sys/fs/fifofs/fifo_vnops.c

   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
 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