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  *   - fi_wgen and fi_seqcount are protected by the pipe mutex.
  63  */
  64 struct fifoinfo {
  65         struct pipe *fi_pipe;
  66         long    fi_readers;
  67         long    fi_writers;
  68         int     fi_wgen;
  69         int     fi_seqcount;
  70 };
  71
  72 #define FIFO_UPDWGEN(fip, pip)  do { \
  73         if ((fip)->fi_wgen == (fip)->fi_seqcount)                       \
  74                 (pip)->pipe_state |= PIPE_SAMEWGEN;                     \
  75         else                                                            \
  76                 (pip)->pipe_state &= ~PIPE_SAMEWGEN;                    \
  77 } while (0)
  78
  79 static vop_print_t      fifo_print;
  80 static vop_open_t       fifo_open;
  81 static vop_close_t      fifo_close;
  82 static vop_pathconf_t   fifo_pathconf;
  83 static vop_advlock_t    fifo_advlock;
  84
  85 struct vop_vector fifo_specops = {
  86         .vop_default =          &default_vnodeops,
  87
  88         .vop_advlock =          fifo_advlock,
  89         .vop_close =            fifo_close,
  90         .vop_create =           VOP_PANIC,
  91         .vop_getattr =          VOP_EBADF,
  92         .vop_ioctl =            VOP_PANIC,
  93         .vop_kqfilter =         VOP_PANIC,
  94         .vop_link =             VOP_PANIC,
  95         .vop_mkdir =            VOP_PANIC,
  96         .vop_mknod =            VOP_PANIC,
  97         .vop_open =             fifo_open,
  98         .vop_pathconf =         fifo_pathconf,
  99         .vop_print =            fifo_print,
 100         .vop_read =             VOP_PANIC,
 101         .vop_readdir =          VOP_PANIC,
 102         .vop_readlink =         VOP_PANIC,
 103         .vop_reallocblks =      VOP_PANIC,
 104         .vop_reclaim =          VOP_NULL,
 105         .vop_remove =           VOP_PANIC,
 106         .vop_rename =           VOP_PANIC,
 107         .vop_rmdir =            VOP_PANIC,
 108         .vop_setattr =          VOP_EBADF,
 109         .vop_symlink =          VOP_PANIC,
 110         .vop_write =            VOP_PANIC,
 111 };
 112
 113 /*
 114  * Dispose of fifo resources.
 115  */
 116 static void
 117 fifo_cleanup(struct vnode *vp)
 118 {
 119         struct fifoinfo *fip;
 120
 121         ASSERT_VOP_ELOCKED(vp, "fifo_cleanup");
 122         fip = vp->v_fifoinfo;
 123         if (fip->fi_readers == 0 && fip->fi_writers == 0) {
 124                 vp->v_fifoinfo = NULL;
 125                 pipe_dtor(fip->fi_pipe);
 126                 free(fip, M_VNODE);
 127         }
 128 }
 129
 130 /*
 131  * Open called to set up a new instance of a fifo or
 132  * to find an active instance of a fifo.
 133  */
 134 /* ARGSUSED */
 135 static int
 136 fifo_open(ap)
 137         struct vop_open_args /* {
 138                 struct vnode *a_vp;
 139                 int  a_mode;
 140                 struct ucred *a_cred;
 141                 struct thread *a_td;
 142                 struct file *a_fp;
 143         } */ *ap;
 144 {
 145         struct vnode *vp;
 146         struct file *fp;
 147         struct thread *td;
 148         struct fifoinfo *fip;
 149         struct pipe *fpipe;
 150         int error;
 151
 152         vp = ap->a_vp;
 153         fp = ap->a_fp;
 154         td = ap->a_td;
 155         ASSERT_VOP_ELOCKED(vp, "fifo_open");
 156         if (fp == NULL)
 157                 return (EINVAL);
 158         if ((fip = vp->v_fifoinfo) == NULL) {
 159                 error = pipe_named_ctor(&fpipe, td);
 160                 if (error != 0)
 161                         return (error);
 162                 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK);
 163                 fip->fi_pipe = fpipe;
 164                 fip->fi_wgen = fip->fi_readers = fip->fi_writers = 0;
 165                 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race"));
 166                 vp->v_fifoinfo = fip;
 167         }
 168         fpipe = fip->fi_pipe;
 169         KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL"));
 170
 171         /*
 172          * Use the pipe mutex here, in addition to the vnode lock,
 173          * in order to allow vnode lock dropping before msleep() calls
 174          * and still avoiding missed wakeups.
 175          */
 176         PIPE_LOCK(fpipe);
 177         if (ap->a_mode & FREAD) {
 178                 fip->fi_readers++;
 179                 if (fip->fi_readers == 1) {
 180                         fpipe->pipe_state &= ~PIPE_EOF;
 181                         if (fip->fi_writers > 0)
 182                                 wakeup(&fip->fi_writers);
 183                 }
 184                 fip->fi_seqcount = fip->fi_wgen - fip->fi_writers;
 185                 FIFO_UPDWGEN(fip, fpipe);
 186         }
 187         if (ap->a_mode & FWRITE) {
 188                 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
 189                         PIPE_UNLOCK(fpipe);
 190                         if (fip->fi_writers == 0)
 191                                 fifo_cleanup(vp);
 192                         return (ENXIO);
 193                 }
 194                 fip->fi_writers++;
 195                 if (fip->fi_writers == 1) {
 196                         fpipe->pipe_state &= ~PIPE_EOF;
 197                         if (fip->fi_readers > 0)
 198                                 wakeup(&fip->fi_readers);
 199                 }
 200         }
 201         if ((ap->a_mode & O_NONBLOCK) == 0) {
 202                 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
 203                         VOP_UNLOCK(vp, 0);
 204                         error = msleep(&fip->fi_readers, PIPE_MTX(fpipe),
 205                             PDROP | PCATCH | PSOCK, "fifoor", 0);
 206                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 207                         if (error) {
 208                                 fip->fi_readers--;
 209                                 if (fip->fi_readers == 0) {
 210                                         PIPE_LOCK(fpipe);
 211                                         fpipe->pipe_state |= PIPE_EOF;
 212                                         if (fpipe->pipe_state & PIPE_WANTW)
 213                                                 wakeup(fpipe);
 214                                         PIPE_UNLOCK(fpipe);
 215                                         fifo_cleanup(vp);
 216                                 }
 217                                 return (error);
 218                         }
 219                         PIPE_LOCK(fpipe);
 220                         /*
 221                          * We must have got woken up because we had a writer.
 222                          * That (and not still having one) is the condition
 223                          * that we must wait for.
 224                          */
 225                 }
 226                 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
 227                         VOP_UNLOCK(vp, 0);
 228                         error = msleep(&fip->fi_writers, PIPE_MTX(fpipe),
 229                             PDROP | PCATCH | PSOCK, "fifoow", 0);
 230                         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 231                         if (error) {
 232                                 fip->fi_writers--;
 233                                 if (fip->fi_writers == 0) {
 234                                         PIPE_LOCK(fpipe);
 235                                         fpipe->pipe_state |= PIPE_EOF;
 236                                         if (fpipe->pipe_state & PIPE_WANTR)
 237                                                 wakeup(fpipe);
 238                                         fip->fi_wgen++;
 239                                         FIFO_UPDWGEN(fip, fpipe);
 240                                         PIPE_UNLOCK(fpipe);
 241                                         fifo_cleanup(vp);
 242                                 }
 243                                 return (error);
 244                         }
 245                         /*
 246                          * We must have got woken up because we had
 247                          * a reader.  That (and not still having one)
 248                          * is the condition that we must wait for.
 249                          */
 250                         PIPE_LOCK(fpipe);
 251                 }
 252         }
 253         PIPE_UNLOCK(fpipe);
 254         KASSERT(fp != NULL, ("can't fifo/vnode bypass"));
 255         KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open"));
 256         finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops);
 257         return (0);
 258 }
 259
 260 /*
 261  * Device close routine
 262  */
 263 /* ARGSUSED */
 264 static int
 265 fifo_close(ap)
 266         struct vop_close_args /* {
 267                 struct vnode *a_vp;
 268                 int  a_fflag;
 269                 struct ucred *a_cred;
 270                 struct thread *a_td;
 271         } */ *ap;
 272 {
 273         struct vnode *vp;
 274         struct fifoinfo *fip;
 275         struct pipe *cpipe;
 276
 277         vp = ap->a_vp;
 278         fip = vp->v_fifoinfo;
 279         cpipe = fip->fi_pipe;
 280         ASSERT_VOP_ELOCKED(vp, "fifo_close");
 281         if (ap->a_fflag & FREAD) {
 282                 fip->fi_readers--;
 283                 if (fip->fi_readers == 0) {
 284                         PIPE_LOCK(cpipe);
 285                         cpipe->pipe_state |= PIPE_EOF;
 286                         if (cpipe->pipe_state & PIPE_WANTW)
 287                                 wakeup(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                                 wakeup(cpipe);
 298                         fip->fi_wgen++;
 299                         FIFO_UPDWGEN(fip, cpipe);
 300                         PIPE_UNLOCK(cpipe);
 301                 }
 302         }
 303         fifo_cleanup(vp);
 304         return (0);
 305 }
 306
 307 /*
 308  * Print out internal contents of a fifo vnode.
 309  */
 310 int
 311 fifo_printinfo(vp)
 312         struct vnode *vp;
 313 {
 314         register struct fifoinfo *fip = vp->v_fifoinfo;
 315
 316         if (fip == NULL){
 317                 printf(", NULL v_fifoinfo");
 318                 return (0);
 319         }
 320         printf(", fifo with %ld readers and %ld writers",
 321                 fip->fi_readers, fip->fi_writers);
 322         return (0);
 323 }
 324
 325 /*
 326  * Print out the contents of a fifo vnode.
 327  */
 328 static int
 329 fifo_print(ap)
 330         struct vop_print_args /* {
 331                 struct vnode *a_vp;
 332         } */ *ap;
 333 {
 334         printf("    ");
 335         fifo_printinfo(ap->a_vp);
 336         printf("\n");
 337         return (0);
 338 }
 339
 340 /*
 341  * Return POSIX pathconf information applicable to fifo's.
 342  */
 343 static int
 344 fifo_pathconf(ap)
 345         struct vop_pathconf_args /* {
 346                 struct vnode *a_vp;
 347                 int a_name;
 348                 int *a_retval;
 349         } */ *ap;
 350 {
 351
 352         switch (ap->a_name) {
 353         case _PC_LINK_MAX:
 354                 *ap->a_retval = LINK_MAX;
 355                 return (0);
 356         case _PC_PIPE_BUF:
 357                 *ap->a_retval = PIPE_BUF;
 358                 return (0);
 359         case _PC_CHOWN_RESTRICTED:
 360                 *ap->a_retval = 1;
 361                 return (0);
 362         default:
 363                 return (EINVAL);
 364         }
 365         /* NOTREACHED */
 366 }
 367
 368 /*
 369  * Fifo advisory byte-level locks.
 370  */
 371 /* ARGSUSED */
 372 static int
 373 fifo_advlock(ap)
 374         struct vop_advlock_args /* {
 375                 struct vnode *a_vp;
 376                 caddr_t  a_id;
 377                 int  a_op;
 378                 struct flock *a_fl;
 379                 int  a_flags;
 380         } */ *ap;
 381 {
 382
 383         return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
 384 }
 385