summaryrefslogtreecommitdiff
path: root/sys/kern/sys_pipe.c
blob: 1df0c0e4dd3d2f5b4ab7d5453cd43dc60cfcb3c9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
/*	$OpenBSD: sys_pipe.c,v 1.91 2019/07/13 06:51:59 semarie Exp $	*/

/*
 * Copyright (c) 1996 John S. Dyson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    this list of conditions, and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Absolutely no warranty of function or purpose is made by the author
 *    John S. Dyson.
 * 4. Modifications may be freely made to this file if the above conditions
 *    are met.
 */

/*
 * This file contains a high-performance replacement for the socket-based
 * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
 * all features of sockets, but does do everything that pipes normally
 * do.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/pool.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/signalvar.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
#include <sys/event.h>
#include <sys/lock.h>
#include <sys/poll.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif

#include <uvm/uvm_extern.h>

#include <sys/pipe.h>

/*
 * interfaces to the outside world
 */
int	pipe_read(struct file *, struct uio *, int);
int	pipe_write(struct file *, struct uio *, int);
int	pipe_close(struct file *, struct proc *);
int	pipe_poll(struct file *, int events, struct proc *);
int	pipe_kqfilter(struct file *fp, struct knote *kn);
int	pipe_ioctl(struct file *, u_long, caddr_t, struct proc *);
int	pipe_stat(struct file *fp, struct stat *ub, struct proc *p);

static struct fileops pipeops = {
	.fo_read	= pipe_read,
	.fo_write	= pipe_write,
	.fo_ioctl	= pipe_ioctl,
	.fo_poll	= pipe_poll,
	.fo_kqfilter	= pipe_kqfilter,
	.fo_stat	= pipe_stat,
	.fo_close	= pipe_close
};

void	filt_pipedetach(struct knote *kn);
int	filt_piperead(struct knote *kn, long hint);
int	filt_pipewrite(struct knote *kn, long hint);

struct filterops pipe_rfiltops =
	{ 1, NULL, filt_pipedetach, filt_piperead };
struct filterops pipe_wfiltops =
	{ 1, NULL, filt_pipedetach, filt_pipewrite };

/*
 * Default pipe buffer size(s), this can be kind-of large now because pipe
 * space is pageable.  The pipe code will try to maintain locality of
 * reference for performance reasons, so small amounts of outstanding I/O
 * will not wipe the cache.
 */
#define MINPIPESIZE (PIPE_SIZE/3)

/*
 * Limit the number of "big" pipes
 */
#define LIMITBIGPIPES	32
unsigned int nbigpipe;
static unsigned int amountpipekva;

struct pool pipe_pool;

int	dopipe(struct proc *, int *, int);
void	pipeclose(struct pipe *);
void	pipe_free_kmem(struct pipe *);
int	pipe_create(struct pipe *);
int	pipelock(struct pipe *);
void	pipeunlock(struct pipe *);
void	pipeselwakeup(struct pipe *);
int	pipespace(struct pipe *, u_int);

/*
 * The pipe system call for the DTYPE_PIPE type of pipes
 */

int
sys_pipe(struct proc *p, void *v, register_t *retval)
{
	struct sys_pipe_args /* {
		syscallarg(int *) fdp;
	} */ *uap = v;

	return (dopipe(p, SCARG(uap, fdp), 0));
}

int
sys_pipe2(struct proc *p, void *v, register_t *retval)
{
	struct sys_pipe2_args /* {
		syscallarg(int *) fdp;
		syscallarg(int) flags;
	} */ *uap = v;

	if (SCARG(uap, flags) & ~(O_CLOEXEC | FNONBLOCK))
		return (EINVAL);

	return (dopipe(p, SCARG(uap, fdp), SCARG(uap, flags)));
}

int
dopipe(struct proc *p, int *ufds, int flags)
{
	struct filedesc *fdp = p->p_fd;
	struct file *rf, *wf;
	struct pipe *rpipe, *wpipe = NULL;
	int fds[2], cloexec, error;

	cloexec = (flags & O_CLOEXEC) ? UF_EXCLOSE : 0;

	rpipe = pool_get(&pipe_pool, PR_WAITOK);
	error = pipe_create(rpipe);
	if (error != 0)
		goto free1;
	wpipe = pool_get(&pipe_pool, PR_WAITOK);
	error = pipe_create(wpipe);
	if (error != 0)
		goto free1;

	fdplock(fdp);

	error = falloc(p, &rf, &fds[0]);
	if (error != 0)
		goto free2;
	rf->f_flag = FREAD | FWRITE | (flags & FNONBLOCK);
	rf->f_type = DTYPE_PIPE;
	rf->f_data = rpipe;
	rf->f_ops = &pipeops;

	error = falloc(p, &wf, &fds[1]);
	if (error != 0)
		goto free3;
	wf->f_flag = FREAD | FWRITE | (flags & FNONBLOCK);
	wf->f_type = DTYPE_PIPE;
	wf->f_data = wpipe;
	wf->f_ops = &pipeops;

	rpipe->pipe_peer = wpipe;
	wpipe->pipe_peer = rpipe;

	fdinsert(fdp, fds[0], cloexec, rf);
	fdinsert(fdp, fds[1], cloexec, wf);

	error = copyout(fds, ufds, sizeof(fds));
	if (error != 0) {
		fdrelease(p, fds[0]);
		fdrelease(p, fds[1]);
	}
#ifdef KTRACE
	else if (KTRPOINT(p, KTR_STRUCT))
		ktrfds(p, fds, 2);
#endif
	fdpunlock(fdp);

	FRELE(rf, p);
	FRELE(wf, p);
	return (error);

free3:
	fdremove(fdp, fds[0]);
	closef(rf, p);
	rpipe = NULL;
free2:
	fdpunlock(fdp);
free1:
	pipeclose(wpipe);
	pipeclose(rpipe);
	return (error);
}

/*
 * Allocate kva for pipe circular buffer, the space is pageable.
 * This routine will 'realloc' the size of a pipe safely, if it fails
 * it will retain the old buffer.
 * If it fails it will return ENOMEM.
 */
int
pipespace(struct pipe *cpipe, u_int size)
{
	caddr_t buffer;

	KERNEL_LOCK();
	buffer = km_alloc(size, &kv_any, &kp_pageable, &kd_waitok);
	KERNEL_UNLOCK();
	if (buffer == NULL) {
		return (ENOMEM);
	}

	/* free old resources if we are resizing */
	pipe_free_kmem(cpipe);
	cpipe->pipe_buffer.buffer = buffer;
	cpipe->pipe_buffer.size = size;
	cpipe->pipe_buffer.in = 0;
	cpipe->pipe_buffer.out = 0;
	cpipe->pipe_buffer.cnt = 0;

	atomic_add_int(&amountpipekva, cpipe->pipe_buffer.size);

	return (0);
}

/*
 * initialize and allocate VM and memory for pipe
 */
int
pipe_create(struct pipe *cpipe)
{
	int error;

	/* so pipe_free_kmem() doesn't follow junk pointer */
	cpipe->pipe_buffer.buffer = NULL;
	/*
	 * protect so pipeclose() doesn't follow a junk pointer
	 * if pipespace() fails.
	 */
	memset(&cpipe->pipe_sel, 0, sizeof(cpipe->pipe_sel));
	cpipe->pipe_state = 0;
	cpipe->pipe_peer = NULL;
	cpipe->pipe_busy = 0;
	sigio_init(&cpipe->pipe_sigio);

	error = pipespace(cpipe, PIPE_SIZE);
	if (error != 0)
		return (error);

	getnanotime(&cpipe->pipe_ctime);
	cpipe->pipe_atime = cpipe->pipe_ctime;
	cpipe->pipe_mtime = cpipe->pipe_ctime;

	return (0);
}


/*
 * lock a pipe for I/O, blocking other access
 */
int
pipelock(struct pipe *cpipe)
{
	int error;
	while (cpipe->pipe_state & PIPE_LOCK) {
		cpipe->pipe_state |= PIPE_LWANT;
		if ((error = tsleep(cpipe, PRIBIO|PCATCH, "pipelk", 0)))
			return error;
	}
	cpipe->pipe_state |= PIPE_LOCK;
	return 0;
}

/*
 * unlock a pipe I/O lock
 */
void
pipeunlock(struct pipe *cpipe)
{
	cpipe->pipe_state &= ~PIPE_LOCK;
	if (cpipe->pipe_state & PIPE_LWANT) {
		cpipe->pipe_state &= ~PIPE_LWANT;
		wakeup(cpipe);
	}
}

void
pipeselwakeup(struct pipe *cpipe)
{
	if (cpipe->pipe_state & PIPE_SEL) {
		cpipe->pipe_state &= ~PIPE_SEL;
		selwakeup(&cpipe->pipe_sel);
	} else
		KNOTE(&cpipe->pipe_sel.si_note, 0);
	if (cpipe->pipe_state & PIPE_ASYNC)
		pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
}

int
pipe_read(struct file *fp, struct uio *uio, int fflags)
{
	struct pipe *rpipe = fp->f_data;
	int error;
	size_t size, nread = 0;

	KERNEL_LOCK();

	error = pipelock(rpipe);
	if (error)
		goto done;

	++rpipe->pipe_busy;

	while (uio->uio_resid) {
		/*
		 * normal pipe buffer receive
		 */
		if (rpipe->pipe_buffer.cnt > 0) {
			size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
			if (size > rpipe->pipe_buffer.cnt)
				size = rpipe->pipe_buffer.cnt;
			if (size > uio->uio_resid)
				size = uio->uio_resid;
			error = uiomove(&rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
					size, uio);
			if (error) {
				break;
			}
			rpipe->pipe_buffer.out += size;
			if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
				rpipe->pipe_buffer.out = 0;

			rpipe->pipe_buffer.cnt -= size;
			/*
			 * If there is no more to read in the pipe, reset
			 * its pointers to the beginning.  This improves
			 * cache hit stats.
			 */
			if (rpipe->pipe_buffer.cnt == 0) {
				rpipe->pipe_buffer.in = 0;
				rpipe->pipe_buffer.out = 0;
			}
			nread += size;
		} else {
			/*
			 * detect EOF condition
			 * read returns 0 on EOF, no need to set error
			 */
			if (rpipe->pipe_state & PIPE_EOF)
				break;

			/*
			 * If the "write-side" has been blocked, wake it up now.
			 */
			if (rpipe->pipe_state & PIPE_WANTW) {
				rpipe->pipe_state &= ~PIPE_WANTW;
				wakeup(rpipe);
			}

			/*
			 * Break if some data was read.
			 */
			if (nread > 0)
				break;

			/*
			 * Unlock the pipe buffer for our remaining processing.
			 * We will either break out with an error or we will
			 * sleep and relock to loop.
			 */
			pipeunlock(rpipe);

			/*
			 * Handle non-blocking mode operation or
			 * wait for more data.
			 */
			if (fp->f_flag & FNONBLOCK) {
				error = EAGAIN;
			} else {
				rpipe->pipe_state |= PIPE_WANTR;
				if ((error = tsleep(rpipe, PRIBIO|PCATCH, "piperd", 0)) == 0)
					error = pipelock(rpipe);
			}
			if (error)
				goto unlocked_error;
		}
	}
	pipeunlock(rpipe);

	if (error == 0)
		getnanotime(&rpipe->pipe_atime);
unlocked_error:
	--rpipe->pipe_busy;

	/*
	 * PIPE_WANT processing only makes sense if pipe_busy is 0.
	 */
	if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
		rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
		wakeup(rpipe);
	} else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
		/*
		 * Handle write blocking hysteresis.
		 */
		if (rpipe->pipe_state & PIPE_WANTW) {
			rpipe->pipe_state &= ~PIPE_WANTW;
			wakeup(rpipe);
		}
	}

	if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
		pipeselwakeup(rpipe);

done:
	KERNEL_UNLOCK();
	return (error);
}

int
pipe_write(struct file *fp, struct uio *uio, int fflags)
{
	int error = 0;
	size_t orig_resid;
	struct pipe *wpipe, *rpipe;

	KERNEL_LOCK();

	rpipe = fp->f_data;
	wpipe = rpipe->pipe_peer;

	/*
	 * detect loss of pipe read side, issue SIGPIPE if lost.
	 */
	if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
		error = EPIPE;
		goto done;
	}
	++wpipe->pipe_busy;

	/*
	 * If it is advantageous to resize the pipe buffer, do
	 * so.
	 */
	if ((uio->uio_resid > PIPE_SIZE) &&
	    (wpipe->pipe_buffer.size <= PIPE_SIZE) &&
	    (wpipe->pipe_buffer.cnt == 0)) {
	    	unsigned int npipe;

		npipe = atomic_inc_int_nv(&nbigpipe);
		if ((npipe <= LIMITBIGPIPES) &&
		    (error = pipelock(wpipe)) == 0) {
			if ((wpipe->pipe_buffer.cnt != 0) ||
			    (pipespace(wpipe, BIG_PIPE_SIZE) != 0))
				atomic_dec_int(&nbigpipe);
			pipeunlock(wpipe);
		} else
			atomic_dec_int(&nbigpipe);
	}

	/*
	 * If an early error occurred unbusy and return, waking up any pending
	 * readers.
	 */
	if (error) {
		--wpipe->pipe_busy;
		if ((wpipe->pipe_busy == 0) &&
		    (wpipe->pipe_state & PIPE_WANT)) {
			wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
			wakeup(wpipe);
		}
		goto done;
	}

	orig_resid = uio->uio_resid;

	while (uio->uio_resid) {
		size_t space;

retrywrite:
		if (wpipe->pipe_state & PIPE_EOF) {
			error = EPIPE;
			break;
		}

		space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;

		/* Writes of size <= PIPE_BUF must be atomic. */
		if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
			space = 0;

		if (space > 0) {
			if ((error = pipelock(wpipe)) == 0) {
				size_t size;	/* Transfer size */
				size_t segsize;	/* first segment to transfer */

				/*
				 * If a process blocked in uiomove, our
				 * value for space might be bad.
				 *
				 * XXX will we be ok if the reader has gone
				 * away here?
				 */
				if (space > wpipe->pipe_buffer.size -
				    wpipe->pipe_buffer.cnt) {
					pipeunlock(wpipe);
					goto retrywrite;
				}

				/*
				 * Transfer size is minimum of uio transfer
				 * and free space in pipe buffer.
				 */
				if (space > uio->uio_resid)
					size = uio->uio_resid;
				else
					size = space;
				/*
				 * First segment to transfer is minimum of
				 * transfer size and contiguous space in
				 * pipe buffer.  If first segment to transfer
				 * is less than the transfer size, we've got
				 * a wraparound in the buffer.
				 */
				segsize = wpipe->pipe_buffer.size -
					wpipe->pipe_buffer.in;
				if (segsize > size)
					segsize = size;

				/* Transfer first segment */

				error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
						segsize, uio);

				if (error == 0 && segsize < size) {
					/*
					 * Transfer remaining part now, to
					 * support atomic writes.  Wraparound
					 * happened.
					 */
#ifdef DIAGNOSTIC
					if (wpipe->pipe_buffer.in + segsize !=
					    wpipe->pipe_buffer.size)
						panic("Expected pipe buffer wraparound disappeared");
#endif

					error = uiomove(&wpipe->pipe_buffer.buffer[0],
							size - segsize, uio);
				}
				if (error == 0) {
					wpipe->pipe_buffer.in += size;
					if (wpipe->pipe_buffer.in >=
					    wpipe->pipe_buffer.size) {
#ifdef DIAGNOSTIC
						if (wpipe->pipe_buffer.in != size - segsize + wpipe->pipe_buffer.size)
							panic("Expected wraparound bad");
#endif
						wpipe->pipe_buffer.in = size - segsize;
					}

					wpipe->pipe_buffer.cnt += size;
#ifdef DIAGNOSTIC
					if (wpipe->pipe_buffer.cnt > wpipe->pipe_buffer.size)
						panic("Pipe buffer overflow");
#endif
				}
				pipeunlock(wpipe);
			}
			if (error)
				break;
		} else {
			/*
			 * If the "read-side" has been blocked, wake it up now.
			 */
			if (wpipe->pipe_state & PIPE_WANTR) {
				wpipe->pipe_state &= ~PIPE_WANTR;
				wakeup(wpipe);
			}

			/*
			 * don't block on non-blocking I/O
			 */
			if (fp->f_flag & FNONBLOCK) {
				error = EAGAIN;
				break;
			}

			/*
			 * We have no more space and have something to offer,
			 * wake up select/poll.
			 */
			pipeselwakeup(wpipe);

			wpipe->pipe_state |= PIPE_WANTW;
			error = tsleep(wpipe, (PRIBIO + 1)|PCATCH,
			    "pipewr", 0);
			if (error)
				break;
			/*
			 * If read side wants to go away, we just issue a
			 * signal to ourselves.
			 */
			if (wpipe->pipe_state & PIPE_EOF) {
				error = EPIPE;
				break;
			}	
		}
	}

	--wpipe->pipe_busy;

	if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
		wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
		wakeup(wpipe);
	} else if (wpipe->pipe_buffer.cnt > 0) {
		/*
		 * If we have put any characters in the buffer, we wake up
		 * the reader.
		 */
		if (wpipe->pipe_state & PIPE_WANTR) {
			wpipe->pipe_state &= ~PIPE_WANTR;
			wakeup(wpipe);
		}
	}

	/*
	 * Don't return EPIPE if I/O was successful
	 */
	if ((wpipe->pipe_buffer.cnt == 0) &&
	    (uio->uio_resid == 0) &&
	    (error == EPIPE)) {
		error = 0;
	}

	if (error == 0)
		getnanotime(&wpipe->pipe_mtime);
	/*
	 * We have something to offer, wake up select/poll.
	 */
	if (wpipe->pipe_buffer.cnt)
		pipeselwakeup(wpipe);

done:
	KERNEL_UNLOCK();
	return (error);
}

/*
 * we implement a very minimal set of ioctls for compatibility with sockets.
 */
int
pipe_ioctl(struct file *fp, u_long cmd, caddr_t data, struct proc *p)
{
	struct pipe *mpipe = fp->f_data;

	switch (cmd) {

	case FIONBIO:
		return (0);

	case FIOASYNC:
		if (*(int *)data) {
			mpipe->pipe_state |= PIPE_ASYNC;
		} else {
			mpipe->pipe_state &= ~PIPE_ASYNC;
		}
		return (0);

	case FIONREAD:
		*(int *)data = mpipe->pipe_buffer.cnt;
		return (0);

	case TIOCSPGRP:
		/* FALLTHROUGH */
	case SIOCSPGRP:
		return (sigio_setown(&mpipe->pipe_sigio, *(int *)data));

	case SIOCGPGRP:
		*(int *)data = sigio_getown(&mpipe->pipe_sigio);
		return (0);

	case TIOCGPGRP:
		*(int *)data = -sigio_getown(&mpipe->pipe_sigio);
		return (0);

	}
	return (ENOTTY);
}

int
pipe_poll(struct file *fp, int events, struct proc *p)
{
	struct pipe *rpipe = fp->f_data;
	struct pipe *wpipe;
	int revents = 0;

	wpipe = rpipe->pipe_peer;
	if (events & (POLLIN | POLLRDNORM)) {
		if ((rpipe->pipe_buffer.cnt > 0) ||
		    (rpipe->pipe_state & PIPE_EOF))
			revents |= events & (POLLIN | POLLRDNORM);
	}

	/* NOTE: POLLHUP and POLLOUT/POLLWRNORM are mutually exclusive */
	if ((rpipe->pipe_state & PIPE_EOF) ||
	    (wpipe == NULL) ||
	    (wpipe->pipe_state & PIPE_EOF))
		revents |= POLLHUP;
	else if (events & (POLLOUT | POLLWRNORM)) {
		if ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF)
			revents |= events & (POLLOUT | POLLWRNORM);
	}

	if (revents == 0) {
		if (events & (POLLIN | POLLRDNORM)) {
			selrecord(p, &rpipe->pipe_sel);
			rpipe->pipe_state |= PIPE_SEL;
		}
		if (events & (POLLOUT | POLLWRNORM)) {
			selrecord(p, &wpipe->pipe_sel);
			wpipe->pipe_state |= PIPE_SEL;
		}
	}
	return (revents);
}

int
pipe_stat(struct file *fp, struct stat *ub, struct proc *p)
{
	struct pipe *pipe = fp->f_data;

	memset(ub, 0, sizeof(*ub));
	ub->st_mode = S_IFIFO;
	ub->st_blksize = pipe->pipe_buffer.size;
	ub->st_size = pipe->pipe_buffer.cnt;
	ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
	ub->st_atim.tv_sec  = pipe->pipe_atime.tv_sec;
	ub->st_atim.tv_nsec = pipe->pipe_atime.tv_nsec;
	ub->st_mtim.tv_sec  = pipe->pipe_mtime.tv_sec;
	ub->st_mtim.tv_nsec = pipe->pipe_mtime.tv_nsec;
	ub->st_ctim.tv_sec  = pipe->pipe_ctime.tv_sec;
	ub->st_ctim.tv_nsec = pipe->pipe_ctime.tv_nsec;
	ub->st_uid = fp->f_cred->cr_uid;
	ub->st_gid = fp->f_cred->cr_gid;
	/*
	 * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
	 * XXX (st_dev, st_ino) should be unique.
	 */
	return (0);
}

int
pipe_close(struct file *fp, struct proc *p)
{
	struct pipe *cpipe = fp->f_data;

	fp->f_ops = NULL;
	fp->f_data = NULL;
	KERNEL_LOCK();
	pipeclose(cpipe);
	KERNEL_UNLOCK();
	return (0);
}

void
pipe_free_kmem(struct pipe *cpipe)
{
	u_int size = cpipe->pipe_buffer.size;

	if (cpipe->pipe_buffer.buffer != NULL) {
		KERNEL_LOCK();
		km_free(cpipe->pipe_buffer.buffer, size, &kv_any, &kp_pageable);
		KERNEL_UNLOCK();
		atomic_sub_int(&amountpipekva, size);
		cpipe->pipe_buffer.buffer = NULL;
		if (size > PIPE_SIZE)
			atomic_dec_int(&nbigpipe);
	}
}

/*
 * shutdown the pipe
 */
void
pipeclose(struct pipe *cpipe)
{
	struct pipe *ppipe;
	if (cpipe) {
		pipeselwakeup(cpipe);
		sigio_free(&cpipe->pipe_sigio);

		/*
		 * If the other side is blocked, wake it up saying that
		 * we want to close it down.
		 */
		cpipe->pipe_state |= PIPE_EOF;
		while (cpipe->pipe_busy) {
			wakeup(cpipe);
			cpipe->pipe_state |= PIPE_WANT;
			tsleep(cpipe, PRIBIO, "pipecl", 0);
		}

		/*
		 * Disconnect from peer
		 */
		if ((ppipe = cpipe->pipe_peer) != NULL) {
			pipeselwakeup(ppipe);

			ppipe->pipe_state |= PIPE_EOF;
			wakeup(ppipe);
			ppipe->pipe_peer = NULL;
		}

		/*
		 * free resources
		 */
		pipe_free_kmem(cpipe);
		pool_put(&pipe_pool, cpipe);
	}
}

int
pipe_kqfilter(struct file *fp, struct knote *kn)
{
	struct pipe *rpipe = kn->kn_fp->f_data;
	struct pipe *wpipe = rpipe->pipe_peer;

	switch (kn->kn_filter) {
	case EVFILT_READ:
		kn->kn_fop = &pipe_rfiltops;
		SLIST_INSERT_HEAD(&rpipe->pipe_sel.si_note, kn, kn_selnext);
		break;
	case EVFILT_WRITE:
		if (wpipe == NULL) {
			/* other end of pipe has been closed */
			return (EPIPE);
		}
		kn->kn_fop = &pipe_wfiltops;
		SLIST_INSERT_HEAD(&wpipe->pipe_sel.si_note, kn, kn_selnext);
		break;
	default:
		return (EINVAL);
	}

	return (0);
}

void
filt_pipedetach(struct knote *kn)
{
	struct pipe *rpipe = kn->kn_fp->f_data;
	struct pipe *wpipe = rpipe->pipe_peer;

	switch (kn->kn_filter) {
	case EVFILT_READ:
		SLIST_REMOVE(&rpipe->pipe_sel.si_note, kn, knote, kn_selnext);
		break;
	case EVFILT_WRITE:
		if (wpipe == NULL)
			return;
		SLIST_REMOVE(&wpipe->pipe_sel.si_note, kn, knote, kn_selnext);
		break;
	}
}

int
filt_piperead(struct knote *kn, long hint)
{
	struct pipe *rpipe = kn->kn_fp->f_data;
	struct pipe *wpipe = rpipe->pipe_peer;

	kn->kn_data = rpipe->pipe_buffer.cnt;

	if ((rpipe->pipe_state & PIPE_EOF) ||
	    (wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
		kn->kn_flags |= EV_EOF; 
		return (1);
	}
	return (kn->kn_data > 0);
}

int
filt_pipewrite(struct knote *kn, long hint)
{
	struct pipe *rpipe = kn->kn_fp->f_data;
	struct pipe *wpipe = rpipe->pipe_peer;

	if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
		kn->kn_data = 0;
		kn->kn_flags |= EV_EOF; 
		return (1);
	}
	kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;

	return (kn->kn_data >= PIPE_BUF);
}

void
pipe_init(void)
{
	pool_init(&pipe_pool, sizeof(struct pipe), 0, IPL_MPFLOOR, PR_WAITOK,
	    "pipepl", NULL);
}