sys/fs/fifofs/fifo_vnops.c

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