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;
 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                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
 192                             PDROP | PCATCH | PSOCK, "fifoor", 0);
 193                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 194                         if (error) {
 195                                 fip->fi_readers--;
 196                                 if (fip->fi_readers == 0) {
 197                                         PIPE_LOCK(fpipe);
 198                                         fpipe->pipe_state |= PIPE_EOF;
 199                                         if (fpipe->pipe_state & PIPE_WANTW)
 200                                                 wakeup(fpipe);
 201                                         PIPE_UNLOCK(fpipe);
 202                                         fifo_cleanup(vp);
 203                                 }
 204                                 return (error);
 205                         }
 206                         PIPE_LOCK(fpipe);
 207                         /*
 208                          * We must have got woken up because we had a writer.
 209                          * That (and not still having one) is the condition
 210                          * that we must wait for.
 211                          */
 212                 }
 213                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
 214                         VOP_UNLOCK(vp, 0);
 215                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
 216                             PDROP | PCATCH | PSOCK, "fifoow", 0);
 217                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 218                         if (error) {
 219                                 fip->fi_writers--;
 220                                 if (fip->fi_writers == 0) {
 221                                         PIPE_LOCK(fpipe);
 222                                         fpipe->pipe_state |= PIPE_EOF;
 223                                         if (fpipe->pipe_state & PIPE_WANTR)
 224                                                 wakeup(fpipe);
 225                                         fpipe->pipe_wgen++;
 226                                         PIPE_UNLOCK(fpipe);
 227                                         fifo_cleanup(vp);
 228                                 }
 229                                 return (error);
 230                         }
 231                         /*
 232                          * We must have got woken up because we had
 233                          * a reader.  That (and not still having one)
 234                          * is the condition that we must wait for.
 235                          */
 236                         PIPE_LOCK(fpipe);
 237                 }
 238         }
 239         PIPE_UNLOCK(fpipe);
 240         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
 241         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
 242         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
 243         return (0);
 244 }
 245
 246 /*
 247  * Device close routine
 248  */
 249 /* ARGSUSED */
 250 static int
 251 fifo_close(ap)
 252         struct vop_close_args /* {
 253                 struct vnode *a_vp;
 254                 int  a_fflag;
 255                 struct ucred *a_cred;
 256                 struct thread *a_td;
 257         } */ *ap;
 258 {
 259         struct vnode *vp;
 260         struct fifoinfo *fip;
 261         struct pipe *cpipe;
 262
 263         vp = ap->a_vp;
 264         fip = vp->v_fifoinfo;
 265         cpipe = fip->fi_pipe;
 266         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 267         if (ap->a_fflag & FREAD) {
 268                 fip->fi_readers--;
 269                 if (fip->fi_readers == 0) {
 270                         PIPE_LOCK(cpipe);
 271                         cpipe->pipe_state |= PIPE_EOF;
 272                         if ((cpipe->pipe_state & PIPE_WANTW)) {
 273                                 cpipe->pipe_state &= ~PIPE_WANTW;
 274                                 wakeup(cpipe);
 275                         }
 276                         pipeselwakeup(cpipe);
 277                         PIPE_UNLOCK(cpipe);
 278                 }
 279         }
 280         if (ap->a_fflag & FWRITE) {
 281                 fip->fi_writers--;
 282                 if (fip->fi_writers == 0) {
 283                         PIPE_LOCK(cpipe);
 284                         cpipe->pipe_state |= PIPE_EOF;
 285                         if ((cpipe->pipe_state & PIPE_WANTR)) {
 286                                 cpipe->pipe_state &= ~PIPE_WANTR;
 287                                 wakeup(cpipe);
 288                         }
 289                         cpipe->pipe_wgen++;
 290                         pipeselwakeup(cpipe);
 291                         PIPE_UNLOCK(cpipe);
 292                 }
 293         }
 294         fifo_cleanup(vp);
 295         return (0);
 296 }
 297
 298 /*
 299  * Print out internal contents of a fifo vnode.
 300  */
 301 int
 302 fifo_printinfo(vp)
 303         struct vnode *vp;
 304 {
 305         register struct fifoinfo *fip = vp->v_fifoinfo;
 306
 307         if (fip == NULL){
 308                 printf(", NULL v_fifoinfo");
 309                 return (0);
 310         }
 311         printf(", fifo with %ld readers and %ld writers",
 312                 fip->fi_readers, fip->fi_writers);
 313         return (0);
 314 }
 315
 316 /*
 317  * Print out the contents of a fifo vnode.
 318  */
 319 static int
 320 fifo_print(ap)
 321         struct vop_print_args /* {
 322                 struct vnode *a_vp;
 323         } */ *ap;
 324 {
 325         printf("    ");
 326         fifo_printinfo(ap->a_vp);
 327         printf("\n");
 328         return (0);
 329 }
 330
 331 /*
 332  * Return POSIX pathconf information applicable to fifo's.
 333  */
 334 static int
 335 fifo_pathconf(ap)
 336         struct vop_pathconf_args /* {
 337                 struct vnode *a_vp;
 338                 int a_name;
 339                 int *a_retval;
 340         } */ *ap;
 341 {
 342
 343         switch (ap->a_name) {
 344         case _PC_LINK_MAX:
 345                 *ap->a_retval = LINK_MAX;
 346                 return (0);
 347         case _PC_PIPE_BUF:
 348                 *ap->a_retval = PIPE_BUF;
 349                 return (0);
 350         case _PC_CHOWN_RESTRICTED:
 351                 *ap->a_retval = 1;
 352                 return (0);
 353         default:
 354                 return (EINVAL);
 355         }
 356         /* NOTREACHED */
 357 }
 358
 359 /*
 360  * Fifo advisory byte-level locks.
 361  */
 362 /* ARGSUSED */
 363 static int
 364 fifo_advlock(ap)
 365         struct vop_advlock_args /* {
 366                 struct vnode *a_vp;
 367                 caddr_t  a_id;
 368                 int  a_op;
 369                 struct flock *a_fl;
 370                 int  a_flags;
 371         } */ *ap;
 372 {
 373
 374         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 375 }
 376