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 };
  68
  69 static vop_print_t      fifo_print;
  70 static vop_open_t       fifo_open;
  71 static vop_close_t      fifo_close;
  72 static vop_pathconf_t   fifo_pathconf;
  73 static vop_advlock_t    fifo_advlock;
  74
  75 struct vop_vector fifo_specops = {
  76         .vop_default =          &default_vnodeops,
  77
  78         .vop_advlock =          fifo_advlock,
  79         .vop_close =            fifo_close,
  80         .vop_create =           VOP_PANIC,
  81         .vop_getattr =          VOP_EBADF,
  82         .vop_ioctl =            VOP_PANIC,
  83         .vop_kqfilter =         VOP_PANIC,
  84         .vop_link =             VOP_PANIC,
  85         .vop_mkdir =            VOP_PANIC,
  86         .vop_mknod =            VOP_PANIC,
  87         .vop_open =             fifo_open,
  88         .vop_pathconf =         fifo_pathconf,
  89         .vop_print =            fifo_print,
  90         .vop_read =             VOP_PANIC,
  91         .vop_readdir =          VOP_PANIC,
  92         .vop_readlink =         VOP_PANIC,
  93         .vop_reallocblks =      VOP_PANIC,
  94         .vop_reclaim =          VOP_NULL,
  95         .vop_remove =           VOP_PANIC,
  96         .vop_rename =           VOP_PANIC,
  97         .vop_rmdir =            VOP_PANIC,
  98         .vop_setattr =          VOP_EBADF,
  99         .vop_symlink =          VOP_PANIC,
 100         .vop_write =            VOP_PANIC,
 101 };
 102
 103 /*
 104  * Dispose of fifo resources.
 105  */
 106 static void
 107 fifo_cleanup(struct vnode *vp)
 108 {
 109         struct fifoinfo *fip;
 110
 111         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
 112         fip = vp->v_fifoinfo;
 113         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
 114                 vp->v_fifoinfo = NULL;
 115                 pipe_dtor(fip->fi_pipe);
 116                 free(fip, M_VNODE);
 117         }
 118 }
 119
 120 /*
 121  * Open called to set up a new instance of a fifo or
 122  * to find an active instance of a fifo.
 123  */
 124 /* ARGSUSED */
 125 static int
 126 fifo_open(ap)
 127         struct vop_open_args /* {
 128                 struct vnode *a_vp;
 129                 int  a_mode;
 130                 struct ucred *a_cred;
 131                 struct thread *a_td;
 132                 struct file *a_fp;
 133         } */ *ap;
 134 {
 135         struct vnode *vp;
 136         struct file *fp;
 137         struct thread *td;
 138         struct fifoinfo *fip;
 139         struct pipe *fpipe;
 140         int error, stops_deferred;
 141
 142         vp = ap->a_vp;
 143         fp = ap->a_fp;
 144         td = ap->a_td;
 145         ASSERT_VOP_ELOCKED(vp, "fifo_open");
 146         if (fp == NULL || (ap->a_mode & FEXEC) != 0)
 147                 return (EINVAL);
 148         if ((fip = vp->v_fifoinfo) == NULL) {
 149                 pipe_named_ctor(&fpipe, td);
 150                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
 151                 fip->fi_pipe = fpipe;
 152                 fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0;
 153                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
 154                 vp->v_fifoinfo = fip;
 155         }
 156         fpipe = fip->fi_pipe;
 157         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
 158
 159         /*
 160          * Use the pipe mutex here, in addition to the vnode lock,
 161          * in order to allow vnode lock dropping before msleep() calls
 162          * and still avoiding missed wakeups.
 163          */
 164         PIPE_LOCK(fpipe);
 165         if (ap->a_mode & FREAD) {
 166                 fip->fi_readers++;
 167                 if (fip->fi_readers == 1) {
 168                         fpipe->pipe_state &= ~PIPE_EOF;
 169                         if (fip->fi_writers > 0)
 170                                 wakeup(&fip->fi_writers);
 171                 }
 172                 fp->f_seqcount = fpipe->pipe_wgen - fip->fi_writers;
 173         }
 174         if (ap->a_mode & FWRITE) {
 175                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
 176                         PIPE_UNLOCK(fpipe);
 177                         if (fip->fi_writers == 0)
 178                                 fifo_cleanup(vp);
 179                         return (ENXIO);
 180                 }
 181                 fip->fi_writers++;
 182                 if (fip->fi_writers == 1) {
 183                         fpipe->pipe_state &= ~PIPE_EOF;
 184                         if (fip->fi_readers > 0)
 185                                 wakeup(&fip->fi_readers);
 186                 }
 187         }
 188         if ((ap->a_mode & O_NONBLOCK) == 0) {
 189                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
 190                         VOP_UNLOCK(vp, 0);
 191                         stops_deferred = sigallowstop();
 192                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
 193                             PDROP | PCATCH | PSOCK, "fifoor", 0);
 194                         if (stops_deferred)
 195                                 sigdeferstop();
 196                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 197                         if (error) {
 198                                 fip->fi_readers--;
 199                                 if (fip->fi_readers == 0) {
 200                                         PIPE_LOCK(fpipe);
 201                                         fpipe->pipe_state |= PIPE_EOF;
 202                                         if (fpipe->pipe_state & PIPE_WANTW)
 203                                                 wakeup(fpipe);
 204                                         PIPE_UNLOCK(fpipe);
 205                                         fifo_cleanup(vp);
 206                                 }
 207                                 return (error);
 208                         }
 209                         PIPE_LOCK(fpipe);
 210                         /*
 211                          * We must have got woken up because we had a writer.
 212                          * That (and not still having one) is the condition
 213                          * that we must wait for.
 214                          */
 215                 }
 216                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
 217                         VOP_UNLOCK(vp, 0);
 218                         stops_deferred = sigallowstop();
 219                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
 220                             PDROP | PCATCH | PSOCK, "fifoow", 0);
 221                         if (stops_deferred)
 222                                 sigdeferstop();
 223                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 224                         if (error) {
 225                                 fip->fi_writers--;
 226                                 if (fip->fi_writers == 0) {
 227                                         PIPE_LOCK(fpipe);
 228                                         fpipe->pipe_state |= PIPE_EOF;
 229                                         if (fpipe->pipe_state & PIPE_WANTR)
 230                                                 wakeup(fpipe);
 231                                         fpipe->pipe_wgen++;
 232                                         PIPE_UNLOCK(fpipe);
 233                                         fifo_cleanup(vp);
 234                                 }
 235                                 return (error);
 236                         }
 237                         /*
 238                          * We must have got woken up because we had
 239                          * a reader.  That (and not still having one)
 240                          * is the condition that we must wait for.
 241                          */
 242                         PIPE_LOCK(fpipe);
 243                 }
 244         }
 245         PIPE_UNLOCK(fpipe);
 246         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
 247         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
 248         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
 249         return (0);
 250 }
 251
 252 /*
 253  * Device close routine
 254  */
 255 /* ARGSUSED */
 256 static int
 257 fifo_close(ap)
 258         struct vop_close_args /* {
 259                 struct vnode *a_vp;
 260                 int  a_fflag;
 261                 struct ucred *a_cred;
 262                 struct thread *a_td;
 263         } */ *ap;
 264 {
 265         struct vnode *vp;
 266         struct fifoinfo *fip;
 267         struct pipe *cpipe;
 268
 269         vp = ap->a_vp;
 270         fip = vp->v_fifoinfo;
 271         cpipe = fip->fi_pipe;
 272         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 273         if (ap->a_fflag & FREAD) {
 274                 fip->fi_readers--;
 275                 if (fip->fi_readers == 0) {
 276                         PIPE_LOCK(cpipe);
 277                         cpipe->pipe_state |= PIPE_EOF;
 278                         if ((cpipe->pipe_state & PIPE_WANTW)) {
 279                                 cpipe->pipe_state &= ~PIPE_WANTW;
 280                                 wakeup(cpipe);
 281                         }
 282                         pipeselwakeup(cpipe);
 283                         PIPE_UNLOCK(cpipe);
 284                 }
 285         }
 286         if (ap->a_fflag & FWRITE) {
 287                 fip->fi_writers--;
 288                 if (fip->fi_writers == 0) {
 289                         PIPE_LOCK(cpipe);
 290                         cpipe->pipe_state |= PIPE_EOF;
 291                         if ((cpipe->pipe_state & PIPE_WANTR)) {
 292                                 cpipe->pipe_state &= ~PIPE_WANTR;
 293                                 wakeup(cpipe);
 294                         }
 295                         cpipe->pipe_wgen++;
 296                         pipeselwakeup(cpipe);
 297                         PIPE_UNLOCK(cpipe);
 298                 }
 299         }
 300         fifo_cleanup(vp);
 301         return (0);
 302 }
 303
 304 /*
 305  * Print out internal contents of a fifo vnode.
 306  */
 307 int
 308 fifo_printinfo(vp)
 309         struct vnode *vp;
 310 {
 311         register struct fifoinfo *fip = vp->v_fifoinfo;
 312
 313         if (fip == NULL){
 314                 printf(", NULL v_fifoinfo");
 315                 return (0);
 316         }
 317         printf(", fifo with %ld readers and %ld writers",
 318                 fip->fi_readers, fip->fi_writers);
 319         return (0);
 320 }
 321
 322 /*
 323  * Print out the contents of a fifo vnode.
 324  */
 325 static int
 326 fifo_print(ap)
 327         struct vop_print_args /* {
 328                 struct vnode *a_vp;
 329         } */ *ap;
 330 {
 331         printf("    ");
 332         fifo_printinfo(ap->a_vp);
 333         printf("\n");
 334         return (0);
 335 }
 336
 337 /*
 338  * Return POSIX pathconf information applicable to fifo's.
 339  */
 340 static int
 341 fifo_pathconf(ap)
 342         struct vop_pathconf_args /* {
 343                 struct vnode *a_vp;
 344                 int a_name;
 345                 int *a_retval;
 346         } */ *ap;
 347 {
 348
 349         switch (ap->a_name) {
 350         case _PC_LINK_MAX:
 351                 *ap->a_retval = LINK_MAX;
 352                 return (0);
 353         case _PC_PIPE_BUF:
 354                 *ap->a_retval = PIPE_BUF;
 355                 return (0);
 356         case _PC_CHOWN_RESTRICTED:
 357                 *ap->a_retval = 1;
 358                 return (0);
 359         default:
 360                 return (EINVAL);
 361         }
 362         /* NOTREACHED */
 363 }
 364
 365 /*
 366  * Fifo advisory byte-level locks.
 367  */
 368 /* ARGSUSED */
 369 static int
 370 fifo_advlock(ap)
 371         struct vop_advlock_args /* {
 372                 struct vnode *a_vp;
 373                 caddr_t  a_id;
 374                 int  a_op;
 375                 struct flock *a_fl;
 376                 int  a_flags;
 377         } */ *ap;
 378 {
 379
 380         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 381 }
 382