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 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993, 1995 5 * The Regents of the University of California. 6 * Copyright (c) 2005 Robert N. M. Watson 7 * Copyright (c) 2012 Giovanni Trematerra 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)fifo_vnops.c 8.10 (Berkeley) 5/27/95 35 * $FreeBSD: releng/12.0/sys/fs/fifofs/fifo_vnops.c 327004 2017-12-19 22:39:05Z jhb $ 36 */ 37 38 #include <sys/param.h> 39 #include <sys/event.h> 40 #include <sys/file.h> 41 #include <sys/filedesc.h> 42 #include <sys/filio.h> 43 #include <sys/fcntl.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mutex.h> 47 #include <sys/malloc.h> 48 #include <sys/selinfo.h> 49 #include <sys/pipe.h> 50 #include <sys/proc.h> 51 #include <sys/signalvar.h> 52 #include <sys/sx.h> 53 #include <sys/systm.h> 54 #include <sys/un.h> 55 #include <sys/unistd.h> 56 #include <sys/vnode.h> 57 58 /* 59 * This structure is associated with the FIFO vnode and stores 60 * the state associated with the FIFO. 61 * Notes about locking: 62 * - fi_pipe is invariant since init time. 63 * - fi_readers and fi_writers are protected by the vnode lock. 64 */ 65 struct fifoinfo { 66 struct pipe *fi_pipe; 67 long fi_readers; 68 long fi_writers; 69 u_int fi_rgen; 70 u_int fi_wgen; 71 }; 72 73 static vop_print_t fifo_print; 74 static vop_open_t fifo_open; 75 static vop_close_t fifo_close; 76 static vop_advlock_t fifo_advlock; 77 78 struct vop_vector fifo_specops = { 79 .vop_default = &default_vnodeops, 80 81 .vop_advlock = fifo_advlock, 82 .vop_close = fifo_close, 83 .vop_create = VOP_PANIC, 84 .vop_getattr = VOP_EBADF, 85 .vop_ioctl = VOP_PANIC, 86 .vop_kqfilter = VOP_PANIC, 87 .vop_link = VOP_PANIC, 88 .vop_mkdir = VOP_PANIC, 89 .vop_mknod = VOP_PANIC, 90 .vop_open = fifo_open, 91 .vop_pathconf = VOP_PANIC, 92 .vop_print = fifo_print, 93 .vop_read = VOP_PANIC, 94 .vop_readdir = VOP_PANIC, 95 .vop_readlink = VOP_PANIC, 96 .vop_reallocblks = VOP_PANIC, 97 .vop_reclaim = VOP_NULL, 98 .vop_remove = VOP_PANIC, 99 .vop_rename = VOP_PANIC, 100 .vop_rmdir = VOP_PANIC, 101 .vop_setattr = VOP_EBADF, 102 .vop_symlink = VOP_PANIC, 103 .vop_write = VOP_PANIC, 104 }; 105 106 /* 107 * Dispose of fifo resources. 108 */ 109 static void 110 fifo_cleanup(struct vnode *vp) 111 { 112 struct fifoinfo *fip; 113 114 ASSERT_VOP_ELOCKED(vp, "fifo_cleanup"); 115 fip = vp->v_fifoinfo; 116 if (fip->fi_readers == 0 && fip->fi_writers == 0) { 117 vp->v_fifoinfo = NULL; 118 pipe_dtor(fip->fi_pipe); 119 free(fip, M_VNODE); 120 } 121 } 122 123 /* 124 * Open called to set up a new instance of a fifo or 125 * to find an active instance of a fifo. 126 */ 127 /* ARGSUSED */ 128 static int 129 fifo_open(ap) 130 struct vop_open_args /* { 131 struct vnode *a_vp; 132 int a_mode; 133 struct ucred *a_cred; 134 struct thread *a_td; 135 struct file *a_fp; 136 } */ *ap; 137 { 138 struct vnode *vp; 139 struct file *fp; 140 struct thread *td; 141 struct fifoinfo *fip; 142 struct pipe *fpipe; 143 u_int gen; 144 int error, stops_deferred; 145 146 vp = ap->a_vp; 147 fp = ap->a_fp; 148 td = ap->a_td; 149 ASSERT_VOP_ELOCKED(vp, "fifo_open"); 150 if (fp == NULL || (ap->a_mode & FEXEC) != 0) 151 return (EINVAL); 152 if ((fip = vp->v_fifoinfo) == NULL) { 153 pipe_named_ctor(&fpipe, td); 154 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK); 155 fip->fi_pipe = fpipe; 156 fpipe->pipe_wgen = fip->fi_readers = fip->fi_writers = 0; 157 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race")); 158 vp->v_fifoinfo = fip; 159 } 160 fpipe = fip->fi_pipe; 161 KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL")); 162 163 /* 164 * Use the pipe mutex here, in addition to the vnode lock, 165 * in order to allow vnode lock dropping before msleep() calls 166 * and still avoiding missed wakeups. 167 */ 168 PIPE_LOCK(fpipe); 169 if (ap->a_mode & FREAD) { 170 fip->fi_readers++; 171 fip->fi_rgen++; 172 if (fip->fi_readers == 1) { 173 fpipe->pipe_state &= ~PIPE_EOF; 174 if (fip->fi_writers > 0) 175 wakeup(&fip->fi_writers); 176 } 177 fp->f_seqcount = fpipe->pipe_wgen - fip->fi_writers; 178 } 179 if (ap->a_mode & FWRITE) { 180 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) { 181 PIPE_UNLOCK(fpipe); 182 if (fip->fi_writers == 0) 183 fifo_cleanup(vp); 184 return (ENXIO); 185 } 186 fip->fi_writers++; 187 fip->fi_wgen++; 188 if (fip->fi_writers == 1) { 189 fpipe->pipe_state &= ~PIPE_EOF; 190 if (fip->fi_readers > 0) 191 wakeup(&fip->fi_readers); 192 } 193 } 194 if ((ap->a_mode & O_NONBLOCK) == 0) { 195 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) { 196 gen = fip->fi_wgen; 197 VOP_UNLOCK(vp, 0); 198 stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); 199 error = msleep(&fip->fi_readers, PIPE_MTX(fpipe), 200 PDROP | PCATCH | PSOCK, "fifoor", 0); 201 sigallowstop(stops_deferred); 202 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 203 if (error != 0 && gen == fip->fi_wgen) { 204 fip->fi_readers--; 205 if (fip->fi_readers == 0) { 206 PIPE_LOCK(fpipe); 207 fpipe->pipe_state |= PIPE_EOF; 208 if (fpipe->pipe_state & PIPE_WANTW) 209 wakeup(fpipe); 210 PIPE_UNLOCK(fpipe); 211 fifo_cleanup(vp); 212 } 213 return (error); 214 } 215 PIPE_LOCK(fpipe); 216 /* 217 * We must have got woken up because we had a writer. 218 * That (and not still having one) is the condition 219 * that we must wait for. 220 */ 221 } 222 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) { 223 gen = fip->fi_rgen; 224 VOP_UNLOCK(vp, 0); 225 stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); 226 error = msleep(&fip->fi_writers, PIPE_MTX(fpipe), 227 PDROP | PCATCH | PSOCK, "fifoow", 0); 228 sigallowstop(stops_deferred); 229 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 230 if (error != 0 && gen == fip->fi_rgen) { 231 fip->fi_writers--; 232 if (fip->fi_writers == 0) { 233 PIPE_LOCK(fpipe); 234 fpipe->pipe_state |= PIPE_EOF; 235 if (fpipe->pipe_state & PIPE_WANTR) 236 wakeup(fpipe); 237 fpipe->pipe_wgen++; 238 PIPE_UNLOCK(fpipe); 239 fifo_cleanup(vp); 240 } 241 return (error); 242 } 243 /* 244 * We must have got woken up because we had 245 * a reader. That (and not still having one) 246 * is the condition that we must wait for. 247 */ 248 PIPE_LOCK(fpipe); 249 } 250 } 251 PIPE_UNLOCK(fpipe); 252 KASSERT(fp != NULL, ("can't fifo/vnode bypass")); 253 KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open")); 254 finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops); 255 return (0); 256 } 257 258 /* 259 * Device close routine 260 */ 261 /* ARGSUSED */ 262 static int 263 fifo_close(ap) 264 struct vop_close_args /* { 265 struct vnode *a_vp; 266 int a_fflag; 267 struct ucred *a_cred; 268 struct thread *a_td; 269 } */ *ap; 270 { 271 struct vnode *vp; 272 struct fifoinfo *fip; 273 struct pipe *cpipe; 274 275 vp = ap->a_vp; 276 fip = vp->v_fifoinfo; 277 cpipe = fip->fi_pipe; 278 ASSERT_VOP_ELOCKED(vp, "fifo_close"); 279 if (ap->a_fflag & FREAD) { 280 fip->fi_readers--; 281 if (fip->fi_readers == 0) { 282 PIPE_LOCK(cpipe); 283 cpipe->pipe_state |= PIPE_EOF; 284 if ((cpipe->pipe_state & PIPE_WANTW)) { 285 cpipe->pipe_state &= ~PIPE_WANTW; 286 wakeup(cpipe); 287 } 288 pipeselwakeup(cpipe); 289 PIPE_UNLOCK(cpipe); 290 } 291 } 292 if (ap->a_fflag & FWRITE) { 293 fip->fi_writers--; 294 if (fip->fi_writers == 0) { 295 PIPE_LOCK(cpipe); 296 cpipe->pipe_state |= PIPE_EOF; 297 if ((cpipe->pipe_state & PIPE_WANTR)) { 298 cpipe->pipe_state &= ~PIPE_WANTR; 299 wakeup(cpipe); 300 } 301 cpipe->pipe_wgen++; 302 pipeselwakeup(cpipe); 303 PIPE_UNLOCK(cpipe); 304 } 305 } 306 fifo_cleanup(vp); 307 return (0); 308 } 309 310 /* 311 * Print out internal contents of a fifo vnode. 312 */ 313 int 314 fifo_printinfo(vp) 315 struct vnode *vp; 316 { 317 struct fifoinfo *fip = vp->v_fifoinfo; 318 319 if (fip == NULL){ 320 printf(", NULL v_fifoinfo"); 321 return (0); 322 } 323 printf(", fifo with %ld readers and %ld writers", 324 fip->fi_readers, fip->fi_writers); 325 return (0); 326 } 327 328 /* 329 * Print out the contents of a fifo vnode. 330 */ 331 static int 332 fifo_print(ap) 333 struct vop_print_args /* { 334 struct vnode *a_vp; 335 } */ *ap; 336 { 337 printf(" "); 338 fifo_printinfo(ap->a_vp); 339 printf("\n"); 340 return (0); 341 } 342 343 /* 344 * Fifo advisory byte-level locks. 345 */ 346 /* ARGSUSED */ 347 static int 348 fifo_advlock(ap) 349 struct vop_advlock_args /* { 350 struct vnode *a_vp; 351 caddr_t a_id; 352 int a_op; 353 struct flock *a_fl; 354 int a_flags; 355 } */ *ap; 356 { 357 358 return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL); 359 } 360
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