xref: /freebsd/sys/fs/autofs/autofs.c (revision 0b3105a37d7adcadcb720112fed4dc4e8040be99)
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 void
322 autofs_flush(struct autofs_mount *amp)
323 {
324 
325 	/*
326 	 * XXX: This will do for now, but ideally we should iterate
327 	 * 	over all the nodes.
328 	 */
329 	amp->am_root->an_cached = false;
330 	AUTOFS_DEBUG("%s flushed", amp->am_mountpoint);
331 }
332 
333 /*
334  * The set/restore sigmask functions are used to (temporarily) overwrite
335  * the thread td_sigmask during triggering.
336  */
337 static void
338 autofs_set_sigmask(sigset_t *oldset)
339 {
340 	sigset_t newset;
341 	int i;
342 
343 	SIGFILLSET(newset);
344 	/* Remove the autofs set of signals from newset */
345 	PROC_LOCK(curproc);
346 	mtx_lock(&curproc->p_sigacts->ps_mtx);
347 	for (i = 0 ; i < sizeof(autofs_sig_set)/sizeof(int) ; i++) {
348 		/*
349 		 * But make sure we leave the ones already masked
350 		 * by the process, i.e. remove the signal from the
351 		 * temporary signalmask only if it wasn't already
352 		 * in p_sigmask.
353 		 */
354 		if (!SIGISMEMBER(curthread->td_sigmask, autofs_sig_set[i]) &&
355 		    !SIGISMEMBER(curproc->p_sigacts->ps_sigignore,
356 		    autofs_sig_set[i])) {
357 			SIGDELSET(newset, autofs_sig_set[i]);
358 		}
359 	}
360 	mtx_unlock(&curproc->p_sigacts->ps_mtx);
361 	kern_sigprocmask(curthread, SIG_SETMASK, &newset, oldset,
362 	    SIGPROCMASK_PROC_LOCKED);
363 	PROC_UNLOCK(curproc);
364 }
365 
366 static void
367 autofs_restore_sigmask(sigset_t *set)
368 {
369 
370 	kern_sigprocmask(curthread, SIG_SETMASK, set, NULL, 0);
371 }
372 
373 static int
374 autofs_trigger_one(struct autofs_node *anp,
375     const char *component, int componentlen)
376 {
377 	sigset_t oldset;
378 	struct autofs_mount *amp;
379 	struct autofs_node *firstanp;
380 	struct autofs_request *ar;
381 	char *key, *path;
382 	int error = 0, request_error, last;
383 	bool wildcards;
384 
385 	amp = anp->an_mount;
386 
387 	sx_assert(&autofs_softc->sc_lock, SA_XLOCKED);
388 
389 	if (anp->an_parent == NULL) {
390 		key = strndup(component, componentlen, M_AUTOFS);
391 	} else {
392 		for (firstanp = anp; firstanp->an_parent->an_parent != NULL;
393 		    firstanp = firstanp->an_parent)
394 			continue;
395 		key = strdup(firstanp->an_name, M_AUTOFS);
396 	}
397 
398 	path = autofs_path(anp);
399 
400 	TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
401 		if (strcmp(ar->ar_path, path) != 0)
402 			continue;
403 		if (strcmp(ar->ar_key, key) != 0)
404 			continue;
405 
406 		KASSERT(strcmp(ar->ar_from, amp->am_from) == 0,
407 		    ("from changed; %s != %s", ar->ar_from, amp->am_from));
408 		KASSERT(strcmp(ar->ar_prefix, amp->am_prefix) == 0,
409 		    ("prefix changed; %s != %s",
410 		     ar->ar_prefix, amp->am_prefix));
411 		KASSERT(strcmp(ar->ar_options, amp->am_options) == 0,
412 		    ("options changed; %s != %s",
413 		     ar->ar_options, amp->am_options));
414 
415 		break;
416 	}
417 
418 	if (ar != NULL) {
419 		refcount_acquire(&ar->ar_refcount);
420 	} else {
421 		ar = uma_zalloc(autofs_request_zone, M_WAITOK | M_ZERO);
422 		ar->ar_mount = amp;
423 
424 		ar->ar_id =
425 		    atomic_fetchadd_int(&autofs_softc->sc_last_request_id, 1);
426 		strlcpy(ar->ar_from, amp->am_from, sizeof(ar->ar_from));
427 		strlcpy(ar->ar_path, path, sizeof(ar->ar_path));
428 		strlcpy(ar->ar_prefix, amp->am_prefix, sizeof(ar->ar_prefix));
429 		strlcpy(ar->ar_key, key, sizeof(ar->ar_key));
430 		strlcpy(ar->ar_options,
431 		    amp->am_options, sizeof(ar->ar_options));
432 
433 		TIMEOUT_TASK_INIT(taskqueue_thread, &ar->ar_task, 0,
434 		    autofs_task, ar);
435 		error = taskqueue_enqueue_timeout(taskqueue_thread,
436 		    &ar->ar_task, autofs_timeout * hz);
437 		if (error != 0) {
438 			AUTOFS_WARN("taskqueue_enqueue_timeout() failed "
439 			    "with error %d", error);
440 		}
441 		refcount_init(&ar->ar_refcount, 1);
442 		TAILQ_INSERT_TAIL(&autofs_softc->sc_requests, ar, ar_next);
443 	}
444 
445 	cv_broadcast(&autofs_softc->sc_cv);
446 	while (ar->ar_done == false) {
447 		if (autofs_interruptible != 0) {
448 			autofs_set_sigmask(&oldset);
449 			error = cv_wait_sig(&autofs_softc->sc_cv,
450 			    &autofs_softc->sc_lock);
451 			autofs_restore_sigmask(&oldset);
452 			if (error != 0) {
453 				AUTOFS_WARN("cv_wait_sig for %s failed "
454 				    "with error %d", ar->ar_path, error);
455 				break;
456 			}
457 		} else {
458 			cv_wait(&autofs_softc->sc_cv, &autofs_softc->sc_lock);
459 		}
460 	}
461 
462 	request_error = ar->ar_error;
463 	if (request_error != 0) {
464 		AUTOFS_WARN("request for %s completed with error %d",
465 		    ar->ar_path, request_error);
466 	}
467 
468 	wildcards = ar->ar_wildcards;
469 
470 	last = refcount_release(&ar->ar_refcount);
471 	if (last) {
472 		TAILQ_REMOVE(&autofs_softc->sc_requests, ar, ar_next);
473 		/*
474 		 * Unlock the sc_lock, so that autofs_task() can complete.
475 		 */
476 		sx_xunlock(&autofs_softc->sc_lock);
477 		taskqueue_cancel_timeout(taskqueue_thread, &ar->ar_task, NULL);
478 		taskqueue_drain_timeout(taskqueue_thread, &ar->ar_task);
479 		uma_zfree(autofs_request_zone, ar);
480 		sx_xlock(&autofs_softc->sc_lock);
481 	}
482 
483 	/*
484 	 * Note that we do not do negative caching on purpose.  This
485 	 * way the user can retry access at any time, e.g. after fixing
486 	 * the failure reason, without waiting for cache timer to expire.
487 	 */
488 	if (error == 0 && request_error == 0 && autofs_cache > 0) {
489 		anp->an_cached = true;
490 		anp->an_wildcards = wildcards;
491 		callout_reset(&anp->an_callout, autofs_cache * hz,
492 		    autofs_cache_callout, anp);
493 	}
494 
495 	free(key, M_AUTOFS);
496 	free(path, M_AUTOFS);
497 
498 	if (error != 0)
499 		return (error);
500 	return (request_error);
501 }
502 
503 /*
504  * Send request to automountd(8) and wait for completion.
505  */
506 int
507 autofs_trigger(struct autofs_node *anp,
508     const char *component, int componentlen)
509 {
510 	int error;
511 
512 	for (;;) {
513 		error = autofs_trigger_one(anp, component, componentlen);
514 		if (error == 0) {
515 			anp->an_retries = 0;
516 			return (0);
517 		}
518 		if (error == EINTR || error == ERESTART) {
519 			AUTOFS_DEBUG("trigger interrupted by signal, "
520 			    "not retrying");
521 			anp->an_retries = 0;
522 			return (error);
523 		}
524 		anp->an_retries++;
525 		if (anp->an_retries >= autofs_retry_attempts) {
526 			AUTOFS_DEBUG("trigger failed %d times; returning "
527 			    "error %d", anp->an_retries, error);
528 			anp->an_retries = 0;
529 			return (error);
530 
531 		}
532 		AUTOFS_DEBUG("trigger failed with error %d; will retry in "
533 		    "%d seconds, %d attempts left", error, autofs_retry_delay,
534 		    autofs_retry_attempts - anp->an_retries);
535 		sx_xunlock(&autofs_softc->sc_lock);
536 		pause("autofs_retry", autofs_retry_delay * hz);
537 		sx_xlock(&autofs_softc->sc_lock);
538 	}
539 }
540 
541 static int
542 autofs_ioctl_request(struct autofs_daemon_request *adr)
543 {
544 	struct autofs_request *ar;
545 	int error;
546 
547 	sx_xlock(&autofs_softc->sc_lock);
548 	for (;;) {
549 		TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
550 			if (ar->ar_done)
551 				continue;
552 			if (ar->ar_in_progress)
553 				continue;
554 
555 			break;
556 		}
557 
558 		if (ar != NULL)
559 			break;
560 
561 		error = cv_wait_sig(&autofs_softc->sc_cv,
562 		    &autofs_softc->sc_lock);
563 		if (error != 0) {
564 			sx_xunlock(&autofs_softc->sc_lock);
565 			return (error);
566 		}
567 	}
568 
569 	ar->ar_in_progress = true;
570 	sx_xunlock(&autofs_softc->sc_lock);
571 
572 	adr->adr_id = ar->ar_id;
573 	strlcpy(adr->adr_from, ar->ar_from, sizeof(adr->adr_from));
574 	strlcpy(adr->adr_path, ar->ar_path, sizeof(adr->adr_path));
575 	strlcpy(adr->adr_prefix, ar->ar_prefix, sizeof(adr->adr_prefix));
576 	strlcpy(adr->adr_key, ar->ar_key, sizeof(adr->adr_key));
577 	strlcpy(adr->adr_options, ar->ar_options, sizeof(adr->adr_options));
578 
579 	PROC_LOCK(curproc);
580 	autofs_softc->sc_dev_sid = curproc->p_session->s_sid;
581 	PROC_UNLOCK(curproc);
582 
583 	return (0);
584 }
585 
586 static int
587 autofs_ioctl_done_101(struct autofs_daemon_done_101 *add)
588 {
589 	struct autofs_request *ar;
590 
591 	sx_xlock(&autofs_softc->sc_lock);
592 	TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
593 		if (ar->ar_id == add->add_id)
594 			break;
595 	}
596 
597 	if (ar == NULL) {
598 		sx_xunlock(&autofs_softc->sc_lock);
599 		AUTOFS_DEBUG("id %d not found", add->add_id);
600 		return (ESRCH);
601 	}
602 
603 	ar->ar_error = add->add_error;
604 	ar->ar_wildcards = true;
605 	ar->ar_done = true;
606 	ar->ar_in_progress = false;
607 	cv_broadcast(&autofs_softc->sc_cv);
608 
609 	sx_xunlock(&autofs_softc->sc_lock);
610 
611 	return (0);
612 }
613 
614 static int
615 autofs_ioctl_done(struct autofs_daemon_done *add)
616 {
617 	struct autofs_request *ar;
618 
619 	sx_xlock(&autofs_softc->sc_lock);
620 	TAILQ_FOREACH(ar, &autofs_softc->sc_requests, ar_next) {
621 		if (ar->ar_id == add->add_id)
622 			break;
623 	}
624 
625 	if (ar == NULL) {
626 		sx_xunlock(&autofs_softc->sc_lock);
627 		AUTOFS_DEBUG("id %d not found", add->add_id);
628 		return (ESRCH);
629 	}
630 
631 	ar->ar_error = add->add_error;
632 	ar->ar_wildcards = add->add_wildcards;
633 	ar->ar_done = true;
634 	ar->ar_in_progress = false;
635 	cv_broadcast(&autofs_softc->sc_cv);
636 
637 	sx_xunlock(&autofs_softc->sc_lock);
638 
639 	return (0);
640 }
641 
642 static int
643 autofs_open(struct cdev *dev, int flags, int fmt, struct thread *td)
644 {
645 
646 	sx_xlock(&autofs_softc->sc_lock);
647 	/*
648 	 * We must never block automountd(8) and its descendants, and we use
649 	 * session ID to determine that: we store session id of the process
650 	 * that opened the device, and then compare it with session ids
651 	 * of triggering processes.  This means running a second automountd(8)
652 	 * instance would break the previous one.  The check below prevents
653 	 * it from happening.
654 	 */
655 	if (autofs_softc->sc_dev_opened) {
656 		sx_xunlock(&autofs_softc->sc_lock);
657 		return (EBUSY);
658 	}
659 
660 	autofs_softc->sc_dev_opened = true;
661 	sx_xunlock(&autofs_softc->sc_lock);
662 
663 	return (0);
664 }
665 
666 static int
667 autofs_close(struct cdev *dev, int flag, int fmt, struct thread *td)
668 {
669 
670 	sx_xlock(&autofs_softc->sc_lock);
671 	KASSERT(autofs_softc->sc_dev_opened, ("not opened?"));
672 	autofs_softc->sc_dev_opened = false;
673 	sx_xunlock(&autofs_softc->sc_lock);
674 
675 	return (0);
676 }
677 
678 static int
679 autofs_ioctl(struct cdev *dev, u_long cmd, caddr_t arg, int mode,
680     struct thread *td)
681 {
682 
683 	KASSERT(autofs_softc->sc_dev_opened, ("not opened?"));
684 
685 	switch (cmd) {
686 	case AUTOFSREQUEST:
687 		return (autofs_ioctl_request(
688 		    (struct autofs_daemon_request *)arg));
689 	case AUTOFSDONE101:
690 		return (autofs_ioctl_done_101(
691 		    (struct autofs_daemon_done_101 *)arg));
692 	case AUTOFSDONE:
693 		return (autofs_ioctl_done(
694 		    (struct autofs_daemon_done *)arg));
695 	default:
696 		AUTOFS_DEBUG("invalid cmd %lx", cmd);
697 		return (EINVAL);
698 	}
699 }
700