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 * $FreeBSD$ 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_link = VOP_PANIC, 87 .vop_mkdir = VOP_PANIC, 88 .vop_mknod = VOP_PANIC, 89 .vop_open = fifo_open, 90 .vop_pathconf = VOP_PANIC, 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 VFS_VOP_VECTOR_REGISTER(fifo_specops); 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 error = pipe_named_ctor(&fpipe, td); 154 if (error != 0) 155 return (error); 156 fip = malloc(sizeof(*fip), M_VNODE, M_WAITOK | M_ZERO); 157 fip->fi_pipe = fpipe; 158 fpipe->pipe_wgen = 0; 159 KASSERT(vp->v_fifoinfo == NULL, ("fifo_open: v_fifoinfo race")); 160 vp->v_fifoinfo = fip; 161 } 162 fpipe = fip->fi_pipe; 163 KASSERT(fpipe != NULL, ("fifo_open: pipe is NULL")); 164 165 /* 166 * Use the pipe mutex here, in addition to the vnode lock, 167 * in order to allow vnode lock dropping before msleep() calls 168 * and still avoiding missed wakeups. 169 */ 170 PIPE_LOCK(fpipe); 171 if (ap->a_mode & FREAD) { 172 fip->fi_readers++; 173 fip->fi_rgen++; 174 if (fip->fi_readers == 1) { 175 fpipe->pipe_state &= ~PIPE_EOF; 176 if (fip->fi_writers > 0) { 177 wakeup(&fip->fi_writers); 178 pipeselwakeup(fpipe); 179 } 180 } 181 fp->f_pipegen = fpipe->pipe_wgen - fip->fi_writers; 182 } 183 if (ap->a_mode & FWRITE) { 184 if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) { 185 PIPE_UNLOCK(fpipe); 186 if (fip->fi_writers == 0) 187 fifo_cleanup(vp); 188 return (ENXIO); 189 } 190 fip->fi_writers++; 191 fip->fi_wgen++; 192 if (fip->fi_writers == 1) { 193 fpipe->pipe_state &= ~PIPE_EOF; 194 if (fip->fi_readers > 0) { 195 wakeup(&fip->fi_readers); 196 pipeselwakeup(fpipe); 197 } 198 } 199 } 200 if ((ap->a_mode & O_NONBLOCK) == 0) { 201 if ((ap->a_mode & FREAD) && fip->fi_writers == 0) { 202 gen = fip->fi_wgen; 203 VOP_UNLOCK(vp); 204 stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); 205 error = msleep(&fip->fi_readers, PIPE_MTX(fpipe), 206 PDROP | PCATCH | PSOCK, "fifoor", 0); 207 sigallowstop(stops_deferred); 208 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 209 if (error != 0 && gen == fip->fi_wgen) { 210 fip->fi_readers--; 211 if (fip->fi_readers == 0) { 212 PIPE_LOCK(fpipe); 213 fpipe->pipe_state |= PIPE_EOF; 214 if (fpipe->pipe_state & PIPE_WANTW) 215 wakeup(fpipe); 216 pipeselwakeup(fpipe); 217 PIPE_UNLOCK(fpipe); 218 fifo_cleanup(vp); 219 } 220 return (error); 221 } 222 PIPE_LOCK(fpipe); 223 /* 224 * We must have got woken up because we had a writer. 225 * That (and not still having one) is the condition 226 * that we must wait for. 227 */ 228 } 229 if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) { 230 gen = fip->fi_rgen; 231 VOP_UNLOCK(vp); 232 stops_deferred = sigdeferstop(SIGDEFERSTOP_OFF); 233 error = msleep(&fip->fi_writers, PIPE_MTX(fpipe), 234 PDROP | PCATCH | PSOCK, "fifoow", 0); 235 sigallowstop(stops_deferred); 236 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 237 if (error != 0 && gen == fip->fi_rgen) { 238 fip->fi_writers--; 239 if (fip->fi_writers == 0) { 240 PIPE_LOCK(fpipe); 241 fpipe->pipe_state |= PIPE_EOF; 242 if (fpipe->pipe_state & PIPE_WANTR) 243 wakeup(fpipe); 244 fpipe->pipe_wgen++; 245 pipeselwakeup(fpipe); 246 PIPE_UNLOCK(fpipe); 247 fifo_cleanup(vp); 248 } 249 return (error); 250 } 251 /* 252 * We must have got woken up because we had 253 * a reader. That (and not still having one) 254 * is the condition that we must wait for. 255 */ 256 PIPE_LOCK(fpipe); 257 } 258 } 259 PIPE_UNLOCK(fpipe); 260 KASSERT(fp != NULL, ("can't fifo/vnode bypass")); 261 KASSERT(fp->f_ops == &badfileops, ("not badfileops in fifo_open")); 262 finit(fp, fp->f_flag, DTYPE_FIFO, fpipe, &pipeops); 263 return (0); 264 } 265 266 /* 267 * Device close routine 268 */ 269 /* ARGSUSED */ 270 static int 271 fifo_close(ap) 272 struct vop_close_args /* { 273 struct vnode *a_vp; 274 int a_fflag; 275 struct ucred *a_cred; 276 struct thread *a_td; 277 } */ *ap; 278 { 279 struct vnode *vp; 280 struct fifoinfo *fip; 281 struct pipe *cpipe; 282 283 vp = ap->a_vp; 284 ASSERT_VOP_ELOCKED(vp, "fifo_close"); 285 fip = vp->v_fifoinfo; 286 287 /* 288 * During open, it is possible that the fifo vnode is relocked 289 * after the vnode is instantiated but before VOP_OPEN() is 290 * done. For instance, vn_open_vnode() might need to upgrade 291 * vnode lock, or ffs_vput_pair() needs to unlock vp to sync 292 * dvp. In this case, reclaim can observe us with v_fifoinfo 293 * equal to NULL. 294 */ 295 if (fip == NULL) 296 return (0); 297 298 cpipe = fip->fi_pipe; 299 if (ap->a_fflag & FREAD) { 300 fip->fi_readers--; 301 if (fip->fi_readers == 0) { 302 PIPE_LOCK(cpipe); 303 cpipe->pipe_state |= PIPE_EOF; 304 if ((cpipe->pipe_state & PIPE_WANTW)) { 305 cpipe->pipe_state &= ~PIPE_WANTW; 306 wakeup(cpipe); 307 } 308 pipeselwakeup(cpipe); 309 PIPE_UNLOCK(cpipe); 310 } 311 } 312 if (ap->a_fflag & FWRITE) { 313 fip->fi_writers--; 314 if (fip->fi_writers == 0) { 315 PIPE_LOCK(cpipe); 316 cpipe->pipe_state |= PIPE_EOF; 317 if ((cpipe->pipe_state & PIPE_WANTR)) { 318 cpipe->pipe_state &= ~PIPE_WANTR; 319 wakeup(cpipe); 320 } 321 cpipe->pipe_wgen++; 322 pipeselwakeup(cpipe); 323 PIPE_UNLOCK(cpipe); 324 } 325 } 326 fifo_cleanup(vp); 327 return (0); 328 } 329 330 /* 331 * Print out internal contents of a fifo vnode. 332 */ 333 int 334 fifo_printinfo(vp) 335 struct vnode *vp; 336 { 337 struct fifoinfo *fip = vp->v_fifoinfo; 338 339 if (fip == NULL){ 340 printf(", NULL v_fifoinfo"); 341 return (0); 342 } 343 printf(", fifo with %ld readers and %ld writers", 344 fip->fi_readers, fip->fi_writers); 345 return (0); 346 } 347 348 /* 349 * Print out the contents of a fifo vnode. 350 */ 351 static int 352 fifo_print(ap) 353 struct vop_print_args /* { 354 struct vnode *a_vp; 355 } */ *ap; 356 { 357 printf(" "); 358 fifo_printinfo(ap->a_vp); 359 printf("\n"); 360 return (0); 361 } 362 363 /* 364 * Fifo advisory byte-level locks. 365 */ 366 /* ARGSUSED */ 367 static int 368 fifo_advlock(ap) 369 struct vop_advlock_args /* { 370 struct vnode *a_vp; 371 caddr_t a_id; 372 int a_op; 373 struct flock *a_fl; 374 int a_flags; 375 } */ *ap; 376 { 377 378 if ((ap->a_flags & F_FLOCK) == 0) 379 return (EINVAL); 380 return (vop_stdadvlock(ap)); 381 }
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