xref: /freebsd/sys/fs/autofs/autofs.c (revision 43d55325406e96e37be661de52289c2592c82ec9)
1 /*-
2  * Copyright (c) 2014 The FreeBSD Foundation
3  * All rights reserved.
4  *
5  * This software was developed by Edward Tomasz Napierala under sponsorship
6  * from the FreeBSD Foundation.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  */
30 /*-
31  * Copyright (c) 1989, 1991, 1993, 1995
32  *	The Regents of the University of California.  All rights reserved.
33  *
34  * This code is derived from software contributed to Berkeley by
35  * Rick Macklem at The University of Guelph.
36  *
37  * Redistribution and use in source and binary forms, with or without
38  * modification, are permitted provided that the following conditions
39  * are met:
40  * 1. Redistributions of source code must retain the above copyright
41  *    notice, this list of conditions and the following disclaimer.
42  * 2. Redistributions in binary form must reproduce the above copyright
43  *    notice, this list of conditions and the following disclaimer in the
44  *    documentation and/or other materials provided with the distribution.
45  * 4. Neither the name of the University nor the names of its contributors
46  *    may be used to endorse or promote products derived from this software
47  *    without specific prior written permission.
48  *
49  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
50  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
51  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
52  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
53  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
54  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
55  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
56  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
57  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
58  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
59  * SUCH DAMAGE.
60  *
61  */
62 
63 #include <sys/cdefs.h>
64  __FBSDID("$FreeBSD$");
65 
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/buf.h>
69 #include <sys/conf.h>
70 #include <sys/dirent.h>
71 #include <sys/ioccom.h>
72 #include <sys/kernel.h>
73 #include <sys/module.h>
74 #include <sys/mount.h>
75 #include <sys/refcount.h>
76 #include <sys/sx.h>
77 #include <sys/sysctl.h>
78 #include <sys/syscallsubr.h>
79 #include <sys/taskqueue.h>
80 #include <sys/vnode.h>
81 #include <machine/atomic.h>
82 #include <vm/uma.h>
83 
84 #include <fs/autofs/autofs.h>
85 #include <fs/autofs/autofs_ioctl.h>
86 
87 MALLOC_DEFINE(M_AUTOFS, "autofs", "Automounter filesystem");
88 
89 uma_zone_t autofs_request_zone;
90 uma_zone_t autofs_node_zone;
91 
92 static int	autofs_open(struct cdev *dev, int flags, int fmt,
93 		    struct thread *td);
94 static int	autofs_close(struct cdev *dev, int flag, int fmt,
95 		    struct thread *td);
96 static int	autofs_ioctl(struct cdev *dev, u_long cmd, caddr_t arg,
97 		    int mode, struct thread *td);
98 
99 static struct cdevsw autofs_cdevsw = {
100      .d_version = D_VERSION,
101      .d_open   = autofs_open,
102      .d_close   = autofs_close,
103      .d_ioctl   = autofs_ioctl,
104      .d_name    = "autofs",
105 };
106 
107 /*
108  * List of signals that can interrupt an autofs trigger.  Might be a good
109  * idea to keep it synchronised with list in sys/fs/nfs/nfs_commonkrpc.c.
110  */
111 int autofs_sig_set[] = {
112 	SIGINT,
113 	SIGTERM,
114 	SIGHUP,
115 	SIGKILL,
116 	SIGQUIT
117 };
118 
119 struct autofs_softc	*autofs_softc;
120 
121 SYSCTL_NODE(_vfs, OID_AUTO, autofs, CTLFLAG_RD, 0, "Automounter filesystem");
122 int autofs_debug = 1;
123 TUNABLE_INT("vfs.autofs.debug", &autofs_debug);
124 SYSCTL_INT(_vfs_autofs, OID_AUTO, debug, CTLFLAG_RWTUN,
125     &autofs_debug, 1, "Enable debug messages");
126 int autofs_mount_on_stat = 0;
127 TUNABLE_INT("vfs.autofs.mount_on_stat", &autofs_mount_on_stat);
128 SYSCTL_INT(_vfs_autofs, OID_AUTO, mount_on_stat, CTLFLAG_RWTUN,
129     &autofs_mount_on_stat, 0, "Trigger mount on stat(2) on mountpoint");
130 int autofs_timeout = 30;
131 TUNABLE_INT("vfs.autofs.timeout", &autofs_timeout);
132 SYSCTL_INT(_vfs_autofs, OID_AUTO, timeout, CTLFLAG_RWTUN,
133     &autofs_timeout, 30, "Number of seconds to wait for automountd(8)");
134 int autofs_cache = 600;
135 TUNABLE_INT("vfs.autofs.cache", &autofs_cache);
136 SYSCTL_INT(_vfs_autofs, OID_AUTO, cache, CTLFLAG_RWTUN,
137     &autofs_cache, 600, "Number of seconds to wait before reinvoking "
138     "automountd(8) for any given file or directory");
139 int autofs_retry_attempts = 3;
140 TUNABLE_INT("vfs.autofs.retry_attempts", &autofs_retry_attempts);
141 SYSCTL_INT(_vfs_autofs, OID_AUTO, retry_attempts, CTLFLAG_RWTUN,
142     &autofs_retry_attempts, 3, "Number of attempts before failing mount");
143 int autofs_retry_delay = 1;
144 TUNABLE_INT("vfs.autofs.retry_delay", &autofs_retry_delay);
145 SYSCTL_INT(_vfs_autofs, OID_AUTO, retry_delay, CTLFLAG_RWTUN,
146     &autofs_retry_delay, 1, "Number of seconds before retrying");
147 int autofs_interruptible = 1;
148 TUNABLE_INT("vfs.autofs.interruptible", &autofs_interruptible);
149 SYSCTL_INT(_vfs_autofs, OID_AUTO, interruptible, CTLFLAG_RWTUN,
150     &autofs_interruptible, 1, "Allow requests to be interrupted by signal");
151 
152 int
153 autofs_init(struct vfsconf *vfsp)
154 {
155 	int error;
156 
157 	KASSERT(autofs_softc == NULL,
158 	    ("softc %p, should be NULL", autofs_softc));
159 
160 	autofs_softc = malloc(sizeof(*autofs_softc), M_AUTOFS,
161 	    M_WAITOK | M_ZERO);
162 
163 	autofs_request_zone = uma_zcreate("autofs_request",
164 	    sizeof(struct autofs_request), NULL, NULL, NULL, NULL,
165 	    UMA_ALIGN_PTR, 0);
166 	autofs_node_zone = uma_zcreate("autofs_node",
167 	    sizeof(struct autofs_node), NULL, NULL, NULL, NULL,
168 	    UMA_ALIGN_PTR, 0);
169 
170 	TAILQ_INIT(&autofs_softc->sc_requests);
171 	cv_init(&autofs_softc->sc_cv, "autofscv");
172 	sx_init(&autofs_softc->sc_lock, "autofslk");
173 
174 	error = make_dev_p(MAKEDEV_CHECKNAME, &autofs_softc->sc_cdev,
175 	    &autofs_cdevsw, NULL, UID_ROOT, GID_WHEEL, 0600, "autofs");
176 	if (error != 0) {
177 		AUTOFS_WARN("failed to create device node, error %d", error);
178 		uma_zdestroy(autofs_request_zone);
179 		uma_zdestroy(autofs_node_zone);
180 		free(autofs_softc, M_AUTOFS);
181 
182 		return (error);
183 	}
184 	autofs_softc->sc_cdev->si_drv1 = autofs_softc;
185 
186 	return (0);
187 }
188 
189 int
190 autofs_uninit(struct vfsconf *vfsp)
191 {
192 
193 	sx_xlock(&autofs_softc->sc_lock);
194 	if (autofs_softc->sc_dev_opened) {
195 		sx_xunlock(&autofs_softc->sc_lock);
196 		return (EBUSY);
197 	}
198 	if (autofs_softc->sc_cdev != NULL)
199 		destroy_dev(autofs_softc->sc_cdev);
200 
201 	uma_zdestroy(autofs_request_zone);
202 	uma_zdestroy(autofs_node_zone);
203 
204 	sx_xunlock(&autofs_softc->sc_lock);
205 	/*
206 	 * XXX: Race with open?
207 	 */
208 	free(autofs_softc, M_AUTOFS);
209 
210 	return (0);
211 }
212 
213 bool
214 autofs_ignore_thread(const struct thread *td)
215 {
216 	struct proc *p;
217 
218 	p = td->td_proc;
219 
220 	if (autofs_softc->sc_dev_opened == false)
221 		return (false);
222 
223 	PROC_LOCK(p);
224 	if (p->p_session->s_sid == autofs_softc->sc_dev_sid) {
225 		PROC_UNLOCK(p);
226 		return (true);
227 	}
228 	PROC_UNLOCK(p);
229 
230 	return (false);
231 }
232 
233 static char *
234 autofs_path(struct autofs_node *anp)
235 {
236 	struct autofs_mount *amp;
237 	char *path, *tmp;
238 
239 	amp = anp->an_mount;
240 
241 	path = strdup("", M_AUTOFS);
242 	for (; anp->an_parent != NULL; anp = anp->an_parent) {
243 		tmp = malloc(strlen(anp->an_name) + strlen(path) + 2,
244 		    M_AUTOFS, M_WAITOK);
245 		strcpy(tmp, anp->an_name);
246 		strcat(tmp, "/");
247 		strcat(tmp, path);
248 		free(path, M_AUTOFS);
249 		path = tmp;
250 	}
251 
252 	tmp = malloc(strlen(amp->am_mountpoint) + strlen(path) + 2,
253 	    M_AUTOFS, M_WAITOK);
254 	strcpy(tmp, amp->am_mountpoint);
255 	strcat(tmp, "/");
256 	strcat(tmp, path);
257 	free(path, M_AUTOFS);
258 	path = tmp;
259 
260 	return (path);
261 }
262 
263 static void
264 autofs_task(void *context, int pending)
265 {
266 	struct autofs_request *ar;
267 
268 	ar = context;
269 
270 	sx_xlock(&autofs_softc->sc_lock);
271 	AUTOFS_WARN("request %d for %s timed out after %d seconds",
272 	    ar->ar_id, ar->ar_path, autofs_timeout);
273 	/*
274 	 * XXX: EIO perhaps?
275 	 */
276 	ar->ar_error = ETIMEDOUT;
277 	ar->ar_wildcards = true;
278 	ar->ar_done = true;
279 	ar->ar_in_progress = false;
280 	cv_broadcast(&autofs_softc->sc_cv);
281 	sx_xunlock(&autofs_softc->sc_lock);
282 }
283 
284 bool
285 autofs_cached(struct autofs_node *anp, const char *component, int componentlen)
286 {
287 	int error;
288 	struct autofs_mount *amp;
289 
290 	amp = anp->an_mount;
291 
292 	AUTOFS_ASSERT_UNLOCKED(amp);
293 
294 	/*
295 	 * For root node we need to request automountd(8) assistance even
296 	 * if the node is marked as cached, but the requested top-level
297 	 * directory does not exist.  This is necessary for wildcard indirect
298 	 * map keys to work.  We don't do this if we know that there are
299 	 * no wildcards.
300 	 */
301 	if (anp->an_parent == NULL && componentlen != 0 && anp->an_wildcards) {
302 		AUTOFS_SLOCK(amp);
303 		error = autofs_node_find(anp, component, componentlen, NULL);
304 		AUTOFS_SUNLOCK(amp);
305 		if (error != 0)
306 			return (false);
307 	}
308 
309 	return (anp->an_cached);
310 }
311 
312 static void
313 autofs_cache_callout(void *context)
314 {
315 	struct autofs_node *anp;
316 
317 	anp = context;
318 	anp->an_cached = false;
319 }
320 
321 /*
322  * The set/restore sigmask functions are used to (temporarily) overwrite
323  * the thread td_sigmask during triggering.
324  */
325 static void
326 autofs_set_sigmask(sigset_t *oldset)
327 {
328 	sigset_t newset;
329 	int i;
330 
331 	SIGFILLSET(newset);
332 	/* Remove the autofs set of signals from newset */
333 	PROC_LOCK(curproc);
334 	mtx_lock(&curproc->p_sigacts->ps_mtx);
335 	for (i = 0 ; i < sizeof(autofs_sig_set)/sizeof(int) ; i++) {
336 		/*
337 		 * But make sure we leave the ones already masked
338 		 * by the process, i.e. remove the signal from the
339 		 * temporary signalmask only if it wasn't already
340 		 * in p_sigmask.
341 		 */
342 		if (!SIGISMEMBER(curthread->td_sigmask, autofs_sig_set[i]) &&
343 		    !SIGISMEMBER(curproc->p_sigacts->ps_sigignore,
344 		    autofs_sig_set[i])) {
345 			SIGDELSET(newset, autofs_sig_set[i]);
346 		}
347 	}
348 	mtx_unlock(&curproc->p_sigacts->ps_mtx);
349 	kern_sigprocmask(curthread, SIG_SETMASK, &newset, oldset,
350 	    SIGPROCMASK_PROC_LOCKED);
351 	PROC_UNLOCK(curproc);
352 }
353 
354 static void
355 autofs_restore_sigmask(sigset_t *set)
356 {
357 
358 	kern_sigprocmask(curthread, SIG_SETMASK, set, NULL, 0);
359 }
360 
361 static int
362 autofs_trigger_one(struct autofs_node *anp,
363     const char *component, int componentlen)
364 {
365 	sigset_t oldset;
366 	struct autofs_mount *amp;
367 	struct autofs_node *firstanp;
368 	struct autofs_request *ar;
369 	char *key, *path;
370 	int error = 0, request_error, last;
371 	bool wildcards;
372 
373 	amp = anp->an_mount;
374 
375 	sx_assert(&autofs_softc->sc_lock, SA_XLOCKED);
376 
377 	if (anp->an_parent == NULL) {
378 		key = strndup(component, componentlen, M_AUTOFS);
379 	} else {
380 		for (firstanp = anp; firstanp->an_parent->an_parent != NULL;
381 		    firstanp = firstanp->an_parent)
382 			continue;
383 		key = strdup(firstanp->an_name, M_AUTOFS);
384 	}
385 
386 	path = autofs_path(anp);
387 
388 	TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
389 		if (strcmp(ar->ar_path, path) != 0)
390 			continue;
391 		if (strcmp(ar->ar_key, key) != 0)
392 			continue;
393 
394 		KASSERT(strcmp(ar->ar_from, amp->am_from) == 0,
395 		    ("from changed; %s != %s", ar->ar_from, amp->am_from));
396 		KASSERT(strcmp(ar->ar_prefix, amp->am_prefix) == 0,
397 		    ("prefix changed; %s != %s",
398 		     ar->ar_prefix, amp->am_prefix));
399 		KASSERT(strcmp(ar->ar_options, amp->am_options) == 0,
400 		    ("options changed; %s != %s",
401 		     ar->ar_options, amp->am_options));
402 
403 		break;
404 	}
405 
406 	if (ar != NULL) {
407 		refcount_acquire(&ar->ar_refcount);
408 	} else {
409 		ar = uma_zalloc(autofs_request_zone, M_WAITOK | M_ZERO);
410 		ar->ar_mount = amp;
411 
412 		ar->ar_id =
413 		    atomic_fetchadd_int(&autofs_softc->sc_last_request_id, 1);
414 		strlcpy(ar->ar_from, amp->am_from, sizeof(ar->ar_from));
415 		strlcpy(ar->ar_path, path, sizeof(ar->ar_path));
416 		strlcpy(ar->ar_prefix, amp->am_prefix, sizeof(ar->ar_prefix));
417 		strlcpy(ar->ar_key, key, sizeof(ar->ar_key));
418 		strlcpy(ar->ar_options,
419 		    amp->am_options, sizeof(ar->ar_options));
420 
421 		TIMEOUT_TASK_INIT(taskqueue_thread, &ar->ar_task, 0,
422 		    autofs_task, ar);
423 		error = taskqueue_enqueue_timeout(taskqueue_thread,
424 		    &ar->ar_task, autofs_timeout * hz);
425 		if (error != 0) {
426 			AUTOFS_WARN("taskqueue_enqueue_timeout() failed "
427 			    "with error %d", error);
428 		}
429 		refcount_init(&ar->ar_refcount, 1);
430 		TAILQ_INSERT_TAIL(&autofs_softc->sc_requests, ar, ar_next);
431 	}
432 
433 	cv_broadcast(&autofs_softc->sc_cv);
434 	while (ar->ar_done == false) {
435 		if (autofs_interruptible != 0) {
436 			autofs_set_sigmask(&oldset);
437 			error = cv_wait_sig(&autofs_softc->sc_cv,
438 			    &autofs_softc->sc_lock);
439 			autofs_restore_sigmask(&oldset);
440 			if (error != 0) {
441 				AUTOFS_WARN("cv_wait_sig for %s failed "
442 				    "with error %d", ar->ar_path, error);
443 				break;
444 			}
445 		} else {
446 			cv_wait(&autofs_softc->sc_cv, &autofs_softc->sc_lock);
447 		}
448 	}
449 
450 	request_error = ar->ar_error;
451 	if (request_error != 0) {
452 		AUTOFS_WARN("request for %s completed with error %d",
453 		    ar->ar_path, request_error);
454 	}
455 
456 	wildcards = ar->ar_wildcards;
457 
458 	last = refcount_release(&ar->ar_refcount);
459 	if (last) {
460 		TAILQ_REMOVE(&autofs_softc->sc_requests, ar, ar_next);
461 		/*
462 		 * Unlock the sc_lock, so that autofs_task() can complete.
463 		 */
464 		sx_xunlock(&autofs_softc->sc_lock);
465 		taskqueue_cancel_timeout(taskqueue_thread, &ar->ar_task, NULL);
466 		taskqueue_drain_timeout(taskqueue_thread, &ar->ar_task);
467 		uma_zfree(autofs_request_zone, ar);
468 		sx_xlock(&autofs_softc->sc_lock);
469 	}
470 
471 	/*
472 	 * Note that we do not do negative caching on purpose.  This
473 	 * way the user can retry access at any time, e.g. after fixing
474 	 * the failure reason, without waiting for cache timer to expire.
475 	 */
476 	if (error == 0 && request_error == 0 && autofs_cache > 0) {
477 		anp->an_cached = true;
478 		anp->an_wildcards = wildcards;
479 		callout_reset(&anp->an_callout, autofs_cache * hz,
480 		    autofs_cache_callout, anp);
481 	}
482 
483 	free(key, M_AUTOFS);
484 	free(path, M_AUTOFS);
485 
486 	if (error != 0)
487 		return (error);
488 	return (request_error);
489 }
490 
491 /*
492  * Send request to automountd(8) and wait for completion.
493  */
494 int
495 autofs_trigger(struct autofs_node *anp,
496     const char *component, int componentlen)
497 {
498 	int error;
499 
500 	for (;;) {
501 		error = autofs_trigger_one(anp, component, componentlen);
502 		if (error == 0) {
503 			anp->an_retries = 0;
504 			return (0);
505 		}
506 		if (error == EINTR || error == ERESTART) {
507 			AUTOFS_DEBUG("trigger interrupted by signal, "
508 			    "not retrying");
509 			anp->an_retries = 0;
510 			return (error);
511 		}
512 		anp->an_retries++;
513 		if (anp->an_retries >= autofs_retry_attempts) {
514 			AUTOFS_DEBUG("trigger failed %d times; returning "
515 			    "error %d", anp->an_retries, error);
516 			anp->an_retries = 0;
517 			return (error);
518 
519 		}
520 		AUTOFS_DEBUG("trigger failed with error %d; will retry in "
521 		    "%d seconds, %d attempts left", error, autofs_retry_delay,
522 		    autofs_retry_attempts - anp->an_retries);
523 		sx_xunlock(&autofs_softc->sc_lock);
524 		pause("autofs_retry", autofs_retry_delay * hz);
525 		sx_xlock(&autofs_softc->sc_lock);
526 	}
527 }
528 
529 static int
530 autofs_ioctl_request(struct autofs_daemon_request *adr)
531 {
532 	struct autofs_request *ar;
533 	int error;
534 
535 	sx_xlock(&autofs_softc->sc_lock);
536 	for (;;) {
537 		TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
538 			if (ar->ar_done)
539 				continue;
540 			if (ar->ar_in_progress)
541 				continue;
542 
543 			break;
544 		}
545 
546 		if (ar != NULL)
547 			break;
548 
549 		error = cv_wait_sig(&autofs_softc->sc_cv,
550 		    &autofs_softc->sc_lock);
551 		if (error != 0) {
552 			sx_xunlock(&autofs_softc->sc_lock);
553 			return (error);
554 		}
555 	}
556 
557 	ar->ar_in_progress = true;
558 	sx_xunlock(&autofs_softc->sc_lock);
559 
560 	adr->adr_id = ar->ar_id;
561 	strlcpy(adr->adr_from, ar->ar_from, sizeof(adr->adr_from));
562 	strlcpy(adr->adr_path, ar->ar_path, sizeof(adr->adr_path));
563 	strlcpy(adr->adr_prefix, ar->ar_prefix, sizeof(adr->adr_prefix));
564 	strlcpy(adr->adr_key, ar->ar_key, sizeof(adr->adr_key));
565 	strlcpy(adr->adr_options, ar->ar_options, sizeof(adr->adr_options));
566 
567 	PROC_LOCK(curproc);
568 	autofs_softc->sc_dev_sid = curproc->p_session->s_sid;
569 	PROC_UNLOCK(curproc);
570 
571 	return (0);
572 }
573 
574 static int
575 autofs_ioctl_done(struct autofs_daemon_done *add)
576 {
577 	struct autofs_request *ar;
578 
579 	sx_xlock(&autofs_softc->sc_lock);
580 	TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
581 		if (ar->ar_id == add->add_id)
582 			break;
583 	}
584 
585 	if (ar == NULL) {
586 		sx_xunlock(&autofs_softc->sc_lock);
587 		AUTOFS_DEBUG("id %d not found", add->add_id);
588 		return (ESRCH);
589 	}
590 
591 	ar->ar_error = add->add_error;
592 	ar->ar_wildcards = add->add_wildcards;
593 	ar->ar_done = true;
594 	ar->ar_in_progress = false;
595 	cv_broadcast(&autofs_softc->sc_cv);
596 
597 	sx_xunlock(&autofs_softc->sc_lock);
598 
599 	return (0);
600 }
601 
602 static int
603 autofs_open(struct cdev *dev, int flags, int fmt, struct thread *td)
604 {
605 
606 	sx_xlock(&autofs_softc->sc_lock);
607 	/*
608 	 * We must never block automountd(8) and its descendants, and we use
609 	 * session ID to determine that: we store session id of the process
610 	 * that opened the device, and then compare it with session ids
611 	 * of triggering processes.  This means running a second automountd(8)
612 	 * instance would break the previous one.  The check below prevents
613 	 * it from happening.
614 	 */
615 	if (autofs_softc->sc_dev_opened) {
616 		sx_xunlock(&autofs_softc->sc_lock);
617 		return (EBUSY);
618 	}
619 
620 	autofs_softc->sc_dev_opened = true;
621 	sx_xunlock(&autofs_softc->sc_lock);
622 
623 	return (0);
624 }
625 
626 static int
627 autofs_close(struct cdev *dev, int flag, int fmt, struct thread *td)
628 {
629 
630 	sx_xlock(&autofs_softc->sc_lock);
631 	KASSERT(autofs_softc->sc_dev_opened, ("not opened?"));
632 	autofs_softc->sc_dev_opened = false;
633 	sx_xunlock(&autofs_softc->sc_lock);
634 
635 	return (0);
636 }
637 
638 static int
639 autofs_ioctl(struct cdev *dev, u_long cmd, caddr_t arg, int mode,
640     struct thread *td)
641 {
642 
643 	KASSERT(autofs_softc->sc_dev_opened, ("not opened?"));
644 
645 	switch (cmd) {
646 	case AUTOFSREQUEST:
647 		return (autofs_ioctl_request(
648 		    (struct autofs_daemon_request *)arg));
649 	case AUTOFSDONE:
650 		return (autofs_ioctl_done(
651 		    (struct autofs_daemon_done *)arg));
652 	default:
653 		AUTOFS_DEBUG("invalid cmd %lx", cmd);
654 		return (EINVAL);
655 	}
656 }
657