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/fs/fifofs/fifo_vnops.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1990, 1993, 1995
    5  *      The Regents of the University of California.
    6  * Copyright (c) 2005 Robert N. M. Watson
    7  * Copyright (c) 2012 Giovanni Trematerra
    8  * All rights reserved.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)fifo_vnops.c        8.10 (Berkeley) 5/27/95
   35  * $FreeBSD: head/sys/fs/fifofs/fifo_vnops.c 327004 2017-12-19 22:39:05Z jhb $
   36  */
   37 
   38 #include <sys/param.h>
   39 #include <sys/event.h>
   40 #include <sys/file.h>
   41 #include <sys/filedesc.h>
   42 #include <sys/filio.h>
   43 #include <sys/fcntl.h>
   44 #include <sys/kernel.h>
   45 #include <sys/lock.h>
   46 #include <sys/mutex.h>
   47 #include <sys/malloc.h>
   48 #include <sys/selinfo.h>
   49 #include <sys/pipe.h>
   50 #include <sys/proc.h>
   51 #include <sys/signalvar.h>
   52 #include <sys/sx.h>
   53 #include <sys/systm.h>
   54 #include <sys/un.h>
   55 #include <sys/unistd.h>
   56 #include <sys/vnode.h>
   57 
   58 /*
   59  * This structure is associated with the FIFO vnode and stores
   60  * the state associated with the FIFO.
   61  * Notes about locking:
   62  *   - fi_pipe is invariant since init time.
   63  *   - fi_readers and fi_writers are protected by the vnode lock.
   64  */
   65 struct fifoinfo {
   66         struct pipe *fi_pipe;
   67         long    fi_readers;
   68         long    fi_writers;
   69         u_int   fi_rgen;
   70         u_int   fi_wgen;
   71 };
   72 
   73 static vop_print_t      fifo_print;
   74 static vop_open_t       fifo_open;
   75 static vop_close_t      fifo_close;
   76 static vop_advlock_t    fifo_advlock;
   77 
   78 struct vop_vector fifo_specops = {
   79         .vop_default =          &default_vnodeops,
   80 
   81         .vop_advlock =          fifo_advlock,
   82         .vop_close =            fifo_close,
   83         .vop_create =           VOP_PANIC,
   84         .vop_getattr =          VOP_EBADF,
   85         .vop_ioctl =            VOP_PANIC,
   86         .vop_kqfilter =         VOP_PANIC,
   87         .vop_link =             VOP_PANIC,
   88         .vop_mkdir =            VOP_PANIC,
   89         .vop_mknod =            VOP_PANIC,
   90         .vop_open =             fifo_open,
   91         .vop_pathconf =         VOP_PANIC,
   92         .vop_print =            fifo_print,
   93         .vop_read =             VOP_PANIC,
   94         .vop_readdir =          VOP_PANIC,
   95         .vop_readlink =         VOP_PANIC,
   96         .vop_reallocblks =      VOP_PANIC,
   97         .vop_reclaim =          VOP_NULL,
   98         .vop_remove =           VOP_PANIC,
   99         .vop_rename =           VOP_PANIC,
  100         .vop_rmdir =            VOP_PANIC,
  101         .vop_setattr =          VOP_EBADF,
  102         .vop_symlink =          VOP_PANIC,
  103         .vop_write =            VOP_PANIC,
  104 };
  105 
  106 /*
  107  * Dispose of fifo resources.
  108  */
  109 static void
  110 fifo_cleanup(struct vnode *vp)
  111 {
  112         struct fifoinfo *fip;
  113 
  114         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
  115         fip = vp->v_fifoinfo;
  116         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
  117                 vp->v_fifoinfo = NULL;
  118                 pipe_dtor(fip->fi_pipe);
  119                 free(fip, M_VNODE);
  120         }
  121 }
  122 
  123 /*
  124  * Open called to set up a new instance of a fifo or
  125  * to find an active instance of a fifo.
  126  */
  127 /* ARGSUSED */
  128 static int
  129 fifo_open(ap)
  130         struct vop_open_args /* {
  131                 struct vnode *a_vp;
  132                 int  a_mode;
  133                 struct ucred *a_cred;
  134                 struct thread *a_td;
  135                 struct file *a_fp;
  136         } */ *ap;
  137 {
  138         struct vnode *vp;
  139         struct file *fp;
  140         struct thread *td;
  141         struct fifoinfo *fip;
  142         struct pipe *fpipe;
  143         u_int gen;
  144         int error, stops_deferred;
  145 
  146         vp = ap->a_vp;
  147         fp = ap->a_fp;
  148         td = ap->a_td;
  149         ASSERT_VOP_ELOCKED(vp, "fifo_open");
  150         if (fp == NULL || (ap->a_mode & FEXEC) != 0)
  151                 return (EINVAL);
  152         if ((fip = vp->v_fifoinfo) == NULL) {
  153                 pipe_named_ctor(&fpipe, td);
  154                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
  155                 fip->fi_pipe = fpipe;
  156                 fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0;
  157                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
  158                 vp->v_fifoinfo = fip;
  159         }
  160         fpipe = fip->fi_pipe;
  161         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
  162 
  163         /*
  164          * Use the pipe mutex here, in addition to the vnode lock,
  165          * in order to allow vnode lock dropping before msleep() calls
  166          * and still avoiding missed wakeups.
  167          */
  168         PIPE_LOCK(fpipe);
  169         if (ap->a_mode & FREAD) {
  170                 fip->fi_readers++;
  171                 fip->fi_rgen++;
  172                 if (fip->fi_readers == 1) {
  173                         fpipe->pipe_state &= ~PIPE_EOF;
  174                         if (fip->fi_writers > 0)
  175                                 wakeup(&fip->fi_writers);
  176                 }
  177                 fp->f_seqcount = fpipe->pipe_wgen - fip->fi_writers;
  178         }
  179         if (ap->a_mode & FWRITE) {
  180                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
  181                         PIPE_UNLOCK(fpipe);
  182                         if (fip->fi_writers == 0)
  183                                 fifo_cleanup(vp);
  184                         return (ENXIO);
  185                 }
  186                 fip->fi_writers++;
  187                 fip->fi_wgen++;
  188                 if (fip->fi_writers == 1) {
  189                         fpipe->pipe_state &= ~PIPE_EOF;
  190                         if (fip->fi_readers > 0)
  191                                 wakeup(&fip->fi_readers);
  192                 }
  193         }
  194         if ((ap->a_mode & O_NONBLOCK) == 0) {
  195                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
  196                         gen = fip->fi_wgen;
  197                         VOP_UNLOCK(vp, 0);
  198                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
  199                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
  200                             PDROP | PCATCH | PSOCK, "fifoor", 0);
  201                         sigallowstop(stops_deferred);
  202                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  203                         if (error != 0 && gen == fip->fi_wgen) {
  204                                 fip->fi_readers--;
  205                                 if (fip->fi_readers == 0) {
  206                                         PIPE_LOCK(fpipe);
  207                                         fpipe->pipe_state |= PIPE_EOF;
  208                                         if (fpipe->pipe_state & PIPE_WANTW)
  209                                                 wakeup(fpipe);
  210                                         PIPE_UNLOCK(fpipe);
  211                                         fifo_cleanup(vp);
  212                                 }
  213                                 return (error);
  214                         }
  215                         PIPE_LOCK(fpipe);
  216                         /*
  217                          * We must have got woken up because we had a writer.
  218                          * That (and not still having one) is the condition
  219                          * that we must wait for.
  220                          */
  221                 }
  222                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
  223                         gen = fip->fi_rgen;
  224                         VOP_UNLOCK(vp, 0);
  225                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
  226                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
  227                             PDROP | PCATCH | PSOCK, "fifoow", 0);
  228                         sigallowstop(stops_deferred);
  229                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  230                         if (error != 0 && gen == fip->fi_rgen) {
  231                                 fip->fi_writers--;
  232                                 if (fip->fi_writers == 0) {
  233                                         PIPE_LOCK(fpipe);
  234                                         fpipe->pipe_state |= PIPE_EOF;
  235                                         if (fpipe->pipe_state & PIPE_WANTR)
  236                                                 wakeup(fpipe);
  237                                         fpipe->pipe_wgen++;
  238                                         PIPE_UNLOCK(fpipe);
  239                                         fifo_cleanup(vp);
  240                                 }
  241                                 return (error);
  242                         }
  243                         /*
  244                          * We must have got woken up because we had
  245                          * a reader.  That (and not still having one)
  246                          * is the condition that we must wait for.
  247                          */
  248                         PIPE_LOCK(fpipe);
  249                 }
  250         }
  251         PIPE_UNLOCK(fpipe);
  252         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
  253         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
  254         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
  255         return (0);
  256 }
  257 
  258 /*
  259  * Device close routine
  260  */
  261 /* ARGSUSED */
  262 static int
  263 fifo_close(ap)
  264         struct vop_close_args /* {
  265                 struct vnode *a_vp;
  266                 int  a_fflag;
  267                 struct ucred *a_cred;
  268                 struct thread *a_td;
  269         } */ *ap;
  270 {
  271         struct vnode *vp;
  272         struct fifoinfo *fip;
  273         struct pipe *cpipe;
  274 
  275         vp = ap->a_vp;
  276         fip = vp->v_fifoinfo;
  277         cpipe = fip->fi_pipe;
  278         ASSERT_VOP_ELOCKED(vp, "fifo_close");
  279         if (ap->a_fflag & FREAD) {
  280                 fip->fi_readers--;
  281                 if (fip->fi_readers == 0) {
  282                         PIPE_LOCK(cpipe);
  283                         cpipe->pipe_state |= PIPE_EOF;
  284                         if ((cpipe->pipe_state & PIPE_WANTW)) {
  285                                 cpipe->pipe_state &= ~PIPE_WANTW;
  286                                 wakeup(cpipe);
  287                         }
  288                         pipeselwakeup(cpipe);
  289                         PIPE_UNLOCK(cpipe);
  290                 }
  291         }
  292         if (ap->a_fflag & FWRITE) {
  293                 fip->fi_writers--;
  294                 if (fip->fi_writers == 0) {
  295                         PIPE_LOCK(cpipe);
  296                         cpipe->pipe_state |= PIPE_EOF;
  297                         if ((cpipe->pipe_state & PIPE_WANTR)) {
  298                                 cpipe->pipe_state &= ~PIPE_WANTR;
  299                                 wakeup(cpipe);
  300                         }
  301                         cpipe->pipe_wgen++;
  302                         pipeselwakeup(cpipe);
  303                         PIPE_UNLOCK(cpipe);
  304                 }
  305         }
  306         fifo_cleanup(vp);
  307         return (0);
  308 }
  309 
  310 /*
  311  * Print out internal contents of a fifo vnode.
  312  */
  313 int
  314 fifo_printinfo(vp)
  315         struct vnode *vp;
  316 {
  317         struct fifoinfo *fip = vp->v_fifoinfo;
  318 
  319         if (fip == NULL){
  320                 printf(", NULL v_fifoinfo");
  321                 return (0);
  322         }
  323         printf(", fifo with %ld readers and %ld writers",
  324                 fip->fi_readers, fip->fi_writers);
  325         return (0);
  326 }
  327 
  328 /*
  329  * Print out the contents of a fifo vnode.
  330  */
  331 static int
  332 fifo_print(ap)
  333         struct vop_print_args /* {
  334                 struct vnode *a_vp;
  335         } */ *ap;
  336 {
  337         printf("    ");
  338         fifo_printinfo(ap->a_vp);
  339         printf("\n");
  340         return (0);
  341 }
  342 
  343 /*
  344  * Fifo advisory byte-level locks.
  345  */
  346 /* ARGSUSED */
  347 static int
  348 fifo_advlock(ap)
  349         struct vop_advlock_args /* {
  350                 struct vnode *a_vp;
  351                 caddr_t  a_id;
  352                 int  a_op;
  353                 struct flock *a_fl;
  354                 int  a_flags;
  355         } */ *ap;
  356 {
  357 
  358         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
  359 }
  360 

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