1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1980, 1991, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <sys/param.h>
33#include <sys/socket.h>
34#include <sys/wait.h>
35#include <sys/stat.h>
36
37#include <ufs/ufs/dinode.h>
38#include <ufs/ffs/fs.h>
39
40#include <protocols/dumprestore.h>
41
42#include <assert.h>
43#include <errno.h>
44#include <fcntl.h>
45#include <limits.h>
46#include <setjmp.h>
47#include <signal.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51#include <time.h>
52#include <unistd.h>
53
54#include "dump.h"
55
56ino_t	curino;			/* current inumber; used globally */
57int	newtape;		/* new tape flag */
58union	u_spcl u_spcl;		/* mapping of variables in a control block */
59
60static	int tapefd;		/* tape file descriptor */
61static	long asize;		/* number of 0.1" units written on cur tape */
62static	int writesize;		/* size of malloc()ed buffer for tape */
63static	int64_t lastspclrec = -1; /* tape block number of last written header */
64static	int trecno = 0;		/* next record to write in current block */
65static	long blocksthisvol;	/* number of blocks on current output file */
66static	char *nexttape;
67static	FILE *popenfp = NULL;
68
69static	int atomic_read(int, void *, int);
70static	int atomic_write(int, const void *, int);
71static	void worker(int, int);
72static	void create_workers(void);
73static	void flushtape(void);
74static	void killall(void);
75static	void rollforward(void);
76
77/*
78 * Concurrent dump mods (Caltech) - disk block reading and tape writing
79 * are exported to several worker processes.  While one worker writes the
80 * tape, the others read disk blocks; they pass control of the tape in
81 * a ring via signals. The parent process traverses the file system and
82 * sends writeheader()'s and lists of daddr's to the workers via pipes.
83 * The following structure defines the instruction packets sent to workers.
84 */
85struct req {
86	ufs2_daddr_t dblk;
87	int count;
88};
89static int reqsiz;
90
91#define WORKERS 3		/* 1 worker writing, 1 reading, 1 for slack */
92static struct worker {
93	int64_t tapea;		/* header number at start of this chunk */
94	int64_t firstrec;	/* record number of this block */
95	int count;		/* count to next header (used for TS_TAPE */
96				/* after EOT) */
97	int inode;		/* inode that we are currently dealing with */
98	int fd;			/* FD for this worker */
99	int pid;		/* PID for this worker */
100	int sent;		/* 1 == we've sent this worker requests */
101	char (*tblock)[TP_BSIZE]; /* buffer for data blocks */
102	struct req *req;	/* buffer for requests */
103} workers[WORKERS+1];
104static struct worker *wp;
105
106static char	(*nextblock)[TP_BSIZE];
107
108static int master;	/* pid of master, for sending error signals */
109static int tenths;	/* length of tape used per block written */
110static volatile sig_atomic_t caught; /* have we caught the signal to proceed? */
111static volatile sig_atomic_t ready; /* reached the lock point without having */
112			/* received the SIGUSR2 signal from the prev worker? */
113static jmp_buf jmpbuf;	/* where to jump to if we are ready when the */
114			/* SIGUSR2 arrives from the previous worker */
115
116int
117alloctape(void)
118{
119	int pgoff = getpagesize() - 1;
120	char *buf;
121	int i;
122
123	writesize = ntrec * TP_BSIZE;
124	reqsiz = (ntrec + 1) * sizeof(struct req);
125	/*
126	 * CDC 92181's and 92185's make 0.8" gaps in 1600-bpi start/stop mode
127	 * (see DEC TU80 User's Guide).  The shorter gaps of 6250-bpi require
128	 * repositioning after stopping, i.e, streaming mode, where the gap is
129	 * variable, 0.30" to 0.45".  The gap is maximal when the tape stops.
130	 */
131	if (blocksperfile == 0 && !unlimited)
132		tenths = writesize / density +
133		    (cartridge ? 16 : density == 625 ? 5 : 8);
134	/*
135	 * Allocate tape buffer contiguous with the array of instruction
136	 * packets, so flushtape() can write them together with one write().
137	 * Align tape buffer on page boundary to speed up tape write().
138	 */
139	for (i = 0; i <= WORKERS; i++) {
140		buf = (char *)
141		    malloc((unsigned)(reqsiz + writesize + pgoff + TP_BSIZE));
142		if (buf == NULL)
143			return(0);
144		workers[i].tblock = (char (*)[TP_BSIZE])
145		    (((long)&buf[ntrec + 1] + pgoff) &~ pgoff);
146		workers[i].req = (struct req *)workers[i].tblock - ntrec - 1;
147	}
148	wp = &workers[0];
149	wp->count = 1;
150	wp->tapea = 0;
151	wp->firstrec = 0;
152	nextblock = wp->tblock;
153	return(1);
154}
155
156void
157writerec(char *dp, int isspcl)
158{
159
160	wp->req[trecno].dblk = (ufs2_daddr_t)0;
161	wp->req[trecno].count = 1;
162	/* Can't do a structure assignment due to alignment problems */
163	bcopy(dp, *(nextblock)++, sizeof (union u_spcl));
164	if (isspcl)
165		lastspclrec = spcl.c_tapea;
166	trecno++;
167	spcl.c_tapea++;
168	if (trecno >= ntrec)
169		flushtape();
170}
171
172void
173dumpblock(ufs2_daddr_t blkno, int size)
174{
175	int avail, tpblks;
176	ufs2_daddr_t dblkno;
177
178	dblkno = fsbtodb(sblock, blkno);
179	tpblks = size >> tp_bshift;
180	while ((avail = MIN(tpblks, ntrec - trecno)) > 0) {
181		wp->req[trecno].dblk = dblkno;
182		wp->req[trecno].count = avail;
183		trecno += avail;
184		spcl.c_tapea += avail;
185		if (trecno >= ntrec)
186			flushtape();
187		dblkno += avail << (tp_bshift - dev_bshift);
188		tpblks -= avail;
189	}
190}
191
192int	nogripe = 0;
193
194void
195tperror(int signo __unused)
196{
197
198	if (pipeout) {
199		msg("write error on %s\n", tape);
200		quit("Cannot recover\n");
201		/* NOTREACHED */
202	}
203	msg("write error %ld blocks into volume %d\n", blocksthisvol, tapeno);
204	broadcast("DUMP WRITE ERROR!\n");
205	if (!query("Do you want to restart?"))
206		dumpabort(0);
207	msg("Closing this volume.  Prepare to restart with new media;\n");
208	msg("this dump volume will be rewritten.\n");
209	killall();
210	nogripe = 1;
211	close_rewind();
212	Exit(X_REWRITE);
213}
214
215void
216sigpipe(int signo __unused)
217{
218
219	quit("Broken pipe\n");
220}
221
222static void
223flushtape(void)
224{
225	int i, blks, got;
226	int64_t lastfirstrec;
227
228	int siz = (char *)nextblock - (char *)wp->req;
229
230	wp->req[trecno].count = 0;			/* Sentinel */
231
232	if (atomic_write(wp->fd, (const void *)wp->req, siz) != siz)
233		quit("error writing command pipe: %s\n", strerror(errno));
234	wp->sent = 1; /* we sent a request, read the response later */
235
236	lastfirstrec = wp->firstrec;
237
238	if (++wp >= &workers[WORKERS])
239		wp = &workers[0];
240
241	/* Read results back from next worker */
242	if (wp->sent) {
243		if (atomic_read(wp->fd, (void *)&got, sizeof got)
244		    != sizeof got) {
245			perror("  DUMP: error reading command pipe in master");
246			dumpabort(0);
247		}
248		wp->sent = 0;
249
250		/* Check for end of tape */
251		if (got < writesize) {
252			msg("End of tape detected\n");
253
254			/*
255			 * Drain the results, don't care what the values were.
256			 * If we read them here then trewind won't...
257			 */
258			for (i = 0; i < WORKERS; i++) {
259				if (workers[i].sent) {
260					if (atomic_read(workers[i].fd,
261					    (void *)&got, sizeof got)
262					    != sizeof got) {
263						perror("  DUMP: error reading command pipe in master");
264						dumpabort(0);
265					}
266					workers[i].sent = 0;
267				}
268			}
269
270			close_rewind();
271			rollforward();
272			return;
273		}
274	}
275
276	blks = 0;
277	if (spcl.c_type != TS_END && spcl.c_type != TS_CLRI &&
278	    spcl.c_type != TS_BITS) {
279		assert(spcl.c_count <= TP_NINDIR);
280		for (i = 0; i < spcl.c_count; i++)
281			if (spcl.c_addr[i] != 0)
282				blks++;
283	}
284	wp->count = lastspclrec + blks + 1 - spcl.c_tapea;
285	wp->tapea = spcl.c_tapea;
286	wp->firstrec = lastfirstrec + ntrec;
287	wp->inode = curino;
288	nextblock = wp->tblock;
289	trecno = 0;
290	asize += tenths;
291	blockswritten += ntrec;
292	blocksthisvol += ntrec;
293	if (!pipeout && !unlimited && (blocksperfile ?
294	    (blocksthisvol >= blocksperfile) : (asize > tsize))) {
295		close_rewind();
296		startnewtape(0);
297	}
298	timeest();
299}
300
301void
302trewind(void)
303{
304	struct stat sb;
305	int f;
306	int got;
307
308	for (f = 0; f < WORKERS; f++) {
309		/*
310		 * Drain the results, but unlike EOT we DO (or should) care
311		 * what the return values were, since if we detect EOT after
312		 * we think we've written the last blocks to the tape anyway,
313		 * we have to replay those blocks with rollforward.
314		 *
315		 * fixme: punt for now.
316		 */
317		if (workers[f].sent) {
318			if (atomic_read(workers[f].fd, (void *)&got, sizeof got)
319			    != sizeof got) {
320				perror("  DUMP: error reading command pipe in master");
321				dumpabort(0);
322			}
323			workers[f].sent = 0;
324			if (got != writesize) {
325				msg("EOT detected in last 2 tape records!\n");
326				msg("Use a longer tape, decrease the size estimate\n");
327				quit("or use no size estimate at all.\n");
328			}
329		}
330		(void) close(workers[f].fd);
331	}
332	while (wait((int *)NULL) >= 0)	/* wait for any signals from workers */
333		/* void */;
334
335	if (pipeout)
336		return;
337
338	msg("Closing %s\n", tape);
339
340	if (popenout) {
341		tapefd = -1;
342		(void)pclose(popenfp);
343		popenfp = NULL;
344		return;
345	}
346#ifdef RDUMP
347	if (host) {
348		rmtclose();
349		while (rmtopen(tape, 0) < 0)
350			sleep(10);
351		rmtclose();
352		return;
353	}
354#endif
355	if (fstat(tapefd, &sb) == 0 && S_ISFIFO(sb.st_mode)) {
356		(void)close(tapefd);
357		return;
358	}
359	(void) close(tapefd);
360	while ((f = open(tape, 0)) < 0)
361		sleep (10);
362	(void) close(f);
363}
364
365void
366close_rewind()
367{
368	time_t tstart_changevol, tend_changevol;
369
370	trewind();
371	if (nexttape)
372		return;
373	(void)time((time_t *)&(tstart_changevol));
374	if (!nogripe) {
375		msg("Change Volumes: Mount volume #%d\n", tapeno+1);
376		broadcast("CHANGE DUMP VOLUMES!\a\a\n");
377	}
378	while (!query("Is the new volume mounted and ready to go?"))
379		if (query("Do you want to abort?")) {
380			dumpabort(0);
381			/*NOTREACHED*/
382		}
383	(void)time((time_t *)&(tend_changevol));
384	if ((tstart_changevol != (time_t)-1) && (tend_changevol != (time_t)-1))
385		tstart_writing += (tend_changevol - tstart_changevol);
386}
387
388void
389rollforward(void)
390{
391	struct req *p, *q, *prev;
392	struct worker *twp;
393	int i, size, got;
394	int64_t savedtapea;
395	union u_spcl *ntb, *otb;
396	twp = &workers[WORKERS];
397	ntb = (union u_spcl *)twp->tblock[1];
398
399	/*
400	 * Each of the N workers should have requests that need to
401	 * be replayed on the next tape.  Use the extra worker buffers
402	 * (workers[WORKERS]) to construct request lists to be sent to
403	 * each worker in turn.
404	 */
405	for (i = 0; i < WORKERS; i++) {
406		q = &twp->req[1];
407		otb = (union u_spcl *)wp->tblock;
408
409		/*
410		 * For each request in the current worker, copy it to twp.
411		 */
412
413		prev = NULL;
414		for (p = wp->req; p->count > 0; p += p->count) {
415			*q = *p;
416			if (p->dblk == 0)
417				*ntb++ = *otb++; /* copy the datablock also */
418			prev = q;
419			q += q->count;
420		}
421		if (prev == NULL)
422			quit("rollforward: protocol botch");
423		if (prev->dblk != 0)
424			prev->count -= 1;
425		else
426			ntb--;
427		q -= 1;
428		q->count = 0;
429		q = &twp->req[0];
430		if (i == 0) {
431			q->dblk = 0;
432			q->count = 1;
433			trecno = 0;
434			nextblock = twp->tblock;
435			savedtapea = spcl.c_tapea;
436			spcl.c_tapea = wp->tapea;
437			startnewtape(0);
438			spcl.c_tapea = savedtapea;
439			lastspclrec = savedtapea - 1;
440		}
441		size = (char *)ntb - (char *)q;
442		if (atomic_write(wp->fd, (const void *)q, size) != size) {
443			perror("  DUMP: error writing command pipe");
444			dumpabort(0);
445		}
446		wp->sent = 1;
447		if (++wp >= &workers[WORKERS])
448			wp = &workers[0];
449
450		q->count = 1;
451
452		if (prev->dblk != 0) {
453			/*
454			 * If the last one was a disk block, make the
455			 * first of this one be the last bit of that disk
456			 * block...
457			 */
458			q->dblk = prev->dblk +
459				prev->count * (TP_BSIZE / DEV_BSIZE);
460			ntb = (union u_spcl *)twp->tblock;
461		} else {
462			/*
463			 * It wasn't a disk block.  Copy the data to its
464			 * new location in the buffer.
465			 */
466			q->dblk = 0;
467			*((union u_spcl *)twp->tblock) = *ntb;
468			ntb = (union u_spcl *)twp->tblock[1];
469		}
470	}
471	wp->req[0] = *q;
472	nextblock = wp->tblock;
473	if (q->dblk == 0)
474		nextblock++;
475	trecno = 1;
476
477	/*
478	 * Clear the first workers' response.  One hopes that it
479	 * worked ok, otherwise the tape is much too short!
480	 */
481	if (wp->sent) {
482		if (atomic_read(wp->fd, (void *)&got, sizeof got)
483		    != sizeof got) {
484			perror("  DUMP: error reading command pipe in master");
485			dumpabort(0);
486		}
487		wp->sent = 0;
488
489		if (got != writesize) {
490			quit("EOT detected at start of the tape!\n");
491		}
492	}
493}
494
495/*
496 * We implement taking and restoring checkpoints on the tape level.
497 * When each tape is opened, a new process is created by forking; this
498 * saves all of the necessary context in the parent.  The child
499 * continues the dump; the parent waits around, saving the context.
500 * If the child returns X_REWRITE, then it had problems writing that tape;
501 * this causes the parent to fork again, duplicating the context, and
502 * everything continues as if nothing had happened.
503 */
504void
505startnewtape(int top)
506{
507	int	parentpid;
508	int	childpid;
509	int	status;
510	char	*p;
511	sig_t	interrupt_save;
512
513	interrupt_save = signal(SIGINT, SIG_IGN);
514	parentpid = getpid();
515
516restore_check_point:
517	(void)signal(SIGINT, interrupt_save);
518	/*
519	 *	All signals are inherited...
520	 */
521	setproctitle(NULL);	/* Restore the proctitle. */
522	childpid = fork();
523	if (childpid < 0) {
524		msg("Context save fork fails in parent %d\n", parentpid);
525		Exit(X_ABORT);
526	}
527	if (childpid != 0) {
528		/*
529		 *	PARENT:
530		 *	save the context by waiting
531		 *	until the child doing all of the work returns.
532		 *	don't catch the interrupt
533		 */
534		signal(SIGINT, SIG_IGN);
535#ifdef TDEBUG
536		msg("Tape: %d; parent process: %d child process %d\n",
537			tapeno+1, parentpid, childpid);
538#endif /* TDEBUG */
539		if (waitpid(childpid, &status, 0) == -1)
540			msg("Waiting for child %d: %s\n", childpid,
541			    strerror(errno));
542		if (status & 0xFF) {
543			msg("Child %d returns LOB status %o\n",
544				childpid, status&0xFF);
545		}
546		status = (status >> 8) & 0xFF;
547#ifdef TDEBUG
548		switch(status) {
549			case X_FINOK:
550				msg("Child %d finishes X_FINOK\n", childpid);
551				break;
552			case X_ABORT:
553				msg("Child %d finishes X_ABORT\n", childpid);
554				break;
555			case X_REWRITE:
556				msg("Child %d finishes X_REWRITE\n", childpid);
557				break;
558			default:
559				msg("Child %d finishes unknown %d\n",
560					childpid, status);
561				break;
562		}
563#endif /* TDEBUG */
564		switch(status) {
565			case X_FINOK:
566				Exit(X_FINOK);
567			case X_ABORT:
568				Exit(X_ABORT);
569			case X_REWRITE:
570				goto restore_check_point;
571			default:
572				msg("Bad return code from dump: %d\n", status);
573				Exit(X_ABORT);
574		}
575		/*NOTREACHED*/
576	} else {	/* we are the child; just continue */
577#ifdef TDEBUG
578		sleep(4);	/* allow time for parent's message to get out */
579		msg("Child on Tape %d has parent %d, my pid = %d\n",
580			tapeno+1, parentpid, getpid());
581#endif /* TDEBUG */
582		/*
583		 * If we have a name like "/dev/rmt0,/dev/rmt1",
584		 * use the name before the comma first, and save
585		 * the remaining names for subsequent volumes.
586		 */
587		tapeno++;               /* current tape sequence */
588		if (nexttape || strchr(tape, ',')) {
589			if (nexttape && *nexttape)
590				tape = nexttape;
591			if ((p = strchr(tape, ',')) != NULL) {
592				*p = '\0';
593				nexttape = p + 1;
594			} else
595				nexttape = NULL;
596			msg("Dumping volume %d on %s\n", tapeno, tape);
597		}
598		if (pipeout) {
599			tapefd = STDOUT_FILENO;
600		} else if (popenout) {
601			char volno[sizeof("2147483647")];
602
603			(void)sprintf(volno, "%d", spcl.c_volume + 1);
604			if (setenv("DUMP_VOLUME", volno, 1) == -1) {
605				msg("Cannot set $DUMP_VOLUME.\n");
606				dumpabort(0);
607			}
608			popenfp = popen(popenout, "w");
609			if (popenfp == NULL) {
610				msg("Cannot open output pipeline \"%s\".\n",
611				    popenout);
612				dumpabort(0);
613			}
614			tapefd = fileno(popenfp);
615		} else {
616#ifdef RDUMP
617			while ((tapefd = (host ? rmtopen(tape, 2) :
618				open(tape, O_WRONLY|O_CREAT, 0666))) < 0)
619#else
620			while ((tapefd =
621			    open(tape, O_WRONLY|O_CREAT, 0666)) < 0)
622#endif
623			    {
624				msg("Cannot open output \"%s\".\n", tape);
625				if (!query("Do you want to retry the open?"))
626					dumpabort(0);
627			}
628		}
629
630		create_workers();  /* Share open tape file descriptor with workers */
631		if (popenout)
632			close(tapefd);	/* Give up our copy of it. */
633		signal(SIGINFO, infosch);
634
635		asize = 0;
636		blocksthisvol = 0;
637		if (top)
638			newtape++;		/* new tape signal */
639		spcl.c_count = wp->count;
640		/*
641		 * measure firstrec in TP_BSIZE units since restore doesn't
642		 * know the correct ntrec value...
643		 */
644		spcl.c_firstrec = wp->firstrec;
645		spcl.c_volume++;
646		spcl.c_type = TS_TAPE;
647		writeheader((ino_t)wp->inode);
648		if (tapeno > 1)
649			msg("Volume %d begins with blocks from inode %d\n",
650				tapeno, wp->inode);
651	}
652}
653
654void
655dumpabort(int signo __unused)
656{
657
658	if (master != 0 && master != getpid())
659		/* Signals master to call dumpabort */
660		(void) kill(master, SIGTERM);
661	else {
662		killall();
663		msg("The ENTIRE dump is aborted.\n");
664	}
665#ifdef RDUMP
666	rmtclose();
667#endif
668	Exit(X_ABORT);
669}
670
671void
672Exit(int status)
673{
674
675#ifdef TDEBUG
676	msg("pid = %d exits with status %d\n", getpid(), status);
677#endif /* TDEBUG */
678	exit(status);
679}
680
681/*
682 * proceed - handler for SIGUSR2, used to synchronize IO between the workers.
683 */
684void
685proceed(int signo __unused)
686{
687
688	if (ready)
689		longjmp(jmpbuf, 1);
690	caught++;
691}
692
693void
694create_workers(void)
695{
696	int cmd[2];
697	int i, j;
698
699	master = getpid();
700
701	signal(SIGTERM, dumpabort);  /* Worker sends SIGTERM on dumpabort() */
702	signal(SIGPIPE, sigpipe);
703	signal(SIGUSR1, tperror);    /* Worker sends SIGUSR1 on tape errors */
704	signal(SIGUSR2, proceed);    /* Worker sends SIGUSR2 to next worker */
705
706	for (i = 0; i < WORKERS; i++) {
707		if (i == wp - &workers[0]) {
708			caught = 1;
709		} else {
710			caught = 0;
711		}
712
713		if (socketpair(AF_UNIX, SOCK_STREAM, 0, cmd) < 0 ||
714		    (workers[i].pid = fork()) < 0)
715			quit("too many workers, %d (recompile smaller): %s\n",
716			    i, strerror(errno));
717
718		workers[i].fd = cmd[1];
719		workers[i].sent = 0;
720		if (workers[i].pid == 0) { 	    /* Worker starts up here */
721			for (j = 0; j <= i; j++)
722			        (void) close(workers[j].fd);
723			signal(SIGINT, SIG_IGN);    /* Master handles this */
724			worker(cmd[0], i);
725			Exit(X_FINOK);
726		}
727	}
728
729	for (i = 0; i < WORKERS; i++)
730		(void) atomic_write(workers[i].fd,
731			      (const void *) &workers[(i + 1) % WORKERS].pid,
732		              sizeof workers[0].pid);
733
734	master = 0;
735}
736
737void
738killall(void)
739{
740	int i;
741
742	for (i = 0; i < WORKERS; i++)
743		if (workers[i].pid > 0) {
744			(void) kill(workers[i].pid, SIGKILL);
745			workers[i].sent = 0;
746		}
747}
748
749/*
750 * Synchronization - each process has a lockfile, and shares file
751 * descriptors to the following process's lockfile.  When our write
752 * completes, we release our lock on the following process's lock-
753 * file, allowing the following process to lock it and proceed. We
754 * get the lock back for the next cycle by swapping descriptors.
755 */
756static void
757worker(int cmd, int worker_number)
758{
759	int nread;
760	int nextworker, size, wrote, eot_count;
761
762	/*
763	 * Need our own seek pointer.
764	 */
765	(void) close(diskfd);
766	if ((diskfd = open(disk, O_RDONLY)) < 0)
767		quit("worker couldn't reopen disk: %s\n", strerror(errno));
768
769	/*
770	 * Need the pid of the next worker in the loop...
771	 */
772	if ((nread = atomic_read(cmd, (void *)&nextworker, sizeof nextworker))
773	    != sizeof nextworker) {
774		quit("master/worker protocol botched - didn't get pid of next worker.\n");
775	}
776
777	/*
778	 * Get list of blocks to dump, read the blocks into tape buffer
779	 */
780	while ((nread = atomic_read(cmd, (void *)wp->req, reqsiz)) == reqsiz) {
781		struct req *p = wp->req;
782
783		for (trecno = 0; trecno < ntrec;
784		     trecno += p->count, p += p->count) {
785			if (p->dblk) {
786				blkread(p->dblk, wp->tblock[trecno],
787					p->count * TP_BSIZE);
788			} else {
789				if (p->count != 1 || atomic_read(cmd,
790				    (void *)wp->tblock[trecno],
791				    TP_BSIZE) != TP_BSIZE)
792				       quit("master/worker protocol botched.\n");
793			}
794		}
795		if (setjmp(jmpbuf) == 0) {
796			ready = 1;
797			if (!caught)
798				(void) pause();
799		}
800		ready = 0;
801		caught = 0;
802
803		/* Try to write the data... */
804		eot_count = 0;
805		size = 0;
806
807		wrote = 0;
808		while (eot_count < 10 && size < writesize) {
809#ifdef RDUMP
810			if (host)
811				wrote = rmtwrite(wp->tblock[0]+size,
812				    writesize-size);
813			else
814#endif
815				wrote = write(tapefd, wp->tblock[0]+size,
816				    writesize-size);
817#ifdef WRITEDEBUG
818			printf("worker %d wrote %d\n", worker_number, wrote);
819#endif
820			if (wrote < 0)
821				break;
822			if (wrote == 0)
823				eot_count++;
824			size += wrote;
825		}
826
827#ifdef WRITEDEBUG
828		if (size != writesize)
829		 printf("worker %d only wrote %d out of %d bytes and gave up.\n",
830		     worker_number, size, writesize);
831#endif
832
833		/*
834		 * Handle ENOSPC as an EOT condition.
835		 */
836		if (wrote < 0 && errno == ENOSPC) {
837			wrote = 0;
838			eot_count++;
839		}
840
841		if (eot_count > 0)
842			size = 0;
843
844		if (wrote < 0) {
845			(void) kill(master, SIGUSR1);
846			for (;;)
847				(void) sigpause(0);
848		} else {
849			/*
850			 * pass size of write back to master
851			 * (for EOT handling)
852			 */
853			(void)atomic_write(cmd, (const void *)&size,
854			    sizeof size);
855		}
856
857		/*
858		 * If partial write, don't want next worker to go.
859		 * Also jolts him awake.
860		 */
861		(void) kill(nextworker, SIGUSR2);
862	}
863	if (nread != 0)
864		quit("error reading command pipe: %s\n", strerror(errno));
865}
866
867/*
868 * Since a read from a pipe may not return all we asked for,
869 * loop until the count is satisfied (or error).
870 */
871static int
872atomic_read(int fd, void *buf, int count)
873{
874	int got, need = count;
875
876	while ((got = read(fd, buf, need)) > 0 && (need -= got) > 0)
877		buf += got;
878	return (got < 0 ? got : count - need);
879}
880
881/*
882 * Since a write to a pipe may not write all we ask if we get a signal,
883 * loop until the count is satisfied (or error).
884 */
885static int
886atomic_write(int fd, const void *buf, int count)
887{
888	int got, need = count;
889
890	while ((got = write(fd, buf, need)) > 0 && (need -= got) > 0)
891		buf += got;
892	return (got < 0 ? got : count - need);
893}
894