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  * 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  * $FreeBSD$
  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_pathconf_t   fifo_pathconf;
  75 static vop_advlock_t    fifo_advlock;
  76
  77 struct vop_vector fifo_specops = {
  78         .vop_default =          &default_vnodeops,
  79
  80         .vop_advlock =          fifo_advlock,
  81         .vop_close =            fifo_close,
  82         .vop_create =           VOP_PANIC,
  83         .vop_getattr =          VOP_EBADF,
  84         .vop_ioctl =            VOP_PANIC,
  85         .vop_kqfilter =         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 =         fifo_pathconf,
  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
 105 /*
 106  * Dispose of fifo resources.
 107  */
 108 static void
 109 fifo_cleanup(struct vnode *vp)
 110 {
 111         struct fifoinfo *fip;
 112
 113         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
 114         fip = vp->v_fifoinfo;
 115         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
 116                 vp->v_fifoinfo = NULL;
 117                 pipe_dtor(fip->fi_pipe);
 118                 free(fip, M_VNODE);
 119         }
 120 }
 121
 122 /*
 123  * Open called to set up a new instance of a fifo or
 124  * to find an active instance of a fifo.
 125  */
 126 /* ARGSUSED */
 127 static int
 128 fifo_open(ap)
 129         struct vop_open_args /* {
 130                 struct vnode *a_vp;
 131                 int  a_mode;
 132                 struct ucred *a_cred;
 133                 struct thread *a_td;
 134                 struct file *a_fp;
 135         } */ *ap;
 136 {
 137         struct vnode *vp;
 138         struct file *fp;
 139         struct thread *td;
 140         struct fifoinfo *fip;
 141         struct pipe *fpipe;
 142         u_int gen;
 143         int error, stops_deferred;
 144
 145         vp = ap->a_vp;
 146         fp = ap->a_fp;
 147         td = ap->a_td;
 148         ASSERT_VOP_ELOCKED(vp, "fifo_open");
 149         if (fp == NULL || (ap->a_mode & FEXEC) != 0)
 150                 return (EINVAL);
 151         if ((fip = vp->v_fifoinfo) == NULL) {
 152                 pipe_named_ctor(&fpipe, td);
 153                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
 154                 fip->fi_pipe = fpipe;
 155                 fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0;
 156                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
 157                 vp->v_fifoinfo = fip;
 158         }
 159         fpipe = fip->fi_pipe;
 160         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
 161
 162         /*
 163          * Use the pipe mutex here, in addition to the vnode lock,
 164          * in order to allow vnode lock dropping before msleep() calls
 165          * and still avoiding missed wakeups.
 166          */
 167         PIPE_LOCK(fpipe);
 168         if (ap->a_mode & FREAD) {
 169                 fip->fi_readers++;
 170                 fip->fi_rgen++;
 171                 if (fip->fi_readers == 1) {
 172                         fpipe->pipe_state &= ~PIPE_EOF;
 173                         if (fip->fi_writers > 0)
 174                                 wakeup(&fip->fi_writers);
 175                 }
 176                 fp->f_seqcount = fpipe->pipe_wgen - fip->fi_writers;
 177         }
 178         if (ap->a_mode & FWRITE) {
 179                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
 180                         PIPE_UNLOCK(fpipe);
 181                         if (fip->fi_writers == 0)
 182                                 fifo_cleanup(vp);
 183                         return (ENXIO);
 184                 }
 185                 fip->fi_writers++;
 186                 fip->fi_wgen++;
 187                 if (fip->fi_writers == 1) {
 188                         fpipe->pipe_state &= ~PIPE_EOF;
 189                         if (fip->fi_readers > 0)
 190                                 wakeup(&fip->fi_readers);
 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, 0);
 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                                         PIPE_UNLOCK(fpipe);
 210                                         fifo_cleanup(vp);
 211                                 }
 212                                 return (error);
 213                         }
 214                         PIPE_LOCK(fpipe);
 215                         /*
 216                          * We must have got woken up because we had a writer.
 217                          * That (and not still having one) is the condition
 218                          * that we must wait for.
 219                          */
 220                 }
 221                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
 222                         gen = fip->fi_rgen;
 223                         VOP_UNLOCK(vp, 0);
 224                         stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF);
 225                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
 226                             PDROP | PCATCH | PSOCK, "fifoow", 0);
 227                         sigallowstop(stops_deferred);
 228                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 229                         if (error != 0 && gen == fip->fi_rgen) {
 230                                 fip->fi_writers--;
 231                                 if (fip->fi_writers == 0) {
 232                                         PIPE_LOCK(fpipe);
 233                                         fpipe->pipe_state |= PIPE_EOF;
 234                                         if (fpipe->pipe_state & PIPE_WANTR)
 235                                                 wakeup(fpipe);
 236                                         fpipe->pipe_wgen++;
 237                                         PIPE_UNLOCK(fpipe);
 238                                         fifo_cleanup(vp);
 239                                 }
 240                                 return (error);
 241                         }
 242                         /*
 243                          * We must have got woken up because we had
 244                          * a reader.  That (and not still having one)
 245                          * is the condition that we must wait for.
 246                          */
 247                         PIPE_LOCK(fpipe);
 248                 }
 249         }
 250         PIPE_UNLOCK(fpipe);
 251         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
 252         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
 253         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
 254         return (0);
 255 }
 256
 257 /*
 258  * Device close routine
 259  */
 260 /* ARGSUSED */
 261 static int
 262 fifo_close(ap)
 263         struct vop_close_args /* {
 264                 struct vnode *a_vp;
 265                 int  a_fflag;
 266                 struct ucred *a_cred;
 267                 struct thread *a_td;
 268         } */ *ap;
 269 {
 270         struct vnode *vp;
 271         struct fifoinfo *fip;
 272         struct pipe *cpipe;
 273
 274         vp = ap->a_vp;
 275         fip = vp->v_fifoinfo;
 276         cpipe = fip->fi_pipe;
 277         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 278         if (ap->a_fflag & FREAD) {
 279                 fip->fi_readers--;
 280                 if (fip->fi_readers == 0) {
 281                         PIPE_LOCK(cpipe);
 282                         cpipe->pipe_state |= PIPE_EOF;
 283                         if ((cpipe->pipe_state & PIPE_WANTW)) {
 284                                 cpipe->pipe_state &= ~PIPE_WANTW;
 285                                 wakeup(cpipe);
 286                         }
 287                         pipeselwakeup(cpipe);
 288                         PIPE_UNLOCK(cpipe);
 289                 }
 290         }
 291         if (ap->a_fflag & FWRITE) {
 292                 fip->fi_writers--;
 293                 if (fip->fi_writers == 0) {
 294                         PIPE_LOCK(cpipe);
 295                         cpipe->pipe_state |= PIPE_EOF;
 296                         if ((cpipe->pipe_state & PIPE_WANTR)) {
 297                                 cpipe->pipe_state &= ~PIPE_WANTR;
 298                                 wakeup(cpipe);
 299                         }
 300                         cpipe->pipe_wgen++;
 301                         pipeselwakeup(cpipe);
 302                         PIPE_UNLOCK(cpipe);
 303                 }
 304         }
 305         fifo_cleanup(vp);
 306         return (0);
 307 }
 308
 309 /*
 310  * Print out internal contents of a fifo vnode.
 311  */
 312 int
 313 fifo_printinfo(vp)
 314         struct vnode *vp;
 315 {
 316         register struct fifoinfo *fip = vp->v_fifoinfo;
 317
 318         if (fip == NULL){
 319                 printf(", NULL v_fifoinfo");
 320                 return (0);
 321         }
 322         printf(", fifo with %ld readers and %ld writers",
 323                 fip->fi_readers, fip->fi_writers);
 324         return (0);
 325 }
 326
 327 /*
 328  * Print out the contents of a fifo vnode.
 329  */
 330 static int
 331 fifo_print(ap)
 332         struct vop_print_args /* {
 333                 struct vnode *a_vp;
 334         } */ *ap;
 335 {
 336         printf("    ");
 337         fifo_printinfo(ap->a_vp);
 338         printf("\n");
 339         return (0);
 340 }
 341
 342 /*
 343  * Return POSIX pathconf information applicable to fifo's.
 344  */
 345 static int
 346 fifo_pathconf(ap)
 347         struct vop_pathconf_args /* {
 348                 struct vnode *a_vp;
 349                 int a_name;
 350                 int *a_retval;
 351         } */ *ap;
 352 {
 353
 354         switch (ap->a_name) {
 355         case _PC_LINK_MAX:
 356                 *ap->a_retval = LINK_MAX;
 357                 return (0);
 358         case _PC_PIPE_BUF:
 359                 *ap->a_retval = PIPE_BUF;
 360                 return (0);
 361         case _PC_CHOWN_RESTRICTED:
 362                 *ap->a_retval = 1;
 363                 return (0);
 364         default:
 365                 return (EINVAL);
 366         }
 367         /* NOTREACHED */
 368 }
 369
 370 /*
 371  * Fifo advisory byte-level locks.
 372  */
 373 /* ARGSUSED */
 374 static int
 375 fifo_advlock(ap)
 376         struct vop_advlock_args /* {
 377                 struct vnode *a_vp;
 378                 caddr_t  a_id;
 379                 int  a_op;
 380                 struct flock *a_fl;
 381                 int  a_flags;
 382         } */ *ap;
 383 {
 384
 385         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 386 }
 387