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

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