MSG
557 * RPC call has succeeded or timed out.
558 * Like all RPC callbacks, it is invoked by the rpciod process, so it
559 * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
560 * chain once more in order to have it removed by lockd itself (which can
561 * then sleep on the file semaphore without disrupting e.g. the nfs client).
563 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
565 struct nlm_rqst *call = data;
566 struct nlm_block *block;
567 unsigned long timeout;
568 struct sockaddr_in *peer_addr = RPC_PEERADDR(task->tk_client);
570 dprintk("lockd: GRANT_MSG RPC callback\n");
571 dprintk("callback: looking for cookie %s, host (%u.%u.%u.%u)\n",
572 nlmdbg_cookie2a(&call->a_args.cookie),
573 NIPQUAD(peer_addr->sin_addr.s_addr));
574 if (!(block = nlmsvc_find_block(&call->a_args.cookie, peer_addr))) {
575 dprintk("lockd: no block for cookie %s, host (%u.%u.%u.%u)\n",
576 nlmdbg_cookie2a(&call->a_args.cookie),
577 NIPQUAD(peer_addr->sin_addr.s_addr));
581 /* Technically, we should down the file semaphore here. Since we
582 * move the block towards the head of the queue only, no harm
583 * can be done, though. */
584 if (task->tk_status < 0) {
585 /* RPC error: Re-insert for retransmission */
587 } else if (block->b_done) {
588 /* Block already removed, kill it for real */
591 /* Call was successful, now wait for client callback */
594 nlmsvc_insert_block(block, timeout);
595 svc_wake_up(block->b_daemon);
598 nlm_release_host(call->a_host);
601 static const struct rpc_call_ops nlmsvc_grant_ops = {
602 .rpc_call_done = nlmsvc_grant_callback,
606 * We received a GRANT_RES callback. Try to find the corresponding
610 nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status)
612 struct nlm_block *block;
613 struct nlm_file *file;
615 dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n",
616 *(unsigned int *)(cookie->data),
617 ntohl(rqstp->rq_addr.sin_addr.s_addr), status);
618 if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr)))
620 file = block->b_file;
624 block = nlmsvc_find_block(cookie, &rqstp->rq_addr);
626 if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
627 /* Try again in a couple of seconds */
628 nlmsvc_insert_block(block, 10 * HZ);
631 /* Lock is now held by client, or has been rejected.
632 * In both cases, the block should be removed. */
634 if (status == NLM_LCK_GRANTED)
635 nlmsvc_delete_block(block, 0);
637 nlmsvc_delete_block(block, 1);
640 nlm_release_file(file);
644 * Retry all blocked locks that have been notified. This is where lockd
645 * picks up locks that can be granted, or grant notifications that must
649 nlmsvc_retry_blocked(void)
651 struct nlm_block *block;
653 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
655 nlm_blocked? nlm_blocked->b_when : 0);
656 while ((block = nlm_blocked) != 0) {
657 if (block->b_when == NLM_NEVER)
659 if (time_after(block->b_when,jiffies))
661 dprintk("nlmsvc_retry_blocked(%p, when=%ld, done=%d)\n",
662 block, block->b_when, block->b_done);
664 nlmsvc_delete_block(block, 0);
666 nlmsvc_grant_blocked(block);
669 if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
670 return (block->b_when - jiffies);
672 return MAX_SCHEDULE_TIMEOUT;