Attachment 213662 Details for Bug 224615 – Updated FIFO/pipe fixes (more context)

[patch] Updated FIFO/pipe fixes (more context)

fifo-fixes.patch (text/plain), 57.24 KB, created by Jan Kokemüller on 2020-04-22 01:48:34 UTC

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Creator: Jan Kokemüller

Created: 2020-04-22 01:48:34 UTC

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patch

obsolete

>commit e59ab0e9d88f705f41c780f6b7907beade0b5cf4
>Author: Jan KokemÃ¼ller <jan.kokemueller@gmail.com>
>Date:   Tue Dec 19 17:24:00 2017 +0100
>
>    fix some FIFO/pipe issues
>    
>    - fix PR 203366
>    - fix PR 224615 (EV_EOF on named pipe)
>    - wake up FIFO readers/writers when a new reader/writer connects
>    - only show POLLIN/POLLRDNORM for FIFO readers, not writers
>    - clear EV_EOF flag if FIFO EOF condition is cleared after a new reader/writer connected
>
>diff --git a/sys/fs/fifofs/fifo_vnops.c b/sys/fs/fifofs/fifo_vnops.c
>index b4fbc7a5e595..d511747b3e58 100644
>--- a/sys/fs/fifofs/fifo_vnops.c
>+++ b/sys/fs/fifofs/fifo_vnops.c
>@@ -1,363 +1,369 @@
> /*-
>  * SPDX-License-Identifier: BSD-3-Clause
>  *
>  * Copyright (c) 1990, 1993, 1995
>  *	The Regents of the University of California.
>  * Copyright (c) 2005 Robert N. M. Watson
>  * Copyright (c) 2012 Giovanni Trematerra
>  * 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, 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. Neither the name of the University nor the names of its contributors
>  *    may be used to endorse or promote products derived from this software
>  *    without specific prior written permission.
>  *
>  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
>  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
>  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
>  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
>  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
>  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
>  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
>  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
>  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
>  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
>  * SUCH DAMAGE.
>  *
>  *	@(#)fifo_vnops.c	8.10 (Berkeley) 5/27/95
>  * $FreeBSD$
>  */
> 
> #include <sys/param.h>
> #include <sys/event.h>
> #include <sys/file.h>
> #include <sys/filedesc.h>
> #include <sys/filio.h>
> #include <sys/fcntl.h>
> #include <sys/kernel.h>
> #include <sys/lock.h>
> #include <sys/mutex.h>
> #include <sys/malloc.h>
> #include <sys/selinfo.h>
> #include <sys/pipe.h>
> #include <sys/proc.h>
> #include <sys/signalvar.h>
> #include <sys/sx.h>
> #include <sys/systm.h>
> #include <sys/un.h>
> #include <sys/unistd.h>
> #include <sys/vnode.h>
> 
> /*
>  * This structure is associated with the FIFO vnode and stores
>  * the state associated with the FIFO.
>  * Notes about locking:
>  *   - fi_pipe is invariant since init time.
>  *   - fi_readers and fi_writers are protected by the vnode lock.
>  */
> struct fifoinfo {
> 	struct pipe *fi_pipe;
> 	long	fi_readers;
> 	long	fi_writers;
> 	u_int	fi_rgen;
> 	u_int	fi_wgen;
> };
> 
> static vop_print_t	fifo_print;
> static vop_open_t	fifo_open;
> static vop_close_t	fifo_close;
> static vop_advlock_t	fifo_advlock;
> 
> struct vop_vector fifo_specops = {
> 	.vop_default =		&default_vnodeops,
> 
> 	.vop_advlock =		fifo_advlock,
> 	.vop_close =		fifo_close,
> 	.vop_create =		VOP_PANIC,
> 	.vop_getattr =		VOP_EBADF,
> 	.vop_ioctl =		VOP_PANIC,
> 	.vop_kqfilter =		VOP_PANIC,
> 	.vop_link =		VOP_PANIC,
> 	.vop_mkdir =		VOP_PANIC,
> 	.vop_mknod =		VOP_PANIC,
> 	.vop_open =		fifo_open,
> 	.vop_pathconf =		VOP_PANIC,
> 	.vop_print =		fifo_print,
> 	.vop_read =		VOP_PANIC,
> 	.vop_readdir =		VOP_PANIC,
> 	.vop_readlink =		VOP_PANIC,
> 	.vop_reallocblks =	VOP_PANIC,
> 	.vop_reclaim =		VOP_NULL,
> 	.vop_remove =		VOP_PANIC,
> 	.vop_rename =		VOP_PANIC,
> 	.vop_rmdir =		VOP_PANIC,
> 	.vop_setattr =		VOP_EBADF,
> 	.vop_symlink =		VOP_PANIC,
> 	.vop_write =		VOP_PANIC,
> };
> VFS_VOP_VECTOR_REGISTER(fifo_specops);
> 
> /*
>  * Dispose of fifo resources.
>  */
> static void
> fifo_cleanup(struct vnode *vp)
> {
> 	struct fifoinfo *fip;
> 
> 	ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
> 	fip = vp->v_fifoinfo;
> 	if (fip->fi_readers == 0 && fip->fi_writers == 0) {
> 		vp->v_fifoinfo = NULL;
> 		pipe_dtor(fip->fi_pipe);
> 		free(fip, M_VNODE);
> 	}
> }
> 
> /*
>  * Open called to set up a new instance of a fifo or
>  * to find an active instance of a fifo.
>  */
> /* ARGSUSED */
> static int
> fifo_open(ap)
> 	struct vop_open_args /* {
> 		struct vnode *a_vp;
> 		int  a_mode;
> 		struct ucred *a_cred;
> 		struct thread *a_td;
> 		struct file *a_fp;
> 	} */ *ap;
> {
> 	struct vnode *vp;
> 	struct file *fp;
> 	struct thread *td;
> 	struct fifoinfo *fip;
> 	struct pipe *fpipe;
> 	u_int gen;
> 	int error, stops_deferred;
> 
> 	vp = ap->a_vp;
> 	fp = ap->a_fp;
> 	td = ap->a_td;
> 	ASSERT_VOP_ELOCKED(vp, "fifo_open");
> 	if (fp == NULL || (ap->a_mode & FEXEC) != 0)
> 		return (EINVAL);
> 	if ((fip = vp->v_fifoinfo) == NULL) {
> 		error = pipe_named_ctor(&fpipe, td);
> 		if (error != 0)
> 			return (error);
> 		fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
> 		fip->fi_pipe = fpipe;
> 		fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0;
>  		KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
> 		vp->v_fifoinfo = fip;
> 	}
> 	fpipe = fip->fi_pipe;
>  	KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
> 
> 	/*
> 	 * Use the pipe mutex here, in addition to the vnode lock,
> 	 * in order to allow vnode lock dropping before msleep() calls
> 	 * and still avoiding missed wakeups.
> 	 */
> 	PIPE_LOCK(fpipe);
> 	if (ap->a_mode & FREAD) {
> 		fip->fi_readers++;
> 		fip->fi_rgen++;
> 		if (fip->fi_readers == 1) {
> 			fpipe->pipe_state &= ~PIPE_EOF;
>-			if (fip->fi_writers > 0)
>+			if (fip->fi_writers > 0) {
> 				wakeup(&fip->fi_writers);
>+				pipeselwakeup(fpipe);
>+			}
> 		}
> 		fp->f_pipegen = fpipe->pipe_wgen - fip->fi_writers;
> 	}
> 	if (ap->a_mode & FWRITE) {
> 		if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
> 			PIPE_UNLOCK(fpipe);
> 			if (fip->fi_writers == 0)
> 				fifo_cleanup(vp);
> 			return (ENXIO);
> 		}
> 		fip->fi_writers++;
> 		fip->fi_wgen++;
> 		if (fip->fi_writers == 1) {
> 			fpipe->pipe_state &= ~PIPE_EOF;
>-			if (fip->fi_readers > 0)
>+			if (fip->fi_readers > 0) {
> 				wakeup(&fip->fi_readers);
>+				pipeselwakeup(fpipe);
>+			}
> 		}
> 	}
> 	if ((ap->a_mode & O_NONBLOCK) == 0) {
> 		if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
> 			gen = fip->fi_wgen;
> 			VOP_UNLOCK(vp);
> 			stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
> 			error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
> 			    PDROP | PCATCH | PSOCK, "fifoor", 0);
> 			sigallowstop(stops_deferred);
> 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
> 			if (error != 0 && gen == fip->fi_wgen) {
> 				fip->fi_readers--;
> 				if (fip->fi_readers == 0) {
> 					PIPE_LOCK(fpipe);
> 					fpipe->pipe_state |= PIPE_EOF;
> 					if (fpipe->pipe_state & PIPE_WANTW)
> 						wakeup(fpipe);
>+					pipeselwakeup(fpipe);
> 					PIPE_UNLOCK(fpipe);
> 					fifo_cleanup(vp);
> 				}
> 				return (error);
> 			}
> 			PIPE_LOCK(fpipe);
> 			/*
> 			 * We must have got woken up because we had a writer.
> 			 * That (and not still having one) is the condition
> 			 * that we must wait for.
> 			 */
> 		}
> 		if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
> 			gen = fip->fi_rgen;
> 			VOP_UNLOCK(vp);
> 			stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
> 			error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
> 			    PDROP | PCATCH | PSOCK, "fifoow", 0);
> 			sigallowstop(stops_deferred);
> 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
> 			if (error != 0 && gen == fip->fi_rgen) {
> 				fip->fi_writers--;
> 				if (fip->fi_writers == 0) {
> 					PIPE_LOCK(fpipe);
> 					fpipe->pipe_state |= PIPE_EOF;
> 					if (fpipe->pipe_state & PIPE_WANTR)
> 						wakeup(fpipe);
> 					fpipe->pipe_wgen++;
>+					pipeselwakeup(fpipe);
> 					PIPE_UNLOCK(fpipe);
> 					fifo_cleanup(vp);
> 				}
> 				return (error);
> 			}
> 			/*
> 			 * We must have got woken up because we had
> 			 * a reader.  That (and not still having one)
> 			 * is the condition that we must wait for.
> 			 */
> 			PIPE_LOCK(fpipe);
> 		}
> 	}
> 	PIPE_UNLOCK(fpipe);
> 	KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
> 	KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
> 	finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
> 	return (0);
> }
> 
> /*
>  * Device close routine
>  */
> /* ARGSUSED */
> static int
> fifo_close(ap)
> 	struct vop_close_args /* {
> 		struct vnode *a_vp;
> 		int  a_fflag;
> 		struct ucred *a_cred;
> 		struct thread *a_td;
> 	} */ *ap;
> {
> 	struct vnode *vp;
> 	struct fifoinfo *fip;
> 	struct pipe *cpipe;
> 
> 	vp = ap->a_vp;
> 	fip = vp->v_fifoinfo;
> 	cpipe = fip->fi_pipe;
> 	ASSERT_VOP_ELOCKED(vp, "fifo_close");
> 	if (ap->a_fflag & FREAD) {
> 		fip->fi_readers--;
> 		if (fip->fi_readers == 0) {
> 			PIPE_LOCK(cpipe);
> 			cpipe->pipe_state |= PIPE_EOF;
> 			if ((cpipe->pipe_state & PIPE_WANTW)) {
> 				cpipe->pipe_state &= ~PIPE_WANTW;
> 				wakeup(cpipe);
> 			}
> 			pipeselwakeup(cpipe);
> 			PIPE_UNLOCK(cpipe);
> 		}
> 	}
> 	if (ap->a_fflag & FWRITE) {
> 		fip->fi_writers--;
> 		if (fip->fi_writers == 0) {
> 			PIPE_LOCK(cpipe);
> 			cpipe->pipe_state |= PIPE_EOF;
> 			if ((cpipe->pipe_state & PIPE_WANTR)) {
> 				cpipe->pipe_state &= ~PIPE_WANTR;
> 				wakeup(cpipe);
> 			}
> 			cpipe->pipe_wgen++;
> 			pipeselwakeup(cpipe);
> 			PIPE_UNLOCK(cpipe);
> 		}
> 	}
> 	fifo_cleanup(vp);
> 	return (0);
> }
> 
> /*
>  * Print out internal contents of a fifo vnode.
>  */
> int
> fifo_printinfo(vp)
> 	struct vnode *vp;
> {
> 	struct fifoinfo *fip = vp->v_fifoinfo;
> 
> 	if (fip == NULL){
> 		printf(", NULL v_fifoinfo");
> 		return (0);
> 	}
> 	printf(", fifo with %ld readers and %ld writers",
> 		fip->fi_readers, fip->fi_writers);
> 	return (0);
> }
> 
> /*
>  * Print out the contents of a fifo vnode.
>  */
> static int
> fifo_print(ap)
> 	struct vop_print_args /* {
> 		struct vnode *a_vp;
> 	} */ *ap;
> {
> 	printf("    ");
> 	fifo_printinfo(ap->a_vp);
> 	printf("\n");
> 	return (0);
> }
> 
> /*
>  * Fifo advisory byte-level locks.
>  */
> /* ARGSUSED */
> static int
> fifo_advlock(ap)
> 	struct vop_advlock_args /* {
> 		struct vnode *a_vp;
> 		caddr_t  a_id;
> 		int  a_op;
> 		struct flock *a_fl;
> 		int  a_flags;
> 	} */ *ap;
> {
> 
> 	return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
> }
> 
>diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
>index 62dfa65c1dd8..19cab545d975 100644
>--- a/sys/kern/sys_pipe.c
>+++ b/sys/kern/sys_pipe.c
>@@ -1,1786 +1,1797 @@
> /*-
>  * SPDX-License-Identifier: BSD-4-Clause
>  *
>  * Copyright (c) 1996 John S. Dyson
>  * Copyright (c) 2012 Giovanni Trematerra
>  * 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.
>  */
> 
> /*
>  * This code has two modes of operation, a small write mode and a large
>  * write mode.  The small write mode acts like conventional pipes with
>  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
>  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
>  * and PIPE_SIZE in size, the sending process pins the underlying pages in
>  * memory, and the receiving process copies directly from these pinned pages
>  * in the sending process.
>  *
>  * If the sending process receives a signal, it is possible that it will
>  * go away, and certainly its address space can change, because control
>  * is returned back to the user-mode side.  In that case, the pipe code
>  * arranges to copy the buffer supplied by the user process, to a pageable
>  * kernel buffer, and the receiving process will grab the data from the
>  * pageable kernel buffer.  Since signals don't happen all that often,
>  * the copy operation is normally eliminated.
>  *
>  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
>  * happen for small transfers so that the system will not spend all of
>  * its time context switching.
>  *
>  * In order to limit the resource use of pipes, two sysctls exist:
>  *
>  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
>  * address space available to us in pipe_map. This value is normally
>  * autotuned, but may also be loader tuned.
>  *
>  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
>  * memory in use by pipes.
>  *
>  * Based on how large pipekva is relative to maxpipekva, the following
>  * will happen:
>  *
>  * 0% - 50%:
>  *     New pipes are given 16K of memory backing, pipes may dynamically
>  *     grow to as large as 64K where needed.
>  * 50% - 75%:
>  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
>  *     existing pipes may NOT grow.
>  * 75% - 100%:
>  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
>  *     existing pipes will be shrunk down to 4K whenever possible.
>  *
>  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
>  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
>  * resize which MUST occur for reverse-direction pipes when they are
>  * first used.
>  *
>  * Additional information about the current state of pipes may be obtained
>  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
>  * and kern.ipc.piperesizefail.
>  *
>  * Locking rules:  There are two locks present here:  A mutex, used via
>  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
>  * the flag, as mutexes can not persist over uiomove.  The mutex
>  * exists only to guard access to the flag, and is not in itself a
>  * locking mechanism.  Also note that there is only a single mutex for
>  * both directions of a pipe.
>  *
>  * As pipelock() may have to sleep before it can acquire the flag, it
>  * is important to reread all data after a call to pipelock(); everything
>  * in the structure may have changed.
>  */
> 
> #include <sys/cdefs.h>
> __FBSDID("$FreeBSD$");
> 
> #include <sys/param.h>
> #include <sys/systm.h>
> #include <sys/conf.h>
> #include <sys/fcntl.h>
> #include <sys/file.h>
> #include <sys/filedesc.h>
> #include <sys/filio.h>
> #include <sys/kernel.h>
> #include <sys/lock.h>
> #include <sys/mutex.h>
> #include <sys/ttycom.h>
> #include <sys/stat.h>
> #include <sys/malloc.h>
> #include <sys/poll.h>
> #include <sys/selinfo.h>
> #include <sys/signalvar.h>
> #include <sys/syscallsubr.h>
> #include <sys/sysctl.h>
> #include <sys/sysproto.h>
> #include <sys/pipe.h>
> #include <sys/proc.h>
> #include <sys/vnode.h>
> #include <sys/uio.h>
> #include <sys/user.h>
> #include <sys/event.h>
> 
> #include <security/mac/mac_framework.h>
> 
> #include <vm/vm.h>
> #include <vm/vm_param.h>
> #include <vm/vm_object.h>
> #include <vm/vm_kern.h>
> #include <vm/vm_extern.h>
> #include <vm/pmap.h>
> #include <vm/vm_map.h>
> #include <vm/vm_page.h>
> #include <vm/uma.h>
> 
> /*
>  * Use this define if you want to disable *fancy* VM things.  Expect an
>  * approx 30% decrease in transfer rate.  This could be useful for
>  * NetBSD or OpenBSD.
>  */
> /* #define PIPE_NODIRECT */
> 
> #define PIPE_PEER(pipe)	\
> 	(((pipe)->pipe_state & PIPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
> 
> /*
>  * interfaces to the outside world
>  */
> static fo_rdwr_t	pipe_read;
> static fo_rdwr_t	pipe_write;
> static fo_truncate_t	pipe_truncate;
> static fo_ioctl_t	pipe_ioctl;
> static fo_poll_t	pipe_poll;
> static fo_kqfilter_t	pipe_kqfilter;
> static fo_stat_t	pipe_stat;
> static fo_close_t	pipe_close;
> static fo_chmod_t	pipe_chmod;
> static fo_chown_t	pipe_chown;
> static fo_fill_kinfo_t	pipe_fill_kinfo;
> 
> struct fileops pipeops = {
> 	.fo_read = pipe_read,
> 	.fo_write = pipe_write,
> 	.fo_truncate = pipe_truncate,
> 	.fo_ioctl = pipe_ioctl,
> 	.fo_poll = pipe_poll,
> 	.fo_kqfilter = pipe_kqfilter,
> 	.fo_stat = pipe_stat,
> 	.fo_close = pipe_close,
> 	.fo_chmod = pipe_chmod,
> 	.fo_chown = pipe_chown,
> 	.fo_sendfile = invfo_sendfile,
> 	.fo_fill_kinfo = pipe_fill_kinfo,
> 	.fo_flags = DFLAG_PASSABLE
> };
> 
> static void	filt_pipedetach(struct knote *kn);
> static void	filt_pipedetach_notsup(struct knote *kn);
> static int	filt_pipenotsup(struct knote *kn, long hint);
> static int	filt_piperead(struct knote *kn, long hint);
> static int	filt_pipewrite(struct knote *kn, long hint);
> 
> static struct filterops pipe_nfiltops = {
> 	.f_isfd = 1,
> 	.f_detach = filt_pipedetach_notsup,
> 	.f_event = filt_pipenotsup
> };
> static struct filterops pipe_rfiltops = {
> 	.f_isfd = 1,
> 	.f_detach = filt_pipedetach,
> 	.f_event = filt_piperead
> };
> static struct filterops pipe_wfiltops = {
> 	.f_isfd = 1,
> 	.f_detach = filt_pipedetach,
> 	.f_event = 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)
> #define MAXPIPESIZE (2*PIPE_SIZE/3)
> 
> static long amountpipekva;
> static int pipefragretry;
> static int pipeallocfail;
> static int piperesizefail;
> static int piperesizeallowed = 1;
> 
> SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
> 	   &maxpipekva, 0, "Pipe KVA limit");
> SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
> 	   &amountpipekva, 0, "Pipe KVA usage");
> SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
> 	  &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
> SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
> 	  &pipeallocfail, 0, "Pipe allocation failures");
> SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
> 	  &piperesizefail, 0, "Pipe resize failures");
> SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
> 	  &piperesizeallowed, 0, "Pipe resizing allowed");
> 
> static void pipeinit(void *dummy __unused);
> static void pipeclose(struct pipe *cpipe);
> static void pipe_free_kmem(struct pipe *cpipe);
> static int pipe_create(struct pipe *pipe, bool backing);
> static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
> static __inline int pipelock(struct pipe *cpipe, int catch);
> static __inline void pipeunlock(struct pipe *cpipe);
> #ifndef PIPE_NODIRECT
> static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
> static void pipe_destroy_write_buffer(struct pipe *wpipe);
> static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
> static void pipe_clone_write_buffer(struct pipe *wpipe);
> #endif
> static int pipespace(struct pipe *cpipe, int size);
> static int pipespace_new(struct pipe *cpipe, int size);
> 
> static int	pipe_zone_ctor(void *mem, int size, void *arg, int flags);
> static int	pipe_zone_init(void *mem, int size, int flags);
> static void	pipe_zone_fini(void *mem, int size);
> 
> static uma_zone_t pipe_zone;
> static struct unrhdr64 pipeino_unr;
> static dev_t pipedev_ino;
> 
> SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
> 
> static void
> pipeinit(void *dummy __unused)
> {
> 
> 	pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
> 	    pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
> 	    UMA_ALIGN_PTR, 0);
> 	KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
> 	new_unrhdr64(&pipeino_unr, 1);
> 	pipedev_ino = devfs_alloc_cdp_inode();
> 	KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
> }
> 
> static int
> pipe_zone_ctor(void *mem, int size, void *arg, int flags)
> {
> 	struct pipepair *pp;
> 	struct pipe *rpipe, *wpipe;
> 
> 	KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
> 
> 	pp = (struct pipepair *)mem;
> 
> 	/*
> 	 * We zero both pipe endpoints to make sure all the kmem pointers
> 	 * are NULL, flag fields are zero'd, etc.  We timestamp both
> 	 * endpoints with the same time.
> 	 */
> 	rpipe = &pp->pp_rpipe;
> 	bzero(rpipe, sizeof(*rpipe));
> 	vfs_timestamp(&rpipe->pipe_ctime);
> 	rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
> 
> 	wpipe = &pp->pp_wpipe;
> 	bzero(wpipe, sizeof(*wpipe));
> 	wpipe->pipe_ctime = rpipe->pipe_ctime;
> 	wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
> 
> 	rpipe->pipe_peer = wpipe;
> 	rpipe->pipe_pair = pp;
> 	wpipe->pipe_peer = rpipe;
> 	wpipe->pipe_pair = pp;
> 
> 	/*
> 	 * Mark both endpoints as present; they will later get free'd
> 	 * one at a time.  When both are free'd, then the whole pair
> 	 * is released.
> 	 */
> 	rpipe->pipe_present = PIPE_ACTIVE;
> 	wpipe->pipe_present = PIPE_ACTIVE;
> 
> 	/*
> 	 * Eventually, the MAC Framework may initialize the label
> 	 * in ctor or init, but for now we do it elswhere to avoid
> 	 * blocking in ctor or init.
> 	 */
> 	pp->pp_label = NULL;
> 
> 	return (0);
> }
> 
> static int
> pipe_zone_init(void *mem, int size, int flags)
> {
> 	struct pipepair *pp;
> 
> 	KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
> 
> 	pp = (struct pipepair *)mem;
> 
> 	mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
> 	return (0);
> }
> 
> static void
> pipe_zone_fini(void *mem, int size)
> {
> 	struct pipepair *pp;
> 
> 	KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
> 
> 	pp = (struct pipepair *)mem;
> 
> 	mtx_destroy(&pp->pp_mtx);
> }
> 
> static int
> pipe_paircreate(struct thread *td, struct pipepair **p_pp)
> {
> 	struct pipepair *pp;
> 	struct pipe *rpipe, *wpipe;
> 	int error;
> 
> 	*p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
> #ifdef MAC
> 	/*
> 	 * The MAC label is shared between the connected endpoints.  As a
> 	 * result mac_pipe_init() and mac_pipe_create() are called once
> 	 * for the pair, and not on the endpoints.
> 	 */
> 	mac_pipe_init(pp);
> 	mac_pipe_create(td->td_ucred, pp);
> #endif
> 	rpipe = &pp->pp_rpipe;
> 	wpipe = &pp->pp_wpipe;
> 
> 	knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
> 	knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
> 
> 	/*
> 	 * Only the forward direction pipe is backed by big buffer by
> 	 * default.
> 	 */
> 	error = pipe_create(rpipe, true);
> 	if (error != 0)
> 		goto fail;
> 	error = pipe_create(wpipe, false);
> 	if (error != 0) {
> 		/*
> 		 * This cleanup leaves the pipe inode number for rpipe
> 		 * still allocated, but never used.  We do not free
> 		 * inode numbers for opened pipes, which is required
> 		 * for correctness because numbers must be unique.
> 		 * But also it avoids any memory use by the unr
> 		 * allocator, so stashing away the transient inode
> 		 * number is reasonable.
> 		 */
> 		pipe_free_kmem(rpipe);
> 		goto fail;
> 	}
> 
> 	rpipe->pipe_state |= PIPE_DIRECTOK;
> 	wpipe->pipe_state |= PIPE_DIRECTOK;
> 	return (0);
> 
> fail:
> 	knlist_destroy(&rpipe->pipe_sel.si_note);
> 	knlist_destroy(&wpipe->pipe_sel.si_note);
> #ifdef MAC
> 	mac_pipe_destroy(pp);
> #endif
> 	return (error);
> }
> 
> int
> pipe_named_ctor(struct pipe **ppipe, struct thread *td)
> {
> 	struct pipepair *pp;
> 	int error;
> 
> 	error = pipe_paircreate(td, &pp);
> 	if (error != 0)
> 		return (error);
> 	pp->pp_rpipe.pipe_state |= PIPE_NAMED;
> 	*ppipe = &pp->pp_rpipe;
> 	return (0);
> }
> 
> void
> pipe_dtor(struct pipe *dpipe)
> {
> 	struct pipe *peer;
> 
> 	peer = (dpipe->pipe_state & PIPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
> 	funsetown(&dpipe->pipe_sigio);
> 	pipeclose(dpipe);
> 	if (peer != NULL) {
> 		funsetown(&peer->pipe_sigio);
> 		pipeclose(peer);
> 	}
> }
> 
> /*
>  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
>  * the zone pick up the pieces via pipeclose().
>  */
> int
> kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
>     struct filecaps *fcaps2)
> {
> 	struct file *rf, *wf;
> 	struct pipe *rpipe, *wpipe;
> 	struct pipepair *pp;
> 	int fd, fflags, error;
> 
> 	error = pipe_paircreate(td, &pp);
> 	if (error != 0)
> 		return (error);
> 	rpipe = &pp->pp_rpipe;
> 	wpipe = &pp->pp_wpipe;
> 	error = falloc_caps(td, &rf, &fd, flags, fcaps1);
> 	if (error) {
> 		pipeclose(rpipe);
> 		pipeclose(wpipe);
> 		return (error);
> 	}
> 	/* An extra reference on `rf' has been held for us by falloc_caps(). */
> 	fildes[0] = fd;
> 
> 	fflags = FREAD | FWRITE;
> 	if ((flags & O_NONBLOCK) != 0)
> 		fflags |= FNONBLOCK;
> 
> 	/*
> 	 * Warning: once we've gotten past allocation of the fd for the
> 	 * read-side, we can only drop the read side via fdrop() in order
> 	 * to avoid races against processes which manage to dup() the read
> 	 * side while we are blocked trying to allocate the write side.
> 	 */
> 	finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
> 	error = falloc_caps(td, &wf, &fd, flags, fcaps2);
> 	if (error) {
> 		fdclose(td, rf, fildes[0]);
> 		fdrop(rf, td);
> 		/* rpipe has been closed by fdrop(). */
> 		pipeclose(wpipe);
> 		return (error);
> 	}
> 	/* An extra reference on `wf' has been held for us by falloc_caps(). */
> 	finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
> 	fdrop(wf, td);
> 	fildes[1] = fd;
> 	fdrop(rf, td);
> 
> 	return (0);
> }
> 
> #ifdef COMPAT_FREEBSD10
> /* ARGSUSED */
> int
> freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
> {
> 	int error;
> 	int fildes[2];
> 
> 	error = kern_pipe(td, fildes, 0, NULL, NULL);
> 	if (error)
> 		return (error);
> 
> 	td->td_retval[0] = fildes[0];
> 	td->td_retval[1] = fildes[1];
> 
> 	return (0);
> }
> #endif
> 
> int
> sys_pipe2(struct thread *td, struct pipe2_args *uap)
> {
> 	int error, fildes[2];
> 
> 	if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
> 		return (EINVAL);
> 	error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
> 	if (error)
> 		return (error);
> 	error = copyout(fildes, uap->fildes, 2 * sizeof(int));
> 	if (error) {
> 		(void)kern_close(td, fildes[0]);
> 		(void)kern_close(td, fildes[1]);
> 	}
> 	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.
>  */
> static int
> pipespace_new(struct pipe *cpipe, int size)
> {
> 	caddr_t buffer;
> 	int error, cnt, firstseg;
> 	static int curfail = 0;
> 	static struct timeval lastfail;
> 
> 	KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
> 	KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
> 		("pipespace: resize of direct writes not allowed"));
> retry:
> 	cnt = cpipe->pipe_buffer.cnt;
> 	if (cnt > size)
> 		size = cnt;
> 
> 	size = round_page(size);
> 	buffer = (caddr_t) vm_map_min(pipe_map);
> 
> 	error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
> 	    VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
> 	if (error != KERN_SUCCESS) {
> 		if (cpipe->pipe_buffer.buffer == NULL &&
> 		    size > SMALL_PIPE_SIZE) {
> 			size = SMALL_PIPE_SIZE;
> 			pipefragretry++;
> 			goto retry;
> 		}
> 		if (cpipe->pipe_buffer.buffer == NULL) {
> 			pipeallocfail++;
> 			if (ppsratecheck(&lastfail, &curfail, 1))
> 				printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
> 		} else {
> 			piperesizefail++;
> 		}
> 		return (ENOMEM);
> 	}
> 
> 	/* copy data, then free old resources if we're resizing */
> 	if (cnt > 0) {
> 		if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
> 			firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
> 			bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
> 				buffer, firstseg);
> 			if ((cnt - firstseg) > 0)
> 				bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
> 					cpipe->pipe_buffer.in);
> 		} else {
> 			bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
> 				buffer, cnt);
> 		}
> 	}
> 	pipe_free_kmem(cpipe);
> 	cpipe->pipe_buffer.buffer = buffer;
> 	cpipe->pipe_buffer.size = size;
> 	cpipe->pipe_buffer.in = cnt;
> 	cpipe->pipe_buffer.out = 0;
> 	cpipe->pipe_buffer.cnt = cnt;
> 	atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
> 	return (0);
> }
> 
> /*
>  * Wrapper for pipespace_new() that performs locking assertions.
>  */
> static int
> pipespace(struct pipe *cpipe, int size)
> {
> 
> 	KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
> 	    ("Unlocked pipe passed to pipespace"));
> 	return (pipespace_new(cpipe, size));
> }
> 
> /*
>  * lock a pipe for I/O, blocking other access
>  */
> static __inline int
> pipelock(struct pipe *cpipe, int catch)
> {
> 	int error;
> 
> 	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
> 	while (cpipe->pipe_state & PIPE_LOCKFL) {
> 		cpipe->pipe_state |= PIPE_LWANT;
> 		error = msleep(cpipe, PIPE_MTX(cpipe),
> 		    catch ? (PRIBIO | PCATCH) : PRIBIO,
> 		    "pipelk", 0);
> 		if (error != 0)
> 			return (error);
> 	}
> 	cpipe->pipe_state |= PIPE_LOCKFL;
> 	return (0);
> }
> 
> /*
>  * unlock a pipe I/O lock
>  */
> static __inline void
> pipeunlock(struct pipe *cpipe)
> {
> 
> 	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
> 	KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
> 		("Unlocked pipe passed to pipeunlock"));
> 	cpipe->pipe_state &= ~PIPE_LOCKFL;
> 	if (cpipe->pipe_state & PIPE_LWANT) {
> 		cpipe->pipe_state &= ~PIPE_LWANT;
> 		wakeup(cpipe);
> 	}
> }
> 
> void
> pipeselwakeup(struct pipe *cpipe)
> {
> 
> 	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
> 	if (cpipe->pipe_state & PIPE_SEL) {
> 		selwakeuppri(&cpipe->pipe_sel, PSOCK);
> 		if (!SEL_WAITING(&cpipe->pipe_sel))
> 			cpipe->pipe_state &= ~PIPE_SEL;
> 	}
> 	if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
> 		pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
> 	KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
> }
> 
> /*
>  * Initialize and allocate VM and memory for pipe.  The structure
>  * will start out zero'd from the ctor, so we just manage the kmem.
>  */
> static int
> pipe_create(struct pipe *pipe, bool large_backing)
> {
> 	int error;
> 
> 	error = pipespace_new(pipe, !large_backing || amountpipekva >
> 	    maxpipekva / 2 ? SMALL_PIPE_SIZE : PIPE_SIZE);
> 	if (error == 0)
> 		pipe->pipe_ino = alloc_unr64(&pipeino_unr);
> 	return (error);
> }
> 
> /* ARGSUSED */
> static int
> pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
>     int flags, struct thread *td)
> {
> 	struct pipe *rpipe;
> 	int error;
> 	int nread = 0;
> 	int size;
> 
> 	rpipe = fp->f_data;
> 	PIPE_LOCK(rpipe);
> 	++rpipe->pipe_busy;
> 	error = pipelock(rpipe, 1);
> 	if (error)
> 		goto unlocked_error;
> 
> #ifdef MAC
> 	error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
> 	if (error)
> 		goto locked_error;
> #endif
> 	if (amountpipekva > (3 * maxpipekva) / 4) {
> 		if ((rpipe->pipe_state & PIPE_DIRECTW) == 0 &&
> 		    rpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
> 		    rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
> 		    piperesizeallowed == 1) {
> 			PIPE_UNLOCK(rpipe);
> 			pipespace(rpipe, SMALL_PIPE_SIZE);
> 			PIPE_LOCK(rpipe);
> 		}
> 	}
> 
> 	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;
> 
> 			PIPE_UNLOCK(rpipe);
> 			error = uiomove(
> 			    &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
> 			    size, uio);
> 			PIPE_LOCK(rpipe);
> 			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;
> #ifndef PIPE_NODIRECT
> 		/*
> 		 * Direct copy, bypassing a kernel buffer.
> 		 */
> 		} else if ((size = rpipe->pipe_map.cnt) != 0) {
> 			if (size > uio->uio_resid)
> 				size = (u_int) uio->uio_resid;
> 			PIPE_UNLOCK(rpipe);
> 			error = uiomove_fromphys(rpipe->pipe_map.ms,
> 			    rpipe->pipe_map.pos, size, uio);
> 			PIPE_LOCK(rpipe);
> 			if (error)
> 				break;
> 			nread += size;
> 			rpipe->pipe_map.pos += size;
> 			rpipe->pipe_map.cnt -= size;
> 			if (rpipe->pipe_map.cnt == 0) {
> 				rpipe->pipe_state &= ~PIPE_WANTW;
> 				wakeup(rpipe);
> 			}
> #endif
> 		} 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 = msleep(rpipe, PIPE_MTX(rpipe),
> 				    PRIBIO | PCATCH,
> 				    "piperd", 0)) == 0)
> 					error = pipelock(rpipe, 1);
> 			}
> 			if (error)
> 				goto unlocked_error;
> 		}
> 	}
> #ifdef MAC
> locked_error:
> #endif
> 	pipeunlock(rpipe);
> 
> 	/* XXX: should probably do this before getting any locks. */
> 	if (error == 0)
> 		vfs_timestamp(&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)
>+	/*
>+	 * Only wake up writers if there was actually something read.
>+	 * Otherwise, when calling read(2) at EOF, a spurious wakeup occurs
>+	 * that might lead to issues like PR 203366.
>+	 */
>+	if (nread > 0 &&
>+	    (rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
> 		pipeselwakeup(rpipe);
> 
> 	PIPE_UNLOCK(rpipe);
> 	return (error);
> }
> 
> #ifndef PIPE_NODIRECT
> /*
>  * Map the sending processes' buffer into kernel space and wire it.
>  * This is similar to a physical write operation.
>  */
> static int
> pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
> {
> 	u_int size;
> 	int i;
> 
> 	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
> 	KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
> 	    ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
> 	KASSERT(wpipe->pipe_map.cnt == 0,
> 	    ("%s: pipe map for %p contains residual data", __func__, wpipe));
> 
> 	if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
>                 size = wpipe->pipe_buffer.size;
> 	else
>                 size = uio->uio_iov->iov_len;
> 
> 	wpipe->pipe_state |= PIPE_DIRECTW;
> 	PIPE_UNLOCK(wpipe);
> 	i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
> 	    (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
> 	    wpipe->pipe_map.ms, PIPENPAGES);
> 	PIPE_LOCK(wpipe);
> 	if (i < 0) {
> 		wpipe->pipe_state &= ~PIPE_DIRECTW;
> 		return (EFAULT);
> 	}
> 
> 	wpipe->pipe_map.npages = i;
> 	wpipe->pipe_map.pos =
> 	    ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
> 	wpipe->pipe_map.cnt = size;
> 
> 	uio->uio_iov->iov_len -= size;
> 	uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
> 	if (uio->uio_iov->iov_len == 0)
> 		uio->uio_iov++;
> 	uio->uio_resid -= size;
> 	uio->uio_offset += size;
> 	return (0);
> }
> 
> /*
>  * Unwire the process buffer.
>  */
> static void
> pipe_destroy_write_buffer(struct pipe *wpipe)
> {
> 
> 	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
> 	KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
> 	    ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
> 	KASSERT(wpipe->pipe_map.cnt == 0,
> 	    ("%s: pipe map for %p contains residual data", __func__, wpipe));
> 
> 	wpipe->pipe_state &= ~PIPE_DIRECTW;
> 	vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
> 	wpipe->pipe_map.npages = 0;
> }
> 
> /*
>  * In the case of a signal, the writing process might go away.  This
>  * code copies the data into the circular buffer so that the source
>  * pages can be freed without loss of data.
>  */
> static void
> pipe_clone_write_buffer(struct pipe *wpipe)
> {
> 	struct uio uio;
> 	struct iovec iov;
> 	int size;
> 	int pos;
> 
> 	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
> 	KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
> 	    ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
> 
> 	size = wpipe->pipe_map.cnt;
> 	pos = wpipe->pipe_map.pos;
> 	wpipe->pipe_map.cnt = 0;
> 
> 	wpipe->pipe_buffer.in = size;
> 	wpipe->pipe_buffer.out = 0;
> 	wpipe->pipe_buffer.cnt = size;
> 
> 	PIPE_UNLOCK(wpipe);
> 	iov.iov_base = wpipe->pipe_buffer.buffer;
> 	iov.iov_len = size;
> 	uio.uio_iov = &iov;
> 	uio.uio_iovcnt = 1;
> 	uio.uio_offset = 0;
> 	uio.uio_resid = size;
> 	uio.uio_segflg = UIO_SYSSPACE;
> 	uio.uio_rw = UIO_READ;
> 	uio.uio_td = curthread;
> 	uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
> 	PIPE_LOCK(wpipe);
> 	pipe_destroy_write_buffer(wpipe);
> }
> 
> /*
>  * This implements the pipe buffer write mechanism.  Note that only
>  * a direct write OR a normal pipe write can be pending at any given time.
>  * If there are any characters in the pipe buffer, the direct write will
>  * be deferred until the receiving process grabs all of the bytes from
>  * the pipe buffer.  Then the direct mapping write is set-up.
>  */
> static int
> pipe_direct_write(struct pipe *wpipe, struct uio *uio)
> {
> 	int error;
> 
> retry:
> 	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
> 	error = pipelock(wpipe, 1);
> 	if (error != 0)
> 		goto error1;
> 	if ((wpipe->pipe_state & PIPE_EOF) != 0) {
> 		error = EPIPE;
> 		pipeunlock(wpipe);
> 		goto error1;
> 	}
> 	if (wpipe->pipe_state & PIPE_DIRECTW) {
> 		if (wpipe->pipe_state & PIPE_WANTR) {
> 			wpipe->pipe_state &= ~PIPE_WANTR;
> 			wakeup(wpipe);
> 		}
> 		pipeselwakeup(wpipe);
> 		wpipe->pipe_state |= PIPE_WANTW;
> 		pipeunlock(wpipe);
> 		error = msleep(wpipe, PIPE_MTX(wpipe),
> 		    PRIBIO | PCATCH, "pipdww", 0);
> 		if (error)
> 			goto error1;
> 		else
> 			goto retry;
> 	}
> 	if (wpipe->pipe_buffer.cnt > 0) {
> 		if (wpipe->pipe_state & PIPE_WANTR) {
> 			wpipe->pipe_state &= ~PIPE_WANTR;
> 			wakeup(wpipe);
> 		}
> 		pipeselwakeup(wpipe);
> 		wpipe->pipe_state |= PIPE_WANTW;
> 		pipeunlock(wpipe);
> 		error = msleep(wpipe, PIPE_MTX(wpipe),
> 		    PRIBIO | PCATCH, "pipdwc", 0);
> 		if (error)
> 			goto error1;
> 		else
> 			goto retry;
> 	}
> 
> 	error = pipe_build_write_buffer(wpipe, uio);
> 	if (error) {
> 		pipeunlock(wpipe);
> 		goto error1;
> 	}
> 
> 	while (wpipe->pipe_map.cnt != 0 &&
> 	    (wpipe->pipe_state & PIPE_EOF) == 0) {
> 		if (wpipe->pipe_state & PIPE_WANTR) {
> 			wpipe->pipe_state &= ~PIPE_WANTR;
> 			wakeup(wpipe);
> 		}
> 		pipeselwakeup(wpipe);
> 		wpipe->pipe_state |= PIPE_WANTW;
> 		pipeunlock(wpipe);
> 		error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
> 		    "pipdwt", 0);
> 		pipelock(wpipe, 0);
> 		if (error != 0)
> 			break;
> 	}
> 
> 	if ((wpipe->pipe_state & PIPE_EOF) != 0) {
> 		wpipe->pipe_map.cnt = 0;
> 		pipe_destroy_write_buffer(wpipe);
> 		pipeselwakeup(wpipe);
> 		error = EPIPE;
> 	} else if (error == EINTR || error == ERESTART) {
> 		pipe_clone_write_buffer(wpipe);
> 	} else {
> 		pipe_destroy_write_buffer(wpipe);
> 	}
> 	pipeunlock(wpipe);
> 	KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
> 	    ("pipe %p leaked PIPE_DIRECTW", wpipe));
> 	return (error);
> 
> error1:
> 	wakeup(wpipe);
> 	return (error);
> }
> #endif
> 
> static int
> pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
>     int flags, struct thread *td)
> {
> 	struct pipe *wpipe, *rpipe;
> 	ssize_t orig_resid;
> 	int desiredsize, error;
> 
> 	rpipe = fp->f_data;
> 	wpipe = PIPE_PEER(rpipe);
> 	PIPE_LOCK(rpipe);
> 	error = pipelock(wpipe, 1);
> 	if (error) {
> 		PIPE_UNLOCK(rpipe);
> 		return (error);
> 	}
> 	/*
> 	 * detect loss of pipe read side, issue SIGPIPE if lost.
> 	 */
> 	if (wpipe->pipe_present != PIPE_ACTIVE ||
> 	    (wpipe->pipe_state & PIPE_EOF)) {
> 		pipeunlock(wpipe);
> 		PIPE_UNLOCK(rpipe);
> 		return (EPIPE);
> 	}
> #ifdef MAC
> 	error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
> 	if (error) {
> 		pipeunlock(wpipe);
> 		PIPE_UNLOCK(rpipe);
> 		return (error);
> 	}
> #endif
> 	++wpipe->pipe_busy;
> 
> 	/* Choose a larger size if it's advantageous */
> 	desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
> 	while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
> 		if (piperesizeallowed != 1)
> 			break;
> 		if (amountpipekva > maxpipekva / 2)
> 			break;
> 		if (desiredsize == BIG_PIPE_SIZE)
> 			break;
> 		desiredsize = desiredsize * 2;
> 	}
> 
> 	/* Choose a smaller size if we're in a OOM situation */
> 	if (amountpipekva > (3 * maxpipekva) / 4 &&
> 	    wpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
> 	    wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
> 	    piperesizeallowed == 1)
> 		desiredsize = SMALL_PIPE_SIZE;
> 
> 	/* Resize if the above determined that a new size was necessary */
> 	if (desiredsize != wpipe->pipe_buffer.size &&
> 	    (wpipe->pipe_state & PIPE_DIRECTW) == 0) {
> 		PIPE_UNLOCK(wpipe);
> 		pipespace(wpipe, desiredsize);
> 		PIPE_LOCK(wpipe);
> 	}
> 	MPASS(wpipe->pipe_buffer.size != 0);
> 
> 	pipeunlock(wpipe);
> 
> 	orig_resid = uio->uio_resid;
> 
> 	while (uio->uio_resid) {
> 		int space;
> 
> 		pipelock(wpipe, 0);
> 		if (wpipe->pipe_state & PIPE_EOF) {
> 			pipeunlock(wpipe);
> 			error = EPIPE;
> 			break;
> 		}
> #ifndef PIPE_NODIRECT
> 		/*
> 		 * If the transfer is large, we can gain performance if
> 		 * we do process-to-process copies directly.
> 		 * If the write is non-blocking, we don't use the
> 		 * direct write mechanism.
> 		 *
> 		 * The direct write mechanism will detect the reader going
> 		 * away on us.
> 		 */
> 		if (uio->uio_segflg == UIO_USERSPACE &&
> 		    uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
> 		    wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
> 		    (fp->f_flag & FNONBLOCK) == 0) {
> 			pipeunlock(wpipe);
> 			error = pipe_direct_write(wpipe, uio);
> 			if (error)
> 				break;
> 			continue;
> 		}
> #endif
> 
> 		/*
> 		 * Pipe buffered writes cannot be coincidental with
> 		 * direct writes.  We wait until the currently executing
> 		 * direct write is completed before we start filling the
> 		 * pipe buffer.  We break out if a signal occurs or the
> 		 * reader goes away.
> 		 */
> 		if (wpipe->pipe_map.cnt != 0) {
> 			if (wpipe->pipe_state & PIPE_WANTR) {
> 				wpipe->pipe_state &= ~PIPE_WANTR;
> 				wakeup(wpipe);
> 			}
> 			pipeselwakeup(wpipe);
> 			wpipe->pipe_state |= PIPE_WANTW;
> 			pipeunlock(wpipe);
> 			error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
> 			    "pipbww", 0);
> 			if (error)
> 				break;
> 			else
> 				continue;
> 		}
> 
> 		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) {
> 			int size;	/* Transfer size */
> 			int segsize;	/* first segment to transfer */
> 
> 			/*
> 			 * 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 */
> 
> 			PIPE_UNLOCK(rpipe);
> 			error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
> 					segsize, uio);
> 			PIPE_LOCK(rpipe);
> 
> 			if (error == 0 && segsize < size) {
> 				KASSERT(wpipe->pipe_buffer.in + segsize ==
> 					wpipe->pipe_buffer.size,
> 					("Pipe buffer wraparound disappeared"));
> 				/*
> 				 * Transfer remaining part now, to
> 				 * support atomic writes.  Wraparound
> 				 * happened.
> 				 */
> 
> 				PIPE_UNLOCK(rpipe);
> 				error = uiomove(
> 				    &wpipe->pipe_buffer.buffer[0],
> 				    size - segsize, uio);
> 				PIPE_LOCK(rpipe);
> 			}
> 			if (error == 0) {
> 				wpipe->pipe_buffer.in += size;
> 				if (wpipe->pipe_buffer.in >=
> 				    wpipe->pipe_buffer.size) {
> 					KASSERT(wpipe->pipe_buffer.in ==
> 						size - segsize +
> 						wpipe->pipe_buffer.size,
> 						("Expected wraparound bad"));
> 					wpipe->pipe_buffer.in = size - segsize;
> 				}
> 
> 				wpipe->pipe_buffer.cnt += size;
> 				KASSERT(wpipe->pipe_buffer.cnt <=
> 					wpipe->pipe_buffer.size,
> 					("Pipe buffer overflow"));
> 			}
> 			pipeunlock(wpipe);
> 			if (error != 0)
> 				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;
> 				pipeunlock(wpipe);
> 				break;
> 			}
> 
> 			/*
> 			 * We have no more space and have something to offer,
> 			 * wake up select/poll.
> 			 */
> 			pipeselwakeup(wpipe);
> 
> 			wpipe->pipe_state |= PIPE_WANTW;
> 			pipeunlock(wpipe);
> 			error = msleep(wpipe, PIPE_MTX(rpipe),
> 			    PRIBIO | PCATCH, "pipewr", 0);
> 			if (error != 0)
> 				break;
> 		}
> 	}
> 
> 	pipelock(wpipe, 0);
> 	--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 any byte was written.
> 	 * EINTR and other interrupts are handled by generic I/O layer.
> 	 * Do not pretend that I/O succeeded for obvious user error
> 	 * like EFAULT.
> 	 */
> 	if (uio->uio_resid != orig_resid && error == EPIPE)
> 		error = 0;
> 
> 	if (error == 0)
> 		vfs_timestamp(&wpipe->pipe_mtime);
> 
> 	/*
> 	 * We have something to offer,
> 	 * wake up select/poll.
> 	 */
> 	if (wpipe->pipe_buffer.cnt)
> 		pipeselwakeup(wpipe);
> 
> 	pipeunlock(wpipe);
> 	PIPE_UNLOCK(rpipe);
> 	return (error);
> }
> 
> /* ARGSUSED */
> static int
> pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
>     struct thread *td)
> {
> 	struct pipe *cpipe;
> 	int error;
> 
> 	cpipe = fp->f_data;
> 	if (cpipe->pipe_state & PIPE_NAMED)
> 		error = vnops.fo_truncate(fp, length, active_cred, td);
> 	else
> 		error = invfo_truncate(fp, length, active_cred, td);
> 	return (error);
> }
> 
> /*
>  * we implement a very minimal set of ioctls for compatibility with sockets.
>  */
> static int
> pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
>     struct thread *td)
> {
> 	struct pipe *mpipe = fp->f_data;
> 	int error;
> 
> 	PIPE_LOCK(mpipe);
> 
> #ifdef MAC
> 	error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
> 	if (error) {
> 		PIPE_UNLOCK(mpipe);
> 		return (error);
> 	}
> #endif
> 
> 	error = 0;
> 	switch (cmd) {
> 
> 	case FIONBIO:
> 		break;
> 
> 	case FIOASYNC:
> 		if (*(int *)data) {
> 			mpipe->pipe_state |= PIPE_ASYNC;
> 		} else {
> 			mpipe->pipe_state &= ~PIPE_ASYNC;
> 		}
> 		break;
> 
> 	case FIONREAD:
> 		if (!(fp->f_flag & FREAD)) {
> 			*(int *)data = 0;
> 			PIPE_UNLOCK(mpipe);
> 			return (0);
> 		}
> 		if (mpipe->pipe_map.cnt != 0)
> 			*(int *)data = mpipe->pipe_map.cnt;
> 		else
> 			*(int *)data = mpipe->pipe_buffer.cnt;
> 		break;
> 
> 	case FIOSETOWN:
> 		PIPE_UNLOCK(mpipe);
> 		error = fsetown(*(int *)data, &mpipe->pipe_sigio);
> 		goto out_unlocked;
> 
> 	case FIOGETOWN:
> 		*(int *)data = fgetown(&mpipe->pipe_sigio);
> 		break;
> 
> 	/* This is deprecated, FIOSETOWN should be used instead. */
> 	case TIOCSPGRP:
> 		PIPE_UNLOCK(mpipe);
> 		error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
> 		goto out_unlocked;
> 
> 	/* This is deprecated, FIOGETOWN should be used instead. */
> 	case TIOCGPGRP:
> 		*(int *)data = -fgetown(&mpipe->pipe_sigio);
> 		break;
> 
> 	default:
> 		error = ENOTTY;
> 		break;
> 	}
> 	PIPE_UNLOCK(mpipe);
> out_unlocked:
> 	return (error);
> }
> 
> static int
> pipe_poll(struct file *fp, int events, struct ucred *active_cred,
>     struct thread *td)
> {
> 	struct pipe *rpipe;
> 	struct pipe *wpipe;
> 	int levents, revents;
> #ifdef MAC
> 	int error;
> #endif
> 
> 	revents = 0;
> 	rpipe = fp->f_data;
> 	wpipe = PIPE_PEER(rpipe);
> 	PIPE_LOCK(rpipe);
> #ifdef MAC
> 	error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
> 	if (error)
> 		goto locked_error;
> #endif
> 	if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
> 		if (rpipe->pipe_map.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
> 			revents |= events & (POLLIN | POLLRDNORM);
> 
> 	if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
> 		if (wpipe->pipe_present != PIPE_ACTIVE ||
> 		    (wpipe->pipe_state & PIPE_EOF) ||
> 		    ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
> 		     ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
> 			 wpipe->pipe_buffer.size == 0)))
> 			revents |= events & (POLLOUT | POLLWRNORM);
> 
> 	levents = events &
> 	    (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
> 	if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
> 	    fp->f_pipegen == rpipe->pipe_wgen)
> 		events |= POLLINIGNEOF;
> 
> 	if ((events & POLLINIGNEOF) == 0) {
> 		if (rpipe->pipe_state & PIPE_EOF) {
>-			revents |= (events & (POLLIN | POLLRDNORM));
>+			if (fp->f_flag & FREAD)
>+				revents |= (events & (POLLIN | POLLRDNORM));
> 			if (wpipe->pipe_present != PIPE_ACTIVE ||
> 			    (wpipe->pipe_state & PIPE_EOF))
> 				revents |= POLLHUP;
> 		}
> 	}
> 
> 	if (revents == 0) {
> 		if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
> 			selrecord(td, &rpipe->pipe_sel);
> 			if (SEL_WAITING(&rpipe->pipe_sel))
> 				rpipe->pipe_state |= PIPE_SEL;
> 		}
> 
> 		if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
> 			selrecord(td, &wpipe->pipe_sel);
> 			if (SEL_WAITING(&wpipe->pipe_sel))
> 				wpipe->pipe_state |= PIPE_SEL;
> 		}
> 	}
> #ifdef MAC
> locked_error:
> #endif
> 	PIPE_UNLOCK(rpipe);
> 
> 	return (revents);
> }
> 
> /*
>  * We shouldn't need locks here as we're doing a read and this should
>  * be a natural race.
>  */
> static int
> pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred,
>     struct thread *td)
> {
> 	struct pipe *pipe;
> #ifdef MAC
> 	int error;
> #endif
> 
> 	pipe = fp->f_data;
> 	PIPE_LOCK(pipe);
> #ifdef MAC
> 	error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
> 	if (error) {
> 		PIPE_UNLOCK(pipe);
> 		return (error);
> 	}
> #endif
> 
> 	/* For named pipes ask the underlying filesystem. */
> 	if (pipe->pipe_state & PIPE_NAMED) {
> 		PIPE_UNLOCK(pipe);
> 		return (vnops.fo_stat(fp, ub, active_cred, td));
> 	}
> 
> 	PIPE_UNLOCK(pipe);
> 
> 	bzero(ub, sizeof(*ub));
> 	ub->st_mode = S_IFIFO;
> 	ub->st_blksize = PAGE_SIZE;
> 	if (pipe->pipe_map.cnt != 0)
> 		ub->st_size = pipe->pipe_map.cnt;
> 	else
> 		ub->st_size = pipe->pipe_buffer.cnt;
> 	ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
> 	ub->st_atim = pipe->pipe_atime;
> 	ub->st_mtim = pipe->pipe_mtime;
> 	ub->st_ctim = pipe->pipe_ctime;
> 	ub->st_uid = fp->f_cred->cr_uid;
> 	ub->st_gid = fp->f_cred->cr_gid;
> 	ub->st_dev = pipedev_ino;
> 	ub->st_ino = pipe->pipe_ino;
> 	/*
> 	 * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
> 	 */
> 	return (0);
> }
> 
> /* ARGSUSED */
> static int
> pipe_close(struct file *fp, struct thread *td)
> {
> 
> 	if (fp->f_vnode != NULL) 
> 		return vnops.fo_close(fp, td);
> 	fp->f_ops = &badfileops;
> 	pipe_dtor(fp->f_data);
> 	fp->f_data = NULL;
> 	return (0);
> }
> 
> static int
> pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
> {
> 	struct pipe *cpipe;
> 	int error;
> 
> 	cpipe = fp->f_data;
> 	if (cpipe->pipe_state & PIPE_NAMED)
> 		error = vn_chmod(fp, mode, active_cred, td);
> 	else
> 		error = invfo_chmod(fp, mode, active_cred, td);
> 	return (error);
> }
> 
> static int
> pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
>     struct thread *td)
> {
> 	struct pipe *cpipe;
> 	int error;
> 
> 	cpipe = fp->f_data;
> 	if (cpipe->pipe_state & PIPE_NAMED)
> 		error = vn_chown(fp, uid, gid, active_cred, td);
> 	else
> 		error = invfo_chown(fp, uid, gid, active_cred, td);
> 	return (error);
> }
> 
> static int
> pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
> {
> 	struct pipe *pi;
> 
> 	if (fp->f_type == DTYPE_FIFO)
> 		return (vn_fill_kinfo(fp, kif, fdp));
> 	kif->kf_type = KF_TYPE_PIPE;
> 	pi = fp->f_data;
> 	kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
> 	kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
> 	kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
> 	return (0);
> }
> 
> static void
> pipe_free_kmem(struct pipe *cpipe)
> {
> 
> 	KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
> 	    ("pipe_free_kmem: pipe mutex locked"));
> 
> 	if (cpipe->pipe_buffer.buffer != NULL) {
> 		atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
> 		vm_map_remove(pipe_map,
> 		    (vm_offset_t)cpipe->pipe_buffer.buffer,
> 		    (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
> 		cpipe->pipe_buffer.buffer = NULL;
> 	}
> #ifndef PIPE_NODIRECT
> 	{
> 		cpipe->pipe_map.cnt = 0;
> 		cpipe->pipe_map.pos = 0;
> 		cpipe->pipe_map.npages = 0;
> 	}
> #endif
> }
> 
> /*
>  * shutdown the pipe
>  */
> static void
> pipeclose(struct pipe *cpipe)
> {
> 	struct pipepair *pp;
> 	struct pipe *ppipe;
> 
> 	KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
> 
> 	PIPE_LOCK(cpipe);
> 	pipelock(cpipe, 0);
> 	pp = cpipe->pipe_pair;
> 
>-	pipeselwakeup(cpipe);
>-
> 	/*
> 	 * 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;
> 		pipeunlock(cpipe);
> 		msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
> 		pipelock(cpipe, 0);
> 	}
> 
>+	pipeselwakeup(cpipe);
>+
> 	/*
> 	 * Disconnect from peer, if any.
> 	 */
> 	ppipe = cpipe->pipe_peer;
> 	if (ppipe->pipe_present == PIPE_ACTIVE) {
>-		pipeselwakeup(ppipe);
>-
> 		ppipe->pipe_state |= PIPE_EOF;
> 		wakeup(ppipe);
>-		KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
>+		pipeselwakeup(ppipe);
> 	}
> 
> 	/*
> 	 * Mark this endpoint as free.  Release kmem resources.  We
> 	 * don't mark this endpoint as unused until we've finished
> 	 * doing that, or the pipe might disappear out from under
> 	 * us.
> 	 */
> 	PIPE_UNLOCK(cpipe);
> 	pipe_free_kmem(cpipe);
> 	PIPE_LOCK(cpipe);
> 	cpipe->pipe_present = PIPE_CLOSING;
> 	pipeunlock(cpipe);
> 
> 	/*
> 	 * knlist_clear() may sleep dropping the PIPE_MTX. Set the
> 	 * PIPE_FINALIZED, that allows other end to free the
> 	 * pipe_pair, only after the knotes are completely dismantled.
> 	 */
> 	knlist_clear(&cpipe->pipe_sel.si_note, 1);
> 	cpipe->pipe_present = PIPE_FINALIZED;
> 	seldrain(&cpipe->pipe_sel);
> 	knlist_destroy(&cpipe->pipe_sel.si_note);
> 
> 	/*
> 	 * If both endpoints are now closed, release the memory for the
> 	 * pipe pair.  If not, unlock.
> 	 */
> 	if (ppipe->pipe_present == PIPE_FINALIZED) {
> 		PIPE_UNLOCK(cpipe);
> #ifdef MAC
> 		mac_pipe_destroy(pp);
> #endif
> 		uma_zfree(pipe_zone, cpipe->pipe_pair);
> 	} else
> 		PIPE_UNLOCK(cpipe);
> }
> 
> /*ARGSUSED*/
> static int
> pipe_kqfilter(struct file *fp, struct knote *kn)
> {
> 	struct pipe *cpipe;
> 
> 	/*
> 	 * If a filter is requested that is not supported by this file
> 	 * descriptor, don't return an error, but also don't ever generate an
> 	 * event.
> 	 */
> 	if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
> 		kn->kn_fop = &pipe_nfiltops;
> 		return (0);
> 	}
> 	if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
> 		kn->kn_fop = &pipe_nfiltops;
> 		return (0);
> 	}
> 	cpipe = fp->f_data;
> 	PIPE_LOCK(cpipe);
> 	switch (kn->kn_filter) {
> 	case EVFILT_READ:
> 		kn->kn_fop = &pipe_rfiltops;
> 		break;
> 	case EVFILT_WRITE:
> 		kn->kn_fop = &pipe_wfiltops;
> 		if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
> 			/* other end of pipe has been closed */
> 			PIPE_UNLOCK(cpipe);
> 			return (EPIPE);
> 		}
> 		cpipe = PIPE_PEER(cpipe);
> 		break;
> 	default:
> 		PIPE_UNLOCK(cpipe);
> 		return (EINVAL);
> 	}
> 
> 	kn->kn_hook = cpipe; 
> 	knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
> 	PIPE_UNLOCK(cpipe);
> 	return (0);
> }
> 
> static void
> filt_pipedetach(struct knote *kn)
> {
> 	struct pipe *cpipe = kn->kn_hook;
> 
> 	PIPE_LOCK(cpipe);
> 	knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
> 	PIPE_UNLOCK(cpipe);
> }
> 
> /*ARGSUSED*/
> static int
> filt_piperead(struct knote *kn, long hint)
> {
>+	struct file *fp = kn->kn_fp;
> 	struct pipe *rpipe = kn->kn_hook;
>-	struct pipe *wpipe = rpipe->pipe_peer;
>-	int ret;
> 
> 	PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
> 	kn->kn_data = rpipe->pipe_buffer.cnt;
> 	if (kn->kn_data == 0)
> 		kn->kn_data = rpipe->pipe_map.cnt;
> 
>-	if ((rpipe->pipe_state & PIPE_EOF) ||
>-	    wpipe->pipe_present != PIPE_ACTIVE ||
>-	    (wpipe->pipe_state & PIPE_EOF)) {
>+	if ((rpipe->pipe_state & PIPE_EOF) &&
>+	    !((rpipe->pipe_state & PIPE_NAMED) &&
>+	        (fp->f_seqcount == rpipe->pipe_wgen))) {
> 		kn->kn_flags |= EV_EOF;
> 		return (1);
> 	}
>-	ret = kn->kn_data > 0;
>-	return ret;
>+	kn->kn_flags &= ~EV_EOF;
>+	return (kn->kn_data > 0);
> }
> 
> /*ARGSUSED*/
> static int
> filt_pipewrite(struct knote *kn, long hint)
> {
> 	struct pipe *wpipe;
> 
> 	/*
> 	 * If this end of the pipe is closed, the knote was removed from the
> 	 * knlist and the list lock (i.e., the pipe lock) is therefore not held.
> 	 */
> 	wpipe = kn->kn_hook;
>+
>+	if (wpipe->pipe_present == PIPE_ACTIVE) {
>+		PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
>+	}
>+
>+	if (wpipe->pipe_state & PIPE_DIRECTW) {
>+		kn->kn_data = 0;
>+	} else if (wpipe->pipe_buffer.size > 0) {
>+		kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
>+	} else {
>+		kn->kn_data = PIPE_BUF;
>+	}
>+
> 	if (wpipe->pipe_present != PIPE_ACTIVE ||
> 	    (wpipe->pipe_state & PIPE_EOF)) {
>-		kn->kn_data = 0;
> 		kn->kn_flags |= EV_EOF;
> 		return (1);
> 	}
>-	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
>-	kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
>-	    (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
>-	if (wpipe->pipe_state & PIPE_DIRECTW)
>-		kn->kn_data = 0;
>-
>+	kn->kn_flags &= ~EV_EOF;
> 	return (kn->kn_data >= PIPE_BUF);
> }
> 
> static void
> filt_pipedetach_notsup(struct knote *kn)
> {
> 
> }
> 
> static int
> filt_pipenotsup(struct knote *kn, long hint)
> {
> 
> 	return (0);
> }

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Attachments on bug 224615: 189130 | 189131 | 213659 | 213662