1 /*- 2 * Copyright (c) 1980, 1991 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 static char sccsid[] = "@(#)tape.c 5.25 (Berkeley) 07/16/92"; 10 #endif /* not lint */ 11 12 #ifdef sunos 13 #include <sys/param.h> 14 #include <stdio.h> 15 #include <ctype.h> 16 #include <sys/stat.h> 17 #include <ufs/fs.h> 18 #else 19 #include <sys/param.h> 20 #include <sys/wait.h> 21 #include <ufs/ffs/fs.h> 22 #endif 23 #include <sys/time.h> 24 #include <ufs/ufs/dinode.h> 25 #include <signal.h> 26 #include <fcntl.h> 27 #include <protocols/dumprestore.h> 28 #include <errno.h> 29 #include <setjmp.h> 30 #ifdef __STDC__ 31 #include <unistd.h> 32 #include <stdlib.h> 33 #include <string.h> 34 #endif 35 #include <sys/socket.h> 36 #include "dump.h" 37 #include "pathnames.h" 38 39 int writesize; /* size of malloc()ed buffer for tape */ 40 long lastspclrec = -1; /* tape block number of last written header */ 41 int trecno = 0; /* next record to write in current block */ 42 extern long blocksperfile; /* number of blocks per output file */ 43 long blocksthisvol; /* number of blocks on current output file */ 44 extern int ntrec; /* blocking factor on tape */ 45 extern int cartridge; 46 extern char *host; 47 char *nexttape; 48 #ifdef RDUMP 49 int rmtopen(), rmtwrite(); 50 void rmtclose(); 51 #endif RDUMP 52 void rollforward(); 53 int atomic(); 54 void doslave(), enslave(), flushtape(), killall(); 55 56 /* 57 * Concurrent dump mods (Caltech) - disk block reading and tape writing 58 * are exported to several slave processes. While one slave writes the 59 * tape, the others read disk blocks; they pass control of the tape in 60 * a ring via signals. The parent process traverses the filesystem and 61 * sends writeheader()'s and lists of daddr's to the slaves via pipes. 62 * The following structure defines the instruction packets sent to slaves. 63 */ 64 struct req { 65 daddr_t dblk; 66 int count; 67 }; 68 int reqsiz; 69 70 #define SLAVES 3 /* 1 slave writing, 1 reading, 1 for slack */ 71 struct slave { 72 int tapea; /* header number at start of this chunk */ 73 int count; /* count to next header (used for TS_TAPE */ 74 /* after EOT) */ 75 int inode; /* inode that we are currently dealing with */ 76 int fd; /* FD for this slave */ 77 int pid; /* PID for this slave */ 78 int sent; /* 1 == we've sent this slave requests */ 79 int firstrec; /* record number of this block */ 80 char (*tblock)[TP_BSIZE]; /* buffer for data blocks */ 81 struct req *req; /* buffer for requests */ 82 } slaves[SLAVES+1]; 83 struct slave *slp; 84 85 char (*nextblock)[TP_BSIZE]; 86 87 int master; /* pid of master, for sending error signals */ 88 int tenths; /* length of tape used per block written */ 89 static int caught; /* have we caught the signal to proceed? */ 90 static int ready; /* have we reached the lock point without having */ 91 /* received the SIGUSR2 signal from the prev slave? */ 92 static jmp_buf jmpbuf; /* where to jump to if we are ready when the */ 93 /* SIGUSR2 arrives from the previous slave */ 94 95 int 96 alloctape() 97 { 98 int pgoff = getpagesize() - 1; 99 char *buf; 100 int i; 101 102 writesize = ntrec * TP_BSIZE; 103 reqsiz = (ntrec + 1) * sizeof(struct req); 104 /* 105 * CDC 92181's and 92185's make 0.8" gaps in 1600-bpi start/stop mode 106 * (see DEC TU80 User's Guide). The shorter gaps of 6250-bpi require 107 * repositioning after stopping, i.e, streaming mode, where the gap is 108 * variable, 0.30" to 0.45". The gap is maximal when the tape stops. 109 */ 110 if (blocksperfile == 0) 111 tenths = writesize / density + 112 (cartridge ? 16 : density == 625 ? 5 : 8); 113 /* 114 * Allocate tape buffer contiguous with the array of instruction 115 * packets, so flushtape() can write them together with one write(). 116 * Align tape buffer on page boundary to speed up tape write(). 117 */ 118 for (i = 0; i <= SLAVES; i++) { 119 buf = (char *) 120 malloc((unsigned)(reqsiz + writesize + pgoff + TP_BSIZE)); 121 if (buf == NULL) 122 return(0); 123 slaves[i].tblock = (char (*)[TP_BSIZE]) 124 (((long)&buf[ntrec + 1] + pgoff) &~ pgoff); 125 slaves[i].req = (struct req *)slaves[i].tblock - ntrec - 1; 126 } 127 slp = &slaves[0]; 128 slp->count = 1; 129 slp->tapea = 0; 130 slp->firstrec = 0; 131 nextblock = slp->tblock; 132 return(1); 133 } 134 135 void 136 writerec(dp, isspcl) 137 char *dp; 138 int isspcl; 139 { 140 141 slp->req[trecno].dblk = (daddr_t)0; 142 slp->req[trecno].count = 1; 143 *(union u_spcl *)(*(nextblock)++) = *(union u_spcl *)dp; 144 if (isspcl) 145 lastspclrec = spcl.c_tapea; 146 trecno++; 147 spcl.c_tapea++; 148 if (trecno >= ntrec) 149 flushtape(); 150 } 151 152 void 153 dumpblock(blkno, size) 154 daddr_t blkno; 155 int size; 156 { 157 int avail, tpblks, dblkno; 158 159 dblkno = fsbtodb(sblock, blkno); 160 tpblks = size >> tp_bshift; 161 while ((avail = MIN(tpblks, ntrec - trecno)) > 0) { 162 slp->req[trecno].dblk = dblkno; 163 slp->req[trecno].count = avail; 164 trecno += avail; 165 spcl.c_tapea += avail; 166 if (trecno >= ntrec) 167 flushtape(); 168 dblkno += avail << (tp_bshift - dev_bshift); 169 tpblks -= avail; 170 } 171 } 172 173 int nogripe = 0; 174 175 void 176 tperror(signo) 177 int signo; 178 { 179 180 if (pipeout) { 181 msg("write error on %s\n", tape); 182 quit("Cannot recover\n"); 183 /* NOTREACHED */ 184 } 185 msg("write error %d blocks into volume %d\n", blocksthisvol, tapeno); 186 broadcast("DUMP WRITE ERROR!\n"); 187 if (!query("Do you want to restart?")) 188 dumpabort(0); 189 msg("Closing this volume. Prepare to restart with new media;\n"); 190 msg("this dump volume will be rewritten.\n"); 191 killall(); 192 nogripe = 1; 193 close_rewind(); 194 Exit(X_REWRITE); 195 } 196 197 void 198 sigpipe(signo) 199 int signo; 200 { 201 202 quit("Broken pipe\n"); 203 } 204 205 void 206 flushtape() 207 { 208 int i, blks, got; 209 long lastfirstrec; 210 #ifndef __STDC__ 211 int write(), read(); 212 #endif 213 214 int siz = (char *)nextblock - (char *)slp->req; 215 216 slp->req[trecno].count = 0; /* Sentinel */ 217 218 if (atomic(write, slp->fd, (char *)slp->req, siz) != siz) 219 quit("error writing command pipe: %s\n", strerror(errno)); 220 slp->sent = 1; /* we sent a request, read the response later */ 221 222 lastfirstrec = slp->firstrec; 223 224 if (++slp >= &slaves[SLAVES]) 225 slp = &slaves[0]; 226 227 /* Read results back from next slave */ 228 if (slp->sent) { 229 if (atomic(read, slp->fd, (char *)&got, sizeof got) 230 != sizeof got) { 231 perror(" DUMP: error reading command pipe in master"); 232 dumpabort(0); 233 } 234 slp->sent = 0; 235 236 /* Check for end of tape */ 237 if (got < writesize) { 238 msg("End of tape detected\n"); 239 240 /* 241 * Drain the results, don't care what the values were. 242 * If we read them here then trewind won't... 243 */ 244 for (i = 0; i < SLAVES; i++) { 245 if (slaves[i].sent) { 246 if (atomic(read, slaves[i].fd, 247 (char *)&got, sizeof got) 248 != sizeof got) { 249 perror(" DUMP: error reading command pipe in master"); 250 dumpabort(0); 251 } 252 slaves[i].sent = 0; 253 } 254 } 255 256 close_rewind(); 257 rollforward(); 258 return; 259 } 260 } 261 262 blks = 0; 263 if (spcl.c_type != TS_END) { 264 for (i = 0; i < spcl.c_count; i++) 265 if (spcl.c_addr[i] != 0) 266 blks++; 267 } 268 slp->count = lastspclrec + blks + 1 - spcl.c_tapea; 269 slp->tapea = spcl.c_tapea; 270 slp->firstrec = lastfirstrec + ntrec; 271 slp->inode = curino; 272 nextblock = slp->tblock; 273 trecno = 0; 274 asize += tenths; 275 blockswritten += ntrec; 276 blocksthisvol += ntrec; 277 if (!pipeout && (blocksperfile ? 278 (blocksthisvol >= blocksperfile) : (asize > tsize))) { 279 close_rewind(); 280 startnewtape(0); 281 } 282 timeest(); 283 } 284 285 void 286 trewind() 287 { 288 int f; 289 int got; 290 291 for (f = 0; f < SLAVES; f++) { 292 /* 293 * Drain the results, but unlike EOT we DO (or should) care 294 * what the return values were, since if we detect EOT after 295 * we think we've written the last blocks to the tape anyway, 296 * we have to replay those blocks with rollforward. 297 * 298 * fixme: punt for now. 299 */ 300 if (slaves[f].sent) { 301 if (atomic(read, slaves[f].fd, (char *)&got, sizeof got) 302 != sizeof got) { 303 perror(" DUMP: error reading command pipe in master"); 304 dumpabort(0); 305 } 306 slaves[f].sent = 0; 307 if (got != writesize) { 308 msg("EOT detected in last 2 tape records!\n"); 309 msg("Use a longer tape, decrease the size estimate\n"); 310 quit("or use no size estimate at all.\n"); 311 } 312 } 313 (void) close(slaves[f].fd); 314 } 315 while (wait((int *)NULL) >= 0) /* wait for any signals from slaves */ 316 /* void */; 317 318 if (pipeout) 319 return; 320 321 msg("Closing %s\n", tape); 322 323 #ifdef RDUMP 324 if (host) { 325 rmtclose(); 326 while (rmtopen(tape, 0) < 0) 327 sleep(10); 328 rmtclose(); 329 return; 330 } 331 #endif 332 (void) close(tapefd); 333 while ((f = open(tape, 0)) < 0) 334 sleep (10); 335 (void) close(f); 336 } 337 338 void 339 close_rewind() 340 { 341 trewind(); 342 if (nexttape) 343 return; 344 if (!nogripe) { 345 msg("Change Volumes: Mount volume #%d\n", tapeno+1); 346 broadcast("CHANGE DUMP VOLUMES!\7\7\n"); 347 } 348 while (!query("Is the new volume mounted and ready to go?")) 349 if (query("Do you want to abort?")) { 350 dumpabort(0); 351 /*NOTREACHED*/ 352 } 353 } 354 355 void 356 rollforward() 357 { 358 register struct req *p, *q, *prev; 359 register struct slave *tslp; 360 int i, size, savedtapea, got; 361 union u_spcl *ntb, *otb; 362 tslp = &slaves[SLAVES]; 363 ntb = (union u_spcl *)tslp->tblock[1]; 364 365 /* 366 * Each of the N slaves should have requests that need to 367 * be replayed on the next tape. Use the extra slave buffers 368 * (slaves[SLAVES]) to construct request lists to be sent to 369 * each slave in turn. 370 */ 371 for (i = 0; i < SLAVES; i++) { 372 q = &tslp->req[1]; 373 otb = (union u_spcl *)slp->tblock; 374 375 /* 376 * For each request in the current slave, copy it to tslp. 377 */ 378 379 for (p = slp->req; p->count > 0; p += p->count) { 380 *q = *p; 381 if (p->dblk == 0) 382 *ntb++ = *otb++; /* copy the datablock also */ 383 prev = q; 384 q += q->count; 385 } 386 if (prev->dblk != 0) 387 prev->count -= 1; 388 else 389 ntb--; 390 q -= 1; 391 q->count = 0; 392 q = &tslp->req[0]; 393 if (i == 0) { 394 q->dblk = 0; 395 q->count = 1; 396 trecno = 0; 397 nextblock = tslp->tblock; 398 savedtapea = spcl.c_tapea; 399 spcl.c_tapea = slp->tapea; 400 startnewtape(0); 401 spcl.c_tapea = savedtapea; 402 lastspclrec = savedtapea - 1; 403 } 404 size = (char *)ntb - (char *)q; 405 if (atomic(write, slp->fd, (char *)q, size) != size) { 406 perror(" DUMP: error writing command pipe"); 407 dumpabort(0); 408 } 409 slp->sent = 1; 410 if (++slp >= &slaves[SLAVES]) 411 slp = &slaves[0]; 412 413 q->count = 1; 414 415 if (prev->dblk != 0) { 416 /* 417 * If the last one was a disk block, make the 418 * first of this one be the last bit of that disk 419 * block... 420 */ 421 q->dblk = prev->dblk + 422 prev->count * (TP_BSIZE / DEV_BSIZE); 423 ntb = (union u_spcl *)tslp->tblock; 424 } else { 425 /* 426 * It wasn't a disk block. Copy the data to its 427 * new location in the buffer. 428 */ 429 q->dblk = 0; 430 *((union u_spcl *)tslp->tblock) = *ntb; 431 ntb = (union u_spcl *)tslp->tblock[1]; 432 } 433 } 434 slp->req[0] = *q; 435 nextblock = slp->tblock; 436 if (q->dblk == 0) 437 nextblock++; 438 trecno = 1; 439 440 /* 441 * Clear the first slaves' response. One hopes that it 442 * worked ok, otherwise the tape is much too short! 443 */ 444 if (slp->sent) { 445 if (atomic(read, slp->fd, (char *)&got, sizeof got) 446 != sizeof got) { 447 perror(" DUMP: error reading command pipe in master"); 448 dumpabort(0); 449 } 450 slp->sent = 0; 451 452 if (got != writesize) { 453 quit("EOT detected at start of the tape!\n"); 454 } 455 } 456 } 457 458 /* 459 * We implement taking and restoring checkpoints on the tape level. 460 * When each tape is opened, a new process is created by forking; this 461 * saves all of the necessary context in the parent. The child 462 * continues the dump; the parent waits around, saving the context. 463 * If the child returns X_REWRITE, then it had problems writing that tape; 464 * this causes the parent to fork again, duplicating the context, and 465 * everything continues as if nothing had happened. 466 */ 467 void 468 startnewtape(top) 469 int top; 470 { 471 int parentpid; 472 int childpid; 473 int status; 474 int waitpid; 475 char *p; 476 #ifdef sunos 477 void (*interrupt_save)(); 478 char *index(); 479 #else 480 sig_t interrupt_save; 481 #endif 482 483 interrupt_save = signal(SIGINT, SIG_IGN); 484 parentpid = getpid(); 485 486 restore_check_point: 487 (void)signal(SIGINT, interrupt_save); 488 /* 489 * All signals are inherited... 490 */ 491 childpid = fork(); 492 if (childpid < 0) { 493 msg("Context save fork fails in parent %d\n", parentpid); 494 Exit(X_ABORT); 495 } 496 if (childpid != 0) { 497 /* 498 * PARENT: 499 * save the context by waiting 500 * until the child doing all of the work returns. 501 * don't catch the interrupt 502 */ 503 signal(SIGINT, SIG_IGN); 504 #ifdef TDEBUG 505 msg("Tape: %d; parent process: %d child process %d\n", 506 tapeno+1, parentpid, childpid); 507 #endif TDEBUG 508 while ((waitpid = wait(&status)) != childpid) 509 msg("Parent %d waiting for child %d has another child %d return\n", 510 parentpid, childpid, waitpid); 511 if (status & 0xFF) { 512 msg("Child %d returns LOB status %o\n", 513 childpid, status&0xFF); 514 } 515 status = (status >> 8) & 0xFF; 516 #ifdef TDEBUG 517 switch(status) { 518 case X_FINOK: 519 msg("Child %d finishes X_FINOK\n", childpid); 520 break; 521 case X_ABORT: 522 msg("Child %d finishes X_ABORT\n", childpid); 523 break; 524 case X_REWRITE: 525 msg("Child %d finishes X_REWRITE\n", childpid); 526 break; 527 default: 528 msg("Child %d finishes unknown %d\n", 529 childpid, status); 530 break; 531 } 532 #endif TDEBUG 533 switch(status) { 534 case X_FINOK: 535 Exit(X_FINOK); 536 case X_ABORT: 537 Exit(X_ABORT); 538 case X_REWRITE: 539 goto restore_check_point; 540 default: 541 msg("Bad return code from dump: %d\n", status); 542 Exit(X_ABORT); 543 } 544 /*NOTREACHED*/ 545 } else { /* we are the child; just continue */ 546 #ifdef TDEBUG 547 sleep(4); /* allow time for parent's message to get out */ 548 msg("Child on Tape %d has parent %d, my pid = %d\n", 549 tapeno+1, parentpid, getpid()); 550 #endif TDEBUG 551 /* 552 * If we have a name like "/dev/rmt0,/dev/rmt1", 553 * use the name before the comma first, and save 554 * the remaining names for subsequent volumes. 555 */ 556 tapeno++; /* current tape sequence */ 557 if (nexttape || index(tape, ',')) { 558 if (nexttape && *nexttape) 559 tape = nexttape; 560 if (p = index(tape, ',')) { 561 *p = '\0'; 562 nexttape = p + 1; 563 } else 564 nexttape = NULL; 565 msg("Dumping volume %d on %s\n", tapeno, tape); 566 } 567 #ifdef RDUMP 568 while ((tapefd = (host ? rmtopen(tape, 2) : 569 pipeout ? 1 : open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 570 #else 571 while ((tapefd = (pipeout ? 1 : 572 open(tape, O_WRONLY|O_CREAT, 0666))) < 0) 573 #endif 574 { 575 msg("Cannot open output \"%s\".\n", tape); 576 if (!query("Do you want to retry the open?")) 577 dumpabort(0); 578 } 579 580 enslave(); /* Share open tape file descriptor with slaves */ 581 582 asize = 0; 583 blocksthisvol = 0; 584 if (top) 585 newtape++; /* new tape signal */ 586 spcl.c_count = slp->count; 587 /* 588 * measure firstrec in TP_BSIZE units since restore doesn't 589 * know the correct ntrec value... 590 */ 591 spcl.c_firstrec = slp->firstrec; 592 spcl.c_volume++; 593 spcl.c_type = TS_TAPE; 594 spcl.c_flags |= DR_NEWHEADER; 595 writeheader((ino_t)slp->inode); 596 spcl.c_flags &=~ DR_NEWHEADER; 597 if (tapeno > 1) 598 msg("Volume %d begins with blocks from inode %d\n", 599 tapeno, slp->inode); 600 } 601 } 602 603 void 604 dumpabort(signo) 605 int signo; 606 { 607 608 if (master != 0 && master != getpid()) 609 /* Signals master to call dumpabort */ 610 (void) kill(master, SIGTERM); 611 else { 612 killall(); 613 msg("The ENTIRE dump is aborted.\n"); 614 } 615 Exit(X_ABORT); 616 } 617 618 void 619 Exit(status) 620 int status; 621 { 622 623 #ifdef TDEBUG 624 msg("pid = %d exits with status %d\n", getpid(), status); 625 #endif TDEBUG 626 (void) exit(status); 627 } 628 629 /* 630 * proceed - handler for SIGUSR2, used to synchronize IO between the slaves. 631 */ 632 void 633 proceed(signo) 634 int signo; 635 { 636 637 if (ready) 638 longjmp(jmpbuf, 1); 639 caught++; 640 } 641 642 void 643 enslave() 644 { 645 int cmd[2]; 646 register int i, j; 647 648 master = getpid(); 649 650 signal(SIGTERM, dumpabort); /* Slave sends SIGTERM on dumpabort() */ 651 signal(SIGPIPE, sigpipe); 652 signal(SIGUSR1, tperror); /* Slave sends SIGUSR1 on tape errors */ 653 signal(SIGUSR2, proceed); /* Slave sends SIGUSR2 to next slave */ 654 655 for (i = 0; i < SLAVES; i++) { 656 if (i == slp - &slaves[0]) { 657 caught = 1; 658 } else { 659 caught = 0; 660 } 661 662 if (socketpair(AF_UNIX, SOCK_STREAM, 0, cmd) < 0 || 663 (slaves[i].pid = fork()) < 0) 664 quit("too many slaves, %d (recompile smaller): %s\n", 665 i, strerror(errno)); 666 667 slaves[i].fd = cmd[1]; 668 slaves[i].sent = 0; 669 if (slaves[i].pid == 0) { /* Slave starts up here */ 670 for (j = 0; j <= i; j++) 671 (void) close(slaves[j].fd); 672 signal(SIGINT, SIG_IGN); /* Master handles this */ 673 doslave(cmd[0], i); 674 Exit(X_FINOK); 675 } 676 } 677 678 for (i = 0; i < SLAVES; i++) 679 (void) atomic(write, slaves[i].fd, 680 (char *) &slaves[(i + 1) % SLAVES].pid, 681 sizeof slaves[0].pid); 682 683 master = 0; 684 } 685 686 void 687 killall() 688 { 689 register int i; 690 691 for (i = 0; i < SLAVES; i++) 692 if (slaves[i].pid > 0) 693 (void) kill(slaves[i].pid, SIGKILL); 694 } 695 696 /* 697 * Synchronization - each process has a lockfile, and shares file 698 * descriptors to the following process's lockfile. When our write 699 * completes, we release our lock on the following process's lock- 700 * file, allowing the following process to lock it and proceed. We 701 * get the lock back for the next cycle by swapping descriptors. 702 */ 703 void 704 doslave(cmd, slave_number) 705 register int cmd; 706 int slave_number; 707 { 708 register int nread; 709 int nextslave, size, wrote, eot_count; 710 #ifndef __STDC__ 711 int read(); 712 #endif 713 714 /* 715 * Need our own seek pointer. 716 */ 717 (void) close(diskfd); 718 if ((diskfd = open(disk, O_RDONLY)) < 0) 719 quit("slave couldn't reopen disk: %s\n", strerror(errno)); 720 721 /* 722 * Need the pid of the next slave in the loop... 723 */ 724 if ((nread = atomic(read, cmd, (char *)&nextslave, sizeof nextslave)) 725 != sizeof nextslave) { 726 quit("master/slave protocol botched - didn't get pid of next slave.\n"); 727 } 728 729 /* 730 * Get list of blocks to dump, read the blocks into tape buffer 731 */ 732 while ((nread = atomic(read, cmd, (char *)slp->req, reqsiz)) == reqsiz) { 733 register struct req *p = slp->req; 734 735 for (trecno = 0; trecno < ntrec; 736 trecno += p->count, p += p->count) { 737 if (p->dblk) { 738 bread(p->dblk, slp->tblock[trecno], 739 p->count * TP_BSIZE); 740 } else { 741 if (p->count != 1 || atomic(read, cmd, 742 (char *)slp->tblock[trecno], 743 TP_BSIZE) != TP_BSIZE) 744 quit("master/slave protocol botched.\n"); 745 } 746 } 747 if (setjmp(jmpbuf) == 0) { 748 ready = 1; 749 if (!caught) 750 (void) pause(); 751 } 752 ready = 0; 753 caught = 0; 754 755 /* Try to write the data... */ 756 eot_count = 0; 757 size = 0; 758 759 while (eot_count < 10 && size < writesize) { 760 #ifdef RDUMP 761 if (host) 762 wrote = rmtwrite(slp->tblock[0]+size, 763 writesize-size); 764 else 765 #endif 766 wrote = write(tapefd, slp->tblock[0]+size, 767 writesize-size); 768 #ifdef WRITEDEBUG 769 printf("slave %d wrote %d\n", slave_number, wrote); 770 #endif 771 if (wrote < 0) 772 break; 773 if (wrote == 0) 774 eot_count++; 775 size += wrote; 776 } 777 778 #ifdef WRITEDEBUG 779 if (size != writesize) 780 printf("slave %d only wrote %d out of %d bytes and gave up.\n", 781 slave_number, size, writesize); 782 #endif 783 784 if (eot_count > 0) 785 size = 0; 786 787 /* 788 * fixme: Pyramids running OSx return ENOSPC 789 * at EOT on 1/2 inch drives. 790 */ 791 if (size < 0) { 792 (void) kill(master, SIGUSR1); 793 for (;;) 794 (void) sigpause(0); 795 } else { 796 /* 797 * pass size of write back to master 798 * (for EOT handling) 799 */ 800 (void) atomic(write, cmd, (char *)&size, sizeof size); 801 } 802 803 /* 804 * If partial write, don't want next slave to go. 805 * Also jolts him awake. 806 */ 807 (void) kill(nextslave, SIGUSR2); 808 } 809 if (nread != 0) 810 quit("error reading command pipe: %s\n", strerror(errno)); 811 } 812 813 /* 814 * Since a read from a pipe may not return all we asked for, 815 * or a write may not write all we ask if we get a signal, 816 * loop until the count is satisfied (or error). 817 */ 818 int 819 atomic(func, fd, buf, count) 820 int (*func)(), fd, count; 821 char *buf; 822 { 823 int got, need = count; 824 825 while ((got = (*func)(fd, buf, need)) > 0 && (need -= got) > 0) 826 buf += got; 827 return (got < 0 ? got : count - need); 828 } 829