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  * $FreeBSD$
   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 VFS_VOP_VECTOR_REGISTER(fifo_specops);
  106 
  107 /*
  108  * Dispose of fifo resources.
  109  */
  110 static void
  111 fifo_cleanup(struct vnode *vp)
  112 {
  113         struct fifoinfo *fip;
  114 
  115         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
  116         fip = vp->v_fifoinfo;
  117         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
  118                 vp->v_fifoinfo = NULL;
  119                 pipe_dtor(fip->fi_pipe);
  120                 free(fip, M_VNODE);
  121         }
  122 }
  123 
  124 /*
  125  * Open called to set up a new instance of a fifo or
  126  * to find an active instance of a fifo.
  127  */
  128 /* ARGSUSED */
  129 static int
  130 fifo_open(ap)
  131         struct vop_open_args /* {
  132                 struct vnode *a_vp;
  133                 int  a_mode;
  134                 struct ucred *a_cred;
  135                 struct thread *a_td;
  136                 struct file *a_fp;
  137         } */ *ap;
  138 {
  139         struct vnode *vp;
  140         struct file *fp;
  141         struct thread *td;
  142         struct fifoinfo *fip;
  143         struct pipe *fpipe;
  144         u_int gen;
  145         int error, stops_deferred;
  146 
  147         vp = ap->a_vp;
  148         fp = ap->a_fp;
  149         td = ap->a_td;
  150         ASSERT_VOP_ELOCKED(vp, "fifo_open");
  151         if (fp == NULL || (ap->a_mode & FEXEC) != 0)
  152                 return (EINVAL);
  153         if ((fip = vp->v_fifoinfo) == NULL) {
  154                 error = pipe_named_ctor(&fpipe, td);
  155                 if (error != 0)
  156                         return (error);
  157                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK | M_ZERO);
  158                 fip->fi_pipe = fpipe;
  159                 fpipe->pipe_wgen = 0;
  160                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
  161                 vp->v_fifoinfo = fip;
  162         }
  163         fpipe = fip->fi_pipe;
  164         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
  165 
  166         /*
  167          * Use the pipe mutex here, in addition to the vnode lock,
  168          * in order to allow vnode lock dropping before msleep() calls
  169          * and still avoiding missed wakeups.
  170          */
  171         PIPE_LOCK(fpipe);
  172         if (ap->a_mode & FREAD) {
  173                 fip->fi_readers++;
  174                 fip->fi_rgen++;
  175                 if (fip->fi_readers == 1) {
  176                         fpipe->pipe_state &= ~PIPE_EOF;
  177                         if (fip->fi_writers > 0) {
  178                                 wakeup(&fip->fi_writers);
  179                                 pipeselwakeup(fpipe);
  180                         }
  181                 }
  182                 fp->f_pipegen = fpipe->pipe_wgen - fip->fi_writers;
  183         }
  184         if (ap->a_mode & FWRITE) {
  185                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
  186                         PIPE_UNLOCK(fpipe);
  187                         if (fip->fi_writers == 0)
  188                                 fifo_cleanup(vp);
  189                         return (ENXIO);
  190                 }
  191                 fip->fi_writers++;
  192                 fip->fi_wgen++;
  193                 if (fip->fi_writers == 1) {
  194                         fpipe->pipe_state &= ~PIPE_EOF;
  195                         if (fip->fi_readers > 0) {
  196                                 wakeup(&fip->fi_readers);
  197                                 pipeselwakeup(fpipe);
  198                         }
  199                 }
  200         }
  201         if ((ap->a_mode & O_NONBLOCK) == 0) {
  202                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
  203                         gen = fip->fi_wgen;
  204                         VOP_UNLOCK(vp);
  205                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
  206                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
  207                             PDROP | PCATCH | PSOCK, "fifoor", 0);
  208                         sigallowstop(stops_deferred);
  209                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  210                         if (error != 0 && gen == fip->fi_wgen) {
  211                                 fip->fi_readers--;
  212                                 if (fip->fi_readers == 0) {
  213                                         PIPE_LOCK(fpipe);
  214                                         fpipe->pipe_state |= PIPE_EOF;
  215                                         if (fpipe->pipe_state & PIPE_WANTW)
  216                                                 wakeup(fpipe);
  217                                         pipeselwakeup(fpipe);
  218                                         PIPE_UNLOCK(fpipe);
  219                                         fifo_cleanup(vp);
  220                                 }
  221                                 return (error);
  222                         }
  223                         PIPE_LOCK(fpipe);
  224                         /*
  225                          * We must have got woken up because we had a writer.
  226                          * That (and not still having one) is the condition
  227                          * that we must wait for.
  228                          */
  229                 }
  230                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
  231                         gen = fip->fi_rgen;
  232                         VOP_UNLOCK(vp);
  233                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
  234                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
  235                             PDROP | PCATCH | PSOCK, "fifoow", 0);
  236                         sigallowstop(stops_deferred);
  237                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  238                         if (error != 0 && gen == fip->fi_rgen) {
  239                                 fip->fi_writers--;
  240                                 if (fip->fi_writers == 0) {
  241                                         PIPE_LOCK(fpipe);
  242                                         fpipe->pipe_state |= PIPE_EOF;
  243                                         if (fpipe->pipe_state & PIPE_WANTR)
  244                                                 wakeup(fpipe);
  245                                         fpipe->pipe_wgen++;
  246                                         pipeselwakeup(fpipe);
  247                                         PIPE_UNLOCK(fpipe);
  248                                         fifo_cleanup(vp);
  249                                 }
  250                                 return (error);
  251                         }
  252                         /*
  253                          * We must have got woken up because we had
  254                          * a reader.  That (and not still having one)
  255                          * is the condition that we must wait for.
  256                          */
  257                         PIPE_LOCK(fpipe);
  258                 }
  259         }
  260         PIPE_UNLOCK(fpipe);
  261         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
  262         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
  263         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
  264         return (0);
  265 }
  266 
  267 /*
  268  * Device close routine
  269  */
  270 /* ARGSUSED */
  271 static int
  272 fifo_close(ap)
  273         struct vop_close_args /* {
  274                 struct vnode *a_vp;
  275                 int  a_fflag;
  276                 struct ucred *a_cred;
  277                 struct thread *a_td;
  278         } */ *ap;
  279 {
  280         struct vnode *vp;
  281         struct fifoinfo *fip;
  282         struct pipe *cpipe;
  283 
  284         vp = ap->a_vp;
  285         ASSERT_VOP_ELOCKED(vp, "fifo_close");
  286         fip = vp->v_fifoinfo;
  287 
  288         /*
  289          * During open, it is possible that the fifo vnode is relocked
  290          * after the vnode is instantiated but before VOP_OPEN() is
  291          * done.  For instance, vn_open_vnode() might need to upgrade
  292          * vnode lock, or ffs_vput_pair() needs to unlock vp to sync
  293          * dvp.  In this case, reclaim can observe us with v_fifoinfo
  294          * equal to NULL.
  295          */
  296         if (fip == NULL)
  297                 return (0);
  298 
  299         cpipe = fip->fi_pipe;
  300         if (ap->a_fflag & FREAD) {
  301                 fip->fi_readers--;
  302                 if (fip->fi_readers == 0) {
  303                         PIPE_LOCK(cpipe);
  304                         cpipe->pipe_state |= PIPE_EOF;
  305                         if ((cpipe->pipe_state & PIPE_WANTW)) {
  306                                 cpipe->pipe_state &= ~PIPE_WANTW;
  307                                 wakeup(cpipe);
  308                         }
  309                         pipeselwakeup(cpipe);
  310                         PIPE_UNLOCK(cpipe);
  311                 }
  312         }
  313         if (ap->a_fflag & FWRITE) {
  314                 fip->fi_writers--;
  315                 if (fip->fi_writers == 0) {
  316                         PIPE_LOCK(cpipe);
  317                         cpipe->pipe_state |= PIPE_EOF;
  318                         if ((cpipe->pipe_state & PIPE_WANTR)) {
  319                                 cpipe->pipe_state &= ~PIPE_WANTR;
  320                                 wakeup(cpipe);
  321                         }
  322                         cpipe->pipe_wgen++;
  323                         pipeselwakeup(cpipe);
  324                         PIPE_UNLOCK(cpipe);
  325                 }
  326         }
  327         fifo_cleanup(vp);
  328         return (0);
  329 }
  330 
  331 /*
  332  * Print out internal contents of a fifo vnode.
  333  */
  334 int
  335 fifo_printinfo(vp)
  336         struct vnode *vp;
  337 {
  338         struct fifoinfo *fip = vp->v_fifoinfo;
  339 
  340         if (fip == NULL){
  341                 printf(", NULL v_fifoinfo");
  342                 return (0);
  343         }
  344         printf(", fifo with %ld readers and %ld writers",
  345                 fip->fi_readers, fip->fi_writers);
  346         return (0);
  347 }
  348 
  349 /*
  350  * Print out the contents of a fifo vnode.
  351  */
  352 static int
  353 fifo_print(ap)
  354         struct vop_print_args /* {
  355                 struct vnode *a_vp;
  356         } */ *ap;
  357 {
  358         printf("    ");
  359         fifo_printinfo(ap->a_vp);
  360         printf("\n");
  361         return (0);
  362 }
  363 
  364 /*
  365  * Fifo advisory byte-level locks.
  366  */
  367 /* ARGSUSED */
  368 static int
  369 fifo_advlock(ap)
  370         struct vop_advlock_args /* {
  371                 struct vnode *a_vp;
  372                 caddr_t  a_id;
  373                 int  a_op;
  374                 struct flock *a_fl;
  375                 int  a_flags;
  376         } */ *ap;
  377 {
  378 
  379         if ((ap->a_flags & F_FLOCK) == 0)
  380                 return (EINVAL);
  381         return (vop_stdadvlock(ap));
  382 }

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