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


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

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    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  */
   19 
   20 /*
   21  * This file contains a high-performance replacement for the socket-based
   22  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   23  * all features of sockets, but does do everything that pipes normally
   24  * do.
   25  */
   26 
   27 /*
   28  * This code has two modes of operation, a small write mode and a large
   29  * write mode.  The small write mode acts like conventional pipes with
   30  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   31  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   32  * and PIPE_SIZE in size, the sending process pins the underlying pages in
   33  * memory, and the receiving process copies directly from these pinned pages
   34  * in the sending process.
   35  *
   36  * If the sending process receives a signal, it is possible that it will
   37  * go away, and certainly its address space can change, because control
   38  * is returned back to the user-mode side.  In that case, the pipe code
   39  * arranges to copy the buffer supplied by the user process, to a pageable
   40  * kernel buffer, and the receiving process will grab the data from the
   41  * pageable kernel buffer.  Since signals don't happen all that often,
   42  * the copy operation is normally eliminated.
   43  *
   44  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   45  * happen for small transfers so that the system will not spend all of
   46  * its time context switching.
   47  *
   48  * In order to limit the resource use of pipes, two sysctls exist:
   49  *
   50  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   51  * address space available to us in pipe_map. This value is normally
   52  * autotuned, but may also be loader tuned.
   53  *
   54  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   55  * memory in use by pipes.
   56  *
   57  * Based on how large pipekva is relative to maxpipekva, the following
   58  * will happen:
   59  *
   60  * 0% - 50%:
   61  *     New pipes are given 16K of memory backing, pipes may dynamically
   62  *     grow to as large as 64K where needed.
   63  * 50% - 75%:
   64  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   65  *     existing pipes may NOT grow.
   66  * 75% - 100%:
   67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   68  *     existing pipes will be shrunk down to 4K whenever possible.
   69  *
   70  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   71  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   72  * resize which MUST occur for reverse-direction pipes when they are
   73  * first used.
   74  *
   75  * Additional information about the current state of pipes may be obtained
   76  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   77  * and kern.ipc.piperesizefail.
   78  *
   79  * Locking rules:  There are two locks present here:  A mutex, used via
   80  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   81  * the flag, as mutexes can not persist over uiomove.  The mutex
   82  * exists only to guard access to the flag, and is not in itself a
   83  * locking mechanism.  Also note that there is only a single mutex for
   84  * both directions of a pipe.
   85  *
   86  * As pipelock() may have to sleep before it can acquire the flag, it
   87  * is important to reread all data after a call to pipelock(); everything
   88  * in the structure may have changed.
   89  */
   90 
   91 #include <sys/cdefs.h>
   92 __FBSDID("$FreeBSD: releng/9.2/sys/kern/sys_pipe.c 248532 2013-03-19 20:18:30Z jkim $");
   93 
   94 #include <sys/param.h>
   95 #include <sys/systm.h>
   96 #include <sys/conf.h>
   97 #include <sys/fcntl.h>
   98 #include <sys/file.h>
   99 #include <sys/filedesc.h>
  100 #include <sys/filio.h>
  101 #include <sys/kernel.h>
  102 #include <sys/lock.h>
  103 #include <sys/mutex.h>
  104 #include <sys/ttycom.h>
  105 #include <sys/stat.h>
  106 #include <sys/malloc.h>
  107 #include <sys/poll.h>
  108 #include <sys/selinfo.h>
  109 #include <sys/signalvar.h>
  110 #include <sys/syscallsubr.h>
  111 #include <sys/sysctl.h>
  112 #include <sys/sysproto.h>
  113 #include <sys/pipe.h>
  114 #include <sys/proc.h>
  115 #include <sys/vnode.h>
  116 #include <sys/uio.h>
  117 #include <sys/event.h>
  118 
  119 #include <security/mac/mac_framework.h>
  120 
  121 #include <vm/vm.h>
  122 #include <vm/vm_param.h>
  123 #include <vm/vm_object.h>
  124 #include <vm/vm_kern.h>
  125 #include <vm/vm_extern.h>
  126 #include <vm/pmap.h>
  127 #include <vm/vm_map.h>
  128 #include <vm/vm_page.h>
  129 #include <vm/uma.h>
  130 
  131 /* XXX */
  132 int     do_pipe(struct thread *td, int fildes[2], int flags);
  133 
  134 /*
  135  * Use this define if you want to disable *fancy* VM things.  Expect an
  136  * approx 30% decrease in transfer rate.  This could be useful for
  137  * NetBSD or OpenBSD.
  138  */
  139 /* #define PIPE_NODIRECT */
  140 
  141 /*
  142  * interfaces to the outside world
  143  */
  144 static fo_rdwr_t        pipe_read;
  145 static fo_rdwr_t        pipe_write;
  146 static fo_truncate_t    pipe_truncate;
  147 static fo_ioctl_t       pipe_ioctl;
  148 static fo_poll_t        pipe_poll;
  149 static fo_kqfilter_t    pipe_kqfilter;
  150 static fo_stat_t        pipe_stat;
  151 static fo_close_t       pipe_close;
  152 
  153 static struct fileops pipeops = {
  154         .fo_read = pipe_read,
  155         .fo_write = pipe_write,
  156         .fo_truncate = pipe_truncate,
  157         .fo_ioctl = pipe_ioctl,
  158         .fo_poll = pipe_poll,
  159         .fo_kqfilter = pipe_kqfilter,
  160         .fo_stat = pipe_stat,
  161         .fo_close = pipe_close,
  162         .fo_chmod = invfo_chmod,
  163         .fo_chown = invfo_chown,
  164         .fo_flags = DFLAG_PASSABLE
  165 };
  166 
  167 static void     filt_pipedetach(struct knote *kn);
  168 static int      filt_piperead(struct knote *kn, long hint);
  169 static int      filt_pipewrite(struct knote *kn, long hint);
  170 
  171 static struct filterops pipe_rfiltops = {
  172         .f_isfd = 1,
  173         .f_detach = filt_pipedetach,
  174         .f_event = filt_piperead
  175 };
  176 static struct filterops pipe_wfiltops = {
  177         .f_isfd = 1,
  178         .f_detach = filt_pipedetach,
  179         .f_event = filt_pipewrite
  180 };
  181 
  182 /*
  183  * Default pipe buffer size(s), this can be kind-of large now because pipe
  184  * space is pageable.  The pipe code will try to maintain locality of
  185  * reference for performance reasons, so small amounts of outstanding I/O
  186  * will not wipe the cache.
  187  */
  188 #define MINPIPESIZE (PIPE_SIZE/3)
  189 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  190 
  191 static long amountpipekva;
  192 static int pipefragretry;
  193 static int pipeallocfail;
  194 static int piperesizefail;
  195 static int piperesizeallowed = 1;
  196 
  197 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  198            &maxpipekva, 0, "Pipe KVA limit");
  199 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  200            &amountpipekva, 0, "Pipe KVA usage");
  201 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  202           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  203 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  204           &pipeallocfail, 0, "Pipe allocation failures");
  205 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  206           &piperesizefail, 0, "Pipe resize failures");
  207 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  208           &piperesizeallowed, 0, "Pipe resizing allowed");
  209 
  210 static void pipeinit(void *dummy __unused);
  211 static void pipeclose(struct pipe *cpipe);
  212 static void pipe_free_kmem(struct pipe *cpipe);
  213 static int pipe_create(struct pipe *pipe, int backing);
  214 static __inline int pipelock(struct pipe *cpipe, int catch);
  215 static __inline void pipeunlock(struct pipe *cpipe);
  216 static __inline void pipeselwakeup(struct pipe *cpipe);
  217 #ifndef PIPE_NODIRECT
  218 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  219 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  220 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  221 static void pipe_clone_write_buffer(struct pipe *wpipe);
  222 #endif
  223 static int pipespace(struct pipe *cpipe, int size);
  224 static int pipespace_new(struct pipe *cpipe, int size);
  225 
  226 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  227 static int      pipe_zone_init(void *mem, int size, int flags);
  228 static void     pipe_zone_fini(void *mem, int size);
  229 
  230 static uma_zone_t pipe_zone;
  231 static struct unrhdr *pipeino_unr;
  232 static dev_t pipedev_ino;
  233 
  234 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  235 
  236 static void
  237 pipeinit(void *dummy __unused)
  238 {
  239 
  240         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
  241             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
  242             UMA_ALIGN_PTR, 0);
  243         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  244         pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
  245         KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
  246         pipedev_ino = devfs_alloc_cdp_inode();
  247         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
  248 }
  249 
  250 static int
  251 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  252 {
  253         struct pipepair *pp;
  254         struct pipe *rpipe, *wpipe;
  255 
  256         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  257 
  258         pp = (struct pipepair *)mem;
  259 
  260         /*
  261          * We zero both pipe endpoints to make sure all the kmem pointers
  262          * are NULL, flag fields are zero'd, etc.  We timestamp both
  263          * endpoints with the same time.
  264          */
  265         rpipe = &pp->pp_rpipe;
  266         bzero(rpipe, sizeof(*rpipe));
  267         vfs_timestamp(&rpipe->pipe_ctime);
  268         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  269 
  270         wpipe = &pp->pp_wpipe;
  271         bzero(wpipe, sizeof(*wpipe));
  272         wpipe->pipe_ctime = rpipe->pipe_ctime;
  273         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  274 
  275         rpipe->pipe_peer = wpipe;
  276         rpipe->pipe_pair = pp;
  277         wpipe->pipe_peer = rpipe;
  278         wpipe->pipe_pair = pp;
  279 
  280         /*
  281          * Mark both endpoints as present; they will later get free'd
  282          * one at a time.  When both are free'd, then the whole pair
  283          * is released.
  284          */
  285         rpipe->pipe_present = PIPE_ACTIVE;
  286         wpipe->pipe_present = PIPE_ACTIVE;
  287 
  288         /*
  289          * Eventually, the MAC Framework may initialize the label
  290          * in ctor or init, but for now we do it elswhere to avoid
  291          * blocking in ctor or init.
  292          */
  293         pp->pp_label = NULL;
  294 
  295         return (0);
  296 }
  297 
  298 static int
  299 pipe_zone_init(void *mem, int size, int flags)
  300 {
  301         struct pipepair *pp;
  302 
  303         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  304 
  305         pp = (struct pipepair *)mem;
  306 
  307         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  308         return (0);
  309 }
  310 
  311 static void
  312 pipe_zone_fini(void *mem, int size)
  313 {
  314         struct pipepair *pp;
  315 
  316         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  317 
  318         pp = (struct pipepair *)mem;
  319 
  320         mtx_destroy(&pp->pp_mtx);
  321 }
  322 
  323 /*
  324  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  325  * the zone pick up the pieces via pipeclose().
  326  */
  327 int
  328 kern_pipe(struct thread *td, int fildes[2])
  329 {
  330 
  331         return (do_pipe(td, fildes, 0));
  332 }
  333 
  334 int
  335 do_pipe(struct thread *td, int fildes[2], int flags)
  336 {
  337         struct filedesc *fdp = td->td_proc->p_fd;
  338         struct file *rf, *wf;
  339         struct pipepair *pp;
  340         struct pipe *rpipe, *wpipe;
  341         int fd, fflags, error;
  342 
  343         pp = uma_zalloc(pipe_zone, M_WAITOK);
  344 #ifdef MAC
  345         /*
  346          * The MAC label is shared between the connected endpoints.  As a
  347          * result mac_pipe_init() and mac_pipe_create() are called once
  348          * for the pair, and not on the endpoints.
  349          */
  350         mac_pipe_init(pp);
  351         mac_pipe_create(td->td_ucred, pp);
  352 #endif
  353         rpipe = &pp->pp_rpipe;
  354         wpipe = &pp->pp_wpipe;
  355 
  356         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  357         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  358 
  359         /* Only the forward direction pipe is backed by default */
  360         if ((error = pipe_create(rpipe, 1)) != 0 ||
  361             (error = pipe_create(wpipe, 0)) != 0) {
  362                 pipeclose(rpipe);
  363                 pipeclose(wpipe);
  364                 return (error);
  365         }
  366 
  367         rpipe->pipe_state |= PIPE_DIRECTOK;
  368         wpipe->pipe_state |= PIPE_DIRECTOK;
  369 
  370         error = falloc(td, &rf, &fd, flags);
  371         if (error) {
  372                 pipeclose(rpipe);
  373                 pipeclose(wpipe);
  374                 return (error);
  375         }
  376         /* An extra reference on `rf' has been held for us by falloc(). */
  377         fildes[0] = fd;
  378 
  379         fflags = FREAD | FWRITE;
  380         if ((flags & O_NONBLOCK) != 0)
  381                 fflags |= FNONBLOCK;
  382 
  383         /*
  384          * Warning: once we've gotten past allocation of the fd for the
  385          * read-side, we can only drop the read side via fdrop() in order
  386          * to avoid races against processes which manage to dup() the read
  387          * side while we are blocked trying to allocate the write side.
  388          */
  389         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
  390         error = falloc(td, &wf, &fd, flags);
  391         if (error) {
  392                 fdclose(fdp, rf, fildes[0], td);
  393                 fdrop(rf, td);
  394                 /* rpipe has been closed by fdrop(). */
  395                 pipeclose(wpipe);
  396                 return (error);
  397         }
  398         /* An extra reference on `wf' has been held for us by falloc(). */
  399         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
  400         fdrop(wf, td);
  401         fildes[1] = fd;
  402         fdrop(rf, td);
  403 
  404         return (0);
  405 }
  406 
  407 /* ARGSUSED */
  408 int
  409 sys_pipe(struct thread *td, struct pipe_args *uap)
  410 {
  411         int error;
  412         int fildes[2];
  413 
  414         error = kern_pipe(td, fildes);
  415         if (error)
  416                 return (error);
  417         
  418         td->td_retval[0] = fildes[0];
  419         td->td_retval[1] = fildes[1];
  420 
  421         return (0);
  422 }
  423 
  424 /*
  425  * Allocate kva for pipe circular buffer, the space is pageable
  426  * This routine will 'realloc' the size of a pipe safely, if it fails
  427  * it will retain the old buffer.
  428  * If it fails it will return ENOMEM.
  429  */
  430 static int
  431 pipespace_new(cpipe, size)
  432         struct pipe *cpipe;
  433         int size;
  434 {
  435         caddr_t buffer;
  436         int error, cnt, firstseg;
  437         static int curfail = 0;
  438         static struct timeval lastfail;
  439 
  440         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  441         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  442                 ("pipespace: resize of direct writes not allowed"));
  443 retry:
  444         cnt = cpipe->pipe_buffer.cnt;
  445         if (cnt > size)
  446                 size = cnt;
  447 
  448         size = round_page(size);
  449         buffer = (caddr_t) vm_map_min(pipe_map);
  450 
  451         error = vm_map_find(pipe_map, NULL, 0,
  452                 (vm_offset_t *) &buffer, size, 1,
  453                 VM_PROT_ALL, VM_PROT_ALL, 0);
  454         if (error != KERN_SUCCESS) {
  455                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  456                         (size > SMALL_PIPE_SIZE)) {
  457                         size = SMALL_PIPE_SIZE;
  458                         pipefragretry++;
  459                         goto retry;
  460                 }
  461                 if (cpipe->pipe_buffer.buffer == NULL) {
  462                         pipeallocfail++;
  463                         if (ppsratecheck(&lastfail, &curfail, 1))
  464                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  465                 } else {
  466                         piperesizefail++;
  467                 }
  468                 return (ENOMEM);
  469         }
  470 
  471         /* copy data, then free old resources if we're resizing */
  472         if (cnt > 0) {
  473                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  474                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  475                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  476                                 buffer, firstseg);
  477                         if ((cnt - firstseg) > 0)
  478                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  479                                         cpipe->pipe_buffer.in);
  480                 } else {
  481                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  482                                 buffer, cnt);
  483                 }
  484         }
  485         pipe_free_kmem(cpipe);
  486         cpipe->pipe_buffer.buffer = buffer;
  487         cpipe->pipe_buffer.size = size;
  488         cpipe->pipe_buffer.in = cnt;
  489         cpipe->pipe_buffer.out = 0;
  490         cpipe->pipe_buffer.cnt = cnt;
  491         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  492         return (0);
  493 }
  494 
  495 /*
  496  * Wrapper for pipespace_new() that performs locking assertions.
  497  */
  498 static int
  499 pipespace(cpipe, size)
  500         struct pipe *cpipe;
  501         int size;
  502 {
  503 
  504         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  505                 ("Unlocked pipe passed to pipespace"));
  506         return (pipespace_new(cpipe, size));
  507 }
  508 
  509 /*
  510  * lock a pipe for I/O, blocking other access
  511  */
  512 static __inline int
  513 pipelock(cpipe, catch)
  514         struct pipe *cpipe;
  515         int catch;
  516 {
  517         int error;
  518 
  519         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  520         while (cpipe->pipe_state & PIPE_LOCKFL) {
  521                 cpipe->pipe_state |= PIPE_LWANT;
  522                 error = msleep(cpipe, PIPE_MTX(cpipe),
  523                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  524                     "pipelk", 0);
  525                 if (error != 0)
  526                         return (error);
  527         }
  528         cpipe->pipe_state |= PIPE_LOCKFL;
  529         return (0);
  530 }
  531 
  532 /*
  533  * unlock a pipe I/O lock
  534  */
  535 static __inline void
  536 pipeunlock(cpipe)
  537         struct pipe *cpipe;
  538 {
  539 
  540         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  541         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  542                 ("Unlocked pipe passed to pipeunlock"));
  543         cpipe->pipe_state &= ~PIPE_LOCKFL;
  544         if (cpipe->pipe_state & PIPE_LWANT) {
  545                 cpipe->pipe_state &= ~PIPE_LWANT;
  546                 wakeup(cpipe);
  547         }
  548 }
  549 
  550 static __inline void
  551 pipeselwakeup(cpipe)
  552         struct pipe *cpipe;
  553 {
  554 
  555         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  556         if (cpipe->pipe_state & PIPE_SEL) {
  557                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  558                 if (!SEL_WAITING(&cpipe->pipe_sel))
  559                         cpipe->pipe_state &= ~PIPE_SEL;
  560         }
  561         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  562                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  563         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  564 }
  565 
  566 /*
  567  * Initialize and allocate VM and memory for pipe.  The structure
  568  * will start out zero'd from the ctor, so we just manage the kmem.
  569  */
  570 static int
  571 pipe_create(pipe, backing)
  572         struct pipe *pipe;
  573         int backing;
  574 {
  575         int error;
  576 
  577         if (backing) {
  578                 if (amountpipekva > maxpipekva / 2)
  579                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  580                 else
  581                         error = pipespace_new(pipe, PIPE_SIZE);
  582         } else {
  583                 /* If we're not backing this pipe, no need to do anything. */
  584                 error = 0;
  585         }
  586         pipe->pipe_ino = -1;
  587         return (error);
  588 }
  589 
  590 /* ARGSUSED */
  591 static int
  592 pipe_read(fp, uio, active_cred, flags, td)
  593         struct file *fp;
  594         struct uio *uio;
  595         struct ucred *active_cred;
  596         struct thread *td;
  597         int flags;
  598 {
  599         struct pipe *rpipe = fp->f_data;
  600         int error;
  601         int nread = 0;
  602         int size;
  603 
  604         PIPE_LOCK(rpipe);
  605         ++rpipe->pipe_busy;
  606         error = pipelock(rpipe, 1);
  607         if (error)
  608                 goto unlocked_error;
  609 
  610 #ifdef MAC
  611         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  612         if (error)
  613                 goto locked_error;
  614 #endif
  615         if (amountpipekva > (3 * maxpipekva) / 4) {
  616                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  617                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  618                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  619                         (piperesizeallowed == 1)) {
  620                         PIPE_UNLOCK(rpipe);
  621                         pipespace(rpipe, SMALL_PIPE_SIZE);
  622                         PIPE_LOCK(rpipe);
  623                 }
  624         }
  625 
  626         while (uio->uio_resid) {
  627                 /*
  628                  * normal pipe buffer receive
  629                  */
  630                 if (rpipe->pipe_buffer.cnt > 0) {
  631                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  632                         if (size > rpipe->pipe_buffer.cnt)
  633                                 size = rpipe->pipe_buffer.cnt;
  634                         if (size > uio->uio_resid)
  635                                 size = uio->uio_resid;
  636 
  637                         PIPE_UNLOCK(rpipe);
  638                         error = uiomove(
  639                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  640                             size, uio);
  641                         PIPE_LOCK(rpipe);
  642                         if (error)
  643                                 break;
  644 
  645                         rpipe->pipe_buffer.out += size;
  646                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  647                                 rpipe->pipe_buffer.out = 0;
  648 
  649                         rpipe->pipe_buffer.cnt -= size;
  650 
  651                         /*
  652                          * If there is no more to read in the pipe, reset
  653                          * its pointers to the beginning.  This improves
  654                          * cache hit stats.
  655                          */
  656                         if (rpipe->pipe_buffer.cnt == 0) {
  657                                 rpipe->pipe_buffer.in = 0;
  658                                 rpipe->pipe_buffer.out = 0;
  659                         }
  660                         nread += size;
  661 #ifndef PIPE_NODIRECT
  662                 /*
  663                  * Direct copy, bypassing a kernel buffer.
  664                  */
  665                 } else if ((size = rpipe->pipe_map.cnt) &&
  666                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  667                         if (size > uio->uio_resid)
  668                                 size = (u_int) uio->uio_resid;
  669 
  670                         PIPE_UNLOCK(rpipe);
  671                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  672                             rpipe->pipe_map.pos, size, uio);
  673                         PIPE_LOCK(rpipe);
  674                         if (error)
  675                                 break;
  676                         nread += size;
  677                         rpipe->pipe_map.pos += size;
  678                         rpipe->pipe_map.cnt -= size;
  679                         if (rpipe->pipe_map.cnt == 0) {
  680                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  681                                 wakeup(rpipe);
  682                         }
  683 #endif
  684                 } else {
  685                         /*
  686                          * detect EOF condition
  687                          * read returns 0 on EOF, no need to set error
  688                          */
  689                         if (rpipe->pipe_state & PIPE_EOF)
  690                                 break;
  691 
  692                         /*
  693                          * If the "write-side" has been blocked, wake it up now.
  694                          */
  695                         if (rpipe->pipe_state & PIPE_WANTW) {
  696                                 rpipe->pipe_state &= ~PIPE_WANTW;
  697                                 wakeup(rpipe);
  698                         }
  699 
  700                         /*
  701                          * Break if some data was read.
  702                          */
  703                         if (nread > 0)
  704                                 break;
  705 
  706                         /*
  707                          * Unlock the pipe buffer for our remaining processing.
  708                          * We will either break out with an error or we will
  709                          * sleep and relock to loop.
  710                          */
  711                         pipeunlock(rpipe);
  712 
  713                         /*
  714                          * Handle non-blocking mode operation or
  715                          * wait for more data.
  716                          */
  717                         if (fp->f_flag & FNONBLOCK) {
  718                                 error = EAGAIN;
  719                         } else {
  720                                 rpipe->pipe_state |= PIPE_WANTR;
  721                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  722                                     PRIBIO | PCATCH,
  723                                     "piperd", 0)) == 0)
  724                                         error = pipelock(rpipe, 1);
  725                         }
  726                         if (error)
  727                                 goto unlocked_error;
  728                 }
  729         }
  730 #ifdef MAC
  731 locked_error:
  732 #endif
  733         pipeunlock(rpipe);
  734 
  735         /* XXX: should probably do this before getting any locks. */
  736         if (error == 0)
  737                 vfs_timestamp(&rpipe->pipe_atime);
  738 unlocked_error:
  739         --rpipe->pipe_busy;
  740 
  741         /*
  742          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  743          */
  744         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  745                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  746                 wakeup(rpipe);
  747         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  748                 /*
  749                  * Handle write blocking hysteresis.
  750                  */
  751                 if (rpipe->pipe_state & PIPE_WANTW) {
  752                         rpipe->pipe_state &= ~PIPE_WANTW;
  753                         wakeup(rpipe);
  754                 }
  755         }
  756 
  757         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  758                 pipeselwakeup(rpipe);
  759 
  760         PIPE_UNLOCK(rpipe);
  761         return (error);
  762 }
  763 
  764 #ifndef PIPE_NODIRECT
  765 /*
  766  * Map the sending processes' buffer into kernel space and wire it.
  767  * This is similar to a physical write operation.
  768  */
  769 static int
  770 pipe_build_write_buffer(wpipe, uio)
  771         struct pipe *wpipe;
  772         struct uio *uio;
  773 {
  774         u_int size;
  775         int i;
  776 
  777         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  778         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  779                 ("Clone attempt on non-direct write pipe!"));
  780 
  781         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
  782                 size = wpipe->pipe_buffer.size;
  783         else
  784                 size = uio->uio_iov->iov_len;
  785 
  786         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  787             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  788             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  789                 return (EFAULT);
  790 
  791 /*
  792  * set up the control block
  793  */
  794         wpipe->pipe_map.npages = i;
  795         wpipe->pipe_map.pos =
  796             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  797         wpipe->pipe_map.cnt = size;
  798 
  799 /*
  800  * and update the uio data
  801  */
  802 
  803         uio->uio_iov->iov_len -= size;
  804         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  805         if (uio->uio_iov->iov_len == 0)
  806                 uio->uio_iov++;
  807         uio->uio_resid -= size;
  808         uio->uio_offset += size;
  809         return (0);
  810 }
  811 
  812 /*
  813  * unmap and unwire the process buffer
  814  */
  815 static void
  816 pipe_destroy_write_buffer(wpipe)
  817         struct pipe *wpipe;
  818 {
  819 
  820         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  821         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  822         wpipe->pipe_map.npages = 0;
  823 }
  824 
  825 /*
  826  * In the case of a signal, the writing process might go away.  This
  827  * code copies the data into the circular buffer so that the source
  828  * pages can be freed without loss of data.
  829  */
  830 static void
  831 pipe_clone_write_buffer(wpipe)
  832         struct pipe *wpipe;
  833 {
  834         struct uio uio;
  835         struct iovec iov;
  836         int size;
  837         int pos;
  838 
  839         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  840         size = wpipe->pipe_map.cnt;
  841         pos = wpipe->pipe_map.pos;
  842 
  843         wpipe->pipe_buffer.in = size;
  844         wpipe->pipe_buffer.out = 0;
  845         wpipe->pipe_buffer.cnt = size;
  846         wpipe->pipe_state &= ~PIPE_DIRECTW;
  847 
  848         PIPE_UNLOCK(wpipe);
  849         iov.iov_base = wpipe->pipe_buffer.buffer;
  850         iov.iov_len = size;
  851         uio.uio_iov = &iov;
  852         uio.uio_iovcnt = 1;
  853         uio.uio_offset = 0;
  854         uio.uio_resid = size;
  855         uio.uio_segflg = UIO_SYSSPACE;
  856         uio.uio_rw = UIO_READ;
  857         uio.uio_td = curthread;
  858         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  859         PIPE_LOCK(wpipe);
  860         pipe_destroy_write_buffer(wpipe);
  861 }
  862 
  863 /*
  864  * This implements the pipe buffer write mechanism.  Note that only
  865  * a direct write OR a normal pipe write can be pending at any given time.
  866  * If there are any characters in the pipe buffer, the direct write will
  867  * be deferred until the receiving process grabs all of the bytes from
  868  * the pipe buffer.  Then the direct mapping write is set-up.
  869  */
  870 static int
  871 pipe_direct_write(wpipe, uio)
  872         struct pipe *wpipe;
  873         struct uio *uio;
  874 {
  875         int error;
  876 
  877 retry:
  878         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  879         error = pipelock(wpipe, 1);
  880         if (wpipe->pipe_state & PIPE_EOF)
  881                 error = EPIPE;
  882         if (error) {
  883                 pipeunlock(wpipe);
  884                 goto error1;
  885         }
  886         while (wpipe->pipe_state & PIPE_DIRECTW) {
  887                 if (wpipe->pipe_state & PIPE_WANTR) {
  888                         wpipe->pipe_state &= ~PIPE_WANTR;
  889                         wakeup(wpipe);
  890                 }
  891                 pipeselwakeup(wpipe);
  892                 wpipe->pipe_state |= PIPE_WANTW;
  893                 pipeunlock(wpipe);
  894                 error = msleep(wpipe, PIPE_MTX(wpipe),
  895                     PRIBIO | PCATCH, "pipdww", 0);
  896                 if (error)
  897                         goto error1;
  898                 else
  899                         goto retry;
  900         }
  901         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  902         if (wpipe->pipe_buffer.cnt > 0) {
  903                 if (wpipe->pipe_state & PIPE_WANTR) {
  904                         wpipe->pipe_state &= ~PIPE_WANTR;
  905                         wakeup(wpipe);
  906                 }
  907                 pipeselwakeup(wpipe);
  908                 wpipe->pipe_state |= PIPE_WANTW;
  909                 pipeunlock(wpipe);
  910                 error = msleep(wpipe, PIPE_MTX(wpipe),
  911                     PRIBIO | PCATCH, "pipdwc", 0);
  912                 if (error)
  913                         goto error1;
  914                 else
  915                         goto retry;
  916         }
  917 
  918         wpipe->pipe_state |= PIPE_DIRECTW;
  919 
  920         PIPE_UNLOCK(wpipe);
  921         error = pipe_build_write_buffer(wpipe, uio);
  922         PIPE_LOCK(wpipe);
  923         if (error) {
  924                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  925                 pipeunlock(wpipe);
  926                 goto error1;
  927         }
  928 
  929         error = 0;
  930         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  931                 if (wpipe->pipe_state & PIPE_EOF) {
  932                         pipe_destroy_write_buffer(wpipe);
  933                         pipeselwakeup(wpipe);
  934                         pipeunlock(wpipe);
  935                         error = EPIPE;
  936                         goto error1;
  937                 }
  938                 if (wpipe->pipe_state & PIPE_WANTR) {
  939                         wpipe->pipe_state &= ~PIPE_WANTR;
  940                         wakeup(wpipe);
  941                 }
  942                 pipeselwakeup(wpipe);
  943                 pipeunlock(wpipe);
  944                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  945                     "pipdwt", 0);
  946                 pipelock(wpipe, 0);
  947         }
  948 
  949         if (wpipe->pipe_state & PIPE_EOF)
  950                 error = EPIPE;
  951         if (wpipe->pipe_state & PIPE_DIRECTW) {
  952                 /*
  953                  * this bit of trickery substitutes a kernel buffer for
  954                  * the process that might be going away.
  955                  */
  956                 pipe_clone_write_buffer(wpipe);
  957         } else {
  958                 pipe_destroy_write_buffer(wpipe);
  959         }
  960         pipeunlock(wpipe);
  961         return (error);
  962 
  963 error1:
  964         wakeup(wpipe);
  965         return (error);
  966 }
  967 #endif
  968 
  969 static int
  970 pipe_write(fp, uio, active_cred, flags, td)
  971         struct file *fp;
  972         struct uio *uio;
  973         struct ucred *active_cred;
  974         struct thread *td;
  975         int flags;
  976 {
  977         int error = 0;
  978         int desiredsize;
  979         ssize_t orig_resid;
  980         struct pipe *wpipe, *rpipe;
  981 
  982         rpipe = fp->f_data;
  983         wpipe = rpipe->pipe_peer;
  984 
  985         PIPE_LOCK(rpipe);
  986         error = pipelock(wpipe, 1);
  987         if (error) {
  988                 PIPE_UNLOCK(rpipe);
  989                 return (error);
  990         }
  991         /*
  992          * detect loss of pipe read side, issue SIGPIPE if lost.
  993          */
  994         if (wpipe->pipe_present != PIPE_ACTIVE ||
  995             (wpipe->pipe_state & PIPE_EOF)) {
  996                 pipeunlock(wpipe);
  997                 PIPE_UNLOCK(rpipe);
  998                 return (EPIPE);
  999         }
 1000 #ifdef MAC
 1001         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
 1002         if (error) {
 1003                 pipeunlock(wpipe);
 1004                 PIPE_UNLOCK(rpipe);
 1005                 return (error);
 1006         }
 1007 #endif
 1008         ++wpipe->pipe_busy;
 1009 
 1010         /* Choose a larger size if it's advantageous */
 1011         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1012         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1013                 if (piperesizeallowed != 1)
 1014                         break;
 1015                 if (amountpipekva > maxpipekva / 2)
 1016                         break;
 1017                 if (desiredsize == BIG_PIPE_SIZE)
 1018                         break;
 1019                 desiredsize = desiredsize * 2;
 1020         }
 1021 
 1022         /* Choose a smaller size if we're in a OOM situation */
 1023         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1024                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1025                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1026                 (piperesizeallowed == 1))
 1027                 desiredsize = SMALL_PIPE_SIZE;
 1028 
 1029         /* Resize if the above determined that a new size was necessary */
 1030         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1031                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1032                 PIPE_UNLOCK(wpipe);
 1033                 pipespace(wpipe, desiredsize);
 1034                 PIPE_LOCK(wpipe);
 1035         }
 1036         if (wpipe->pipe_buffer.size == 0) {
 1037                 /*
 1038                  * This can only happen for reverse direction use of pipes
 1039                  * in a complete OOM situation.
 1040                  */
 1041                 error = ENOMEM;
 1042                 --wpipe->pipe_busy;
 1043                 pipeunlock(wpipe);
 1044                 PIPE_UNLOCK(wpipe);
 1045                 return (error);
 1046         }
 1047 
 1048         pipeunlock(wpipe);
 1049 
 1050         orig_resid = uio->uio_resid;
 1051 
 1052         while (uio->uio_resid) {
 1053                 int space;
 1054 
 1055                 pipelock(wpipe, 0);
 1056                 if (wpipe->pipe_state & PIPE_EOF) {
 1057                         pipeunlock(wpipe);
 1058                         error = EPIPE;
 1059                         break;
 1060                 }
 1061 #ifndef PIPE_NODIRECT
 1062                 /*
 1063                  * If the transfer is large, we can gain performance if
 1064                  * we do process-to-process copies directly.
 1065                  * If the write is non-blocking, we don't use the
 1066                  * direct write mechanism.
 1067                  *
 1068                  * The direct write mechanism will detect the reader going
 1069                  * away on us.
 1070                  */
 1071                 if (uio->uio_segflg == UIO_USERSPACE &&
 1072                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1073                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1074                     (fp->f_flag & FNONBLOCK) == 0) {
 1075                         pipeunlock(wpipe);
 1076                         error = pipe_direct_write(wpipe, uio);
 1077                         if (error)
 1078                                 break;
 1079                         continue;
 1080                 }
 1081 #endif
 1082 
 1083                 /*
 1084                  * Pipe buffered writes cannot be coincidental with
 1085                  * direct writes.  We wait until the currently executing
 1086                  * direct write is completed before we start filling the
 1087                  * pipe buffer.  We break out if a signal occurs or the
 1088                  * reader goes away.
 1089                  */
 1090                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1091                         if (wpipe->pipe_state & PIPE_WANTR) {
 1092                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1093                                 wakeup(wpipe);
 1094                         }
 1095                         pipeselwakeup(wpipe);
 1096                         wpipe->pipe_state |= PIPE_WANTW;
 1097                         pipeunlock(wpipe);
 1098                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1099                             "pipbww", 0);
 1100                         if (error)
 1101                                 break;
 1102                         else
 1103                                 continue;
 1104                 }
 1105 
 1106                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1107 
 1108                 /* Writes of size <= PIPE_BUF must be atomic. */
 1109                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1110                         space = 0;
 1111 
 1112                 if (space > 0) {
 1113                         int size;       /* Transfer size */
 1114                         int segsize;    /* first segment to transfer */
 1115 
 1116                         /*
 1117                          * Transfer size is minimum of uio transfer
 1118                          * and free space in pipe buffer.
 1119                          */
 1120                         if (space > uio->uio_resid)
 1121                                 size = uio->uio_resid;
 1122                         else
 1123                                 size = space;
 1124                         /*
 1125                          * First segment to transfer is minimum of
 1126                          * transfer size and contiguous space in
 1127                          * pipe buffer.  If first segment to transfer
 1128                          * is less than the transfer size, we've got
 1129                          * a wraparound in the buffer.
 1130                          */
 1131                         segsize = wpipe->pipe_buffer.size -
 1132                                 wpipe->pipe_buffer.in;
 1133                         if (segsize > size)
 1134                                 segsize = size;
 1135 
 1136                         /* Transfer first segment */
 1137 
 1138                         PIPE_UNLOCK(rpipe);
 1139                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1140                                         segsize, uio);
 1141                         PIPE_LOCK(rpipe);
 1142 
 1143                         if (error == 0 && segsize < size) {
 1144                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1145                                         wpipe->pipe_buffer.size,
 1146                                         ("Pipe buffer wraparound disappeared"));
 1147                                 /*
 1148                                  * Transfer remaining part now, to
 1149                                  * support atomic writes.  Wraparound
 1150                                  * happened.
 1151                                  */
 1152 
 1153                                 PIPE_UNLOCK(rpipe);
 1154                                 error = uiomove(
 1155                                     &wpipe->pipe_buffer.buffer[0],
 1156                                     size - segsize, uio);
 1157                                 PIPE_LOCK(rpipe);
 1158                         }
 1159                         if (error == 0) {
 1160                                 wpipe->pipe_buffer.in += size;
 1161                                 if (wpipe->pipe_buffer.in >=
 1162                                     wpipe->pipe_buffer.size) {
 1163                                         KASSERT(wpipe->pipe_buffer.in ==
 1164                                                 size - segsize +
 1165                                                 wpipe->pipe_buffer.size,
 1166                                                 ("Expected wraparound bad"));
 1167                                         wpipe->pipe_buffer.in = size - segsize;
 1168                                 }
 1169 
 1170                                 wpipe->pipe_buffer.cnt += size;
 1171                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1172                                         wpipe->pipe_buffer.size,
 1173                                         ("Pipe buffer overflow"));
 1174                         }
 1175                         pipeunlock(wpipe);
 1176                         if (error != 0)
 1177                                 break;
 1178                 } else {
 1179                         /*
 1180                          * If the "read-side" has been blocked, wake it up now.
 1181                          */
 1182                         if (wpipe->pipe_state & PIPE_WANTR) {
 1183                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1184                                 wakeup(wpipe);
 1185                         }
 1186 
 1187                         /*
 1188                          * don't block on non-blocking I/O
 1189                          */
 1190                         if (fp->f_flag & FNONBLOCK) {
 1191                                 error = EAGAIN;
 1192                                 pipeunlock(wpipe);
 1193                                 break;
 1194                         }
 1195 
 1196                         /*
 1197                          * We have no more space and have something to offer,
 1198                          * wake up select/poll.
 1199                          */
 1200                         pipeselwakeup(wpipe);
 1201 
 1202                         wpipe->pipe_state |= PIPE_WANTW;
 1203                         pipeunlock(wpipe);
 1204                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1205                             PRIBIO | PCATCH, "pipewr", 0);
 1206                         if (error != 0)
 1207                                 break;
 1208                 }
 1209         }
 1210 
 1211         pipelock(wpipe, 0);
 1212         --wpipe->pipe_busy;
 1213 
 1214         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1215                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1216                 wakeup(wpipe);
 1217         } else if (wpipe->pipe_buffer.cnt > 0) {
 1218                 /*
 1219                  * If we have put any characters in the buffer, we wake up
 1220                  * the reader.
 1221                  */
 1222                 if (wpipe->pipe_state & PIPE_WANTR) {
 1223                         wpipe->pipe_state &= ~PIPE_WANTR;
 1224                         wakeup(wpipe);
 1225                 }
 1226         }
 1227 
 1228         /*
 1229          * Don't return EPIPE if I/O was successful
 1230          */
 1231         if ((wpipe->pipe_buffer.cnt == 0) &&
 1232             (uio->uio_resid == 0) &&
 1233             (error == EPIPE)) {
 1234                 error = 0;
 1235         }
 1236 
 1237         if (error == 0)
 1238                 vfs_timestamp(&wpipe->pipe_mtime);
 1239 
 1240         /*
 1241          * We have something to offer,
 1242          * wake up select/poll.
 1243          */
 1244         if (wpipe->pipe_buffer.cnt)
 1245                 pipeselwakeup(wpipe);
 1246 
 1247         pipeunlock(wpipe);
 1248         PIPE_UNLOCK(rpipe);
 1249         return (error);
 1250 }
 1251 
 1252 /* ARGSUSED */
 1253 static int
 1254 pipe_truncate(fp, length, active_cred, td)
 1255         struct file *fp;
 1256         off_t length;
 1257         struct ucred *active_cred;
 1258         struct thread *td;
 1259 {
 1260 
 1261         return (EINVAL);
 1262 }
 1263 
 1264 /*
 1265  * we implement a very minimal set of ioctls for compatibility with sockets.
 1266  */
 1267 static int
 1268 pipe_ioctl(fp, cmd, data, active_cred, td)
 1269         struct file *fp;
 1270         u_long cmd;
 1271         void *data;
 1272         struct ucred *active_cred;
 1273         struct thread *td;
 1274 {
 1275         struct pipe *mpipe = fp->f_data;
 1276         int error;
 1277 
 1278         PIPE_LOCK(mpipe);
 1279 
 1280 #ifdef MAC
 1281         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1282         if (error) {
 1283                 PIPE_UNLOCK(mpipe);
 1284                 return (error);
 1285         }
 1286 #endif
 1287 
 1288         error = 0;
 1289         switch (cmd) {
 1290 
 1291         case FIONBIO:
 1292                 break;
 1293 
 1294         case FIOASYNC:
 1295                 if (*(int *)data) {
 1296                         mpipe->pipe_state |= PIPE_ASYNC;
 1297                 } else {
 1298                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1299                 }
 1300                 break;
 1301 
 1302         case FIONREAD:
 1303                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1304                         *(int *)data = mpipe->pipe_map.cnt;
 1305                 else
 1306                         *(int *)data = mpipe->pipe_buffer.cnt;
 1307                 break;
 1308 
 1309         case FIOSETOWN:
 1310                 PIPE_UNLOCK(mpipe);
 1311                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1312                 goto out_unlocked;
 1313 
 1314         case FIOGETOWN:
 1315                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1316                 break;
 1317 
 1318         /* This is deprecated, FIOSETOWN should be used instead. */
 1319         case TIOCSPGRP:
 1320                 PIPE_UNLOCK(mpipe);
 1321                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1322                 goto out_unlocked;
 1323 
 1324         /* This is deprecated, FIOGETOWN should be used instead. */
 1325         case TIOCGPGRP:
 1326                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1327                 break;
 1328 
 1329         default:
 1330                 error = ENOTTY;
 1331                 break;
 1332         }
 1333         PIPE_UNLOCK(mpipe);
 1334 out_unlocked:
 1335         return (error);
 1336 }
 1337 
 1338 static int
 1339 pipe_poll(fp, events, active_cred, td)
 1340         struct file *fp;
 1341         int events;
 1342         struct ucred *active_cred;
 1343         struct thread *td;
 1344 {
 1345         struct pipe *rpipe = fp->f_data;
 1346         struct pipe *wpipe;
 1347         int revents = 0;
 1348 #ifdef MAC
 1349         int error;
 1350 #endif
 1351 
 1352         wpipe = rpipe->pipe_peer;
 1353         PIPE_LOCK(rpipe);
 1354 #ifdef MAC
 1355         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1356         if (error)
 1357                 goto locked_error;
 1358 #endif
 1359         if (events & (POLLIN | POLLRDNORM))
 1360                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1361                     (rpipe->pipe_buffer.cnt > 0))
 1362                         revents |= events & (POLLIN | POLLRDNORM);
 1363 
 1364         if (events & (POLLOUT | POLLWRNORM))
 1365                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1366                     (wpipe->pipe_state & PIPE_EOF) ||
 1367                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1368                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
 1369                          wpipe->pipe_buffer.size == 0)))
 1370                         revents |= events & (POLLOUT | POLLWRNORM);
 1371 
 1372         if ((events & POLLINIGNEOF) == 0) {
 1373                 if (rpipe->pipe_state & PIPE_EOF) {
 1374                         revents |= (events & (POLLIN | POLLRDNORM));
 1375                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1376                             (wpipe->pipe_state & PIPE_EOF))
 1377                                 revents |= POLLHUP;
 1378                 }
 1379         }
 1380 
 1381         if (revents == 0) {
 1382                 if (events & (POLLIN | POLLRDNORM)) {
 1383                         selrecord(td, &rpipe->pipe_sel);
 1384                         if (SEL_WAITING(&rpipe->pipe_sel))
 1385                                 rpipe->pipe_state |= PIPE_SEL;
 1386                 }
 1387 
 1388                 if (events & (POLLOUT | POLLWRNORM)) {
 1389                         selrecord(td, &wpipe->pipe_sel);
 1390                         if (SEL_WAITING(&wpipe->pipe_sel))
 1391                                 wpipe->pipe_state |= PIPE_SEL;
 1392                 }
 1393         }
 1394 #ifdef MAC
 1395 locked_error:
 1396 #endif
 1397         PIPE_UNLOCK(rpipe);
 1398 
 1399         return (revents);
 1400 }
 1401 
 1402 /*
 1403  * We shouldn't need locks here as we're doing a read and this should
 1404  * be a natural race.
 1405  */
 1406 static int
 1407 pipe_stat(fp, ub, active_cred, td)
 1408         struct file *fp;
 1409         struct stat *ub;
 1410         struct ucred *active_cred;
 1411         struct thread *td;
 1412 {
 1413         struct pipe *pipe;
 1414         int new_unr;
 1415 #ifdef MAC
 1416         int error;
 1417 #endif
 1418 
 1419         pipe = fp->f_data;
 1420         PIPE_LOCK(pipe);
 1421 #ifdef MAC
 1422         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1423         if (error) {
 1424                 PIPE_UNLOCK(pipe);
 1425                 return (error);
 1426         }
 1427 #endif
 1428         /*
 1429          * Lazily allocate an inode number for the pipe.  Most pipe
 1430          * users do not call fstat(2) on the pipe, which means that
 1431          * postponing the inode allocation until it is must be
 1432          * returned to userland is useful.  If alloc_unr failed,
 1433          * assign st_ino zero instead of returning an error.
 1434          * Special pipe_ino values:
 1435          *  -1 - not yet initialized;
 1436          *  0  - alloc_unr failed, return 0 as st_ino forever.
 1437          */
 1438         if (pipe->pipe_ino == (ino_t)-1) {
 1439                 new_unr = alloc_unr(pipeino_unr);
 1440                 if (new_unr != -1)
 1441                         pipe->pipe_ino = new_unr;
 1442                 else
 1443                         pipe->pipe_ino = 0;
 1444         }
 1445         PIPE_UNLOCK(pipe);
 1446 
 1447         bzero(ub, sizeof(*ub));
 1448         ub->st_mode = S_IFIFO;
 1449         ub->st_blksize = PAGE_SIZE;
 1450         if (pipe->pipe_state & PIPE_DIRECTW)
 1451                 ub->st_size = pipe->pipe_map.cnt;
 1452         else
 1453                 ub->st_size = pipe->pipe_buffer.cnt;
 1454         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1455         ub->st_atim = pipe->pipe_atime;
 1456         ub->st_mtim = pipe->pipe_mtime;
 1457         ub->st_ctim = pipe->pipe_ctime;
 1458         ub->st_uid = fp->f_cred->cr_uid;
 1459         ub->st_gid = fp->f_cred->cr_gid;
 1460         ub->st_dev = pipedev_ino;
 1461         ub->st_ino = pipe->pipe_ino;
 1462         /*
 1463          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1464          */
 1465         return (0);
 1466 }
 1467 
 1468 /* ARGSUSED */
 1469 static int
 1470 pipe_close(fp, td)
 1471         struct file *fp;
 1472         struct thread *td;
 1473 {
 1474         struct pipe *cpipe = fp->f_data;
 1475 
 1476         fp->f_ops = &badfileops;
 1477         fp->f_data = NULL;
 1478         funsetown(&cpipe->pipe_sigio);
 1479         pipeclose(cpipe);
 1480         return (0);
 1481 }
 1482 
 1483 static void
 1484 pipe_free_kmem(cpipe)
 1485         struct pipe *cpipe;
 1486 {
 1487 
 1488         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1489             ("pipe_free_kmem: pipe mutex locked"));
 1490 
 1491         if (cpipe->pipe_buffer.buffer != NULL) {
 1492                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1493                 vm_map_remove(pipe_map,
 1494                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1495                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1496                 cpipe->pipe_buffer.buffer = NULL;
 1497         }
 1498 #ifndef PIPE_NODIRECT
 1499         {
 1500                 cpipe->pipe_map.cnt = 0;
 1501                 cpipe->pipe_map.pos = 0;
 1502                 cpipe->pipe_map.npages = 0;
 1503         }
 1504 #endif
 1505 }
 1506 
 1507 /*
 1508  * shutdown the pipe
 1509  */
 1510 static void
 1511 pipeclose(cpipe)
 1512         struct pipe *cpipe;
 1513 {
 1514         struct pipepair *pp;
 1515         struct pipe *ppipe;
 1516         ino_t ino;
 1517 
 1518         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1519 
 1520         PIPE_LOCK(cpipe);
 1521         pipelock(cpipe, 0);
 1522         pp = cpipe->pipe_pair;
 1523 
 1524         pipeselwakeup(cpipe);
 1525 
 1526         /*
 1527          * If the other side is blocked, wake it up saying that
 1528          * we want to close it down.
 1529          */
 1530         cpipe->pipe_state |= PIPE_EOF;
 1531         while (cpipe->pipe_busy) {
 1532                 wakeup(cpipe);
 1533                 cpipe->pipe_state |= PIPE_WANT;
 1534                 pipeunlock(cpipe);
 1535                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1536                 pipelock(cpipe, 0);
 1537         }
 1538 
 1539 
 1540         /*
 1541          * Disconnect from peer, if any.
 1542          */
 1543         ppipe = cpipe->pipe_peer;
 1544         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1545                 pipeselwakeup(ppipe);
 1546 
 1547                 ppipe->pipe_state |= PIPE_EOF;
 1548                 wakeup(ppipe);
 1549                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1550         }
 1551 
 1552         /*
 1553          * Mark this endpoint as free.  Release kmem resources.  We
 1554          * don't mark this endpoint as unused until we've finished
 1555          * doing that, or the pipe might disappear out from under
 1556          * us.
 1557          */
 1558         PIPE_UNLOCK(cpipe);
 1559         pipe_free_kmem(cpipe);
 1560         PIPE_LOCK(cpipe);
 1561         cpipe->pipe_present = PIPE_CLOSING;
 1562         pipeunlock(cpipe);
 1563 
 1564         /*
 1565          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1566          * PIPE_FINALIZED, that allows other end to free the
 1567          * pipe_pair, only after the knotes are completely dismantled.
 1568          */
 1569         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1570         cpipe->pipe_present = PIPE_FINALIZED;
 1571         seldrain(&cpipe->pipe_sel);
 1572         knlist_destroy(&cpipe->pipe_sel.si_note);
 1573 
 1574         /*
 1575          * Postpone the destroy of the fake inode number allocated for
 1576          * our end, until pipe mtx is unlocked.
 1577          */
 1578         ino = cpipe->pipe_ino;
 1579 
 1580         /*
 1581          * If both endpoints are now closed, release the memory for the
 1582          * pipe pair.  If not, unlock.
 1583          */
 1584         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1585                 PIPE_UNLOCK(cpipe);
 1586 #ifdef MAC
 1587                 mac_pipe_destroy(pp);
 1588 #endif
 1589                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1590         } else
 1591                 PIPE_UNLOCK(cpipe);
 1592 
 1593         if (ino != 0 && ino != (ino_t)-1)
 1594                 free_unr(pipeino_unr, ino);
 1595 }
 1596 
 1597 /*ARGSUSED*/
 1598 static int
 1599 pipe_kqfilter(struct file *fp, struct knote *kn)
 1600 {
 1601         struct pipe *cpipe;
 1602 
 1603         cpipe = kn->kn_fp->f_data;
 1604         PIPE_LOCK(cpipe);
 1605         switch (kn->kn_filter) {
 1606         case EVFILT_READ:
 1607                 kn->kn_fop = &pipe_rfiltops;
 1608                 break;
 1609         case EVFILT_WRITE:
 1610                 kn->kn_fop = &pipe_wfiltops;
 1611                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1612                         /* other end of pipe has been closed */
 1613                         PIPE_UNLOCK(cpipe);
 1614                         return (EPIPE);
 1615                 }
 1616                 cpipe = cpipe->pipe_peer;
 1617                 break;
 1618         default:
 1619                 PIPE_UNLOCK(cpipe);
 1620                 return (EINVAL);
 1621         }
 1622 
 1623         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1624         PIPE_UNLOCK(cpipe);
 1625         return (0);
 1626 }
 1627 
 1628 static void
 1629 filt_pipedetach(struct knote *kn)
 1630 {
 1631         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1632 
 1633         PIPE_LOCK(cpipe);
 1634         if (kn->kn_filter == EVFILT_WRITE)
 1635                 cpipe = cpipe->pipe_peer;
 1636         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1637         PIPE_UNLOCK(cpipe);
 1638 }
 1639 
 1640 /*ARGSUSED*/
 1641 static int
 1642 filt_piperead(struct knote *kn, long hint)
 1643 {
 1644         struct pipe *rpipe = kn->kn_fp->f_data;
 1645         struct pipe *wpipe = rpipe->pipe_peer;
 1646         int ret;
 1647 
 1648         PIPE_LOCK(rpipe);
 1649         kn->kn_data = rpipe->pipe_buffer.cnt;
 1650         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1651                 kn->kn_data = rpipe->pipe_map.cnt;
 1652 
 1653         if ((rpipe->pipe_state & PIPE_EOF) ||
 1654             wpipe->pipe_present != PIPE_ACTIVE ||
 1655             (wpipe->pipe_state & PIPE_EOF)) {
 1656                 kn->kn_flags |= EV_EOF;
 1657                 PIPE_UNLOCK(rpipe);
 1658                 return (1);
 1659         }
 1660         ret = kn->kn_data > 0;
 1661         PIPE_UNLOCK(rpipe);
 1662         return ret;
 1663 }
 1664 
 1665 /*ARGSUSED*/
 1666 static int
 1667 filt_pipewrite(struct knote *kn, long hint)
 1668 {
 1669         struct pipe *rpipe = kn->kn_fp->f_data;
 1670         struct pipe *wpipe = rpipe->pipe_peer;
 1671 
 1672         PIPE_LOCK(rpipe);
 1673         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1674             (wpipe->pipe_state & PIPE_EOF)) {
 1675                 kn->kn_data = 0;
 1676                 kn->kn_flags |= EV_EOF;
 1677                 PIPE_UNLOCK(rpipe);
 1678                 return (1);
 1679         }
 1680         kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
 1681             (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
 1682         if (wpipe->pipe_state & PIPE_DIRECTW)
 1683                 kn->kn_data = 0;
 1684 
 1685         PIPE_UNLOCK(rpipe);
 1686         return (kn->kn_data >= PIPE_BUF);
 1687 }

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