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  * 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: releng/10.0/sys/fs/fifofs/fifo_vnops.c 238936 2012-07-31 05:48:35Z davidxu $
   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 };
   68 
   69 static vop_print_t      fifo_print;
   70 static vop_open_t       fifo_open;
   71 static vop_close_t      fifo_close;
   72 static vop_pathconf_t   fifo_pathconf;
   73 static vop_advlock_t    fifo_advlock;
   74 
   75 struct vop_vector fifo_specops = {
   76         .vop_default =          &default_vnodeops,
   77 
   78         .vop_advlock =          fifo_advlock,
   79         .vop_close =            fifo_close,
   80         .vop_create =           VOP_PANIC,
   81         .vop_getattr =          VOP_EBADF,
   82         .vop_ioctl =            VOP_PANIC,
   83         .vop_kqfilter =         VOP_PANIC,
   84         .vop_link =             VOP_PANIC,
   85         .vop_mkdir =            VOP_PANIC,
   86         .vop_mknod =            VOP_PANIC,
   87         .vop_open =             fifo_open,
   88         .vop_pathconf =         fifo_pathconf,
   89         .vop_print =            fifo_print,
   90         .vop_read =             VOP_PANIC,
   91         .vop_readdir =          VOP_PANIC,
   92         .vop_readlink =         VOP_PANIC,
   93         .vop_reallocblks =      VOP_PANIC,
   94         .vop_reclaim =          VOP_NULL,
   95         .vop_remove =           VOP_PANIC,
   96         .vop_rename =           VOP_PANIC,
   97         .vop_rmdir =            VOP_PANIC,
   98         .vop_setattr =          VOP_EBADF,
   99         .vop_symlink =          VOP_PANIC,
  100         .vop_write =            VOP_PANIC,
  101 };
  102 
  103 /*
  104  * Dispose of fifo resources.
  105  */
  106 static void
  107 fifo_cleanup(struct vnode *vp)
  108 {
  109         struct fifoinfo *fip;
  110 
  111         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
  112         fip = vp->v_fifoinfo;
  113         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
  114                 vp->v_fifoinfo = NULL;
  115                 pipe_dtor(fip->fi_pipe);
  116                 free(fip, M_VNODE);
  117         }
  118 }
  119 
  120 /*
  121  * Open called to set up a new instance of a fifo or
  122  * to find an active instance of a fifo.
  123  */
  124 /* ARGSUSED */
  125 static int
  126 fifo_open(ap)
  127         struct vop_open_args /* {
  128                 struct vnode *a_vp;
  129                 int  a_mode;
  130                 struct ucred *a_cred;
  131                 struct thread *a_td;
  132                 struct file *a_fp;
  133         } */ *ap;
  134 {
  135         struct vnode *vp;
  136         struct file *fp;
  137         struct thread *td;
  138         struct fifoinfo *fip;
  139         struct pipe *fpipe;
  140         int error;
  141 
  142         vp = ap->a_vp;
  143         fp = ap->a_fp;
  144         td = ap->a_td;
  145         ASSERT_VOP_ELOCKED(vp, "fifo_open");
  146         if (fp == NULL)
  147                 return (EINVAL);
  148         if ((fip = vp->v_fifoinfo) == NULL) {
  149                 error = pipe_named_ctor(&fpipe, td);
  150                 if (error != 0)
  151                         return (error);
  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                 if (fip->fi_readers == 1) {
  170                         fpipe->pipe_state &= ~PIPE_EOF;
  171                         if (fip->fi_writers > 0)
  172                                 wakeup(&fip->fi_writers);
  173                 }
  174                 fp->f_seqcount = fpipe->pipe_wgen - fip->fi_writers;
  175         }
  176         if (ap->a_mode & FWRITE) {
  177                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
  178                         PIPE_UNLOCK(fpipe);
  179                         if (fip->fi_writers == 0)
  180                                 fifo_cleanup(vp);
  181                         return (ENXIO);
  182                 }
  183                 fip->fi_writers++;
  184                 if (fip->fi_writers == 1) {
  185                         fpipe->pipe_state &= ~PIPE_EOF;
  186                         if (fip->fi_readers > 0)
  187                                 wakeup(&fip->fi_readers);
  188                 }
  189         }
  190         if ((ap->a_mode & O_NONBLOCK) == 0) {
  191                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
  192                         VOP_UNLOCK(vp, 0);
  193                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
  194                             PDROP | PCATCH | PSOCK, "fifoor", 0);
  195                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  196                         if (error) {
  197                                 fip->fi_readers--;
  198                                 if (fip->fi_readers == 0) {
  199                                         PIPE_LOCK(fpipe);
  200                                         fpipe->pipe_state |= PIPE_EOF;
  201                                         if (fpipe->pipe_state & PIPE_WANTW)
  202                                                 wakeup(fpipe);
  203                                         PIPE_UNLOCK(fpipe);
  204                                         fifo_cleanup(vp);
  205                                 }
  206                                 return (error);
  207                         }
  208                         PIPE_LOCK(fpipe);
  209                         /*
  210                          * We must have got woken up because we had a writer.
  211                          * That (and not still having one) is the condition
  212                          * that we must wait for.
  213                          */
  214                 }
  215                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
  216                         VOP_UNLOCK(vp, 0);
  217                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
  218                             PDROP | PCATCH | PSOCK, "fifoow", 0);
  219                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  220                         if (error) {
  221                                 fip->fi_writers--;
  222                                 if (fip->fi_writers == 0) {
  223                                         PIPE_LOCK(fpipe);
  224                                         fpipe->pipe_state |= PIPE_EOF;
  225                                         if (fpipe->pipe_state & PIPE_WANTR)
  226                                                 wakeup(fpipe);
  227                                         fpipe->pipe_wgen++;
  228                                         PIPE_UNLOCK(fpipe);
  229                                         fifo_cleanup(vp);
  230                                 }
  231                                 return (error);
  232                         }
  233                         /*
  234                          * We must have got woken up because we had
  235                          * a reader.  That (and not still having one)
  236                          * is the condition that we must wait for.
  237                          */
  238                         PIPE_LOCK(fpipe);
  239                 }
  240         }
  241         PIPE_UNLOCK(fpipe);
  242         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
  243         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
  244         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
  245         return (0);
  246 }
  247 
  248 /*
  249  * Device close routine
  250  */
  251 /* ARGSUSED */
  252 static int
  253 fifo_close(ap)
  254         struct vop_close_args /* {
  255                 struct vnode *a_vp;
  256                 int  a_fflag;
  257                 struct ucred *a_cred;
  258                 struct thread *a_td;
  259         } */ *ap;
  260 {
  261         struct vnode *vp;
  262         struct fifoinfo *fip;
  263         struct pipe *cpipe;
  264 
  265         vp = ap->a_vp;
  266         fip = vp->v_fifoinfo;
  267         cpipe = fip->fi_pipe;
  268         ASSERT_VOP_ELOCKED(vp, "fifo_close");
  269         if (ap->a_fflag & FREAD) {
  270                 fip->fi_readers--;
  271                 if (fip->fi_readers == 0) {
  272                         PIPE_LOCK(cpipe);
  273                         cpipe->pipe_state |= PIPE_EOF;
  274                         if ((cpipe->pipe_state & PIPE_WANTW)) {
  275                                 cpipe->pipe_state &= ~PIPE_WANTW;
  276                                 wakeup(cpipe);
  277                         }
  278                         pipeselwakeup(cpipe);
  279                         PIPE_UNLOCK(cpipe);
  280                 }
  281         }
  282         if (ap->a_fflag & FWRITE) {
  283                 fip->fi_writers--;
  284                 if (fip->fi_writers == 0) {
  285                         PIPE_LOCK(cpipe);
  286                         cpipe->pipe_state |= PIPE_EOF;
  287                         if ((cpipe->pipe_state & PIPE_WANTR)) {
  288                                 cpipe->pipe_state &= ~PIPE_WANTR;
  289                                 wakeup(cpipe);
  290                         }
  291                         cpipe->pipe_wgen++;
  292                         pipeselwakeup(cpipe);
  293                         PIPE_UNLOCK(cpipe);
  294                 }
  295         }
  296         fifo_cleanup(vp);
  297         return (0);
  298 }
  299 
  300 /*
  301  * Print out internal contents of a fifo vnode.
  302  */
  303 int
  304 fifo_printinfo(vp)
  305         struct vnode *vp;
  306 {
  307         register struct fifoinfo *fip = vp->v_fifoinfo;
  308 
  309         if (fip == NULL){
  310                 printf(", NULL v_fifoinfo");
  311                 return (0);
  312         }
  313         printf(", fifo with %ld readers and %ld writers",
  314                 fip->fi_readers, fip->fi_writers);
  315         return (0);
  316 }
  317 
  318 /*
  319  * Print out the contents of a fifo vnode.
  320  */
  321 static int
  322 fifo_print(ap)
  323         struct vop_print_args /* {
  324                 struct vnode *a_vp;
  325         } */ *ap;
  326 {
  327         printf("    ");
  328         fifo_printinfo(ap->a_vp);
  329         printf("\n");
  330         return (0);
  331 }
  332 
  333 /*
  334  * Return POSIX pathconf information applicable to fifo's.
  335  */
  336 static int
  337 fifo_pathconf(ap)
  338         struct vop_pathconf_args /* {
  339                 struct vnode *a_vp;
  340                 int a_name;
  341                 int *a_retval;
  342         } */ *ap;
  343 {
  344 
  345         switch (ap->a_name) {
  346         case _PC_LINK_MAX:
  347                 *ap->a_retval = LINK_MAX;
  348                 return (0);
  349         case _PC_PIPE_BUF:
  350                 *ap->a_retval = PIPE_BUF;
  351                 return (0);
  352         case _PC_CHOWN_RESTRICTED:
  353                 *ap->a_retval = 1;
  354                 return (0);
  355         default:
  356                 return (EINVAL);
  357         }
  358         /* NOTREACHED */
  359 }
  360 
  361 /*
  362  * Fifo advisory byte-level locks.
  363  */
  364 /* ARGSUSED */
  365 static int
  366 fifo_advlock(ap)
  367         struct vop_advlock_args /* {
  368                 struct vnode *a_vp;
  369                 caddr_t  a_id;
  370                 int  a_op;
  371                 struct flock *a_fl;
  372                 int  a_flags;
  373         } */ *ap;
  374 {
  375 
  376         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
  377 }
  378 

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