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_link =             VOP_PANIC,
  87         .vop_mkdir =            VOP_PANIC,
  88         .vop_mknod =            VOP_PANIC,
  89         .vop_open =             fifo_open,
  90         .vop_pathconf =         VOP_PANIC,
  91         .vop_print =            fifo_print,
  92         .vop_read =             VOP_PANIC,
  93         .vop_readdir =          VOP_PANIC,
  94         .vop_readlink =         VOP_PANIC,
  95         .vop_reallocblks =      VOP_PANIC,
  96         .vop_reclaim =          VOP_NULL,
  97         .vop_remove =           VOP_PANIC,
  98         .vop_rename =           VOP_PANIC,
  99         .vop_rmdir =            VOP_PANIC,
 100         .vop_setattr =          VOP_EBADF,
 101         .vop_symlink =          VOP_PANIC,
 102         .vop_write =            VOP_PANIC,
 103 };
 104 VFS_VOP_VECTOR_REGISTER(fifo_specops);
 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(struct vop_open_args *ap)
 130 {
 131         struct vnode *vp;
 132         struct file *fp;
 133         struct thread *td;
 134         struct fifoinfo *fip;
 135         struct pipe *fpipe;
 136         u_int gen;
 137         int error, stops_deferred;
 138
 139         vp = ap->a_vp;
 140         fp = ap->a_fp;
 141         td = ap->a_td;
 142         ASSERT_VOP_ELOCKED(vp, "fifo_open");
 143         if (fp == NULL || (ap->a_mode & FEXEC) != 0)
 144                 return (EINVAL);
 145         if ((fip = vp->v_fifoinfo) == NULL) {
 146                 error = pipe_named_ctor(&fpipe, td);
 147                 if (error != 0)
 148                         return (error);
 149                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK | M_ZERO);
 150                 fip->fi_pipe = fpipe;
 151                 fpipe->pipe_wgen = 0;
 152                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
 153                 vp->v_fifoinfo = fip;
 154         }
 155         fpipe = fip->fi_pipe;
 156         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
 157
 158         /*
 159          * Use the pipe mutex here, in addition to the vnode lock,
 160          * in order to allow vnode lock dropping before msleep() calls
 161          * and still avoiding missed wakeups.
 162          */
 163         PIPE_LOCK(fpipe);
 164         if (ap->a_mode & FREAD) {
 165                 fip->fi_readers++;
 166                 fip->fi_rgen++;
 167                 if (fip->fi_readers == 1) {
 168                         fpipe->pipe_state &= ~PIPE_EOF;
 169                         if (fip->fi_writers > 0) {
 170                                 wakeup(&fip->fi_writers);
 171                                 pipeselwakeup(fpipe);
 172                         }
 173                 }
 174                 fp->f_pipegen = 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                 fip->fi_wgen++;
 185                 if (fip->fi_writers == 1) {
 186                         fpipe->pipe_state &= ~PIPE_EOF;
 187                         if (fip->fi_readers > 0) {
 188                                 wakeup(&fip->fi_readers);
 189                                 pipeselwakeup(fpipe);
 190                         }
 191                 }
 192         }
 193         if ((ap->a_mode & O_NONBLOCK) == 0) {
 194                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
 195                         gen = fip->fi_wgen;
 196                         VOP_UNLOCK(vp);
 197                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
 198                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
 199                             PDROP | PCATCH | PSOCK, "fifoor", 0);
 200                         sigallowstop(stops_deferred);
 201                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 202                         if (error != 0 && gen == fip->fi_wgen) {
 203                                 fip->fi_readers--;
 204                                 if (fip->fi_readers == 0) {
 205                                         PIPE_LOCK(fpipe);
 206                                         fpipe->pipe_state |= PIPE_EOF;
 207                                         if (fpipe->pipe_state & PIPE_WANTW)
 208                                                 wakeup(fpipe);
 209                                         pipeselwakeup(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);
 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                                         pipeselwakeup(fpipe);
 239                                         PIPE_UNLOCK(fpipe);
 240                                         fifo_cleanup(vp);
 241                                 }
 242                                 return (error);
 243                         }
 244                         /*
 245                          * We must have got woken up because we had
 246                          * a reader.  That (and not still having one)
 247                          * is the condition that we must wait for.
 248                          */
 249                         PIPE_LOCK(fpipe);
 250                 }
 251         }
 252         PIPE_UNLOCK(fpipe);
 253         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
 254         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
 255         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
 256         return (0);
 257 }
 258
 259 /*
 260  * Device close routine
 261  */
 262 /* ARGSUSED */
 263 static int
 264 fifo_close(struct vop_close_args *ap)
 265 {
 266         struct vnode *vp;
 267         struct fifoinfo *fip;
 268         struct pipe *cpipe;
 269
 270         vp = ap->a_vp;
 271         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 272         fip = vp->v_fifoinfo;
 273
 274         /*
 275          * During open, it is possible that the fifo vnode is relocked
 276          * after the vnode is instantiated but before VOP_OPEN() is
 277          * done.  For instance, vn_open_vnode() might need to upgrade
 278          * vnode lock, or ffs_vput_pair() needs to unlock vp to sync
 279          * dvp.  In this case, reclaim can observe us with v_fifoinfo
 280          * equal to NULL.
 281          */
 282         if (fip == NULL)
 283                 return (0);
 284
 285         cpipe = fip->fi_pipe;
 286         if (ap->a_fflag & FREAD) {
 287                 fip->fi_readers--;
 288                 if (fip->fi_readers == 0) {
 289                         PIPE_LOCK(cpipe);
 290                         cpipe->pipe_state |= PIPE_EOF;
 291                         if ((cpipe->pipe_state & PIPE_WANTW)) {
 292                                 cpipe->pipe_state &= ~PIPE_WANTW;
 293                                 wakeup(cpipe);
 294                         }
 295                         pipeselwakeup(cpipe);
 296                         PIPE_UNLOCK(cpipe);
 297                 }
 298         }
 299         if (ap->a_fflag & FWRITE) {
 300                 fip->fi_writers--;
 301                 if (fip->fi_writers == 0) {
 302                         PIPE_LOCK(cpipe);
 303                         cpipe->pipe_state |= PIPE_EOF;
 304                         if ((cpipe->pipe_state & PIPE_WANTR)) {
 305                                 cpipe->pipe_state &= ~PIPE_WANTR;
 306                                 wakeup(cpipe);
 307                         }
 308                         cpipe->pipe_wgen++;
 309                         pipeselwakeup(cpipe);
 310                         PIPE_UNLOCK(cpipe);
 311                 }
 312         }
 313         fifo_cleanup(vp);
 314         return (0);
 315 }
 316
 317 /*
 318  * Print out internal contents of a fifo vnode.
 319  */
 320 int
 321 fifo_printinfo(struct vnode *vp)
 322 {
 323         struct fifoinfo *fip = vp->v_fifoinfo;
 324
 325         if (fip == NULL){
 326                 printf(", NULL v_fifoinfo");
 327                 return (0);
 328         }
 329         printf(", fifo with %ld readers and %ld writers",
 330                 fip->fi_readers, fip->fi_writers);
 331         return (0);
 332 }
 333
 334 /*
 335  * Print out the contents of a fifo vnode.
 336  */
 337 static int
 338 fifo_print(struct vop_print_args *ap)
 339 {
 340         printf("    ");
 341         fifo_printinfo(ap->a_vp);
 342         printf("\n");
 343         return (0);
 344 }
 345
 346 /*
 347  * Fifo advisory byte-level locks.
 348  */
 349 /* ARGSUSED */
 350 static int
 351 fifo_advlock(struct vop_advlock_args *ap)
 352 {
 353
 354         if ((ap->a_flags & F_FLOCK) == 0)
 355                 return (EINVAL);
 356         return (vop_stdadvlock(ap));
 357 }