The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/kern/sys_pipe.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * Copyright (c) 2012 Giovanni Trematerra
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice immediately at the beginning of the file, without modification,
   11  *    this list of conditions, and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Absolutely no warranty of function or purpose is made by the author
   16  *    John S. Dyson.
   17  * 4. Modifications may be freely made to this file if the above conditions
   18  *    are met.
   19  */
   20 
   21 /*
   22  * This file contains a high-performance replacement for the socket-based
   23  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   24  * all features of sockets, but does do everything that pipes normally
   25  * do.
   26  */
   27 
   28 /*
   29  * This code has two modes of operation, a small write mode and a large
   30  * write mode.  The small write mode acts like conventional pipes with
   31  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   32  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   33  * and PIPE_SIZE in size, the sending process pins the underlying pages in
   34  * memory, and the receiving process copies directly from these pinned pages
   35  * in the sending process.
   36  *
   37  * If the sending process receives a signal, it is possible that it will
   38  * go away, and certainly its address space can change, because control
   39  * is returned back to the user-mode side.  In that case, the pipe code
   40  * arranges to copy the buffer supplied by the user process, to a pageable
   41  * kernel buffer, and the receiving process will grab the data from the
   42  * pageable kernel buffer.  Since signals don't happen all that often,
   43  * the copy operation is normally eliminated.
   44  *
   45  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   46  * happen for small transfers so that the system will not spend all of
   47  * its time context switching.
   48  *
   49  * In order to limit the resource use of pipes, two sysctls exist:
   50  *
   51  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   52  * address space available to us in pipe_map. This value is normally
   53  * autotuned, but may also be loader tuned.
   54  *
   55  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   56  * memory in use by pipes.
   57  *
   58  * Based on how large pipekva is relative to maxpipekva, the following
   59  * will happen:
   60  *
   61  * 0% - 50%:
   62  *     New pipes are given 16K of memory backing, pipes may dynamically
   63  *     grow to as large as 64K where needed.
   64  * 50% - 75%:
   65  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   66  *     existing pipes may NOT grow.
   67  * 75% - 100%:
   68  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   69  *     existing pipes will be shrunk down to 4K whenever possible.
   70  *
   71  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   72  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   73  * resize which MUST occur for reverse-direction pipes when they are
   74  * first used.
   75  *
   76  * Additional information about the current state of pipes may be obtained
   77  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   78  * and kern.ipc.piperesizefail.
   79  *
   80  * Locking rules:  There are two locks present here:  A mutex, used via
   81  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   82  * the flag, as mutexes can not persist over uiomove.  The mutex
   83  * exists only to guard access to the flag, and is not in itself a
   84  * locking mechanism.  Also note that there is only a single mutex for
   85  * both directions of a pipe.
   86  *
   87  * As pipelock() may have to sleep before it can acquire the flag, it
   88  * is important to reread all data after a call to pipelock(); everything
   89  * in the structure may have changed.
   90  */
   91 
   92 #include <sys/cdefs.h>
   93 __FBSDID("$FreeBSD: releng/10.0/sys/kern/sys_pipe.c 255426 2013-09-09 18:11:59Z jhb $");
   94 
   95 #include <sys/param.h>
   96 #include <sys/systm.h>
   97 #include <sys/conf.h>
   98 #include <sys/fcntl.h>
   99 #include <sys/file.h>
  100 #include <sys/filedesc.h>
  101 #include <sys/filio.h>
  102 #include <sys/kernel.h>
  103 #include <sys/lock.h>
  104 #include <sys/mutex.h>
  105 #include <sys/ttycom.h>
  106 #include <sys/stat.h>
  107 #include <sys/malloc.h>
  108 #include <sys/poll.h>
  109 #include <sys/selinfo.h>
  110 #include <sys/signalvar.h>
  111 #include <sys/syscallsubr.h>
  112 #include <sys/sysctl.h>
  113 #include <sys/sysproto.h>
  114 #include <sys/pipe.h>
  115 #include <sys/proc.h>
  116 #include <sys/vnode.h>
  117 #include <sys/uio.h>
  118 #include <sys/event.h>
  119 
  120 #include <security/mac/mac_framework.h>
  121 
  122 #include <vm/vm.h>
  123 #include <vm/vm_param.h>
  124 #include <vm/vm_object.h>
  125 #include <vm/vm_kern.h>
  126 #include <vm/vm_extern.h>
  127 #include <vm/pmap.h>
  128 #include <vm/vm_map.h>
  129 #include <vm/vm_page.h>
  130 #include <vm/uma.h>
  131 
  132 /*
  133  * Use this define if you want to disable *fancy* VM things.  Expect an
  134  * approx 30% decrease in transfer rate.  This could be useful for
  135  * NetBSD or OpenBSD.
  136  */
  137 /* #define PIPE_NODIRECT */
  138 
  139 #define PIPE_PEER(pipe) \
  140         (((pipe)->pipe_state & PIPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
  141 
  142 /*
  143  * interfaces to the outside world
  144  */
  145 static fo_rdwr_t        pipe_read;
  146 static fo_rdwr_t        pipe_write;
  147 static fo_truncate_t    pipe_truncate;
  148 static fo_ioctl_t       pipe_ioctl;
  149 static fo_poll_t        pipe_poll;
  150 static fo_kqfilter_t    pipe_kqfilter;
  151 static fo_stat_t        pipe_stat;
  152 static fo_close_t       pipe_close;
  153 static fo_chmod_t       pipe_chmod;
  154 static fo_chown_t       pipe_chown;
  155 
  156 struct fileops pipeops = {
  157         .fo_read = pipe_read,
  158         .fo_write = pipe_write,
  159         .fo_truncate = pipe_truncate,
  160         .fo_ioctl = pipe_ioctl,
  161         .fo_poll = pipe_poll,
  162         .fo_kqfilter = pipe_kqfilter,
  163         .fo_stat = pipe_stat,
  164         .fo_close = pipe_close,
  165         .fo_chmod = pipe_chmod,
  166         .fo_chown = pipe_chown,
  167         .fo_sendfile = invfo_sendfile,
  168         .fo_flags = DFLAG_PASSABLE
  169 };
  170 
  171 static void     filt_pipedetach(struct knote *kn);
  172 static void     filt_pipedetach_notsup(struct knote *kn);
  173 static int      filt_pipenotsup(struct knote *kn, long hint);
  174 static int      filt_piperead(struct knote *kn, long hint);
  175 static int      filt_pipewrite(struct knote *kn, long hint);
  176 
  177 static struct filterops pipe_nfiltops = {
  178         .f_isfd = 1,
  179         .f_detach = filt_pipedetach_notsup,
  180         .f_event = filt_pipenotsup
  181 };
  182 static struct filterops pipe_rfiltops = {
  183         .f_isfd = 1,
  184         .f_detach = filt_pipedetach,
  185         .f_event = filt_piperead
  186 };
  187 static struct filterops pipe_wfiltops = {
  188         .f_isfd = 1,
  189         .f_detach = filt_pipedetach,
  190         .f_event = filt_pipewrite
  191 };
  192 
  193 /*
  194  * Default pipe buffer size(s), this can be kind-of large now because pipe
  195  * space is pageable.  The pipe code will try to maintain locality of
  196  * reference for performance reasons, so small amounts of outstanding I/O
  197  * will not wipe the cache.
  198  */
  199 #define MINPIPESIZE (PIPE_SIZE/3)
  200 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  201 
  202 static long amountpipekva;
  203 static int pipefragretry;
  204 static int pipeallocfail;
  205 static int piperesizefail;
  206 static int piperesizeallowed = 1;
  207 
  208 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  209            &maxpipekva, 0, "Pipe KVA limit");
  210 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  211            &amountpipekva, 0, "Pipe KVA usage");
  212 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  213           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  214 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  215           &pipeallocfail, 0, "Pipe allocation failures");
  216 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  217           &piperesizefail, 0, "Pipe resize failures");
  218 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  219           &piperesizeallowed, 0, "Pipe resizing allowed");
  220 
  221 static void pipeinit(void *dummy __unused);
  222 static void pipeclose(struct pipe *cpipe);
  223 static void pipe_free_kmem(struct pipe *cpipe);
  224 static int pipe_create(struct pipe *pipe, int backing);
  225 static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
  226 static __inline int pipelock(struct pipe *cpipe, int catch);
  227 static __inline void pipeunlock(struct pipe *cpipe);
  228 #ifndef PIPE_NODIRECT
  229 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  230 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  231 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  232 static void pipe_clone_write_buffer(struct pipe *wpipe);
  233 #endif
  234 static int pipespace(struct pipe *cpipe, int size);
  235 static int pipespace_new(struct pipe *cpipe, int size);
  236 
  237 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  238 static int      pipe_zone_init(void *mem, int size, int flags);
  239 static void     pipe_zone_fini(void *mem, int size);
  240 
  241 static uma_zone_t pipe_zone;
  242 static struct unrhdr *pipeino_unr;
  243 static dev_t pipedev_ino;
  244 
  245 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  246 
  247 static void
  248 pipeinit(void *dummy __unused)
  249 {
  250 
  251         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
  252             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
  253             UMA_ALIGN_PTR, 0);
  254         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  255         pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
  256         KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
  257         pipedev_ino = devfs_alloc_cdp_inode();
  258         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
  259 }
  260 
  261 static int
  262 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  263 {
  264         struct pipepair *pp;
  265         struct pipe *rpipe, *wpipe;
  266 
  267         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  268 
  269         pp = (struct pipepair *)mem;
  270 
  271         /*
  272          * We zero both pipe endpoints to make sure all the kmem pointers
  273          * are NULL, flag fields are zero'd, etc.  We timestamp both
  274          * endpoints with the same time.
  275          */
  276         rpipe = &pp->pp_rpipe;
  277         bzero(rpipe, sizeof(*rpipe));
  278         vfs_timestamp(&rpipe->pipe_ctime);
  279         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  280 
  281         wpipe = &pp->pp_wpipe;
  282         bzero(wpipe, sizeof(*wpipe));
  283         wpipe->pipe_ctime = rpipe->pipe_ctime;
  284         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  285 
  286         rpipe->pipe_peer = wpipe;
  287         rpipe->pipe_pair = pp;
  288         wpipe->pipe_peer = rpipe;
  289         wpipe->pipe_pair = pp;
  290 
  291         /*
  292          * Mark both endpoints as present; they will later get free'd
  293          * one at a time.  When both are free'd, then the whole pair
  294          * is released.
  295          */
  296         rpipe->pipe_present = PIPE_ACTIVE;
  297         wpipe->pipe_present = PIPE_ACTIVE;
  298 
  299         /*
  300          * Eventually, the MAC Framework may initialize the label
  301          * in ctor or init, but for now we do it elswhere to avoid
  302          * blocking in ctor or init.
  303          */
  304         pp->pp_label = NULL;
  305 
  306         return (0);
  307 }
  308 
  309 static int
  310 pipe_zone_init(void *mem, int size, int flags)
  311 {
  312         struct pipepair *pp;
  313 
  314         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  315 
  316         pp = (struct pipepair *)mem;
  317 
  318         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  319         return (0);
  320 }
  321 
  322 static void
  323 pipe_zone_fini(void *mem, int size)
  324 {
  325         struct pipepair *pp;
  326 
  327         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  328 
  329         pp = (struct pipepair *)mem;
  330 
  331         mtx_destroy(&pp->pp_mtx);
  332 }
  333 
  334 static int
  335 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
  336 {
  337         struct pipepair *pp;
  338         struct pipe *rpipe, *wpipe;
  339         int error;
  340 
  341         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
  342 #ifdef MAC
  343         /*
  344          * The MAC label is shared between the connected endpoints.  As a
  345          * result mac_pipe_init() and mac_pipe_create() are called once
  346          * for the pair, and not on the endpoints.
  347          */
  348         mac_pipe_init(pp);
  349         mac_pipe_create(td->td_ucred, pp);
  350 #endif
  351         rpipe = &pp->pp_rpipe;
  352         wpipe = &pp->pp_wpipe;
  353 
  354         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  355         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  356 
  357         /* Only the forward direction pipe is backed by default */
  358         if ((error = pipe_create(rpipe, 1)) != 0 ||
  359             (error = pipe_create(wpipe, 0)) != 0) {
  360                 pipeclose(rpipe);
  361                 pipeclose(wpipe);
  362                 return (error);
  363         }
  364 
  365         rpipe->pipe_state |= PIPE_DIRECTOK;
  366         wpipe->pipe_state |= PIPE_DIRECTOK;
  367         return (0);
  368 }
  369 
  370 int
  371 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
  372 {
  373         struct pipepair *pp;
  374         int error;
  375 
  376         error = pipe_paircreate(td, &pp);
  377         if (error != 0)
  378                 return (error);
  379         pp->pp_rpipe.pipe_state |= PIPE_NAMED;
  380         *ppipe = &pp->pp_rpipe;
  381         return (0);
  382 }
  383 
  384 void
  385 pipe_dtor(struct pipe *dpipe)
  386 {
  387         ino_t ino;
  388 
  389         ino = dpipe->pipe_ino;
  390         funsetown(&dpipe->pipe_sigio);
  391         pipeclose(dpipe);
  392         if (dpipe->pipe_state & PIPE_NAMED) {
  393                 dpipe = dpipe->pipe_peer;
  394                 funsetown(&dpipe->pipe_sigio);
  395                 pipeclose(dpipe);
  396         }
  397         if (ino != 0 && ino != (ino_t)-1)
  398                 free_unr(pipeino_unr, ino);
  399 }
  400 
  401 /*
  402  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  403  * the zone pick up the pieces via pipeclose().
  404  */
  405 int
  406 kern_pipe(struct thread *td, int fildes[2])
  407 {
  408 
  409         return (kern_pipe2(td, fildes, 0));
  410 }
  411 
  412 int
  413 kern_pipe2(struct thread *td, int fildes[2], int flags)
  414 {
  415         struct filedesc *fdp; 
  416         struct file *rf, *wf;
  417         struct pipe *rpipe, *wpipe;
  418         struct pipepair *pp;
  419         int fd, fflags, error;
  420 
  421         fdp = td->td_proc->p_fd;
  422         error = pipe_paircreate(td, &pp);
  423         if (error != 0)
  424                 return (error);
  425         rpipe = &pp->pp_rpipe;
  426         wpipe = &pp->pp_wpipe;
  427         error = falloc(td, &rf, &fd, flags);
  428         if (error) {
  429                 pipeclose(rpipe);
  430                 pipeclose(wpipe);
  431                 return (error);
  432         }
  433         /* An extra reference on `rf' has been held for us by falloc(). */
  434         fildes[0] = fd;
  435 
  436         fflags = FREAD | FWRITE;
  437         if ((flags & O_NONBLOCK) != 0)
  438                 fflags |= FNONBLOCK;
  439 
  440         /*
  441          * Warning: once we've gotten past allocation of the fd for the
  442          * read-side, we can only drop the read side via fdrop() in order
  443          * to avoid races against processes which manage to dup() the read
  444          * side while we are blocked trying to allocate the write side.
  445          */
  446         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
  447         error = falloc(td, &wf, &fd, flags);
  448         if (error) {
  449                 fdclose(fdp, rf, fildes[0], td);
  450                 fdrop(rf, td);
  451                 /* rpipe has been closed by fdrop(). */
  452                 pipeclose(wpipe);
  453                 return (error);
  454         }
  455         /* An extra reference on `wf' has been held for us by falloc(). */
  456         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
  457         fdrop(wf, td);
  458         fildes[1] = fd;
  459         fdrop(rf, td);
  460 
  461         return (0);
  462 }
  463 
  464 /* ARGSUSED */
  465 int
  466 sys_pipe(struct thread *td, struct pipe_args *uap)
  467 {
  468         int error;
  469         int fildes[2];
  470 
  471         error = kern_pipe(td, fildes);
  472         if (error)
  473                 return (error);
  474 
  475         td->td_retval[0] = fildes[0];
  476         td->td_retval[1] = fildes[1];
  477 
  478         return (0);
  479 }
  480 
  481 int
  482 sys_pipe2(struct thread *td, struct pipe2_args *uap)
  483 {
  484         int error, fildes[2];
  485 
  486         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
  487                 return (EINVAL);
  488         error = kern_pipe2(td, fildes, uap->flags);
  489         if (error)
  490                 return (error);
  491         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
  492         if (error) {
  493                 (void)kern_close(td, fildes[0]);
  494                 (void)kern_close(td, fildes[1]);
  495         }
  496         return (error);
  497 }
  498 
  499 /*
  500  * Allocate kva for pipe circular buffer, the space is pageable
  501  * This routine will 'realloc' the size of a pipe safely, if it fails
  502  * it will retain the old buffer.
  503  * If it fails it will return ENOMEM.
  504  */
  505 static int
  506 pipespace_new(cpipe, size)
  507         struct pipe *cpipe;
  508         int size;
  509 {
  510         caddr_t buffer;
  511         int error, cnt, firstseg;
  512         static int curfail = 0;
  513         static struct timeval lastfail;
  514 
  515         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  516         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  517                 ("pipespace: resize of direct writes not allowed"));
  518 retry:
  519         cnt = cpipe->pipe_buffer.cnt;
  520         if (cnt > size)
  521                 size = cnt;
  522 
  523         size = round_page(size);
  524         buffer = (caddr_t) vm_map_min(pipe_map);
  525 
  526         error = vm_map_find(pipe_map, NULL, 0,
  527                 (vm_offset_t *) &buffer, size, 0, VMFS_ANY_SPACE,
  528                 VM_PROT_ALL, VM_PROT_ALL, 0);
  529         if (error != KERN_SUCCESS) {
  530                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  531                         (size > SMALL_PIPE_SIZE)) {
  532                         size = SMALL_PIPE_SIZE;
  533                         pipefragretry++;
  534                         goto retry;
  535                 }
  536                 if (cpipe->pipe_buffer.buffer == NULL) {
  537                         pipeallocfail++;
  538                         if (ppsratecheck(&lastfail, &curfail, 1))
  539                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  540                 } else {
  541                         piperesizefail++;
  542                 }
  543                 return (ENOMEM);
  544         }
  545 
  546         /* copy data, then free old resources if we're resizing */
  547         if (cnt > 0) {
  548                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  549                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  550                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  551                                 buffer, firstseg);
  552                         if ((cnt - firstseg) > 0)
  553                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  554                                         cpipe->pipe_buffer.in);
  555                 } else {
  556                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  557                                 buffer, cnt);
  558                 }
  559         }
  560         pipe_free_kmem(cpipe);
  561         cpipe->pipe_buffer.buffer = buffer;
  562         cpipe->pipe_buffer.size = size;
  563         cpipe->pipe_buffer.in = cnt;
  564         cpipe->pipe_buffer.out = 0;
  565         cpipe->pipe_buffer.cnt = cnt;
  566         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  567         return (0);
  568 }
  569 
  570 /*
  571  * Wrapper for pipespace_new() that performs locking assertions.
  572  */
  573 static int
  574 pipespace(cpipe, size)
  575         struct pipe *cpipe;
  576         int size;
  577 {
  578 
  579         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  580                 ("Unlocked pipe passed to pipespace"));
  581         return (pipespace_new(cpipe, size));
  582 }
  583 
  584 /*
  585  * lock a pipe for I/O, blocking other access
  586  */
  587 static __inline int
  588 pipelock(cpipe, catch)
  589         struct pipe *cpipe;
  590         int catch;
  591 {
  592         int error;
  593 
  594         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  595         while (cpipe->pipe_state & PIPE_LOCKFL) {
  596                 cpipe->pipe_state |= PIPE_LWANT;
  597                 error = msleep(cpipe, PIPE_MTX(cpipe),
  598                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  599                     "pipelk", 0);
  600                 if (error != 0)
  601                         return (error);
  602         }
  603         cpipe->pipe_state |= PIPE_LOCKFL;
  604         return (0);
  605 }
  606 
  607 /*
  608  * unlock a pipe I/O lock
  609  */
  610 static __inline void
  611 pipeunlock(cpipe)
  612         struct pipe *cpipe;
  613 {
  614 
  615         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  616         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  617                 ("Unlocked pipe passed to pipeunlock"));
  618         cpipe->pipe_state &= ~PIPE_LOCKFL;
  619         if (cpipe->pipe_state & PIPE_LWANT) {
  620                 cpipe->pipe_state &= ~PIPE_LWANT;
  621                 wakeup(cpipe);
  622         }
  623 }
  624 
  625 void
  626 pipeselwakeup(cpipe)
  627         struct pipe *cpipe;
  628 {
  629 
  630         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  631         if (cpipe->pipe_state & PIPE_SEL) {
  632                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  633                 if (!SEL_WAITING(&cpipe->pipe_sel))
  634                         cpipe->pipe_state &= ~PIPE_SEL;
  635         }
  636         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  637                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  638         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  639 }
  640 
  641 /*
  642  * Initialize and allocate VM and memory for pipe.  The structure
  643  * will start out zero'd from the ctor, so we just manage the kmem.
  644  */
  645 static int
  646 pipe_create(pipe, backing)
  647         struct pipe *pipe;
  648         int backing;
  649 {
  650         int error;
  651 
  652         if (backing) {
  653                 if (amountpipekva > maxpipekva / 2)
  654                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  655                 else
  656                         error = pipespace_new(pipe, PIPE_SIZE);
  657         } else {
  658                 /* If we're not backing this pipe, no need to do anything. */
  659                 error = 0;
  660         }
  661         pipe->pipe_ino = -1;
  662         return (error);
  663 }
  664 
  665 /* ARGSUSED */
  666 static int
  667 pipe_read(fp, uio, active_cred, flags, td)
  668         struct file *fp;
  669         struct uio *uio;
  670         struct ucred *active_cred;
  671         struct thread *td;
  672         int flags;
  673 {
  674         struct pipe *rpipe;
  675         int error;
  676         int nread = 0;
  677         int size;
  678 
  679         rpipe = fp->f_data;
  680         PIPE_LOCK(rpipe);
  681         ++rpipe->pipe_busy;
  682         error = pipelock(rpipe, 1);
  683         if (error)
  684                 goto unlocked_error;
  685 
  686 #ifdef MAC
  687         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  688         if (error)
  689                 goto locked_error;
  690 #endif
  691         if (amountpipekva > (3 * maxpipekva) / 4) {
  692                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  693                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  694                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  695                         (piperesizeallowed == 1)) {
  696                         PIPE_UNLOCK(rpipe);
  697                         pipespace(rpipe, SMALL_PIPE_SIZE);
  698                         PIPE_LOCK(rpipe);
  699                 }
  700         }
  701 
  702         while (uio->uio_resid) {
  703                 /*
  704                  * normal pipe buffer receive
  705                  */
  706                 if (rpipe->pipe_buffer.cnt > 0) {
  707                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  708                         if (size > rpipe->pipe_buffer.cnt)
  709                                 size = rpipe->pipe_buffer.cnt;
  710                         if (size > uio->uio_resid)
  711                                 size = uio->uio_resid;
  712 
  713                         PIPE_UNLOCK(rpipe);
  714                         error = uiomove(
  715                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  716                             size, uio);
  717                         PIPE_LOCK(rpipe);
  718                         if (error)
  719                                 break;
  720 
  721                         rpipe->pipe_buffer.out += size;
  722                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  723                                 rpipe->pipe_buffer.out = 0;
  724 
  725                         rpipe->pipe_buffer.cnt -= size;
  726 
  727                         /*
  728                          * If there is no more to read in the pipe, reset
  729                          * its pointers to the beginning.  This improves
  730                          * cache hit stats.
  731                          */
  732                         if (rpipe->pipe_buffer.cnt == 0) {
  733                                 rpipe->pipe_buffer.in = 0;
  734                                 rpipe->pipe_buffer.out = 0;
  735                         }
  736                         nread += size;
  737 #ifndef PIPE_NODIRECT
  738                 /*
  739                  * Direct copy, bypassing a kernel buffer.
  740                  */
  741                 } else if ((size = rpipe->pipe_map.cnt) &&
  742                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  743                         if (size > uio->uio_resid)
  744                                 size = (u_int) uio->uio_resid;
  745 
  746                         PIPE_UNLOCK(rpipe);
  747                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  748                             rpipe->pipe_map.pos, size, uio);
  749                         PIPE_LOCK(rpipe);
  750                         if (error)
  751                                 break;
  752                         nread += size;
  753                         rpipe->pipe_map.pos += size;
  754                         rpipe->pipe_map.cnt -= size;
  755                         if (rpipe->pipe_map.cnt == 0) {
  756                                 rpipe->pipe_state &= ~(PIPE_DIRECTW|PIPE_WANTW);
  757                                 wakeup(rpipe);
  758                         }
  759 #endif
  760                 } else {
  761                         /*
  762                          * detect EOF condition
  763                          * read returns 0 on EOF, no need to set error
  764                          */
  765                         if (rpipe->pipe_state & PIPE_EOF)
  766                                 break;
  767 
  768                         /*
  769                          * If the "write-side" has been blocked, wake it up now.
  770                          */
  771                         if (rpipe->pipe_state & PIPE_WANTW) {
  772                                 rpipe->pipe_state &= ~PIPE_WANTW;
  773                                 wakeup(rpipe);
  774                         }
  775 
  776                         /*
  777                          * Break if some data was read.
  778                          */
  779                         if (nread > 0)
  780                                 break;
  781 
  782                         /*
  783                          * Unlock the pipe buffer for our remaining processing.
  784                          * We will either break out with an error or we will
  785                          * sleep and relock to loop.
  786                          */
  787                         pipeunlock(rpipe);
  788 
  789                         /*
  790                          * Handle non-blocking mode operation or
  791                          * wait for more data.
  792                          */
  793                         if (fp->f_flag & FNONBLOCK) {
  794                                 error = EAGAIN;
  795                         } else {
  796                                 rpipe->pipe_state |= PIPE_WANTR;
  797                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  798                                     PRIBIO | PCATCH,
  799                                     "piperd", 0)) == 0)
  800                                         error = pipelock(rpipe, 1);
  801                         }
  802                         if (error)
  803                                 goto unlocked_error;
  804                 }
  805         }
  806 #ifdef MAC
  807 locked_error:
  808 #endif
  809         pipeunlock(rpipe);
  810 
  811         /* XXX: should probably do this before getting any locks. */
  812         if (error == 0)
  813                 vfs_timestamp(&rpipe->pipe_atime);
  814 unlocked_error:
  815         --rpipe->pipe_busy;
  816 
  817         /*
  818          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  819          */
  820         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  821                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  822                 wakeup(rpipe);
  823         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  824                 /*
  825                  * Handle write blocking hysteresis.
  826                  */
  827                 if (rpipe->pipe_state & PIPE_WANTW) {
  828                         rpipe->pipe_state &= ~PIPE_WANTW;
  829                         wakeup(rpipe);
  830                 }
  831         }
  832 
  833         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  834                 pipeselwakeup(rpipe);
  835 
  836         PIPE_UNLOCK(rpipe);
  837         return (error);
  838 }
  839 
  840 #ifndef PIPE_NODIRECT
  841 /*
  842  * Map the sending processes' buffer into kernel space and wire it.
  843  * This is similar to a physical write operation.
  844  */
  845 static int
  846 pipe_build_write_buffer(wpipe, uio)
  847         struct pipe *wpipe;
  848         struct uio *uio;
  849 {
  850         u_int size;
  851         int i;
  852 
  853         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  854         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  855                 ("Clone attempt on non-direct write pipe!"));
  856 
  857         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
  858                 size = wpipe->pipe_buffer.size;
  859         else
  860                 size = uio->uio_iov->iov_len;
  861 
  862         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  863             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  864             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  865                 return (EFAULT);
  866 
  867 /*
  868  * set up the control block
  869  */
  870         wpipe->pipe_map.npages = i;
  871         wpipe->pipe_map.pos =
  872             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  873         wpipe->pipe_map.cnt = size;
  874 
  875 /*
  876  * and update the uio data
  877  */
  878 
  879         uio->uio_iov->iov_len -= size;
  880         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  881         if (uio->uio_iov->iov_len == 0)
  882                 uio->uio_iov++;
  883         uio->uio_resid -= size;
  884         uio->uio_offset += size;
  885         return (0);
  886 }
  887 
  888 /*
  889  * unmap and unwire the process buffer
  890  */
  891 static void
  892 pipe_destroy_write_buffer(wpipe)
  893         struct pipe *wpipe;
  894 {
  895 
  896         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  897         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  898         wpipe->pipe_map.npages = 0;
  899 }
  900 
  901 /*
  902  * In the case of a signal, the writing process might go away.  This
  903  * code copies the data into the circular buffer so that the source
  904  * pages can be freed without loss of data.
  905  */
  906 static void
  907 pipe_clone_write_buffer(wpipe)
  908         struct pipe *wpipe;
  909 {
  910         struct uio uio;
  911         struct iovec iov;
  912         int size;
  913         int pos;
  914 
  915         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  916         size = wpipe->pipe_map.cnt;
  917         pos = wpipe->pipe_map.pos;
  918 
  919         wpipe->pipe_buffer.in = size;
  920         wpipe->pipe_buffer.out = 0;
  921         wpipe->pipe_buffer.cnt = size;
  922         wpipe->pipe_state &= ~PIPE_DIRECTW;
  923 
  924         PIPE_UNLOCK(wpipe);
  925         iov.iov_base = wpipe->pipe_buffer.buffer;
  926         iov.iov_len = size;
  927         uio.uio_iov = &iov;
  928         uio.uio_iovcnt = 1;
  929         uio.uio_offset = 0;
  930         uio.uio_resid = size;
  931         uio.uio_segflg = UIO_SYSSPACE;
  932         uio.uio_rw = UIO_READ;
  933         uio.uio_td = curthread;
  934         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  935         PIPE_LOCK(wpipe);
  936         pipe_destroy_write_buffer(wpipe);
  937 }
  938 
  939 /*
  940  * This implements the pipe buffer write mechanism.  Note that only
  941  * a direct write OR a normal pipe write can be pending at any given time.
  942  * If there are any characters in the pipe buffer, the direct write will
  943  * be deferred until the receiving process grabs all of the bytes from
  944  * the pipe buffer.  Then the direct mapping write is set-up.
  945  */
  946 static int
  947 pipe_direct_write(wpipe, uio)
  948         struct pipe *wpipe;
  949         struct uio *uio;
  950 {
  951         int error;
  952 
  953 retry:
  954         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  955         error = pipelock(wpipe, 1);
  956         if (wpipe->pipe_state & PIPE_EOF)
  957                 error = EPIPE;
  958         if (error) {
  959                 pipeunlock(wpipe);
  960                 goto error1;
  961         }
  962         while (wpipe->pipe_state & PIPE_DIRECTW) {
  963                 if (wpipe->pipe_state & PIPE_WANTR) {
  964                         wpipe->pipe_state &= ~PIPE_WANTR;
  965                         wakeup(wpipe);
  966                 }
  967                 pipeselwakeup(wpipe);
  968                 wpipe->pipe_state |= PIPE_WANTW;
  969                 pipeunlock(wpipe);
  970                 error = msleep(wpipe, PIPE_MTX(wpipe),
  971                     PRIBIO | PCATCH, "pipdww", 0);
  972                 if (error)
  973                         goto error1;
  974                 else
  975                         goto retry;
  976         }
  977         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  978         if (wpipe->pipe_buffer.cnt > 0) {
  979                 if (wpipe->pipe_state & PIPE_WANTR) {
  980                         wpipe->pipe_state &= ~PIPE_WANTR;
  981                         wakeup(wpipe);
  982                 }
  983                 pipeselwakeup(wpipe);
  984                 wpipe->pipe_state |= PIPE_WANTW;
  985                 pipeunlock(wpipe);
  986                 error = msleep(wpipe, PIPE_MTX(wpipe),
  987                     PRIBIO | PCATCH, "pipdwc", 0);
  988                 if (error)
  989                         goto error1;
  990                 else
  991                         goto retry;
  992         }
  993 
  994         wpipe->pipe_state |= PIPE_DIRECTW;
  995 
  996         PIPE_UNLOCK(wpipe);
  997         error = pipe_build_write_buffer(wpipe, uio);
  998         PIPE_LOCK(wpipe);
  999         if (error) {
 1000                 wpipe->pipe_state &= ~PIPE_DIRECTW;
 1001                 pipeunlock(wpipe);
 1002                 goto error1;
 1003         }
 1004 
 1005         error = 0;
 1006         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
 1007                 if (wpipe->pipe_state & PIPE_EOF) {
 1008                         pipe_destroy_write_buffer(wpipe);
 1009                         pipeselwakeup(wpipe);
 1010                         pipeunlock(wpipe);
 1011                         error = EPIPE;
 1012                         goto error1;
 1013                 }
 1014                 if (wpipe->pipe_state & PIPE_WANTR) {
 1015                         wpipe->pipe_state &= ~PIPE_WANTR;
 1016                         wakeup(wpipe);
 1017                 }
 1018                 pipeselwakeup(wpipe);
 1019                 wpipe->pipe_state |= PIPE_WANTW;
 1020                 pipeunlock(wpipe);
 1021                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
 1022                     "pipdwt", 0);
 1023                 pipelock(wpipe, 0);
 1024         }
 1025 
 1026         if (wpipe->pipe_state & PIPE_EOF)
 1027                 error = EPIPE;
 1028         if (wpipe->pipe_state & PIPE_DIRECTW) {
 1029                 /*
 1030                  * this bit of trickery substitutes a kernel buffer for
 1031                  * the process that might be going away.
 1032                  */
 1033                 pipe_clone_write_buffer(wpipe);
 1034         } else {
 1035                 pipe_destroy_write_buffer(wpipe);
 1036         }
 1037         pipeunlock(wpipe);
 1038         return (error);
 1039 
 1040 error1:
 1041         wakeup(wpipe);
 1042         return (error);
 1043 }
 1044 #endif
 1045 
 1046 static int
 1047 pipe_write(fp, uio, active_cred, flags, td)
 1048         struct file *fp;
 1049         struct uio *uio;
 1050         struct ucred *active_cred;
 1051         struct thread *td;
 1052         int flags;
 1053 {
 1054         int error = 0;
 1055         int desiredsize;
 1056         ssize_t orig_resid;
 1057         struct pipe *wpipe, *rpipe;
 1058 
 1059         rpipe = fp->f_data;
 1060         wpipe = PIPE_PEER(rpipe);
 1061         PIPE_LOCK(rpipe);
 1062         error = pipelock(wpipe, 1);
 1063         if (error) {
 1064                 PIPE_UNLOCK(rpipe);
 1065                 return (error);
 1066         }
 1067         /*
 1068          * detect loss of pipe read side, issue SIGPIPE if lost.
 1069          */
 1070         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1071             (wpipe->pipe_state & PIPE_EOF)) {
 1072                 pipeunlock(wpipe);
 1073                 PIPE_UNLOCK(rpipe);
 1074                 return (EPIPE);
 1075         }
 1076 #ifdef MAC
 1077         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
 1078         if (error) {
 1079                 pipeunlock(wpipe);
 1080                 PIPE_UNLOCK(rpipe);
 1081                 return (error);
 1082         }
 1083 #endif
 1084         ++wpipe->pipe_busy;
 1085 
 1086         /* Choose a larger size if it's advantageous */
 1087         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1088         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1089                 if (piperesizeallowed != 1)
 1090                         break;
 1091                 if (amountpipekva > maxpipekva / 2)
 1092                         break;
 1093                 if (desiredsize == BIG_PIPE_SIZE)
 1094                         break;
 1095                 desiredsize = desiredsize * 2;
 1096         }
 1097 
 1098         /* Choose a smaller size if we're in a OOM situation */
 1099         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1100                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1101                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1102                 (piperesizeallowed == 1))
 1103                 desiredsize = SMALL_PIPE_SIZE;
 1104 
 1105         /* Resize if the above determined that a new size was necessary */
 1106         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1107                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1108                 PIPE_UNLOCK(wpipe);
 1109                 pipespace(wpipe, desiredsize);
 1110                 PIPE_LOCK(wpipe);
 1111         }
 1112         if (wpipe->pipe_buffer.size == 0) {
 1113                 /*
 1114                  * This can only happen for reverse direction use of pipes
 1115                  * in a complete OOM situation.
 1116                  */
 1117                 error = ENOMEM;
 1118                 --wpipe->pipe_busy;
 1119                 pipeunlock(wpipe);
 1120                 PIPE_UNLOCK(wpipe);
 1121                 return (error);
 1122         }
 1123 
 1124         pipeunlock(wpipe);
 1125 
 1126         orig_resid = uio->uio_resid;
 1127 
 1128         while (uio->uio_resid) {
 1129                 int space;
 1130 
 1131                 pipelock(wpipe, 0);
 1132                 if (wpipe->pipe_state & PIPE_EOF) {
 1133                         pipeunlock(wpipe);
 1134                         error = EPIPE;
 1135                         break;
 1136                 }
 1137 #ifndef PIPE_NODIRECT
 1138                 /*
 1139                  * If the transfer is large, we can gain performance if
 1140                  * we do process-to-process copies directly.
 1141                  * If the write is non-blocking, we don't use the
 1142                  * direct write mechanism.
 1143                  *
 1144                  * The direct write mechanism will detect the reader going
 1145                  * away on us.
 1146                  */
 1147                 if (uio->uio_segflg == UIO_USERSPACE &&
 1148                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1149                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1150                     (fp->f_flag & FNONBLOCK) == 0) {
 1151                         pipeunlock(wpipe);
 1152                         error = pipe_direct_write(wpipe, uio);
 1153                         if (error)
 1154                                 break;
 1155                         continue;
 1156                 }
 1157 #endif
 1158 
 1159                 /*
 1160                  * Pipe buffered writes cannot be coincidental with
 1161                  * direct writes.  We wait until the currently executing
 1162                  * direct write is completed before we start filling the
 1163                  * pipe buffer.  We break out if a signal occurs or the
 1164                  * reader goes away.
 1165                  */
 1166                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1167                         if (wpipe->pipe_state & PIPE_WANTR) {
 1168                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1169                                 wakeup(wpipe);
 1170                         }
 1171                         pipeselwakeup(wpipe);
 1172                         wpipe->pipe_state |= PIPE_WANTW;
 1173                         pipeunlock(wpipe);
 1174                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1175                             "pipbww", 0);
 1176                         if (error)
 1177                                 break;
 1178                         else
 1179                                 continue;
 1180                 }
 1181 
 1182                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1183 
 1184                 /* Writes of size <= PIPE_BUF must be atomic. */
 1185                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1186                         space = 0;
 1187 
 1188                 if (space > 0) {
 1189                         int size;       /* Transfer size */
 1190                         int segsize;    /* first segment to transfer */
 1191 
 1192                         /*
 1193                          * Transfer size is minimum of uio transfer
 1194                          * and free space in pipe buffer.
 1195                          */
 1196                         if (space > uio->uio_resid)
 1197                                 size = uio->uio_resid;
 1198                         else
 1199                                 size = space;
 1200                         /*
 1201                          * First segment to transfer is minimum of
 1202                          * transfer size and contiguous space in
 1203                          * pipe buffer.  If first segment to transfer
 1204                          * is less than the transfer size, we've got
 1205                          * a wraparound in the buffer.
 1206                          */
 1207                         segsize = wpipe->pipe_buffer.size -
 1208                                 wpipe->pipe_buffer.in;
 1209                         if (segsize > size)
 1210                                 segsize = size;
 1211 
 1212                         /* Transfer first segment */
 1213 
 1214                         PIPE_UNLOCK(rpipe);
 1215                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1216                                         segsize, uio);
 1217                         PIPE_LOCK(rpipe);
 1218 
 1219                         if (error == 0 && segsize < size) {
 1220                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1221                                         wpipe->pipe_buffer.size,
 1222                                         ("Pipe buffer wraparound disappeared"));
 1223                                 /*
 1224                                  * Transfer remaining part now, to
 1225                                  * support atomic writes.  Wraparound
 1226                                  * happened.
 1227                                  */
 1228 
 1229                                 PIPE_UNLOCK(rpipe);
 1230                                 error = uiomove(
 1231                                     &wpipe->pipe_buffer.buffer[0],
 1232                                     size - segsize, uio);
 1233                                 PIPE_LOCK(rpipe);
 1234                         }
 1235                         if (error == 0) {
 1236                                 wpipe->pipe_buffer.in += size;
 1237                                 if (wpipe->pipe_buffer.in >=
 1238                                     wpipe->pipe_buffer.size) {
 1239                                         KASSERT(wpipe->pipe_buffer.in ==
 1240                                                 size - segsize +
 1241                                                 wpipe->pipe_buffer.size,
 1242                                                 ("Expected wraparound bad"));
 1243                                         wpipe->pipe_buffer.in = size - segsize;
 1244                                 }
 1245 
 1246                                 wpipe->pipe_buffer.cnt += size;
 1247                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1248                                         wpipe->pipe_buffer.size,
 1249                                         ("Pipe buffer overflow"));
 1250                         }
 1251                         pipeunlock(wpipe);
 1252                         if (error != 0)
 1253                                 break;
 1254                 } else {
 1255                         /*
 1256                          * If the "read-side" has been blocked, wake it up now.
 1257                          */
 1258                         if (wpipe->pipe_state & PIPE_WANTR) {
 1259                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1260                                 wakeup(wpipe);
 1261                         }
 1262 
 1263                         /*
 1264                          * don't block on non-blocking I/O
 1265                          */
 1266                         if (fp->f_flag & FNONBLOCK) {
 1267                                 error = EAGAIN;
 1268                                 pipeunlock(wpipe);
 1269                                 break;
 1270                         }
 1271 
 1272                         /*
 1273                          * We have no more space and have something to offer,
 1274                          * wake up select/poll.
 1275                          */
 1276                         pipeselwakeup(wpipe);
 1277 
 1278                         wpipe->pipe_state |= PIPE_WANTW;
 1279                         pipeunlock(wpipe);
 1280                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1281                             PRIBIO | PCATCH, "pipewr", 0);
 1282                         if (error != 0)
 1283                                 break;
 1284                 }
 1285         }
 1286 
 1287         pipelock(wpipe, 0);
 1288         --wpipe->pipe_busy;
 1289 
 1290         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1291                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1292                 wakeup(wpipe);
 1293         } else if (wpipe->pipe_buffer.cnt > 0) {
 1294                 /*
 1295                  * If we have put any characters in the buffer, we wake up
 1296                  * the reader.
 1297                  */
 1298                 if (wpipe->pipe_state & PIPE_WANTR) {
 1299                         wpipe->pipe_state &= ~PIPE_WANTR;
 1300                         wakeup(wpipe);
 1301                 }
 1302         }
 1303 
 1304         /*
 1305          * Don't return EPIPE if I/O was successful
 1306          */
 1307         if ((wpipe->pipe_buffer.cnt == 0) &&
 1308             (uio->uio_resid == 0) &&
 1309             (error == EPIPE)) {
 1310                 error = 0;
 1311         }
 1312 
 1313         if (error == 0)
 1314                 vfs_timestamp(&wpipe->pipe_mtime);
 1315 
 1316         /*
 1317          * We have something to offer,
 1318          * wake up select/poll.
 1319          */
 1320         if (wpipe->pipe_buffer.cnt)
 1321                 pipeselwakeup(wpipe);
 1322 
 1323         pipeunlock(wpipe);
 1324         PIPE_UNLOCK(rpipe);
 1325         return (error);
 1326 }
 1327 
 1328 /* ARGSUSED */
 1329 static int
 1330 pipe_truncate(fp, length, active_cred, td)
 1331         struct file *fp;
 1332         off_t length;
 1333         struct ucred *active_cred;
 1334         struct thread *td;
 1335 {
 1336 
 1337         /* For named pipes call the vnode operation. */
 1338         if (fp->f_vnode != NULL)
 1339                 return (vnops.fo_truncate(fp, length, active_cred, td));
 1340         return (EINVAL);
 1341 }
 1342 
 1343 /*
 1344  * we implement a very minimal set of ioctls for compatibility with sockets.
 1345  */
 1346 static int
 1347 pipe_ioctl(fp, cmd, data, active_cred, td)
 1348         struct file *fp;
 1349         u_long cmd;
 1350         void *data;
 1351         struct ucred *active_cred;
 1352         struct thread *td;
 1353 {
 1354         struct pipe *mpipe = fp->f_data;
 1355         int error;
 1356 
 1357         PIPE_LOCK(mpipe);
 1358 
 1359 #ifdef MAC
 1360         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1361         if (error) {
 1362                 PIPE_UNLOCK(mpipe);
 1363                 return (error);
 1364         }
 1365 #endif
 1366 
 1367         error = 0;
 1368         switch (cmd) {
 1369 
 1370         case FIONBIO:
 1371                 break;
 1372 
 1373         case FIOASYNC:
 1374                 if (*(int *)data) {
 1375                         mpipe->pipe_state |= PIPE_ASYNC;
 1376                 } else {
 1377                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1378                 }
 1379                 break;
 1380 
 1381         case FIONREAD:
 1382                 if (!(fp->f_flag & FREAD)) {
 1383                         *(int *)data = 0;
 1384                         PIPE_UNLOCK(mpipe);
 1385                         return (0);
 1386                 }
 1387                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1388                         *(int *)data = mpipe->pipe_map.cnt;
 1389                 else
 1390                         *(int *)data = mpipe->pipe_buffer.cnt;
 1391                 break;
 1392 
 1393         case FIOSETOWN:
 1394                 PIPE_UNLOCK(mpipe);
 1395                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1396                 goto out_unlocked;
 1397 
 1398         case FIOGETOWN:
 1399                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1400                 break;
 1401 
 1402         /* This is deprecated, FIOSETOWN should be used instead. */
 1403         case TIOCSPGRP:
 1404                 PIPE_UNLOCK(mpipe);
 1405                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1406                 goto out_unlocked;
 1407 
 1408         /* This is deprecated, FIOGETOWN should be used instead. */
 1409         case TIOCGPGRP:
 1410                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1411                 break;
 1412 
 1413         default:
 1414                 error = ENOTTY;
 1415                 break;
 1416         }
 1417         PIPE_UNLOCK(mpipe);
 1418 out_unlocked:
 1419         return (error);
 1420 }
 1421 
 1422 static int
 1423 pipe_poll(fp, events, active_cred, td)
 1424         struct file *fp;
 1425         int events;
 1426         struct ucred *active_cred;
 1427         struct thread *td;
 1428 {
 1429         struct pipe *rpipe;
 1430         struct pipe *wpipe;
 1431         int levents, revents;
 1432 #ifdef MAC
 1433         int error;
 1434 #endif
 1435 
 1436         revents = 0;
 1437         rpipe = fp->f_data;
 1438         wpipe = PIPE_PEER(rpipe);
 1439         PIPE_LOCK(rpipe);
 1440 #ifdef MAC
 1441         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1442         if (error)
 1443                 goto locked_error;
 1444 #endif
 1445         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
 1446                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1447                     (rpipe->pipe_buffer.cnt > 0))
 1448                         revents |= events & (POLLIN | POLLRDNORM);
 1449 
 1450         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
 1451                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1452                     (wpipe->pipe_state & PIPE_EOF) ||
 1453                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1454                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
 1455                          wpipe->pipe_buffer.size == 0)))
 1456                         revents |= events & (POLLOUT | POLLWRNORM);
 1457 
 1458         levents = events &
 1459             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
 1460         if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
 1461             fp->f_seqcount == rpipe->pipe_wgen)
 1462                 events |= POLLINIGNEOF;
 1463 
 1464         if ((events & POLLINIGNEOF) == 0) {
 1465                 if (rpipe->pipe_state & PIPE_EOF) {
 1466                         revents |= (events & (POLLIN | POLLRDNORM));
 1467                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1468                             (wpipe->pipe_state & PIPE_EOF))
 1469                                 revents |= POLLHUP;
 1470                 }
 1471         }
 1472 
 1473         if (revents == 0) {
 1474                 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
 1475                         selrecord(td, &rpipe->pipe_sel);
 1476                         if (SEL_WAITING(&rpipe->pipe_sel))
 1477                                 rpipe->pipe_state |= PIPE_SEL;
 1478                 }
 1479 
 1480                 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
 1481                         selrecord(td, &wpipe->pipe_sel);
 1482                         if (SEL_WAITING(&wpipe->pipe_sel))
 1483                                 wpipe->pipe_state |= PIPE_SEL;
 1484                 }
 1485         }
 1486 #ifdef MAC
 1487 locked_error:
 1488 #endif
 1489         PIPE_UNLOCK(rpipe);
 1490 
 1491         return (revents);
 1492 }
 1493 
 1494 /*
 1495  * We shouldn't need locks here as we're doing a read and this should
 1496  * be a natural race.
 1497  */
 1498 static int
 1499 pipe_stat(fp, ub, active_cred, td)
 1500         struct file *fp;
 1501         struct stat *ub;
 1502         struct ucred *active_cred;
 1503         struct thread *td;
 1504 {
 1505         struct pipe *pipe;
 1506         int new_unr;
 1507 #ifdef MAC
 1508         int error;
 1509 #endif
 1510 
 1511         pipe = fp->f_data;
 1512         PIPE_LOCK(pipe);
 1513 #ifdef MAC
 1514         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1515         if (error) {
 1516                 PIPE_UNLOCK(pipe);
 1517                 return (error);
 1518         }
 1519 #endif
 1520 
 1521         /* For named pipes ask the underlying filesystem. */
 1522         if (pipe->pipe_state & PIPE_NAMED) {
 1523                 PIPE_UNLOCK(pipe);
 1524                 return (vnops.fo_stat(fp, ub, active_cred, td));
 1525         }
 1526 
 1527         /*
 1528          * Lazily allocate an inode number for the pipe.  Most pipe
 1529          * users do not call fstat(2) on the pipe, which means that
 1530          * postponing the inode allocation until it is must be
 1531          * returned to userland is useful.  If alloc_unr failed,
 1532          * assign st_ino zero instead of returning an error.
 1533          * Special pipe_ino values:
 1534          *  -1 - not yet initialized;
 1535          *  0  - alloc_unr failed, return 0 as st_ino forever.
 1536          */
 1537         if (pipe->pipe_ino == (ino_t)-1) {
 1538                 new_unr = alloc_unr(pipeino_unr);
 1539                 if (new_unr != -1)
 1540                         pipe->pipe_ino = new_unr;
 1541                 else
 1542                         pipe->pipe_ino = 0;
 1543         }
 1544         PIPE_UNLOCK(pipe);
 1545 
 1546         bzero(ub, sizeof(*ub));
 1547         ub->st_mode = S_IFIFO;
 1548         ub->st_blksize = PAGE_SIZE;
 1549         if (pipe->pipe_state & PIPE_DIRECTW)
 1550                 ub->st_size = pipe->pipe_map.cnt;
 1551         else
 1552                 ub->st_size = pipe->pipe_buffer.cnt;
 1553         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1554         ub->st_atim = pipe->pipe_atime;
 1555         ub->st_mtim = pipe->pipe_mtime;
 1556         ub->st_ctim = pipe->pipe_ctime;
 1557         ub->st_uid = fp->f_cred->cr_uid;
 1558         ub->st_gid = fp->f_cred->cr_gid;
 1559         ub->st_dev = pipedev_ino;
 1560         ub->st_ino = pipe->pipe_ino;
 1561         /*
 1562          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1563          */
 1564         return (0);
 1565 }
 1566 
 1567 /* ARGSUSED */
 1568 static int
 1569 pipe_close(fp, td)
 1570         struct file *fp;
 1571         struct thread *td;
 1572 {
 1573 
 1574         if (fp->f_vnode != NULL) 
 1575                 return vnops.fo_close(fp, td);
 1576         fp->f_ops = &badfileops;
 1577         pipe_dtor(fp->f_data);
 1578         fp->f_data = NULL;
 1579         return (0);
 1580 }
 1581 
 1582 static int
 1583 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
 1584 {
 1585         struct pipe *cpipe;
 1586         int error;
 1587 
 1588         cpipe = fp->f_data;
 1589         if (cpipe->pipe_state & PIPE_NAMED)
 1590                 error = vn_chmod(fp, mode, active_cred, td);
 1591         else
 1592                 error = invfo_chmod(fp, mode, active_cred, td);
 1593         return (error);
 1594 }
 1595 
 1596 static int
 1597 pipe_chown(fp, uid, gid, active_cred, td)
 1598         struct file *fp;
 1599         uid_t uid;
 1600         gid_t gid;
 1601         struct ucred *active_cred;
 1602         struct thread *td;
 1603 {
 1604         struct pipe *cpipe;
 1605         int error;
 1606 
 1607         cpipe = fp->f_data;
 1608         if (cpipe->pipe_state & PIPE_NAMED)
 1609                 error = vn_chown(fp, uid, gid, active_cred, td);
 1610         else
 1611                 error = invfo_chown(fp, uid, gid, active_cred, td);
 1612         return (error);
 1613 }
 1614 
 1615 static void
 1616 pipe_free_kmem(cpipe)
 1617         struct pipe *cpipe;
 1618 {
 1619 
 1620         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1621             ("pipe_free_kmem: pipe mutex locked"));
 1622 
 1623         if (cpipe->pipe_buffer.buffer != NULL) {
 1624                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1625                 vm_map_remove(pipe_map,
 1626                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1627                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1628                 cpipe->pipe_buffer.buffer = NULL;
 1629         }
 1630 #ifndef PIPE_NODIRECT
 1631         {
 1632                 cpipe->pipe_map.cnt = 0;
 1633                 cpipe->pipe_map.pos = 0;
 1634                 cpipe->pipe_map.npages = 0;
 1635         }
 1636 #endif
 1637 }
 1638 
 1639 /*
 1640  * shutdown the pipe
 1641  */
 1642 static void
 1643 pipeclose(cpipe)
 1644         struct pipe *cpipe;
 1645 {
 1646         struct pipepair *pp;
 1647         struct pipe *ppipe;
 1648 
 1649         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1650 
 1651         PIPE_LOCK(cpipe);
 1652         pipelock(cpipe, 0);
 1653         pp = cpipe->pipe_pair;
 1654 
 1655         pipeselwakeup(cpipe);
 1656 
 1657         /*
 1658          * If the other side is blocked, wake it up saying that
 1659          * we want to close it down.
 1660          */
 1661         cpipe->pipe_state |= PIPE_EOF;
 1662         while (cpipe->pipe_busy) {
 1663                 wakeup(cpipe);
 1664                 cpipe->pipe_state |= PIPE_WANT;
 1665                 pipeunlock(cpipe);
 1666                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1667                 pipelock(cpipe, 0);
 1668         }
 1669 
 1670 
 1671         /*
 1672          * Disconnect from peer, if any.
 1673          */
 1674         ppipe = cpipe->pipe_peer;
 1675         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1676                 pipeselwakeup(ppipe);
 1677 
 1678                 ppipe->pipe_state |= PIPE_EOF;
 1679                 wakeup(ppipe);
 1680                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1681         }
 1682 
 1683         /*
 1684          * Mark this endpoint as free.  Release kmem resources.  We
 1685          * don't mark this endpoint as unused until we've finished
 1686          * doing that, or the pipe might disappear out from under
 1687          * us.
 1688          */
 1689         PIPE_UNLOCK(cpipe);
 1690         pipe_free_kmem(cpipe);
 1691         PIPE_LOCK(cpipe);
 1692         cpipe->pipe_present = PIPE_CLOSING;
 1693         pipeunlock(cpipe);
 1694 
 1695         /*
 1696          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1697          * PIPE_FINALIZED, that allows other end to free the
 1698          * pipe_pair, only after the knotes are completely dismantled.
 1699          */
 1700         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1701         cpipe->pipe_present = PIPE_FINALIZED;
 1702         seldrain(&cpipe->pipe_sel);
 1703         knlist_destroy(&cpipe->pipe_sel.si_note);
 1704 
 1705         /*
 1706          * If both endpoints are now closed, release the memory for the
 1707          * pipe pair.  If not, unlock.
 1708          */
 1709         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1710                 PIPE_UNLOCK(cpipe);
 1711 #ifdef MAC
 1712                 mac_pipe_destroy(pp);
 1713 #endif
 1714                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1715         } else
 1716                 PIPE_UNLOCK(cpipe);
 1717 }
 1718 
 1719 /*ARGSUSED*/
 1720 static int
 1721 pipe_kqfilter(struct file *fp, struct knote *kn)
 1722 {
 1723         struct pipe *cpipe;
 1724 
 1725         /*
 1726          * If a filter is requested that is not supported by this file
 1727          * descriptor, don't return an error, but also don't ever generate an
 1728          * event.
 1729          */
 1730         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
 1731                 kn->kn_fop = &pipe_nfiltops;
 1732                 return (0);
 1733         }
 1734         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
 1735                 kn->kn_fop = &pipe_nfiltops;
 1736                 return (0);
 1737         }
 1738         cpipe = fp->f_data;
 1739         PIPE_LOCK(cpipe);
 1740         switch (kn->kn_filter) {
 1741         case EVFILT_READ:
 1742                 kn->kn_fop = &pipe_rfiltops;
 1743                 break;
 1744         case EVFILT_WRITE:
 1745                 kn->kn_fop = &pipe_wfiltops;
 1746                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1747                         /* other end of pipe has been closed */
 1748                         PIPE_UNLOCK(cpipe);
 1749                         return (EPIPE);
 1750                 }
 1751                 cpipe = PIPE_PEER(cpipe);
 1752                 break;
 1753         default:
 1754                 PIPE_UNLOCK(cpipe);
 1755                 return (EINVAL);
 1756         }
 1757 
 1758         kn->kn_hook = cpipe; 
 1759         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1760         PIPE_UNLOCK(cpipe);
 1761         return (0);
 1762 }
 1763 
 1764 static void
 1765 filt_pipedetach(struct knote *kn)
 1766 {
 1767         struct pipe *cpipe = kn->kn_hook;
 1768 
 1769         PIPE_LOCK(cpipe);
 1770         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1771         PIPE_UNLOCK(cpipe);
 1772 }
 1773 
 1774 /*ARGSUSED*/
 1775 static int
 1776 filt_piperead(struct knote *kn, long hint)
 1777 {
 1778         struct pipe *rpipe = kn->kn_hook;
 1779         struct pipe *wpipe = rpipe->pipe_peer;
 1780         int ret;
 1781 
 1782         PIPE_LOCK(rpipe);
 1783         kn->kn_data = rpipe->pipe_buffer.cnt;
 1784         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1785                 kn->kn_data = rpipe->pipe_map.cnt;
 1786 
 1787         if ((rpipe->pipe_state & PIPE_EOF) ||
 1788             wpipe->pipe_present != PIPE_ACTIVE ||
 1789             (wpipe->pipe_state & PIPE_EOF)) {
 1790                 kn->kn_flags |= EV_EOF;
 1791                 PIPE_UNLOCK(rpipe);
 1792                 return (1);
 1793         }
 1794         ret = kn->kn_data > 0;
 1795         PIPE_UNLOCK(rpipe);
 1796         return ret;
 1797 }
 1798 
 1799 /*ARGSUSED*/
 1800 static int
 1801 filt_pipewrite(struct knote *kn, long hint)
 1802 {
 1803         struct pipe *wpipe;
 1804    
 1805         wpipe = kn->kn_hook;
 1806         PIPE_LOCK(wpipe);
 1807         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1808             (wpipe->pipe_state & PIPE_EOF)) {
 1809                 kn->kn_data = 0;
 1810                 kn->kn_flags |= EV_EOF;
 1811                 PIPE_UNLOCK(wpipe);
 1812                 return (1);
 1813         }
 1814         kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
 1815             (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
 1816         if (wpipe->pipe_state & PIPE_DIRECTW)
 1817                 kn->kn_data = 0;
 1818 
 1819         PIPE_UNLOCK(wpipe);
 1820         return (kn->kn_data >= PIPE_BUF);
 1821 }
 1822 
 1823 static void
 1824 filt_pipedetach_notsup(struct knote *kn)
 1825 {
 1826 
 1827 }
 1828 
 1829 static int
 1830 filt_pipenotsup(struct knote *kn, long hint)
 1831 {
 1832 
 1833         return (0);
 1834 }

Cache object: 86f9730dc997e3889ad9613752d4a588


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.