xref: /freebsd/sys/kern/vfs_default.c (revision 84b3c4547afa496b37e86c5e649e99237c8afc6e)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1989, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed
8  * to Berkeley by John Heidemann of the UCLA Ficus project.
9  *
10  * Source: * @(#)i405_init.c 2.10 92/04/27 UCLA Ficus project
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright
18  *    notice, this list of conditions and the following disclaimer in the
19  *    documentation and/or other materials provided with the distribution.
20  * 3. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36 
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
39 
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/bio.h>
43 #include <sys/buf.h>
44 #include <sys/conf.h>
45 #include <sys/event.h>
46 #include <sys/filio.h>
47 #include <sys/kernel.h>
48 #include <sys/limits.h>
49 #include <sys/lock.h>
50 #include <sys/lockf.h>
51 #include <sys/malloc.h>
52 #include <sys/mount.h>
53 #include <sys/namei.h>
54 #include <sys/rwlock.h>
55 #include <sys/fcntl.h>
56 #include <sys/unistd.h>
57 #include <sys/vnode.h>
58 #include <sys/dirent.h>
59 #include <sys/poll.h>
60 
61 #include <security/mac/mac_framework.h>
62 
63 #include <vm/vm.h>
64 #include <vm/vm_object.h>
65 #include <vm/vm_extern.h>
66 #include <vm/pmap.h>
67 #include <vm/vm_map.h>
68 #include <vm/vm_page.h>
69 #include <vm/vm_pager.h>
70 #include <vm/vnode_pager.h>
71 
72 static int	vop_nolookup(struct vop_lookup_args *);
73 static int	vop_norename(struct vop_rename_args *);
74 static int	vop_nostrategy(struct vop_strategy_args *);
75 static int	get_next_dirent(struct vnode *vp, struct dirent **dpp,
76 				char *dirbuf, int dirbuflen, off_t *off,
77 				char **cpos, int *len, int *eofflag,
78 				struct thread *td);
79 static int	dirent_exists(struct vnode *vp, const char *dirname,
80 			      struct thread *td);
81 
82 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
83 
84 static int vop_stdis_text(struct vop_is_text_args *ap);
85 static int vop_stdunset_text(struct vop_unset_text_args *ap);
86 static int vop_stdadd_writecount(struct vop_add_writecount_args *ap);
87 static int vop_stdcopy_file_range(struct vop_copy_file_range_args *ap);
88 static int vop_stdfdatasync(struct vop_fdatasync_args *ap);
89 static int vop_stdgetpages_async(struct vop_getpages_async_args *ap);
90 
91 /*
92  * This vnode table stores what we want to do if the filesystem doesn't
93  * implement a particular VOP.
94  *
95  * If there is no specific entry here, we will return EOPNOTSUPP.
96  *
97  * Note that every filesystem has to implement either vop_access
98  * or vop_accessx; failing to do so will result in immediate crash
99  * due to stack overflow, as vop_stdaccess() calls vop_stdaccessx(),
100  * which calls vop_stdaccess() etc.
101  */
102 
103 struct vop_vector default_vnodeops = {
104 	.vop_default =		NULL,
105 	.vop_bypass =		VOP_EOPNOTSUPP,
106 
107 	.vop_access =		vop_stdaccess,
108 	.vop_accessx =		vop_stdaccessx,
109 	.vop_advise =		vop_stdadvise,
110 	.vop_advlock =		vop_stdadvlock,
111 	.vop_advlockasync =	vop_stdadvlockasync,
112 	.vop_advlockpurge =	vop_stdadvlockpurge,
113 	.vop_allocate =		vop_stdallocate,
114 	.vop_bmap =		vop_stdbmap,
115 	.vop_close =		VOP_NULL,
116 	.vop_fsync =		VOP_NULL,
117 	.vop_fdatasync =	vop_stdfdatasync,
118 	.vop_getpages =		vop_stdgetpages,
119 	.vop_getpages_async =	vop_stdgetpages_async,
120 	.vop_getwritemount = 	vop_stdgetwritemount,
121 	.vop_inactive =		VOP_NULL,
122 	.vop_need_inactive =	vop_stdneed_inactive,
123 	.vop_ioctl =		vop_stdioctl,
124 	.vop_kqfilter =		vop_stdkqfilter,
125 	.vop_islocked =		vop_stdislocked,
126 	.vop_lock1 =		vop_stdlock,
127 	.vop_lookup =		vop_nolookup,
128 	.vop_open =		VOP_NULL,
129 	.vop_pathconf =		VOP_EINVAL,
130 	.vop_poll =		vop_nopoll,
131 	.vop_putpages =		vop_stdputpages,
132 	.vop_readlink =		VOP_EINVAL,
133 	.vop_rename =		vop_norename,
134 	.vop_revoke =		VOP_PANIC,
135 	.vop_strategy =		vop_nostrategy,
136 	.vop_unlock =		vop_stdunlock,
137 	.vop_vptocnp =		vop_stdvptocnp,
138 	.vop_vptofh =		vop_stdvptofh,
139 	.vop_unp_bind =		vop_stdunp_bind,
140 	.vop_unp_connect =	vop_stdunp_connect,
141 	.vop_unp_detach =	vop_stdunp_detach,
142 	.vop_is_text =		vop_stdis_text,
143 	.vop_set_text =		vop_stdset_text,
144 	.vop_unset_text =	vop_stdunset_text,
145 	.vop_add_writecount =	vop_stdadd_writecount,
146 	.vop_copy_file_range =	vop_stdcopy_file_range,
147 };
148 VFS_VOP_VECTOR_REGISTER(default_vnodeops);
149 
150 /*
151  * Series of placeholder functions for various error returns for
152  * VOPs.
153  */
154 
155 int
156 vop_eopnotsupp(struct vop_generic_args *ap)
157 {
158 	/*
159 	printf("vop_notsupp[%s]\n", ap->a_desc->vdesc_name);
160 	*/
161 
162 	return (EOPNOTSUPP);
163 }
164 
165 int
166 vop_ebadf(struct vop_generic_args *ap)
167 {
168 
169 	return (EBADF);
170 }
171 
172 int
173 vop_enotty(struct vop_generic_args *ap)
174 {
175 
176 	return (ENOTTY);
177 }
178 
179 int
180 vop_einval(struct vop_generic_args *ap)
181 {
182 
183 	return (EINVAL);
184 }
185 
186 int
187 vop_enoent(struct vop_generic_args *ap)
188 {
189 
190 	return (ENOENT);
191 }
192 
193 int
194 vop_null(struct vop_generic_args *ap)
195 {
196 
197 	return (0);
198 }
199 
200 /*
201  * Helper function to panic on some bad VOPs in some filesystems.
202  */
203 int
204 vop_panic(struct vop_generic_args *ap)
205 {
206 
207 	panic("filesystem goof: vop_panic[%s]", ap->a_desc->vdesc_name);
208 }
209 
210 /*
211  * vop_std<something> and vop_no<something> are default functions for use by
212  * filesystems that need the "default reasonable" implementation for a
213  * particular operation.
214  *
215  * The documentation for the operations they implement exists (if it exists)
216  * in the VOP_<SOMETHING>(9) manpage (all uppercase).
217  */
218 
219 /*
220  * Default vop for filesystems that do not support name lookup
221  */
222 static int
223 vop_nolookup(ap)
224 	struct vop_lookup_args /* {
225 		struct vnode *a_dvp;
226 		struct vnode **a_vpp;
227 		struct componentname *a_cnp;
228 	} */ *ap;
229 {
230 
231 	*ap->a_vpp = NULL;
232 	return (ENOTDIR);
233 }
234 
235 /*
236  * vop_norename:
237  *
238  * Handle unlock and reference counting for arguments of vop_rename
239  * for filesystems that do not implement rename operation.
240  */
241 static int
242 vop_norename(struct vop_rename_args *ap)
243 {
244 
245 	vop_rename_fail(ap);
246 	return (EOPNOTSUPP);
247 }
248 
249 /*
250  *	vop_nostrategy:
251  *
252  *	Strategy routine for VFS devices that have none.
253  *
254  *	BIO_ERROR and B_INVAL must be cleared prior to calling any strategy
255  *	routine.  Typically this is done for a BIO_READ strategy call.
256  *	Typically B_INVAL is assumed to already be clear prior to a write
257  *	and should not be cleared manually unless you just made the buffer
258  *	invalid.  BIO_ERROR should be cleared either way.
259  */
260 
261 static int
262 vop_nostrategy (struct vop_strategy_args *ap)
263 {
264 	printf("No strategy for buffer at %p\n", ap->a_bp);
265 	vn_printf(ap->a_vp, "vnode ");
266 	ap->a_bp->b_ioflags |= BIO_ERROR;
267 	ap->a_bp->b_error = EOPNOTSUPP;
268 	bufdone(ap->a_bp);
269 	return (EOPNOTSUPP);
270 }
271 
272 static int
273 get_next_dirent(struct vnode *vp, struct dirent **dpp, char *dirbuf,
274 		int dirbuflen, off_t *off, char **cpos, int *len,
275 		int *eofflag, struct thread *td)
276 {
277 	int error, reclen;
278 	struct uio uio;
279 	struct iovec iov;
280 	struct dirent *dp;
281 
282 	KASSERT(VOP_ISLOCKED(vp), ("vp %p is not locked", vp));
283 	KASSERT(vp->v_type == VDIR, ("vp %p is not a directory", vp));
284 
285 	if (*len == 0) {
286 		iov.iov_base = dirbuf;
287 		iov.iov_len = dirbuflen;
288 
289 		uio.uio_iov = &iov;
290 		uio.uio_iovcnt = 1;
291 		uio.uio_offset = *off;
292 		uio.uio_resid = dirbuflen;
293 		uio.uio_segflg = UIO_SYSSPACE;
294 		uio.uio_rw = UIO_READ;
295 		uio.uio_td = td;
296 
297 		*eofflag = 0;
298 
299 #ifdef MAC
300 		error = mac_vnode_check_readdir(td->td_ucred, vp);
301 		if (error == 0)
302 #endif
303 			error = VOP_READDIR(vp, &uio, td->td_ucred, eofflag,
304 		    		NULL, NULL);
305 		if (error)
306 			return (error);
307 
308 		*off = uio.uio_offset;
309 
310 		*cpos = dirbuf;
311 		*len = (dirbuflen - uio.uio_resid);
312 
313 		if (*len == 0)
314 			return (ENOENT);
315 	}
316 
317 	dp = (struct dirent *)(*cpos);
318 	reclen = dp->d_reclen;
319 	*dpp = dp;
320 
321 	/* check for malformed directory.. */
322 	if (reclen < DIRENT_MINSIZE)
323 		return (EINVAL);
324 
325 	*cpos += reclen;
326 	*len -= reclen;
327 
328 	return (0);
329 }
330 
331 /*
332  * Check if a named file exists in a given directory vnode.
333  */
334 static int
335 dirent_exists(struct vnode *vp, const char *dirname, struct thread *td)
336 {
337 	char *dirbuf, *cpos;
338 	int error, eofflag, dirbuflen, len, found;
339 	off_t off;
340 	struct dirent *dp;
341 	struct vattr va;
342 
343 	KASSERT(VOP_ISLOCKED(vp), ("vp %p is not locked", vp));
344 	KASSERT(vp->v_type == VDIR, ("vp %p is not a directory", vp));
345 
346 	found = 0;
347 
348 	error = VOP_GETATTR(vp, &va, td->td_ucred);
349 	if (error)
350 		return (found);
351 
352 	dirbuflen = DEV_BSIZE;
353 	if (dirbuflen < va.va_blocksize)
354 		dirbuflen = va.va_blocksize;
355 	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
356 
357 	off = 0;
358 	len = 0;
359 	do {
360 		error = get_next_dirent(vp, &dp, dirbuf, dirbuflen, &off,
361 					&cpos, &len, &eofflag, td);
362 		if (error)
363 			goto out;
364 
365 		if (dp->d_type != DT_WHT && dp->d_fileno != 0 &&
366 		    strcmp(dp->d_name, dirname) == 0) {
367 			found = 1;
368 			goto out;
369 		}
370 	} while (len > 0 || !eofflag);
371 
372 out:
373 	free(dirbuf, M_TEMP);
374 	return (found);
375 }
376 
377 int
378 vop_stdaccess(struct vop_access_args *ap)
379 {
380 
381 	KASSERT((ap->a_accmode & ~(VEXEC | VWRITE | VREAD | VADMIN |
382 	    VAPPEND)) == 0, ("invalid bit in accmode"));
383 
384 	return (VOP_ACCESSX(ap->a_vp, ap->a_accmode, ap->a_cred, ap->a_td));
385 }
386 
387 int
388 vop_stdaccessx(struct vop_accessx_args *ap)
389 {
390 	int error;
391 	accmode_t accmode = ap->a_accmode;
392 
393 	error = vfs_unixify_accmode(&accmode);
394 	if (error != 0)
395 		return (error);
396 
397 	if (accmode == 0)
398 		return (0);
399 
400 	return (VOP_ACCESS(ap->a_vp, accmode, ap->a_cred, ap->a_td));
401 }
402 
403 /*
404  * Advisory record locking support
405  */
406 int
407 vop_stdadvlock(struct vop_advlock_args *ap)
408 {
409 	struct vnode *vp;
410 	struct vattr vattr;
411 	int error;
412 
413 	vp = ap->a_vp;
414 	if (ap->a_fl->l_whence == SEEK_END) {
415 		/*
416 		 * The NFSv4 server must avoid doing a vn_lock() here, since it
417 		 * can deadlock the nfsd threads, due to a LOR.  Fortunately
418 		 * the NFSv4 server always uses SEEK_SET and this code is
419 		 * only required for the SEEK_END case.
420 		 */
421 		vn_lock(vp, LK_SHARED | LK_RETRY);
422 		error = VOP_GETATTR(vp, &vattr, curthread->td_ucred);
423 		VOP_UNLOCK(vp);
424 		if (error)
425 			return (error);
426 	} else
427 		vattr.va_size = 0;
428 
429 	return (lf_advlock(ap, &(vp->v_lockf), vattr.va_size));
430 }
431 
432 int
433 vop_stdadvlockasync(struct vop_advlockasync_args *ap)
434 {
435 	struct vnode *vp;
436 	struct vattr vattr;
437 	int error;
438 
439 	vp = ap->a_vp;
440 	if (ap->a_fl->l_whence == SEEK_END) {
441 		/* The size argument is only needed for SEEK_END. */
442 		vn_lock(vp, LK_SHARED | LK_RETRY);
443 		error = VOP_GETATTR(vp, &vattr, curthread->td_ucred);
444 		VOP_UNLOCK(vp);
445 		if (error)
446 			return (error);
447 	} else
448 		vattr.va_size = 0;
449 
450 	return (lf_advlockasync(ap, &(vp->v_lockf), vattr.va_size));
451 }
452 
453 int
454 vop_stdadvlockpurge(struct vop_advlockpurge_args *ap)
455 {
456 	struct vnode *vp;
457 
458 	vp = ap->a_vp;
459 	lf_purgelocks(vp, &vp->v_lockf);
460 	return (0);
461 }
462 
463 /*
464  * vop_stdpathconf:
465  *
466  * Standard implementation of POSIX pathconf, to get information about limits
467  * for a filesystem.
468  * Override per filesystem for the case where the filesystem has smaller
469  * limits.
470  */
471 int
472 vop_stdpathconf(ap)
473 	struct vop_pathconf_args /* {
474 	struct vnode *a_vp;
475 	int a_name;
476 	int *a_retval;
477 	} */ *ap;
478 {
479 
480 	switch (ap->a_name) {
481 		case _PC_ASYNC_IO:
482 			*ap->a_retval = _POSIX_ASYNCHRONOUS_IO;
483 			return (0);
484 		case _PC_PATH_MAX:
485 			*ap->a_retval = PATH_MAX;
486 			return (0);
487 		case _PC_ACL_EXTENDED:
488 		case _PC_ACL_NFS4:
489 		case _PC_CAP_PRESENT:
490 		case _PC_INF_PRESENT:
491 		case _PC_MAC_PRESENT:
492 			*ap->a_retval = 0;
493 			return (0);
494 		default:
495 			return (EINVAL);
496 	}
497 	/* NOTREACHED */
498 }
499 
500 /*
501  * Standard lock, unlock and islocked functions.
502  */
503 int
504 vop_stdlock(ap)
505 	struct vop_lock1_args /* {
506 		struct vnode *a_vp;
507 		int a_flags;
508 		char *file;
509 		int line;
510 	} */ *ap;
511 {
512 	struct vnode *vp = ap->a_vp;
513 	struct mtx *ilk;
514 
515 	ilk = VI_MTX(vp);
516 	return (lockmgr_lock_flags(vp->v_vnlock, ap->a_flags,
517 	    &ilk->lock_object, ap->a_file, ap->a_line));
518 }
519 
520 /* See above. */
521 int
522 vop_stdunlock(ap)
523 	struct vop_unlock_args /* {
524 		struct vnode *a_vp;
525 	} */ *ap;
526 {
527 	struct vnode *vp = ap->a_vp;
528 
529 	return (lockmgr_unlock(vp->v_vnlock));
530 }
531 
532 /* See above. */
533 int
534 vop_stdislocked(ap)
535 	struct vop_islocked_args /* {
536 		struct vnode *a_vp;
537 	} */ *ap;
538 {
539 
540 	return (lockstatus(ap->a_vp->v_vnlock));
541 }
542 
543 /*
544  * Variants of the above set.
545  *
546  * Differences are:
547  * - shared locking disablement is not supported
548  * - v_vnlock pointer is not honored
549  */
550 int
551 vop_lock(ap)
552 	struct vop_lock1_args /* {
553 		struct vnode *a_vp;
554 		int a_flags;
555 		char *file;
556 		int line;
557 	} */ *ap;
558 {
559 	struct vnode *vp = ap->a_vp;
560 	int flags = ap->a_flags;
561 	struct mtx *ilk;
562 
563 	MPASS(vp->v_vnlock == &vp->v_lock);
564 
565 	if (__predict_false((flags & ~(LK_TYPE_MASK | LK_NODDLKTREAT | LK_RETRY)) != 0))
566 		goto other;
567 
568 	switch (flags & LK_TYPE_MASK) {
569 	case LK_SHARED:
570 		return (lockmgr_slock(&vp->v_lock, flags, ap->a_file, ap->a_line));
571 	case LK_EXCLUSIVE:
572 		return (lockmgr_xlock(&vp->v_lock, flags, ap->a_file, ap->a_line));
573 	}
574 other:
575 	ilk = VI_MTX(vp);
576 	return (lockmgr_lock_flags(&vp->v_lock, flags,
577 	    &ilk->lock_object, ap->a_file, ap->a_line));
578 }
579 
580 int
581 vop_unlock(ap)
582 	struct vop_unlock_args /* {
583 		struct vnode *a_vp;
584 	} */ *ap;
585 {
586 	struct vnode *vp = ap->a_vp;
587 
588 	MPASS(vp->v_vnlock == &vp->v_lock);
589 
590 	return (lockmgr_unlock(&vp->v_lock));
591 }
592 
593 int
594 vop_islocked(ap)
595 	struct vop_islocked_args /* {
596 		struct vnode *a_vp;
597 	} */ *ap;
598 {
599 	struct vnode *vp = ap->a_vp;
600 
601 	MPASS(vp->v_vnlock == &vp->v_lock);
602 
603 	return (lockstatus(&vp->v_lock));
604 }
605 
606 /*
607  * Return true for select/poll.
608  */
609 int
610 vop_nopoll(ap)
611 	struct vop_poll_args /* {
612 		struct vnode *a_vp;
613 		int  a_events;
614 		struct ucred *a_cred;
615 		struct thread *a_td;
616 	} */ *ap;
617 {
618 
619 	return (poll_no_poll(ap->a_events));
620 }
621 
622 /*
623  * Implement poll for local filesystems that support it.
624  */
625 int
626 vop_stdpoll(ap)
627 	struct vop_poll_args /* {
628 		struct vnode *a_vp;
629 		int  a_events;
630 		struct ucred *a_cred;
631 		struct thread *a_td;
632 	} */ *ap;
633 {
634 	if (ap->a_events & ~POLLSTANDARD)
635 		return (vn_pollrecord(ap->a_vp, ap->a_td, ap->a_events));
636 	return (ap->a_events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
637 }
638 
639 /*
640  * Return our mount point, as we will take charge of the writes.
641  */
642 int
643 vop_stdgetwritemount(ap)
644 	struct vop_getwritemount_args /* {
645 		struct vnode *a_vp;
646 		struct mount **a_mpp;
647 	} */ *ap;
648 {
649 	struct mount *mp;
650 	struct vnode *vp;
651 
652 	/*
653 	 * Note that having a reference does not prevent forced unmount from
654 	 * setting ->v_mount to NULL after the lock gets released. This is of
655 	 * no consequence for typical consumers (most notably vn_start_write)
656 	 * since in this case the vnode is VIRF_DOOMED. Unmount might have
657 	 * progressed far enough that its completion is only delayed by the
658 	 * reference obtained here. The consumer only needs to concern itself
659 	 * with releasing it.
660 	 */
661 	vp = ap->a_vp;
662 	mp = vp->v_mount;
663 	if (mp == NULL) {
664 		*(ap->a_mpp) = NULL;
665 		return (0);
666 	}
667 	if (vfs_op_thread_enter(mp)) {
668 		if (mp == vp->v_mount) {
669 			vfs_mp_count_add_pcpu(mp, ref, 1);
670 			vfs_op_thread_exit(mp);
671 		} else {
672 			vfs_op_thread_exit(mp);
673 			mp = NULL;
674 		}
675 	} else {
676 		MNT_ILOCK(mp);
677 		if (mp == vp->v_mount) {
678 			MNT_REF(mp);
679 			MNT_IUNLOCK(mp);
680 		} else {
681 			MNT_IUNLOCK(mp);
682 			mp = NULL;
683 		}
684 	}
685 	*(ap->a_mpp) = mp;
686 	return (0);
687 }
688 
689 /*
690  * If the file system doesn't implement VOP_BMAP, then return sensible defaults:
691  * - Return the vnode's bufobj instead of any underlying device's bufobj
692  * - Calculate the physical block number as if there were equal size
693  *   consecutive blocks, but
694  * - Report no contiguous runs of blocks.
695  */
696 int
697 vop_stdbmap(ap)
698 	struct vop_bmap_args /* {
699 		struct vnode *a_vp;
700 		daddr_t  a_bn;
701 		struct bufobj **a_bop;
702 		daddr_t *a_bnp;
703 		int *a_runp;
704 		int *a_runb;
705 	} */ *ap;
706 {
707 
708 	if (ap->a_bop != NULL)
709 		*ap->a_bop = &ap->a_vp->v_bufobj;
710 	if (ap->a_bnp != NULL)
711 		*ap->a_bnp = ap->a_bn * btodb(ap->a_vp->v_mount->mnt_stat.f_iosize);
712 	if (ap->a_runp != NULL)
713 		*ap->a_runp = 0;
714 	if (ap->a_runb != NULL)
715 		*ap->a_runb = 0;
716 	return (0);
717 }
718 
719 int
720 vop_stdfsync(ap)
721 	struct vop_fsync_args /* {
722 		struct vnode *a_vp;
723 		int a_waitfor;
724 		struct thread *a_td;
725 	} */ *ap;
726 {
727 
728 	return (vn_fsync_buf(ap->a_vp, ap->a_waitfor));
729 }
730 
731 static int
732 vop_stdfdatasync(struct vop_fdatasync_args *ap)
733 {
734 
735 	return (VOP_FSYNC(ap->a_vp, MNT_WAIT, ap->a_td));
736 }
737 
738 int
739 vop_stdfdatasync_buf(struct vop_fdatasync_args *ap)
740 {
741 
742 	return (vn_fsync_buf(ap->a_vp, MNT_WAIT));
743 }
744 
745 /* XXX Needs good comment and more info in the manpage (VOP_GETPAGES(9)). */
746 int
747 vop_stdgetpages(ap)
748 	struct vop_getpages_args /* {
749 		struct vnode *a_vp;
750 		vm_page_t *a_m;
751 		int a_count;
752 		int *a_rbehind;
753 		int *a_rahead;
754 	} */ *ap;
755 {
756 
757 	return vnode_pager_generic_getpages(ap->a_vp, ap->a_m,
758 	    ap->a_count, ap->a_rbehind, ap->a_rahead, NULL, NULL);
759 }
760 
761 static int
762 vop_stdgetpages_async(struct vop_getpages_async_args *ap)
763 {
764 	int error;
765 
766 	error = VOP_GETPAGES(ap->a_vp, ap->a_m, ap->a_count, ap->a_rbehind,
767 	    ap->a_rahead);
768 	ap->a_iodone(ap->a_arg, ap->a_m, ap->a_count, error);
769 	return (error);
770 }
771 
772 int
773 vop_stdkqfilter(struct vop_kqfilter_args *ap)
774 {
775 	return vfs_kqfilter(ap);
776 }
777 
778 /* XXX Needs good comment and more info in the manpage (VOP_PUTPAGES(9)). */
779 int
780 vop_stdputpages(ap)
781 	struct vop_putpages_args /* {
782 		struct vnode *a_vp;
783 		vm_page_t *a_m;
784 		int a_count;
785 		int a_sync;
786 		int *a_rtvals;
787 	} */ *ap;
788 {
789 
790 	return vnode_pager_generic_putpages(ap->a_vp, ap->a_m, ap->a_count,
791 	     ap->a_sync, ap->a_rtvals);
792 }
793 
794 int
795 vop_stdvptofh(struct vop_vptofh_args *ap)
796 {
797 	return (EOPNOTSUPP);
798 }
799 
800 int
801 vop_stdvptocnp(struct vop_vptocnp_args *ap)
802 {
803 	struct vnode *vp = ap->a_vp;
804 	struct vnode **dvp = ap->a_vpp;
805 	struct ucred *cred = ap->a_cred;
806 	char *buf = ap->a_buf;
807 	size_t *buflen = ap->a_buflen;
808 	char *dirbuf, *cpos;
809 	int i, error, eofflag, dirbuflen, flags, locked, len, covered;
810 	off_t off;
811 	ino_t fileno;
812 	struct vattr va;
813 	struct nameidata nd;
814 	struct thread *td;
815 	struct dirent *dp;
816 	struct vnode *mvp;
817 
818 	i = *buflen;
819 	error = 0;
820 	covered = 0;
821 	td = curthread;
822 
823 	if (vp->v_type != VDIR)
824 		return (ENOENT);
825 
826 	error = VOP_GETATTR(vp, &va, cred);
827 	if (error)
828 		return (error);
829 
830 	VREF(vp);
831 	locked = VOP_ISLOCKED(vp);
832 	VOP_UNLOCK(vp);
833 	NDINIT_ATVP(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF, UIO_SYSSPACE,
834 	    "..", vp, td);
835 	flags = FREAD;
836 	error = vn_open_cred(&nd, &flags, 0, VN_OPEN_NOAUDIT, cred, NULL);
837 	if (error) {
838 		vn_lock(vp, locked | LK_RETRY);
839 		return (error);
840 	}
841 	NDFREE(&nd, NDF_ONLY_PNBUF);
842 
843 	mvp = *dvp = nd.ni_vp;
844 
845 	if (vp->v_mount != (*dvp)->v_mount &&
846 	    ((*dvp)->v_vflag & VV_ROOT) &&
847 	    ((*dvp)->v_mount->mnt_flag & MNT_UNION)) {
848 		*dvp = (*dvp)->v_mount->mnt_vnodecovered;
849 		VREF(mvp);
850 		VOP_UNLOCK(mvp);
851 		vn_close(mvp, FREAD, cred, td);
852 		VREF(*dvp);
853 		vn_lock(*dvp, LK_SHARED | LK_RETRY);
854 		covered = 1;
855 	}
856 
857 	fileno = va.va_fileid;
858 
859 	dirbuflen = DEV_BSIZE;
860 	if (dirbuflen < va.va_blocksize)
861 		dirbuflen = va.va_blocksize;
862 	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
863 
864 	if ((*dvp)->v_type != VDIR) {
865 		error = ENOENT;
866 		goto out;
867 	}
868 
869 	off = 0;
870 	len = 0;
871 	do {
872 		/* call VOP_READDIR of parent */
873 		error = get_next_dirent(*dvp, &dp, dirbuf, dirbuflen, &off,
874 					&cpos, &len, &eofflag, td);
875 		if (error)
876 			goto out;
877 
878 		if ((dp->d_type != DT_WHT) &&
879 		    (dp->d_fileno == fileno)) {
880 			if (covered) {
881 				VOP_UNLOCK(*dvp);
882 				vn_lock(mvp, LK_SHARED | LK_RETRY);
883 				if (dirent_exists(mvp, dp->d_name, td)) {
884 					error = ENOENT;
885 					VOP_UNLOCK(mvp);
886 					vn_lock(*dvp, LK_SHARED | LK_RETRY);
887 					goto out;
888 				}
889 				VOP_UNLOCK(mvp);
890 				vn_lock(*dvp, LK_SHARED | LK_RETRY);
891 			}
892 			i -= dp->d_namlen;
893 
894 			if (i < 0) {
895 				error = ENOMEM;
896 				goto out;
897 			}
898 			if (dp->d_namlen == 1 && dp->d_name[0] == '.') {
899 				error = ENOENT;
900 			} else {
901 				bcopy(dp->d_name, buf + i, dp->d_namlen);
902 				error = 0;
903 			}
904 			goto out;
905 		}
906 	} while (len > 0 || !eofflag);
907 	error = ENOENT;
908 
909 out:
910 	free(dirbuf, M_TEMP);
911 	if (!error) {
912 		*buflen = i;
913 		vref(*dvp);
914 	}
915 	if (covered) {
916 		vput(*dvp);
917 		vrele(mvp);
918 	} else {
919 		VOP_UNLOCK(mvp);
920 		vn_close(mvp, FREAD, cred, td);
921 	}
922 	vn_lock(vp, locked | LK_RETRY);
923 	return (error);
924 }
925 
926 int
927 vop_stdallocate(struct vop_allocate_args *ap)
928 {
929 #ifdef __notyet__
930 	struct statfs *sfs;
931 	off_t maxfilesize = 0;
932 #endif
933 	struct iovec aiov;
934 	struct vattr vattr, *vap;
935 	struct uio auio;
936 	off_t fsize, len, cur, offset;
937 	uint8_t *buf;
938 	struct thread *td;
939 	struct vnode *vp;
940 	size_t iosize;
941 	int error;
942 
943 	buf = NULL;
944 	error = 0;
945 	td = curthread;
946 	vap = &vattr;
947 	vp = ap->a_vp;
948 	len = *ap->a_len;
949 	offset = *ap->a_offset;
950 
951 	error = VOP_GETATTR(vp, vap, td->td_ucred);
952 	if (error != 0)
953 		goto out;
954 	fsize = vap->va_size;
955 	iosize = vap->va_blocksize;
956 	if (iosize == 0)
957 		iosize = BLKDEV_IOSIZE;
958 	if (iosize > MAXPHYS)
959 		iosize = MAXPHYS;
960 	buf = malloc(iosize, M_TEMP, M_WAITOK);
961 
962 #ifdef __notyet__
963 	/*
964 	 * Check if the filesystem sets f_maxfilesize; if not use
965 	 * VOP_SETATTR to perform the check.
966 	 */
967 	sfs = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK);
968 	error = VFS_STATFS(vp->v_mount, sfs, td);
969 	if (error == 0)
970 		maxfilesize = sfs->f_maxfilesize;
971 	free(sfs, M_STATFS);
972 	if (error != 0)
973 		goto out;
974 	if (maxfilesize) {
975 		if (offset > maxfilesize || len > maxfilesize ||
976 		    offset + len > maxfilesize) {
977 			error = EFBIG;
978 			goto out;
979 		}
980 	} else
981 #endif
982 	if (offset + len > vap->va_size) {
983 		/*
984 		 * Test offset + len against the filesystem's maxfilesize.
985 		 */
986 		VATTR_NULL(vap);
987 		vap->va_size = offset + len;
988 		error = VOP_SETATTR(vp, vap, td->td_ucred);
989 		if (error != 0)
990 			goto out;
991 		VATTR_NULL(vap);
992 		vap->va_size = fsize;
993 		error = VOP_SETATTR(vp, vap, td->td_ucred);
994 		if (error != 0)
995 			goto out;
996 	}
997 
998 	for (;;) {
999 		/*
1000 		 * Read and write back anything below the nominal file
1001 		 * size.  There's currently no way outside the filesystem
1002 		 * to know whether this area is sparse or not.
1003 		 */
1004 		cur = iosize;
1005 		if ((offset % iosize) != 0)
1006 			cur -= (offset % iosize);
1007 		if (cur > len)
1008 			cur = len;
1009 		if (offset < fsize) {
1010 			aiov.iov_base = buf;
1011 			aiov.iov_len = cur;
1012 			auio.uio_iov = &aiov;
1013 			auio.uio_iovcnt = 1;
1014 			auio.uio_offset = offset;
1015 			auio.uio_resid = cur;
1016 			auio.uio_segflg = UIO_SYSSPACE;
1017 			auio.uio_rw = UIO_READ;
1018 			auio.uio_td = td;
1019 			error = VOP_READ(vp, &auio, 0, td->td_ucred);
1020 			if (error != 0)
1021 				break;
1022 			if (auio.uio_resid > 0) {
1023 				bzero(buf + cur - auio.uio_resid,
1024 				    auio.uio_resid);
1025 			}
1026 		} else {
1027 			bzero(buf, cur);
1028 		}
1029 
1030 		aiov.iov_base = buf;
1031 		aiov.iov_len = cur;
1032 		auio.uio_iov = &aiov;
1033 		auio.uio_iovcnt = 1;
1034 		auio.uio_offset = offset;
1035 		auio.uio_resid = cur;
1036 		auio.uio_segflg = UIO_SYSSPACE;
1037 		auio.uio_rw = UIO_WRITE;
1038 		auio.uio_td = td;
1039 
1040 		error = VOP_WRITE(vp, &auio, 0, td->td_ucred);
1041 		if (error != 0)
1042 			break;
1043 
1044 		len -= cur;
1045 		offset += cur;
1046 		if (len == 0)
1047 			break;
1048 		if (should_yield())
1049 			break;
1050 	}
1051 
1052  out:
1053 	*ap->a_len = len;
1054 	*ap->a_offset = offset;
1055 	free(buf, M_TEMP);
1056 	return (error);
1057 }
1058 
1059 int
1060 vop_stdadvise(struct vop_advise_args *ap)
1061 {
1062 	struct vnode *vp;
1063 	struct bufobj *bo;
1064 	daddr_t startn, endn;
1065 	off_t bstart, bend, start, end;
1066 	int bsize, error;
1067 
1068 	vp = ap->a_vp;
1069 	switch (ap->a_advice) {
1070 	case POSIX_FADV_WILLNEED:
1071 		/*
1072 		 * Do nothing for now.  Filesystems should provide a
1073 		 * custom method which starts an asynchronous read of
1074 		 * the requested region.
1075 		 */
1076 		error = 0;
1077 		break;
1078 	case POSIX_FADV_DONTNEED:
1079 		error = 0;
1080 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
1081 		if (VN_IS_DOOMED(vp)) {
1082 			VOP_UNLOCK(vp);
1083 			break;
1084 		}
1085 
1086 		/*
1087 		 * Round to block boundaries (and later possibly further to
1088 		 * page boundaries).  Applications cannot reasonably be aware
1089 		 * of the boundaries, and the rounding must be to expand at
1090 		 * both extremities to cover enough.  It still doesn't cover
1091 		 * read-ahead.  For partial blocks, this gives unnecessary
1092 		 * discarding of buffers but is efficient enough since the
1093 		 * pages usually remain in VMIO for some time.
1094 		 */
1095 		bsize = vp->v_bufobj.bo_bsize;
1096 		bstart = rounddown(ap->a_start, bsize);
1097 		bend = roundup(ap->a_end, bsize);
1098 
1099 		/*
1100 		 * Deactivate pages in the specified range from the backing VM
1101 		 * object.  Pages that are resident in the buffer cache will
1102 		 * remain wired until their corresponding buffers are released
1103 		 * below.
1104 		 */
1105 		if (vp->v_object != NULL) {
1106 			start = trunc_page(bstart);
1107 			end = round_page(bend);
1108 			VM_OBJECT_RLOCK(vp->v_object);
1109 			vm_object_page_noreuse(vp->v_object, OFF_TO_IDX(start),
1110 			    OFF_TO_IDX(end));
1111 			VM_OBJECT_RUNLOCK(vp->v_object);
1112 		}
1113 
1114 		bo = &vp->v_bufobj;
1115 		BO_RLOCK(bo);
1116 		startn = bstart / bsize;
1117 		endn = bend / bsize;
1118 		error = bnoreuselist(&bo->bo_clean, bo, startn, endn);
1119 		if (error == 0)
1120 			error = bnoreuselist(&bo->bo_dirty, bo, startn, endn);
1121 		BO_RUNLOCK(bo);
1122 		VOP_UNLOCK(vp);
1123 		break;
1124 	default:
1125 		error = EINVAL;
1126 		break;
1127 	}
1128 	return (error);
1129 }
1130 
1131 int
1132 vop_stdunp_bind(struct vop_unp_bind_args *ap)
1133 {
1134 
1135 	ap->a_vp->v_unpcb = ap->a_unpcb;
1136 	return (0);
1137 }
1138 
1139 int
1140 vop_stdunp_connect(struct vop_unp_connect_args *ap)
1141 {
1142 
1143 	*ap->a_unpcb = ap->a_vp->v_unpcb;
1144 	return (0);
1145 }
1146 
1147 int
1148 vop_stdunp_detach(struct vop_unp_detach_args *ap)
1149 {
1150 
1151 	ap->a_vp->v_unpcb = NULL;
1152 	return (0);
1153 }
1154 
1155 static int
1156 vop_stdis_text(struct vop_is_text_args *ap)
1157 {
1158 
1159 	return (ap->a_vp->v_writecount < 0);
1160 }
1161 
1162 int
1163 vop_stdset_text(struct vop_set_text_args *ap)
1164 {
1165 	struct vnode *vp;
1166 	struct mount *mp;
1167 	int error;
1168 
1169 	vp = ap->a_vp;
1170 	VI_LOCK(vp);
1171 	if (vp->v_writecount > 0) {
1172 		error = ETXTBSY;
1173 	} else {
1174 		/*
1175 		 * If requested by fs, keep a use reference to the
1176 		 * vnode until the last text reference is released.
1177 		 */
1178 		mp = vp->v_mount;
1179 		if (mp != NULL && (mp->mnt_kern_flag & MNTK_TEXT_REFS) != 0 &&
1180 		    vp->v_writecount == 0) {
1181 			vp->v_iflag |= VI_TEXT_REF;
1182 			vrefl(vp);
1183 		}
1184 
1185 		vp->v_writecount--;
1186 		error = 0;
1187 	}
1188 	VI_UNLOCK(vp);
1189 	return (error);
1190 }
1191 
1192 static int
1193 vop_stdunset_text(struct vop_unset_text_args *ap)
1194 {
1195 	struct vnode *vp;
1196 	int error;
1197 	bool last;
1198 
1199 	vp = ap->a_vp;
1200 	last = false;
1201 	VI_LOCK(vp);
1202 	if (vp->v_writecount < 0) {
1203 		if ((vp->v_iflag & VI_TEXT_REF) != 0 &&
1204 		    vp->v_writecount == -1) {
1205 			last = true;
1206 			vp->v_iflag &= ~VI_TEXT_REF;
1207 		}
1208 		vp->v_writecount++;
1209 		error = 0;
1210 	} else {
1211 		error = EINVAL;
1212 	}
1213 	VI_UNLOCK(vp);
1214 	if (last)
1215 		vunref(vp);
1216 	return (error);
1217 }
1218 
1219 static int
1220 vop_stdadd_writecount(struct vop_add_writecount_args *ap)
1221 {
1222 	struct vnode *vp;
1223 	struct mount *mp;
1224 	int error;
1225 
1226 	vp = ap->a_vp;
1227 	VI_LOCK_FLAGS(vp, MTX_DUPOK);
1228 	if (vp->v_writecount < 0) {
1229 		error = ETXTBSY;
1230 	} else {
1231 		VNASSERT(vp->v_writecount + ap->a_inc >= 0, vp,
1232 		    ("neg writecount increment %d", ap->a_inc));
1233 		if (vp->v_writecount == 0) {
1234 			mp = vp->v_mount;
1235 			if (mp != NULL && (mp->mnt_kern_flag & MNTK_NOMSYNC) == 0)
1236 				vlazy(vp);
1237 		}
1238 		vp->v_writecount += ap->a_inc;
1239 		error = 0;
1240 	}
1241 	VI_UNLOCK(vp);
1242 	return (error);
1243 }
1244 
1245 int
1246 vop_stdneed_inactive(struct vop_need_inactive_args *ap)
1247 {
1248 
1249 	return (1);
1250 }
1251 
1252 int
1253 vop_stdioctl(struct vop_ioctl_args *ap)
1254 {
1255 	struct vnode *vp;
1256 	struct vattr va;
1257 	off_t *offp;
1258 	int error;
1259 
1260 	switch (ap->a_command) {
1261 	case FIOSEEKDATA:
1262 	case FIOSEEKHOLE:
1263 		vp = ap->a_vp;
1264 		error = vn_lock(vp, LK_SHARED);
1265 		if (error != 0)
1266 			return (EBADF);
1267 		if (vp->v_type == VREG)
1268 			error = VOP_GETATTR(vp, &va, ap->a_cred);
1269 		else
1270 			error = ENOTTY;
1271 		if (error == 0) {
1272 			offp = ap->a_data;
1273 			if (*offp < 0 || *offp >= va.va_size)
1274 				error = ENXIO;
1275 			else if (ap->a_command == FIOSEEKHOLE)
1276 				*offp = va.va_size;
1277 		}
1278 		VOP_UNLOCK(vp);
1279 		break;
1280 	default:
1281 		error = ENOTTY;
1282 		break;
1283 	}
1284 	return (error);
1285 }
1286 
1287 /*
1288  * vfs default ops
1289  * used to fill the vfs function table to get reasonable default return values.
1290  */
1291 int
1292 vfs_stdroot (mp, flags, vpp)
1293 	struct mount *mp;
1294 	int flags;
1295 	struct vnode **vpp;
1296 {
1297 
1298 	return (EOPNOTSUPP);
1299 }
1300 
1301 int
1302 vfs_stdstatfs (mp, sbp)
1303 	struct mount *mp;
1304 	struct statfs *sbp;
1305 {
1306 
1307 	return (EOPNOTSUPP);
1308 }
1309 
1310 int
1311 vfs_stdquotactl (mp, cmds, uid, arg)
1312 	struct mount *mp;
1313 	int cmds;
1314 	uid_t uid;
1315 	void *arg;
1316 {
1317 
1318 	return (EOPNOTSUPP);
1319 }
1320 
1321 int
1322 vfs_stdsync(mp, waitfor)
1323 	struct mount *mp;
1324 	int waitfor;
1325 {
1326 	struct vnode *vp, *mvp;
1327 	struct thread *td;
1328 	int error, lockreq, allerror = 0;
1329 
1330 	td = curthread;
1331 	lockreq = LK_EXCLUSIVE | LK_INTERLOCK;
1332 	if (waitfor != MNT_WAIT)
1333 		lockreq |= LK_NOWAIT;
1334 	/*
1335 	 * Force stale buffer cache information to be flushed.
1336 	 */
1337 loop:
1338 	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
1339 		if (vp->v_bufobj.bo_dirty.bv_cnt == 0) {
1340 			VI_UNLOCK(vp);
1341 			continue;
1342 		}
1343 		if ((error = vget(vp, lockreq, td)) != 0) {
1344 			if (error == ENOENT) {
1345 				MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
1346 				goto loop;
1347 			}
1348 			continue;
1349 		}
1350 		error = VOP_FSYNC(vp, waitfor, td);
1351 		if (error)
1352 			allerror = error;
1353 		vput(vp);
1354 	}
1355 	return (allerror);
1356 }
1357 
1358 int
1359 vfs_stdnosync (mp, waitfor)
1360 	struct mount *mp;
1361 	int waitfor;
1362 {
1363 
1364 	return (0);
1365 }
1366 
1367 static int
1368 vop_stdcopy_file_range(struct vop_copy_file_range_args *ap)
1369 {
1370 	int error;
1371 
1372 	error = vn_generic_copy_file_range(ap->a_invp, ap->a_inoffp,
1373 	    ap->a_outvp, ap->a_outoffp, ap->a_lenp, ap->a_flags, ap->a_incred,
1374 	    ap->a_outcred, ap->a_fsizetd);
1375 	return (error);
1376 }
1377 
1378 int
1379 vfs_stdvget (mp, ino, flags, vpp)
1380 	struct mount *mp;
1381 	ino_t ino;
1382 	int flags;
1383 	struct vnode **vpp;
1384 {
1385 
1386 	return (EOPNOTSUPP);
1387 }
1388 
1389 int
1390 vfs_stdfhtovp (mp, fhp, flags, vpp)
1391 	struct mount *mp;
1392 	struct fid *fhp;
1393 	int flags;
1394 	struct vnode **vpp;
1395 {
1396 
1397 	return (EOPNOTSUPP);
1398 }
1399 
1400 int
1401 vfs_stdinit (vfsp)
1402 	struct vfsconf *vfsp;
1403 {
1404 
1405 	return (0);
1406 }
1407 
1408 int
1409 vfs_stduninit (vfsp)
1410 	struct vfsconf *vfsp;
1411 {
1412 
1413 	return(0);
1414 }
1415 
1416 int
1417 vfs_stdextattrctl(mp, cmd, filename_vp, attrnamespace, attrname)
1418 	struct mount *mp;
1419 	int cmd;
1420 	struct vnode *filename_vp;
1421 	int attrnamespace;
1422 	const char *attrname;
1423 {
1424 
1425 	if (filename_vp != NULL)
1426 		VOP_UNLOCK(filename_vp);
1427 	return (EOPNOTSUPP);
1428 }
1429 
1430 int
1431 vfs_stdsysctl(mp, op, req)
1432 	struct mount *mp;
1433 	fsctlop_t op;
1434 	struct sysctl_req *req;
1435 {
1436 
1437 	return (EOPNOTSUPP);
1438 }
1439 
1440 static vop_bypass_t *
1441 bp_by_off(struct vop_vector *vop, struct vop_generic_args *a)
1442 {
1443 
1444 	return (*(vop_bypass_t **)((char *)vop + a->a_desc->vdesc_vop_offset));
1445 }
1446 
1447 int
1448 vop_sigdefer(struct vop_vector *vop, struct vop_generic_args *a)
1449 {
1450 	vop_bypass_t *bp;
1451 	int prev_stops, rc;
1452 
1453 	bp = bp_by_off(vop, a);
1454 	MPASS(bp != NULL);
1455 
1456 	prev_stops = sigdeferstop(SIGDEFERSTOP_SILENT);
1457 	rc = bp(a);
1458 	sigallowstop(prev_stops);
1459 	return (rc);
1460 }
1461