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 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);
 158                 fip->fi_pipe = fpipe;
 159                 fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 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         fip = vp->v_fifoinfo;
 286         cpipe = fip->fi_pipe;
 287         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 288         if (ap->a_fflag & FREAD) {
 289                 fip->fi_readers--;
 290                 if (fip->fi_readers == 0) {
 291                         PIPE_LOCK(cpipe);
 292                         cpipe->pipe_state |= PIPE_EOF;
 293                         if ((cpipe->pipe_state & PIPE_WANTW)) {
 294                                 cpipe->pipe_state &= ~PIPE_WANTW;
 295                                 wakeup(cpipe);
 296                         }
 297                         pipeselwakeup(cpipe);
 298                         PIPE_UNLOCK(cpipe);
 299                 }
 300         }
 301         if (ap->a_fflag & FWRITE) {
 302                 fip->fi_writers--;
 303                 if (fip->fi_writers == 0) {
 304                         PIPE_LOCK(cpipe);
 305                         cpipe->pipe_state |= PIPE_EOF;
 306                         if ((cpipe->pipe_state & PIPE_WANTR)) {
 307                                 cpipe->pipe_state &= ~PIPE_WANTR;
 308                                 wakeup(cpipe);
 309                         }
 310                         cpipe->pipe_wgen++;
 311                         pipeselwakeup(cpipe);
 312                         PIPE_UNLOCK(cpipe);
 313                 }
 314         }
 315         fifo_cleanup(vp);
 316         return (0);
 317 }
 318
 319 /*
 320  * Print out internal contents of a fifo vnode.
 321  */
 322 int
 323 fifo_printinfo(vp)
 324         struct vnode *vp;
 325 {
 326         struct fifoinfo *fip = vp->v_fifoinfo;
 327
 328         if (fip == NULL){
 329                 printf(", NULL v_fifoinfo");
 330                 return (0);
 331         }
 332         printf(", fifo with %ld readers and %ld writers",
 333                 fip->fi_readers, fip->fi_writers);
 334         return (0);
 335 }
 336
 337 /*
 338  * Print out the contents of a fifo vnode.
 339  */
 340 static int
 341 fifo_print(ap)
 342         struct vop_print_args /* {
 343                 struct vnode *a_vp;
 344         } */ *ap;
 345 {
 346         printf("    ");
 347         fifo_printinfo(ap->a_vp);
 348         printf("\n");
 349         return (0);
 350 }
 351
 352 /*
 353  * Fifo advisory byte-level locks.
 354  */
 355 /* ARGSUSED */
 356 static int
 357 fifo_advlock(ap)
 358         struct vop_advlock_args /* {
 359                 struct vnode *a_vp;
 360                 caddr_t  a_id;
 361                 int  a_op;
 362                 struct flock *a_fl;
 363                 int  a_flags;
 364         } */ *ap;
 365 {
 366
 367         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 368 }
 369