2 * SPDX-License-Identifier: BSD-4-Clause
4 * Copyright (c) 1996 John S. Dyson
5 * Copyright (c) 2012 Giovanni Trematerra
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice immediately at the beginning of the file, without modification,
13 * this list of conditions, and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Absolutely no warranty of function or purpose is made by the author
19 * 4. Modifications may be freely made to this file if the above conditions
24 * This file contains a high-performance replacement for the socket-based
25 * pipes scheme originally used in FreeBSD/4.4Lite. It does not support
26 * all features of sockets, but does do everything that pipes normally
31 * This code has two modes of operation, a small write mode and a large
32 * write mode. The small write mode acts like conventional pipes with
33 * a kernel buffer. If the buffer is less than PIPE_MINDIRECT, then the
34 * "normal" pipe buffering is done. If the buffer is between PIPE_MINDIRECT
35 * and PIPE_SIZE in size, the sending process pins the underlying pages in
36 * memory, and the receiving process copies directly from these pinned pages
37 * in the sending process.
39 * If the sending process receives a signal, it is possible that it will
40 * go away, and certainly its address space can change, because control
41 * is returned back to the user-mode side. In that case, the pipe code
42 * arranges to copy the buffer supplied by the user process, to a pageable
43 * kernel buffer, and the receiving process will grab the data from the
44 * pageable kernel buffer. Since signals don't happen all that often,
45 * the copy operation is normally eliminated.
47 * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
48 * happen for small transfers so that the system will not spend all of
49 * its time context switching.
51 * In order to limit the resource use of pipes, two sysctls exist:
53 * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
54 * address space available to us in pipe_map. This value is normally
55 * autotuned, but may also be loader tuned.
57 * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
58 * memory in use by pipes.
60 * Based on how large pipekva is relative to maxpipekva, the following
64 * New pipes are given 16K of memory backing, pipes may dynamically
65 * grow to as large as 64K where needed.
67 * New pipes are given 4K (or PAGE_SIZE) of memory backing,
68 * existing pipes may NOT grow.
70 * New pipes are given 4K (or PAGE_SIZE) of memory backing,
71 * existing pipes will be shrunk down to 4K whenever possible.
73 * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0. If
74 * that is set, the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
75 * resize which MUST occur for reverse-direction pipes when they are
78 * Additional information about the current state of pipes may be obtained
79 * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
80 * and kern.ipc.piperesizefail.
82 * Locking rules: There are two locks present here: A mutex, used via
83 * PIPE_LOCK, and a flag, used via pipelock(). All locking is done via
84 * the flag, as mutexes can not persist over uiomove. The mutex
85 * exists only to guard access to the flag, and is not in itself a
86 * locking mechanism. Also note that there is only a single mutex for
87 * both directions of a pipe.
89 * As pipelock() may have to sleep before it can acquire the flag, it
90 * is important to reread all data after a call to pipelock(); everything
91 * in the structure may have changed.
94 #include <sys/cdefs.h>
95 __FBSDID("$FreeBSD$");
97 #include <sys/param.h>
98 #include <sys/systm.h>
100 #include <sys/fcntl.h>
101 #include <sys/file.h>
102 #include <sys/filedesc.h>
103 #include <sys/filio.h>
104 #include <sys/kernel.h>
105 #include <sys/lock.h>
106 #include <sys/mutex.h>
107 #include <sys/ttycom.h>
108 #include <sys/stat.h>
109 #include <sys/malloc.h>
110 #include <sys/poll.h>
111 #include <sys/selinfo.h>
112 #include <sys/signalvar.h>
113 #include <sys/syscallsubr.h>
114 #include <sys/sysctl.h>
115 #include <sys/sysproto.h>
116 #include <sys/pipe.h>
117 #include <sys/proc.h>
118 #include <sys/vnode.h>
120 #include <sys/user.h>
121 #include <sys/event.h>
123 #include <security/mac/mac_framework.h>
126 #include <vm/vm_param.h>
127 #include <vm/vm_object.h>
128 #include <vm/vm_kern.h>
129 #include <vm/vm_extern.h>
131 #include <vm/vm_map.h>
132 #include <vm/vm_page.h>
136 * Use this define if you want to disable *fancy* VM things. Expect an
137 * approx 30% decrease in transfer rate. This could be useful for
140 /* #define PIPE_NODIRECT */
142 #define PIPE_PEER(pipe) \
143 (((pipe)->pipe_state & PIPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
146 * interfaces to the outside world
148 static fo_rdwr_t pipe_read;
149 static fo_rdwr_t pipe_write;
150 static fo_truncate_t pipe_truncate;
151 static fo_ioctl_t pipe_ioctl;
152 static fo_poll_t pipe_poll;
153 static fo_kqfilter_t pipe_kqfilter;
154 static fo_stat_t pipe_stat;
155 static fo_close_t pipe_close;
156 static fo_chmod_t pipe_chmod;
157 static fo_chown_t pipe_chown;
158 static fo_fill_kinfo_t pipe_fill_kinfo;
160 struct fileops pipeops = {
161 .fo_read = pipe_read,
162 .fo_write = pipe_write,
163 .fo_truncate = pipe_truncate,
164 .fo_ioctl = pipe_ioctl,
165 .fo_poll = pipe_poll,
166 .fo_kqfilter = pipe_kqfilter,
167 .fo_stat = pipe_stat,
168 .fo_close = pipe_close,
169 .fo_chmod = pipe_chmod,
170 .fo_chown = pipe_chown,
171 .fo_sendfile = invfo_sendfile,
172 .fo_fill_kinfo = pipe_fill_kinfo,
173 .fo_flags = DFLAG_PASSABLE
176 static void filt_pipedetach(struct knote *kn);
177 static void filt_pipedetach_notsup(struct knote *kn);
178 static int filt_pipenotsup(struct knote *kn, long hint);
179 static int filt_piperead(struct knote *kn, long hint);
180 static int filt_pipewrite(struct knote *kn, long hint);
182 static struct filterops pipe_nfiltops = {
184 .f_detach = filt_pipedetach_notsup,
185 .f_event = filt_pipenotsup
187 static struct filterops pipe_rfiltops = {
189 .f_detach = filt_pipedetach,
190 .f_event = filt_piperead
192 static struct filterops pipe_wfiltops = {
194 .f_detach = filt_pipedetach,
195 .f_event = filt_pipewrite
199 * Default pipe buffer size(s), this can be kind-of large now because pipe
200 * space is pageable. The pipe code will try to maintain locality of
201 * reference for performance reasons, so small amounts of outstanding I/O
202 * will not wipe the cache.
204 #define MINPIPESIZE (PIPE_SIZE/3)
205 #define MAXPIPESIZE (2*PIPE_SIZE/3)
207 static long amountpipekva;
208 static int pipefragretry;
209 static int pipeallocfail;
210 static int piperesizefail;
211 static int piperesizeallowed = 1;
213 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
214 &maxpipekva, 0, "Pipe KVA limit");
215 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
216 &amountpipekva, 0, "Pipe KVA usage");
217 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
218 &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
219 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
220 &pipeallocfail, 0, "Pipe allocation failures");
221 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
222 &piperesizefail, 0, "Pipe resize failures");
223 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
224 &piperesizeallowed, 0, "Pipe resizing allowed");
226 static void pipeinit(void *dummy __unused);
227 static void pipeclose(struct pipe *cpipe);
228 static void pipe_free_kmem(struct pipe *cpipe);
229 static void pipe_create(struct pipe *pipe, int backing);
230 static void pipe_paircreate(struct thread *td, struct pipepair **p_pp);
231 static __inline int pipelock(struct pipe *cpipe, int catch);
232 static __inline void pipeunlock(struct pipe *cpipe);
233 #ifndef PIPE_NODIRECT
234 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
235 static void pipe_destroy_write_buffer(struct pipe *wpipe);
236 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
237 static void pipe_clone_write_buffer(struct pipe *wpipe);
239 static int pipespace(struct pipe *cpipe, int size);
240 static int pipespace_new(struct pipe *cpipe, int size);
242 static int pipe_zone_ctor(void *mem, int size, void *arg, int flags);
243 static int pipe_zone_init(void *mem, int size, int flags);
244 static void pipe_zone_fini(void *mem, int size);
246 static uma_zone_t pipe_zone;
247 static struct unrhdr64 pipeino_unr;
248 static dev_t pipedev_ino;
250 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
253 pipeinit(void *dummy __unused)
256 pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
257 pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
259 KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
260 new_unrhdr64(&pipeino_unr, 1);
261 pipedev_ino = devfs_alloc_cdp_inode();
262 KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
266 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
269 struct pipe *rpipe, *wpipe;
271 KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
273 pp = (struct pipepair *)mem;
276 * We zero both pipe endpoints to make sure all the kmem pointers
277 * are NULL, flag fields are zero'd, etc. We timestamp both
278 * endpoints with the same time.
280 rpipe = &pp->pp_rpipe;
281 bzero(rpipe, sizeof(*rpipe));
282 vfs_timestamp(&rpipe->pipe_ctime);
283 rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
285 wpipe = &pp->pp_wpipe;
286 bzero(wpipe, sizeof(*wpipe));
287 wpipe->pipe_ctime = rpipe->pipe_ctime;
288 wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
290 rpipe->pipe_peer = wpipe;
291 rpipe->pipe_pair = pp;
292 wpipe->pipe_peer = rpipe;
293 wpipe->pipe_pair = pp;
296 * Mark both endpoints as present; they will later get free'd
297 * one at a time. When both are free'd, then the whole pair
300 rpipe->pipe_present = PIPE_ACTIVE;
301 wpipe->pipe_present = PIPE_ACTIVE;
304 * Eventually, the MAC Framework may initialize the label
305 * in ctor or init, but for now we do it elswhere to avoid
306 * blocking in ctor or init.
314 pipe_zone_init(void *mem, int size, int flags)
318 KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
320 pp = (struct pipepair *)mem;
322 mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
327 pipe_zone_fini(void *mem, int size)
331 KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
333 pp = (struct pipepair *)mem;
335 mtx_destroy(&pp->pp_mtx);
339 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
342 struct pipe *rpipe, *wpipe;
344 *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
347 * The MAC label is shared between the connected endpoints. As a
348 * result mac_pipe_init() and mac_pipe_create() are called once
349 * for the pair, and not on the endpoints.
352 mac_pipe_create(td->td_ucred, pp);
354 rpipe = &pp->pp_rpipe;
355 wpipe = &pp->pp_wpipe;
357 knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
358 knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
360 /* Only the forward direction pipe is backed by default */
361 pipe_create(rpipe, 1);
362 pipe_create(wpipe, 0);
364 rpipe->pipe_state |= PIPE_DIRECTOK;
365 wpipe->pipe_state |= PIPE_DIRECTOK;
369 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
373 pipe_paircreate(td, &pp);
374 pp->pp_rpipe.pipe_state |= PIPE_NAMED;
375 *ppipe = &pp->pp_rpipe;
379 pipe_dtor(struct pipe *dpipe)
383 peer = (dpipe->pipe_state & PIPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
384 funsetown(&dpipe->pipe_sigio);
387 funsetown(&peer->pipe_sigio);
393 * The pipe system call for the DTYPE_PIPE type of pipes. If we fail, let
394 * the zone pick up the pieces via pipeclose().
397 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
398 struct filecaps *fcaps2)
400 struct file *rf, *wf;
401 struct pipe *rpipe, *wpipe;
403 int fd, fflags, error;
405 pipe_paircreate(td, &pp);
406 rpipe = &pp->pp_rpipe;
407 wpipe = &pp->pp_wpipe;
408 error = falloc_caps(td, &rf, &fd, flags, fcaps1);
414 /* An extra reference on `rf' has been held for us by falloc_caps(). */
417 fflags = FREAD | FWRITE;
418 if ((flags & O_NONBLOCK) != 0)
422 * Warning: once we've gotten past allocation of the fd for the
423 * read-side, we can only drop the read side via fdrop() in order
424 * to avoid races against processes which manage to dup() the read
425 * side while we are blocked trying to allocate the write side.
427 finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
428 error = falloc_caps(td, &wf, &fd, flags, fcaps2);
430 fdclose(td, rf, fildes[0]);
432 /* rpipe has been closed by fdrop(). */
436 /* An extra reference on `wf' has been held for us by falloc_caps(). */
437 finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
445 #ifdef COMPAT_FREEBSD10
448 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
453 error = kern_pipe(td, fildes, 0, NULL, NULL);
457 td->td_retval[0] = fildes[0];
458 td->td_retval[1] = fildes[1];
465 sys_pipe2(struct thread *td, struct pipe2_args *uap)
467 int error, fildes[2];
469 if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
471 error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
474 error = copyout(fildes, uap->fildes, 2 * sizeof(int));
476 (void)kern_close(td, fildes[0]);
477 (void)kern_close(td, fildes[1]);
483 * Allocate kva for pipe circular buffer, the space is pageable
484 * This routine will 'realloc' the size of a pipe safely, if it fails
485 * it will retain the old buffer.
486 * If it fails it will return ENOMEM.
489 pipespace_new(struct pipe *cpipe, int size)
492 int error, cnt, firstseg;
493 static int curfail = 0;
494 static struct timeval lastfail;
496 KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
497 KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
498 ("pipespace: resize of direct writes not allowed"));
500 cnt = cpipe->pipe_buffer.cnt;
504 size = round_page(size);
505 buffer = (caddr_t) vm_map_min(pipe_map);
507 error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
508 VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
509 if (error != KERN_SUCCESS) {
510 if ((cpipe->pipe_buffer.buffer == NULL) &&
511 (size > SMALL_PIPE_SIZE)) {
512 size = SMALL_PIPE_SIZE;
516 if (cpipe->pipe_buffer.buffer == NULL) {
518 if (ppsratecheck(&lastfail, &curfail, 1))
519 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
526 /* copy data, then free old resources if we're resizing */
528 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
529 firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
530 bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
532 if ((cnt - firstseg) > 0)
533 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
534 cpipe->pipe_buffer.in);
536 bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
540 pipe_free_kmem(cpipe);
541 cpipe->pipe_buffer.buffer = buffer;
542 cpipe->pipe_buffer.size = size;
543 cpipe->pipe_buffer.in = cnt;
544 cpipe->pipe_buffer.out = 0;
545 cpipe->pipe_buffer.cnt = cnt;
546 atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
551 * Wrapper for pipespace_new() that performs locking assertions.
554 pipespace(struct pipe *cpipe, int size)
557 KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
558 ("Unlocked pipe passed to pipespace"));
559 return (pipespace_new(cpipe, size));
563 * lock a pipe for I/O, blocking other access
566 pipelock(struct pipe *cpipe, int catch)
570 PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
571 while (cpipe->pipe_state & PIPE_LOCKFL) {
572 cpipe->pipe_state |= PIPE_LWANT;
573 error = msleep(cpipe, PIPE_MTX(cpipe),
574 catch ? (PRIBIO | PCATCH) : PRIBIO,
579 cpipe->pipe_state |= PIPE_LOCKFL;
584 * unlock a pipe I/O lock
587 pipeunlock(struct pipe *cpipe)
590 PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
591 KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
592 ("Unlocked pipe passed to pipeunlock"));
593 cpipe->pipe_state &= ~PIPE_LOCKFL;
594 if (cpipe->pipe_state & PIPE_LWANT) {
595 cpipe->pipe_state &= ~PIPE_LWANT;
601 pipeselwakeup(struct pipe *cpipe)
604 PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
605 if (cpipe->pipe_state & PIPE_SEL) {
606 selwakeuppri(&cpipe->pipe_sel, PSOCK);
607 if (!SEL_WAITING(&cpipe->pipe_sel))
608 cpipe->pipe_state &= ~PIPE_SEL;
610 if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
611 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
612 KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
616 * Initialize and allocate VM and memory for pipe. The structure
617 * will start out zero'd from the ctor, so we just manage the kmem.
620 pipe_create(struct pipe *pipe, int backing)
625 * Note that these functions can fail if pipe map is exhausted
626 * (as a result of too many pipes created), but we ignore the
627 * error as it is not fatal and could be provoked by
628 * unprivileged users. The only consequence is worse performance
631 if (amountpipekva > maxpipekva / 2)
632 (void)pipespace_new(pipe, SMALL_PIPE_SIZE);
634 (void)pipespace_new(pipe, PIPE_SIZE);
637 pipe->pipe_ino = alloc_unr64(&pipeino_unr);
642 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
643 int flags, struct thread *td)
653 error = pipelock(rpipe, 1);
658 error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
662 if (amountpipekva > (3 * maxpipekva) / 4) {
663 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
664 (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
665 (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
666 (piperesizeallowed == 1)) {
668 pipespace(rpipe, SMALL_PIPE_SIZE);
673 while (uio->uio_resid) {
675 * normal pipe buffer receive
677 if (rpipe->pipe_buffer.cnt > 0) {
678 size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
679 if (size > rpipe->pipe_buffer.cnt)
680 size = rpipe->pipe_buffer.cnt;
681 if (size > uio->uio_resid)
682 size = uio->uio_resid;
686 &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
692 rpipe->pipe_buffer.out += size;
693 if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
694 rpipe->pipe_buffer.out = 0;
696 rpipe->pipe_buffer.cnt -= size;
699 * If there is no more to read in the pipe, reset
700 * its pointers to the beginning. This improves
703 if (rpipe->pipe_buffer.cnt == 0) {
704 rpipe->pipe_buffer.in = 0;
705 rpipe->pipe_buffer.out = 0;
708 #ifndef PIPE_NODIRECT
710 * Direct copy, bypassing a kernel buffer.
712 } else if ((size = rpipe->pipe_map.cnt) != 0) {
713 if (size > uio->uio_resid)
714 size = (u_int) uio->uio_resid;
716 error = uiomove_fromphys(rpipe->pipe_map.ms,
717 rpipe->pipe_map.pos, size, uio);
722 rpipe->pipe_map.pos += size;
723 rpipe->pipe_map.cnt -= size;
724 if (rpipe->pipe_map.cnt == 0) {
725 rpipe->pipe_state &= ~PIPE_WANTW;
731 * detect EOF condition
732 * read returns 0 on EOF, no need to set error
734 if (rpipe->pipe_state & PIPE_EOF)
738 * If the "write-side" has been blocked, wake it up now.
740 if (rpipe->pipe_state & PIPE_WANTW) {
741 rpipe->pipe_state &= ~PIPE_WANTW;
746 * Break if some data was read.
752 * Unlock the pipe buffer for our remaining processing.
753 * We will either break out with an error or we will
754 * sleep and relock to loop.
759 * Handle non-blocking mode operation or
760 * wait for more data.
762 if (fp->f_flag & FNONBLOCK) {
765 rpipe->pipe_state |= PIPE_WANTR;
766 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
769 error = pipelock(rpipe, 1);
780 /* XXX: should probably do this before getting any locks. */
782 vfs_timestamp(&rpipe->pipe_atime);
787 * PIPE_WANT processing only makes sense if pipe_busy is 0.
789 if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
790 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
792 } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
794 * Handle write blocking hysteresis.
796 if (rpipe->pipe_state & PIPE_WANTW) {
797 rpipe->pipe_state &= ~PIPE_WANTW;
802 if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
803 pipeselwakeup(rpipe);
809 #ifndef PIPE_NODIRECT
811 * Map the sending processes' buffer into kernel space and wire it.
812 * This is similar to a physical write operation.
815 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
820 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
821 KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
822 ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
823 KASSERT(wpipe->pipe_map.cnt == 0,
824 ("%s: pipe map for %p contains residual data", __func__, wpipe));
826 if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
827 size = wpipe->pipe_buffer.size;
829 size = uio->uio_iov->iov_len;
831 wpipe->pipe_state |= PIPE_DIRECTW;
833 i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
834 (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
835 wpipe->pipe_map.ms, PIPENPAGES);
838 wpipe->pipe_state &= ~PIPE_DIRECTW;
842 wpipe->pipe_map.npages = i;
843 wpipe->pipe_map.pos =
844 ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
845 wpipe->pipe_map.cnt = size;
847 uio->uio_iov->iov_len -= size;
848 uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
849 if (uio->uio_iov->iov_len == 0)
851 uio->uio_resid -= size;
852 uio->uio_offset += size;
857 * Unwire the process buffer.
860 pipe_destroy_write_buffer(struct pipe *wpipe)
863 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
864 KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
865 ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
866 KASSERT(wpipe->pipe_map.cnt == 0,
867 ("%s: pipe map for %p contains residual data", __func__, wpipe));
869 wpipe->pipe_state &= ~PIPE_DIRECTW;
870 vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
871 wpipe->pipe_map.npages = 0;
875 * In the case of a signal, the writing process might go away. This
876 * code copies the data into the circular buffer so that the source
877 * pages can be freed without loss of data.
880 pipe_clone_write_buffer(struct pipe *wpipe)
887 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
888 KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
889 ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
891 size = wpipe->pipe_map.cnt;
892 pos = wpipe->pipe_map.pos;
893 wpipe->pipe_map.cnt = 0;
895 wpipe->pipe_buffer.in = size;
896 wpipe->pipe_buffer.out = 0;
897 wpipe->pipe_buffer.cnt = size;
900 iov.iov_base = wpipe->pipe_buffer.buffer;
905 uio.uio_resid = size;
906 uio.uio_segflg = UIO_SYSSPACE;
907 uio.uio_rw = UIO_READ;
908 uio.uio_td = curthread;
909 uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
911 pipe_destroy_write_buffer(wpipe);
915 * This implements the pipe buffer write mechanism. Note that only
916 * a direct write OR a normal pipe write can be pending at any given time.
917 * If there are any characters in the pipe buffer, the direct write will
918 * be deferred until the receiving process grabs all of the bytes from
919 * the pipe buffer. Then the direct mapping write is set-up.
922 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
927 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
928 error = pipelock(wpipe, 1);
931 if ((wpipe->pipe_state & PIPE_EOF) != 0) {
936 if (wpipe->pipe_state & PIPE_DIRECTW) {
937 if (wpipe->pipe_state & PIPE_WANTR) {
938 wpipe->pipe_state &= ~PIPE_WANTR;
941 pipeselwakeup(wpipe);
942 wpipe->pipe_state |= PIPE_WANTW;
944 error = msleep(wpipe, PIPE_MTX(wpipe),
945 PRIBIO | PCATCH, "pipdww", 0);
951 if (wpipe->pipe_buffer.cnt > 0) {
952 if (wpipe->pipe_state & PIPE_WANTR) {
953 wpipe->pipe_state &= ~PIPE_WANTR;
956 pipeselwakeup(wpipe);
957 wpipe->pipe_state |= PIPE_WANTW;
959 error = msleep(wpipe, PIPE_MTX(wpipe),
960 PRIBIO | PCATCH, "pipdwc", 0);
967 error = pipe_build_write_buffer(wpipe, uio);
973 while (wpipe->pipe_map.cnt != 0) {
974 if (wpipe->pipe_state & PIPE_EOF) {
975 wpipe->pipe_map.cnt = 0;
976 pipe_destroy_write_buffer(wpipe);
977 pipeselwakeup(wpipe);
982 if (wpipe->pipe_state & PIPE_WANTR) {
983 wpipe->pipe_state &= ~PIPE_WANTR;
986 pipeselwakeup(wpipe);
987 wpipe->pipe_state |= PIPE_WANTW;
989 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
996 if (wpipe->pipe_state & PIPE_EOF)
998 if (error == EINTR || error == ERESTART)
999 pipe_clone_write_buffer(wpipe);
1001 pipe_destroy_write_buffer(wpipe);
1003 KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
1004 ("pipe %p leaked PIPE_DIRECTW", wpipe));
1014 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
1015 int flags, struct thread *td)
1020 struct pipe *wpipe, *rpipe;
1023 wpipe = PIPE_PEER(rpipe);
1025 error = pipelock(wpipe, 1);
1031 * detect loss of pipe read side, issue SIGPIPE if lost.
1033 if (wpipe->pipe_present != PIPE_ACTIVE ||
1034 (wpipe->pipe_state & PIPE_EOF)) {
1040 error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
1049 /* Choose a larger size if it's advantageous */
1050 desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
1051 while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
1052 if (piperesizeallowed != 1)
1054 if (amountpipekva > maxpipekva / 2)
1056 if (desiredsize == BIG_PIPE_SIZE)
1058 desiredsize = desiredsize * 2;
1061 /* Choose a smaller size if we're in a OOM situation */
1062 if ((amountpipekva > (3 * maxpipekva) / 4) &&
1063 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
1064 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
1065 (piperesizeallowed == 1))
1066 desiredsize = SMALL_PIPE_SIZE;
1068 /* Resize if the above determined that a new size was necessary */
1069 if ((desiredsize != wpipe->pipe_buffer.size) &&
1070 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
1072 pipespace(wpipe, desiredsize);
1075 if (wpipe->pipe_buffer.size == 0) {
1077 * This can only happen for reverse direction use of pipes
1078 * in a complete OOM situation.
1089 orig_resid = uio->uio_resid;
1091 while (uio->uio_resid) {
1095 if (wpipe->pipe_state & PIPE_EOF) {
1100 #ifndef PIPE_NODIRECT
1102 * If the transfer is large, we can gain performance if
1103 * we do process-to-process copies directly.
1104 * If the write is non-blocking, we don't use the
1105 * direct write mechanism.
1107 * The direct write mechanism will detect the reader going
1110 if (uio->uio_segflg == UIO_USERSPACE &&
1111 uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
1112 wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
1113 (fp->f_flag & FNONBLOCK) == 0) {
1115 error = pipe_direct_write(wpipe, uio);
1123 * Pipe buffered writes cannot be coincidental with
1124 * direct writes. We wait until the currently executing
1125 * direct write is completed before we start filling the
1126 * pipe buffer. We break out if a signal occurs or the
1129 if (wpipe->pipe_map.cnt != 0) {
1130 if (wpipe->pipe_state & PIPE_WANTR) {
1131 wpipe->pipe_state &= ~PIPE_WANTR;
1134 pipeselwakeup(wpipe);
1135 wpipe->pipe_state |= PIPE_WANTW;
1137 error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
1145 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
1147 /* Writes of size <= PIPE_BUF must be atomic. */
1148 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
1152 int size; /* Transfer size */
1153 int segsize; /* first segment to transfer */
1156 * Transfer size is minimum of uio transfer
1157 * and free space in pipe buffer.
1159 if (space > uio->uio_resid)
1160 size = uio->uio_resid;
1164 * First segment to transfer is minimum of
1165 * transfer size and contiguous space in
1166 * pipe buffer. If first segment to transfer
1167 * is less than the transfer size, we've got
1168 * a wraparound in the buffer.
1170 segsize = wpipe->pipe_buffer.size -
1171 wpipe->pipe_buffer.in;
1175 /* Transfer first segment */
1178 error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
1182 if (error == 0 && segsize < size) {
1183 KASSERT(wpipe->pipe_buffer.in + segsize ==
1184 wpipe->pipe_buffer.size,
1185 ("Pipe buffer wraparound disappeared"));
1187 * Transfer remaining part now, to
1188 * support atomic writes. Wraparound
1194 &wpipe->pipe_buffer.buffer[0],
1195 size - segsize, uio);
1199 wpipe->pipe_buffer.in += size;
1200 if (wpipe->pipe_buffer.in >=
1201 wpipe->pipe_buffer.size) {
1202 KASSERT(wpipe->pipe_buffer.in ==
1204 wpipe->pipe_buffer.size,
1205 ("Expected wraparound bad"));
1206 wpipe->pipe_buffer.in = size - segsize;
1209 wpipe->pipe_buffer.cnt += size;
1210 KASSERT(wpipe->pipe_buffer.cnt <=
1211 wpipe->pipe_buffer.size,
1212 ("Pipe buffer overflow"));
1219 * If the "read-side" has been blocked, wake it up now.
1221 if (wpipe->pipe_state & PIPE_WANTR) {
1222 wpipe->pipe_state &= ~PIPE_WANTR;
1227 * don't block on non-blocking I/O
1229 if (fp->f_flag & FNONBLOCK) {
1236 * We have no more space and have something to offer,
1237 * wake up select/poll.
1239 pipeselwakeup(wpipe);
1241 wpipe->pipe_state |= PIPE_WANTW;
1243 error = msleep(wpipe, PIPE_MTX(rpipe),
1244 PRIBIO | PCATCH, "pipewr", 0);
1253 if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
1254 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
1256 } else if (wpipe->pipe_buffer.cnt > 0) {
1258 * If we have put any characters in the buffer, we wake up
1261 if (wpipe->pipe_state & PIPE_WANTR) {
1262 wpipe->pipe_state &= ~PIPE_WANTR;
1268 * Don't return EPIPE if any byte was written.
1269 * EINTR and other interrupts are handled by generic I/O layer.
1270 * Do not pretend that I/O succeeded for obvious user error
1273 if (uio->uio_resid != orig_resid && error == EPIPE)
1277 vfs_timestamp(&wpipe->pipe_mtime);
1280 * We have something to offer,
1281 * wake up select/poll.
1283 if (wpipe->pipe_buffer.cnt)
1284 pipeselwakeup(wpipe);
1293 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
1300 if (cpipe->pipe_state & PIPE_NAMED)
1301 error = vnops.fo_truncate(fp, length, active_cred, td);
1303 error = invfo_truncate(fp, length, active_cred, td);
1308 * we implement a very minimal set of ioctls for compatibility with sockets.
1311 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
1314 struct pipe *mpipe = fp->f_data;
1320 error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
1335 mpipe->pipe_state |= PIPE_ASYNC;
1337 mpipe->pipe_state &= ~PIPE_ASYNC;
1342 if (!(fp->f_flag & FREAD)) {
1347 if (mpipe->pipe_map.cnt != 0)
1348 *(int *)data = mpipe->pipe_map.cnt;
1350 *(int *)data = mpipe->pipe_buffer.cnt;
1355 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1359 *(int *)data = fgetown(&mpipe->pipe_sigio);
1362 /* This is deprecated, FIOSETOWN should be used instead. */
1365 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1368 /* This is deprecated, FIOGETOWN should be used instead. */
1370 *(int *)data = -fgetown(&mpipe->pipe_sigio);
1383 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
1388 int levents, revents;
1395 wpipe = PIPE_PEER(rpipe);
1398 error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
1402 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
1403 if (rpipe->pipe_map.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
1404 revents |= events & (POLLIN | POLLRDNORM);
1406 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
1407 if (wpipe->pipe_present != PIPE_ACTIVE ||
1408 (wpipe->pipe_state & PIPE_EOF) ||
1409 ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
1410 ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
1411 wpipe->pipe_buffer.size == 0)))
1412 revents |= events & (POLLOUT | POLLWRNORM);
1415 (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
1416 if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
1417 fp->f_pipegen == rpipe->pipe_wgen)
1418 events |= POLLINIGNEOF;
1420 if ((events & POLLINIGNEOF) == 0) {
1421 if (rpipe->pipe_state & PIPE_EOF) {
1422 revents |= (events & (POLLIN | POLLRDNORM));
1423 if (wpipe->pipe_present != PIPE_ACTIVE ||
1424 (wpipe->pipe_state & PIPE_EOF))
1430 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
1431 selrecord(td, &rpipe->pipe_sel);
1432 if (SEL_WAITING(&rpipe->pipe_sel))
1433 rpipe->pipe_state |= PIPE_SEL;
1436 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
1437 selrecord(td, &wpipe->pipe_sel);
1438 if (SEL_WAITING(&wpipe->pipe_sel))
1439 wpipe->pipe_state |= PIPE_SEL;
1451 * We shouldn't need locks here as we're doing a read and this should
1452 * be a natural race.
1455 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred,
1466 error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
1473 /* For named pipes ask the underlying filesystem. */
1474 if (pipe->pipe_state & PIPE_NAMED) {
1476 return (vnops.fo_stat(fp, ub, active_cred, td));
1481 bzero(ub, sizeof(*ub));
1482 ub->st_mode = S_IFIFO;
1483 ub->st_blksize = PAGE_SIZE;
1484 if (pipe->pipe_map.cnt != 0)
1485 ub->st_size = pipe->pipe_map.cnt;
1487 ub->st_size = pipe->pipe_buffer.cnt;
1488 ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
1489 ub->st_atim = pipe->pipe_atime;
1490 ub->st_mtim = pipe->pipe_mtime;
1491 ub->st_ctim = pipe->pipe_ctime;
1492 ub->st_uid = fp->f_cred->cr_uid;
1493 ub->st_gid = fp->f_cred->cr_gid;
1494 ub->st_dev = pipedev_ino;
1495 ub->st_ino = pipe->pipe_ino;
1497 * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
1504 pipe_close(struct file *fp, struct thread *td)
1507 if (fp->f_vnode != NULL)
1508 return vnops.fo_close(fp, td);
1509 fp->f_ops = &badfileops;
1510 pipe_dtor(fp->f_data);
1516 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
1522 if (cpipe->pipe_state & PIPE_NAMED)
1523 error = vn_chmod(fp, mode, active_cred, td);
1525 error = invfo_chmod(fp, mode, active_cred, td);
1530 pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1537 if (cpipe->pipe_state & PIPE_NAMED)
1538 error = vn_chown(fp, uid, gid, active_cred, td);
1540 error = invfo_chown(fp, uid, gid, active_cred, td);
1545 pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1549 if (fp->f_type == DTYPE_FIFO)
1550 return (vn_fill_kinfo(fp, kif, fdp));
1551 kif->kf_type = KF_TYPE_PIPE;
1553 kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
1554 kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
1555 kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
1560 pipe_free_kmem(struct pipe *cpipe)
1563 KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
1564 ("pipe_free_kmem: pipe mutex locked"));
1566 if (cpipe->pipe_buffer.buffer != NULL) {
1567 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
1568 vm_map_remove(pipe_map,
1569 (vm_offset_t)cpipe->pipe_buffer.buffer,
1570 (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
1571 cpipe->pipe_buffer.buffer = NULL;
1573 #ifndef PIPE_NODIRECT
1575 cpipe->pipe_map.cnt = 0;
1576 cpipe->pipe_map.pos = 0;
1577 cpipe->pipe_map.npages = 0;
1586 pipeclose(struct pipe *cpipe)
1588 struct pipepair *pp;
1591 KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
1595 pp = cpipe->pipe_pair;
1597 pipeselwakeup(cpipe);
1600 * If the other side is blocked, wake it up saying that
1601 * we want to close it down.
1603 cpipe->pipe_state |= PIPE_EOF;
1604 while (cpipe->pipe_busy) {
1606 cpipe->pipe_state |= PIPE_WANT;
1608 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
1614 * Disconnect from peer, if any.
1616 ppipe = cpipe->pipe_peer;
1617 if (ppipe->pipe_present == PIPE_ACTIVE) {
1618 pipeselwakeup(ppipe);
1620 ppipe->pipe_state |= PIPE_EOF;
1622 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
1626 * Mark this endpoint as free. Release kmem resources. We
1627 * don't mark this endpoint as unused until we've finished
1628 * doing that, or the pipe might disappear out from under
1632 pipe_free_kmem(cpipe);
1634 cpipe->pipe_present = PIPE_CLOSING;
1638 * knlist_clear() may sleep dropping the PIPE_MTX. Set the
1639 * PIPE_FINALIZED, that allows other end to free the
1640 * pipe_pair, only after the knotes are completely dismantled.
1642 knlist_clear(&cpipe->pipe_sel.si_note, 1);
1643 cpipe->pipe_present = PIPE_FINALIZED;
1644 seldrain(&cpipe->pipe_sel);
1645 knlist_destroy(&cpipe->pipe_sel.si_note);
1648 * If both endpoints are now closed, release the memory for the
1649 * pipe pair. If not, unlock.
1651 if (ppipe->pipe_present == PIPE_FINALIZED) {
1654 mac_pipe_destroy(pp);
1656 uma_zfree(pipe_zone, cpipe->pipe_pair);
1663 pipe_kqfilter(struct file *fp, struct knote *kn)
1668 * If a filter is requested that is not supported by this file
1669 * descriptor, don't return an error, but also don't ever generate an
1672 if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
1673 kn->kn_fop = &pipe_nfiltops;
1676 if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
1677 kn->kn_fop = &pipe_nfiltops;
1682 switch (kn->kn_filter) {
1684 kn->kn_fop = &pipe_rfiltops;
1687 kn->kn_fop = &pipe_wfiltops;
1688 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
1689 /* other end of pipe has been closed */
1693 cpipe = PIPE_PEER(cpipe);
1700 kn->kn_hook = cpipe;
1701 knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
1707 filt_pipedetach(struct knote *kn)
1709 struct pipe *cpipe = kn->kn_hook;
1712 knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
1718 filt_piperead(struct knote *kn, long hint)
1720 struct pipe *rpipe = kn->kn_hook;
1721 struct pipe *wpipe = rpipe->pipe_peer;
1724 PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
1725 kn->kn_data = rpipe->pipe_buffer.cnt;
1726 if (kn->kn_data == 0)
1727 kn->kn_data = rpipe->pipe_map.cnt;
1729 if ((rpipe->pipe_state & PIPE_EOF) ||
1730 wpipe->pipe_present != PIPE_ACTIVE ||
1731 (wpipe->pipe_state & PIPE_EOF)) {
1732 kn->kn_flags |= EV_EOF;
1735 ret = kn->kn_data > 0;
1741 filt_pipewrite(struct knote *kn, long hint)
1746 * If this end of the pipe is closed, the knote was removed from the
1747 * knlist and the list lock (i.e., the pipe lock) is therefore not held.
1749 wpipe = kn->kn_hook;
1750 if (wpipe->pipe_present != PIPE_ACTIVE ||
1751 (wpipe->pipe_state & PIPE_EOF)) {
1753 kn->kn_flags |= EV_EOF;
1756 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1757 kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
1758 (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
1759 if (wpipe->pipe_state & PIPE_DIRECTW)
1762 return (kn->kn_data >= PIPE_BUF);
1766 filt_pipedetach_notsup(struct knote *kn)
1772 filt_pipenotsup(struct knote *kn, long hint)