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sys_pipe.c
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sys_pipe.c
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/* $NetBSD: sys_pipe.c,v 1.140 2014/09/05 09:20:59 matt Exp $ */
/*-
* Copyright (c) 2003, 2007, 2008, 2009 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Paul Kranenburg, and by Andrew Doran.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* 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. 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 it is mapped read-only into the kernel address space
* using the UVM page loan facility from where the receiving process can copy
* the data directly from the pages in the sending process.
*
* 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. PIPE_SIZE is constrained by the
* amount of kernel virtual memory.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sys_pipe.c,v 1.140 2014/09/05 09:20:59 matt Exp $");
#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/filio.h>
#include <sys/kernel.h>
#include <sys/ttycom.h>
#include <sys/stat.h>
#include <sys/poll.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/uio.h>
#include <sys/select.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
#include <sys/sysctl.h>
#include <sys/kauth.h>
#include <sys/atomic.h>
#include <sys/pipe.h>
#include <uvm/uvm_extern.h>
/*
* Use this to disable direct I/O and decrease the code size:
* #define PIPE_NODIRECT
*/
/* XXX Disabled for now; rare hangs switching between direct/buffered */
#define PIPE_NODIRECT
static int pipe_read(file_t *, off_t *, struct uio *, kauth_cred_t, int);
static int pipe_write(file_t *, off_t *, struct uio *, kauth_cred_t, int);
static int pipe_close(file_t *);
static int pipe_poll(file_t *, int);
static int pipe_kqfilter(file_t *, struct knote *);
static int pipe_stat(file_t *, struct stat *);
static int pipe_ioctl(file_t *, u_long, void *);
static void pipe_restart(file_t *);
static const struct fileops pipeops = {
.fo_read = pipe_read,
.fo_write = pipe_write,
.fo_ioctl = pipe_ioctl,
.fo_fcntl = fnullop_fcntl,
.fo_poll = pipe_poll,
.fo_stat = pipe_stat,
.fo_close = pipe_close,
.fo_kqfilter = pipe_kqfilter,
.fo_restart = pipe_restart,
};
/*
* 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)
/*
* Maximum amount of kva for pipes -- this is kind-of a soft limit, but
* is there so that on large systems, we don't exhaust it.
*/
#define MAXPIPEKVA (8 * 1024 * 1024)
static u_int maxpipekva = MAXPIPEKVA;
/*
* Limit for direct transfers, we cannot, of course limit
* the amount of kva for pipes in general though.
*/
#define LIMITPIPEKVA (16 * 1024 * 1024)
static u_int limitpipekva = LIMITPIPEKVA;
/*
* Limit the number of "big" pipes
*/
#define LIMITBIGPIPES 32
static u_int maxbigpipes = LIMITBIGPIPES;
static u_int nbigpipe = 0;
/*
* Amount of KVA consumed by pipe buffers.
*/
static u_int amountpipekva = 0;
static void pipeclose(struct pipe *);
static void pipe_free_kmem(struct pipe *);
static int pipe_create(struct pipe **, pool_cache_t);
static int pipelock(struct pipe *, bool);
static inline void pipeunlock(struct pipe *);
static void pipeselwakeup(struct pipe *, struct pipe *, int);
#ifndef PIPE_NODIRECT
static int pipe_direct_write(file_t *, struct pipe *, struct uio *);
#endif
static int pipespace(struct pipe *, int);
static int pipe_ctor(void *, void *, int);
static void pipe_dtor(void *, void *);
#ifndef PIPE_NODIRECT
static int pipe_loan_alloc(struct pipe *, int);
static void pipe_loan_free(struct pipe *);
#endif /* PIPE_NODIRECT */
static pool_cache_t pipe_wr_cache;
static pool_cache_t pipe_rd_cache;
void
pipe_init(void)
{
/* Writer side is not automatically allocated KVA. */
pipe_wr_cache = pool_cache_init(sizeof(struct pipe), 0, 0, 0, "pipewr",
NULL, IPL_NONE, pipe_ctor, pipe_dtor, NULL);
KASSERT(pipe_wr_cache != NULL);
/* Reader side gets preallocated KVA. */
pipe_rd_cache = pool_cache_init(sizeof(struct pipe), 0, 0, 0, "piperd",
NULL, IPL_NONE, pipe_ctor, pipe_dtor, (void *)1);
KASSERT(pipe_rd_cache != NULL);
}
static int
pipe_ctor(void *arg, void *obj, int flags)
{
struct pipe *pipe;
vaddr_t va;
pipe = obj;
memset(pipe, 0, sizeof(struct pipe));
if (arg != NULL) {
/* Preallocate space. */
va = uvm_km_alloc(kernel_map, PIPE_SIZE, 0,
UVM_KMF_PAGEABLE | UVM_KMF_WAITVA);
KASSERT(va != 0);
pipe->pipe_kmem = va;
atomic_add_int(&amountpipekva, PIPE_SIZE);
}
cv_init(&pipe->pipe_rcv, "pipe_rd");
cv_init(&pipe->pipe_wcv, "pipe_wr");
cv_init(&pipe->pipe_draincv, "pipe_drn");
cv_init(&pipe->pipe_lkcv, "pipe_lk");
selinit(&pipe->pipe_sel);
pipe->pipe_state = PIPE_SIGNALR;
return 0;
}
static void
pipe_dtor(void *arg, void *obj)
{
struct pipe *pipe;
pipe = obj;
cv_destroy(&pipe->pipe_rcv);
cv_destroy(&pipe->pipe_wcv);
cv_destroy(&pipe->pipe_draincv);
cv_destroy(&pipe->pipe_lkcv);
seldestroy(&pipe->pipe_sel);
if (pipe->pipe_kmem != 0) {
uvm_km_free(kernel_map, pipe->pipe_kmem, PIPE_SIZE,
UVM_KMF_PAGEABLE);
atomic_add_int(&amountpipekva, -PIPE_SIZE);
}
}
/*
* The pipe system call for the DTYPE_PIPE type of pipes
*/
int
pipe1(struct lwp *l, register_t *retval, int flags)
{
struct pipe *rpipe, *wpipe;
file_t *rf, *wf;
int fd, error;
proc_t *p;
if (flags & ~(O_CLOEXEC|O_NONBLOCK|O_NOSIGPIPE))
return EINVAL;
p = curproc;
rpipe = wpipe = NULL;
if ((error = pipe_create(&rpipe, pipe_rd_cache)) ||
(error = pipe_create(&wpipe, pipe_wr_cache))) {
goto free2;
}
rpipe->pipe_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
wpipe->pipe_lock = rpipe->pipe_lock;
mutex_obj_hold(wpipe->pipe_lock);
error = fd_allocfile(&rf, &fd);
if (error)
goto free2;
retval[0] = fd;
error = fd_allocfile(&wf, &fd);
if (error)
goto free3;
retval[1] = fd;
rf->f_flag = FREAD | flags;
rf->f_type = DTYPE_PIPE;
rf->f_pipe = rpipe;
rf->f_ops = &pipeops;
fd_set_exclose(l, (int)retval[0], (flags & O_CLOEXEC) != 0);
wf->f_flag = FWRITE | flags;
wf->f_type = DTYPE_PIPE;
wf->f_pipe = wpipe;
wf->f_ops = &pipeops;
fd_set_exclose(l, (int)retval[1], (flags & O_CLOEXEC) != 0);
rpipe->pipe_peer = wpipe;
wpipe->pipe_peer = rpipe;
fd_affix(p, rf, (int)retval[0]);
fd_affix(p, wf, (int)retval[1]);
return (0);
free3:
fd_abort(p, rf, (int)retval[0]);
free2:
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.
*/
static int
pipespace(struct pipe *pipe, int size)
{
void *buffer;
/*
* Allocate pageable virtual address space. Physical memory is
* allocated on demand.
*/
if (size == PIPE_SIZE && pipe->pipe_kmem != 0) {
buffer = (void *)pipe->pipe_kmem;
} else {
buffer = (void *)uvm_km_alloc(kernel_map, round_page(size),
0, UVM_KMF_PAGEABLE);
if (buffer == NULL)
return (ENOMEM);
atomic_add_int(&amountpipekva, size);
}
/* free old resources if we're resizing */
pipe_free_kmem(pipe);
pipe->pipe_buffer.buffer = buffer;
pipe->pipe_buffer.size = size;
pipe->pipe_buffer.in = 0;
pipe->pipe_buffer.out = 0;
pipe->pipe_buffer.cnt = 0;
return (0);
}
/*
* Initialize and allocate VM and memory for pipe.
*/
static int
pipe_create(struct pipe **pipep, pool_cache_t cache)
{
struct pipe *pipe;
int error;
pipe = pool_cache_get(cache, PR_WAITOK);
KASSERT(pipe != NULL);
*pipep = pipe;
error = 0;
getnanotime(&pipe->pipe_btime);
pipe->pipe_atime = pipe->pipe_mtime = pipe->pipe_btime;
pipe->pipe_lock = NULL;
if (cache == pipe_rd_cache) {
error = pipespace(pipe, PIPE_SIZE);
} else {
pipe->pipe_buffer.buffer = NULL;
pipe->pipe_buffer.size = 0;
pipe->pipe_buffer.in = 0;
pipe->pipe_buffer.out = 0;
pipe->pipe_buffer.cnt = 0;
}
return error;
}
/*
* Lock a pipe for I/O, blocking other access
* Called with pipe spin lock held.
*/
static int
pipelock(struct pipe *pipe, bool catch_p)
{
int error;
KASSERT(mutex_owned(pipe->pipe_lock));
while (pipe->pipe_state & PIPE_LOCKFL) {
pipe->pipe_state |= PIPE_LWANT;
if (catch_p) {
error = cv_wait_sig(&pipe->pipe_lkcv, pipe->pipe_lock);
if (error != 0)
return error;
} else
cv_wait(&pipe->pipe_lkcv, pipe->pipe_lock);
}
pipe->pipe_state |= PIPE_LOCKFL;
return 0;
}
/*
* unlock a pipe I/O lock
*/
static inline void
pipeunlock(struct pipe *pipe)
{
KASSERT(pipe->pipe_state & PIPE_LOCKFL);
pipe->pipe_state &= ~PIPE_LOCKFL;
if (pipe->pipe_state & PIPE_LWANT) {
pipe->pipe_state &= ~PIPE_LWANT;
cv_broadcast(&pipe->pipe_lkcv);
}
}
/*
* Select/poll wakup. This also sends SIGIO to peer connected to
* 'sigpipe' side of pipe.
*/
static void
pipeselwakeup(struct pipe *selp, struct pipe *sigp, int code)
{
int band;
switch (code) {
case POLL_IN:
band = POLLIN|POLLRDNORM;
break;
case POLL_OUT:
band = POLLOUT|POLLWRNORM;
break;
case POLL_HUP:
band = POLLHUP;
break;
case POLL_ERR:
band = POLLERR;
break;
default:
band = 0;
#ifdef DIAGNOSTIC
printf("bad siginfo code %d in pipe notification.\n", code);
#endif
break;
}
selnotify(&selp->pipe_sel, band, NOTE_SUBMIT);
if (sigp == NULL || (sigp->pipe_state & PIPE_ASYNC) == 0)
return;
fownsignal(sigp->pipe_pgid, SIGIO, code, band, selp);
}
static int
pipe_read(file_t *fp, off_t *offset, struct uio *uio, kauth_cred_t cred,
int flags)
{
struct pipe *rpipe = fp->f_pipe;
struct pipebuf *bp = &rpipe->pipe_buffer;
kmutex_t *lock = rpipe->pipe_lock;
int error;
size_t nread = 0;
size_t size;
size_t ocnt;
unsigned int wakeup_state = 0;
mutex_enter(lock);
++rpipe->pipe_busy;
ocnt = bp->cnt;
again:
error = pipelock(rpipe, true);
if (error)
goto unlocked_error;
while (uio->uio_resid) {
/*
* Normal pipe buffer receive.
*/
if (bp->cnt > 0) {
size = bp->size - bp->out;
if (size > bp->cnt)
size = bp->cnt;
if (size > uio->uio_resid)
size = uio->uio_resid;
mutex_exit(lock);
error = uiomove((char *)bp->buffer + bp->out, size, uio);
mutex_enter(lock);
if (error)
break;
bp->out += size;
if (bp->out >= bp->size)
bp->out = 0;
bp->cnt -= size;
/*
* If there is no more to read in the pipe, reset
* its pointers to the beginning. This improves
* cache hit stats.
*/
if (bp->cnt == 0) {
bp->in = 0;
bp->out = 0;
}
nread += size;
continue;
}
#ifndef PIPE_NODIRECT
if ((rpipe->pipe_state & PIPE_DIRECTR) != 0) {
struct pipemapping * const rmap = &rpipe->pipe_map;
/*
* Direct copy, bypassing a kernel buffer.
*/
void *va;
u_int gen;
KASSERT(rpipe->pipe_state & PIPE_DIRECTW);
size = rmap->cnt;
if (size > uio->uio_resid)
size = uio->uio_resid;
va = (char *)rmap->kva + rmap->pos;
gen = rmap->egen;
mutex_exit(lock);
/*
* Consume emap and read the data from loaned pages.
*/
uvm_emap_consume(gen);
error = uiomove(va, size, uio);
mutex_enter(lock);
if (error)
break;
nread += size;
rmap->pos += size;
rmap->cnt -= size;
if (rmap->cnt == 0) {
rpipe->pipe_state &= ~PIPE_DIRECTR;
cv_broadcast(&rpipe->pipe_wcv);
}
continue;
}
#endif
/*
* Break if some data was read.
*/
if (nread > 0)
break;
/*
* Detect EOF condition.
* Read returns 0 on EOF, no need to set error.
*/
if (rpipe->pipe_state & PIPE_EOF)
break;
/*
* Don't block on non-blocking I/O.
*/
if (fp->f_flag & FNONBLOCK) {
error = EAGAIN;
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);
/*
* Re-check to see if more direct writes are pending.
*/
if ((rpipe->pipe_state & PIPE_DIRECTR) != 0)
goto again;
#if 1 /* XXX (dsl) I'm sure these aren't needed here ... */
/*
* We want to read more, wake up select/poll.
*/
pipeselwakeup(rpipe, rpipe->pipe_peer, POLL_OUT);
/*
* If the "write-side" is blocked, wake it up now.
*/
cv_broadcast(&rpipe->pipe_wcv);
#endif
if (wakeup_state & PIPE_RESTART) {
error = ERESTART;
goto unlocked_error;
}
/* Now wait until the pipe is filled */
error = cv_wait_sig(&rpipe->pipe_rcv, lock);
if (error != 0)
goto unlocked_error;
wakeup_state = rpipe->pipe_state;
goto again;
}
if (error == 0)
getnanotime(&rpipe->pipe_atime);
pipeunlock(rpipe);
unlocked_error:
--rpipe->pipe_busy;
if (rpipe->pipe_busy == 0) {
rpipe->pipe_state &= ~PIPE_RESTART;
cv_broadcast(&rpipe->pipe_draincv);
}
if (bp->cnt < MINPIPESIZE) {
cv_broadcast(&rpipe->pipe_wcv);
}
/*
* If anything was read off the buffer, signal to the writer it's
* possible to write more data. Also send signal if we are here for the
* first time after last write.
*/
if ((bp->size - bp->cnt) >= PIPE_BUF
&& (ocnt != bp->cnt || (rpipe->pipe_state & PIPE_SIGNALR))) {
pipeselwakeup(rpipe, rpipe->pipe_peer, POLL_OUT);
rpipe->pipe_state &= ~PIPE_SIGNALR;
}
mutex_exit(lock);
return (error);
}
#ifndef PIPE_NODIRECT
/*
* Allocate structure for loan transfer.
*/
static int
pipe_loan_alloc(struct pipe *wpipe, int npages)
{
struct pipemapping * const wmap = &wpipe->pipe_map;
const vsize_t len = ptoa(npages);
atomic_add_int(&amountpipekva, len);
wmap->kva = uvm_km_alloc(kernel_map, len, 0,
UVM_KMF_COLORMATCH | UVM_KMF_VAONLY | UVM_KMF_WAITVA);
if (wmap->kva == 0) {
atomic_add_int(&amountpipekva, -len);
return (ENOMEM);
}
wmap->npages = npages;
wmap->pgs = kmem_alloc(npages * sizeof(struct vm_page *), KM_SLEEP);
return (0);
}
/*
* Free resources allocated for loan transfer.
*/
static void
pipe_loan_free(struct pipe *wpipe)
{
struct pipemapping * const wmap = &wpipe->pipe_map;
const vsize_t len = ptoa(wmap->npages);
uvm_emap_remove(wmap->kva, len); /* XXX */
uvm_km_free(kernel_map, wmap->kva, len, UVM_KMF_VAONLY);
wmap->kva = 0;
atomic_add_int(&amountpipekva, -len);
kmem_free(wmap->pgs, wmap->npages * sizeof(struct vm_page *));
wmap->pgs = NULL;
#if 0
wmap->npages = 0;
wmap->pos = 0;
wmap->cnt = 0;
#endif
}
/*
* NetBSD direct write, using uvm_loan() mechanism.
* 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.
*
* Called with the long-term pipe lock held.
*/
static int
pipe_direct_write(file_t *fp, struct pipe *wpipe, struct uio *uio)
{
struct pipemapping * const wmap = &wpipe->pipe_map;
kmutex_t * const lock = wpipe->pipe_lock;
struct vm_page **pgs;
vaddr_t bbase, base, bend;
vsize_t blen, bcnt;
int error, npages;
voff_t bpos;
u_int starting_color;
KASSERT(mutex_owned(wpipe->pipe_lock));
KASSERT(wmap->cnt == 0);
mutex_exit(lock);
/*
* Handle first PIPE_CHUNK_SIZE bytes of buffer. Deal with buffers
* not aligned to PAGE_SIZE.
*/
bbase = (vaddr_t)uio->uio_iov->iov_base;
base = trunc_page(bbase);
bend = round_page(bbase + uio->uio_iov->iov_len);
blen = bend - base;
bpos = bbase - base;
if (blen > PIPE_DIRECT_CHUNK) {
blen = PIPE_DIRECT_CHUNK;
bend = base + blen;
bcnt = PIPE_DIRECT_CHUNK - bpos;
} else {
bcnt = uio->uio_iov->iov_len;
}
npages = atop(blen);
starting_color = atop(base) & uvmexp.colormask;
/*
* Free the old kva if we need more pages than we have
* allocated.
*/
if (wmap->kva != 0 && starting_color + npages > wmap->npages)
pipe_loan_free(wpipe);
/* Allocate new kva. */
if (wmap->kva == 0) {
error = pipe_loan_alloc(wpipe, starting_color + npages);
if (error) {
mutex_enter(lock);
return (error);
}
}
/* Loan the write buffer memory from writer process */
pgs = wmap->pgs + starting_color;
error = uvm_loan(&uio->uio_vmspace->vm_map, base, blen,
pgs, UVM_LOAN_TOPAGE);
if (error) {
pipe_loan_free(wpipe);
mutex_enter(lock);
return (ENOMEM); /* so that caller fallback to ordinary write */
}
/* Enter the loaned pages to KVA, produce new emap generation number. */
uvm_emap_enter(wmap->kva + ptoa(starting_color), pgs, npages);
wmap->egen = uvm_emap_produce();
/* Now we can put the pipe in direct write mode */
wmap->pos = bpos + ptoa(starting_color);
wmap->cnt = bcnt;
/*
* But before we can let someone do a direct read, we
* have to wait until the pipe is drained. Release the
* pipe lock while we wait.
*/
mutex_enter(lock);
wpipe->pipe_state |= PIPE_DIRECTW;
pipeunlock(wpipe);
while (error == 0 && wpipe->pipe_buffer.cnt > 0) {
cv_broadcast(&wpipe->pipe_rcv);
error = cv_wait_sig(&wpipe->pipe_wcv, lock);
if (error == 0 && wpipe->pipe_state & PIPE_EOF)
error = EPIPE;
}
/* Pipe is drained; next read will off the direct buffer */
wpipe->pipe_state |= PIPE_DIRECTR;
/* Wait until the reader is done */
while (error == 0 && (wpipe->pipe_state & PIPE_DIRECTR)) {
cv_broadcast(&wpipe->pipe_rcv);
pipeselwakeup(wpipe, wpipe, POLL_IN);
error = cv_wait_sig(&wpipe->pipe_wcv, lock);
if (error == 0 && wpipe->pipe_state & PIPE_EOF)
error = EPIPE;
}
/* Take pipe out of direct write mode */
wpipe->pipe_state &= ~(PIPE_DIRECTW | PIPE_DIRECTR);
/* Acquire the pipe lock and cleanup */
(void)pipelock(wpipe, false);
mutex_exit(lock);
if (pgs != NULL) {
/* XXX: uvm_emap_remove */
uvm_unloan(pgs, npages, UVM_LOAN_TOPAGE);
}
if (error || amountpipekva > maxpipekva)
pipe_loan_free(wpipe);
mutex_enter(lock);
if (error) {
pipeselwakeup(wpipe, wpipe, POLL_ERR);
/*
* If nothing was read from what we offered, return error
* straight on. Otherwise update uio resid first. Caller
* will deal with the error condition, returning short
* write, error, or restarting the write(2) as appropriate.
*/
if (wmap->cnt == bcnt) {
wmap->cnt = 0;
cv_broadcast(&wpipe->pipe_wcv);
return (error);
}
bcnt -= wpipe->cnt;
}
uio->uio_resid -= bcnt;
/* uio_offset not updated, not set/used for write(2) */
uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + bcnt;
uio->uio_iov->iov_len -= bcnt;
if (uio->uio_iov->iov_len == 0) {
uio->uio_iov++;
uio->uio_iovcnt--;
}
wmap->cnt = 0;
return (error);
}
#endif /* !PIPE_NODIRECT */
static int
pipe_write(file_t *fp, off_t *offset, struct uio *uio, kauth_cred_t cred,
int flags)
{
struct pipe *wpipe, *rpipe;
struct pipebuf *bp;
kmutex_t *lock;
int error;
unsigned int wakeup_state = 0;
/* We want to write to our peer */
rpipe = fp->f_pipe;
lock = rpipe->pipe_lock;
error = 0;
mutex_enter(lock);
wpipe = rpipe->pipe_peer;
/*
* Detect loss of pipe read side, issue SIGPIPE if lost.
*/
if (wpipe == NULL || (wpipe->pipe_state & PIPE_EOF) != 0) {
mutex_exit(lock);
return EPIPE;
}
++wpipe->pipe_busy;
/* Aquire the long-term pipe lock */
if ((error = pipelock(wpipe, true)) != 0) {
--wpipe->pipe_busy;
if (wpipe->pipe_busy == 0) {
wpipe->pipe_state &= ~PIPE_RESTART;
cv_broadcast(&wpipe->pipe_draincv);
}
mutex_exit(lock);
return (error);
}
bp = &wpipe->pipe_buffer;
/*
* If it is advantageous to resize the pipe buffer, do so.
*/
if ((uio->uio_resid > PIPE_SIZE) &&
(nbigpipe < maxbigpipes) &&
#ifndef PIPE_NODIRECT
(wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
#endif
(bp->size <= PIPE_SIZE) && (bp->cnt == 0)) {
if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
atomic_inc_uint(&nbigpipe);
}
while (uio->uio_resid) {
size_t space;
#ifndef PIPE_NODIRECT
/*
* Pipe buffered writes cannot be coincidental with
* direct writes. Also, only one direct write can be
* in progress at any one time. We wait until the currently
* executing direct write is completed before continuing.
*
* We break out if a signal occurs or the reader goes away.
*/
while (error == 0 && wpipe->pipe_state & PIPE_DIRECTW) {
cv_broadcast(&wpipe->pipe_rcv);
pipeunlock(wpipe);
error = cv_wait_sig(&wpipe->pipe_wcv, lock);
(void)pipelock(wpipe, false);
if (wpipe->pipe_state & PIPE_EOF)
error = EPIPE;
}
if (error)
break;
/*
* 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_iov->iov_len >= PIPE_MINDIRECT) &&
(fp->f_flag & FNONBLOCK) == 0 &&
(wmap->kva || (amountpipekva < limitpipekva))) {
error = pipe_direct_write(fp, wpipe, uio);
/*
* Break out if error occurred, unless it's ENOMEM.
* ENOMEM means we failed to allocate some resources
* for direct write, so we just fallback to ordinary
* write. If the direct write was successful,
* process rest of data via ordinary write.
*/
if (error == 0)
continue;
if (error != ENOMEM)
break;
}
#endif /* PIPE_NODIRECT */
space = bp->size - bp->cnt;
/* Writes of size <= PIPE_BUF must be atomic. */
if ((space < uio->uio_resid) && (uio->uio_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 = bp->size - bp->in;
if (segsize > size)
segsize = size;
/* Transfer first segment */
mutex_exit(lock);
error = uiomove((char *)bp->buffer + bp->in, segsize,
uio);
if (error == 0 && segsize < size) {
/*
* Transfer remaining part now, to
* support atomic writes. Wraparound
* happened.
*/
KASSERT(bp->in + segsize == bp->size);
error = uiomove(bp->buffer,
size - segsize, uio);
}
mutex_enter(lock);
if (error)
break;
bp->in += size;
if (bp->in >= bp->size) {
KASSERT(bp->in == size - segsize + bp->size);
bp->in = size - segsize;
}
bp->cnt += size;
KASSERT(bp->cnt <= bp->size);
wakeup_state = 0;
} else {
/*
* If the "read-side" has been blocked, wake it up now.
*/
cv_broadcast(&wpipe->pipe_rcv);
/*