Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/fs/fifofs/fifo_vnops.c
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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: releng/11.1/sys/fs/fifofs/fifo_vnops.c 302215 2016-06-26 20:07:24Z kib $ 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
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