applylog.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

						fprint(2, "stopped updating log apply time because of %s\n", name);
					skip = 1;
					continue;
				}
				SET(checkedmatch4);
				if(resolve1 == 's'){
					USED(checkedmatch4);
					SET(checkedmatch2);
					goto DoCreate;
				}
				else if(resolve1 == 'c')
					break;
				conflict(name, "locally removed; will not update metadata");
				skip = 1;
				continue;
			}
			if(!(dbd.mode&DMDIR) && (dbd.mtime != ld.mtime || dbd.length != ld.length)){	/* this check might be overkill */
				if(notexists(remote)){
					addce(local);
					/* no skip=1 */
					break;
				}
				if(!ismatch(name)){
					if(!skip)
						fprint(2, "stopped updating log apply time because of %s\n", name);
					skip = 1;
					continue;
				}
				SET(checkedmatch4);
				if(resolve1 == 's')
					goto DoMeta;
				else if(resolve1 == 'c')
					break;
				conflict(name, "contents locally modified (%s); will not update metadata to %s %s %luo",
					dbd.mtime != ld.mtime ? "mtime" :
					dbd.length != ld.length ? "length" : 
					"unknown",
					rd.uid, rd.gid, rd.mode);
				skip = 1;
				continue;
			}
			if((douid && strcmp(ld.uid, dbd.uid)!=0) || strcmp(ld.gid, dbd.gid)!=0 || ld.mode!=dbd.mode){
				if(notexists(remote)){
					addce(local);
					/* no skip=1 */
					break;
				}
				if(!ismatch(name)){
					if(!skip)
						fprint(2, "stopped updating log apply time because of %s\n", name);
					skip = 1;
					continue;
				}
				SET(checkedmatch4);
				if(resolve1 == 's')
					goto DoMeta;
				else if(resolve1 == 'c')
					break;
				conflict(name, "metadata locally changed; will not update metadata to %s %s %luo", rd.uid, rd.gid, rd.mode);
				skip = 1;
				continue;
			}
			if(!ismatch(name)){
				if(!skip)
					fprint(2, "stopped updating log apply time because of %s\n", name);
				skip = 1;
				continue;
			}
			SET(checkedmatch4);
		    DoMeta:
			USED(checkedmatch4);
			assert(ismatch(name));
			if(notexists(remote)){
				addce(local);
				/* no skip=1 */
				break;
			}
			chat("m %q %luo %q %q %lud\n", name, rd.mode, rd.uid, rd.gid, rd.mtime);
			if(donothing)
				break;
			nulldir(&nd);
			nd.gid = rd.gid;
			nd.mode = rd.mode;
			if(douid)
				nd.uid = rd.uid;
			if(dirwstat(local, &nd) < 0){
				error("dirwstat %q: %r", name);
				skip = 1;
				continue;
			}
		    DoMetaDb:
			USED(checkedmatch4);
			assert(ismatch(name));
			if(!havedb){
				if(havelocal)
					dbd = ld;
				else
					dbd = rd;
			}
			if(dbd.mode&DMDIR)
				dbd.mtime = now;
			dbd.gid = rd.gid;
			dbd.mode = rd.mode;
			if(douid)
				dbd.uid = rd.uid;
			insertdb(clientdb, name, &dbd);
			break;
		}
		if(!skip && !donothing){
			maxnow = now;
			maxn = n;
		}
	}

	w = avlwalk(copyerr->avl);
	while(e = (Entry*)avlnext(w))
		error("copying %q: %s\n", e->name, e->d.name);

	if(timefile)
		writetimefile();
	if(nconf)
		exits("conflicts");

	if(errors)
		exits("errors");
	exits(nil);
}


char*
mkname(char *buf, int nbuf, char *a, char *b)
{
	if(strlen(a)+strlen(b)+2 > nbuf)
		sysfatal("name too long");

	strcpy(buf, a);
	if(a[strlen(a)-1] != '/')
		strcat(buf, "/");
	strcat(buf, b);
	return buf;
}

int
isdir(char *s)
{
	ulong m;
	Dir *d;

	if((d = dirstat(s)) == nil)
		return 0;
	m = d->mode;
	free(d);
	return (m&DMDIR) != 0;
}

void
conflict(char *name, char *f, ...)
{
	char *s;
	va_list arg;

	va_start(arg, f);
	s = vsmprint(f, arg);
	va_end(arg);

	fprint(2, "%s: %s\n", name, s);
	free(s);

	nconf++;
//	if(nconf%16 == 0)
//		conf = erealloc(conf, (nconf+16)*sizeof(conf[0]));
//	conf[nconf++] = estrdup(name);
}

void
error(char *f, ...)
{
	char *s;
	va_list arg;

	va_start(arg, f);
	s = vsmprint(f, arg);
	va_end(arg);
	fprint(2, "error: %s\n", s);
	free(s);
	errors = 1;
}

int
ismatch(char *s)
{
	int i, len;

	if(nmatch == 0)
		return 1;
	for(i=0; i<nmatch; i++){
		len = strlen(match[i]);
		if(len == 0)
			return 1;
		if(strncmp(s, match[i], len) == 0 && (s[len]=='/' || s[len] == 0))
			return 1;
	}
	return 0;
}

int
localdirstat(char *name, Dir *d)
{
	static Dir *d2;

	free(d2);
	if((d2 = dirstat(name)) == nil)
		return -1;
	*d = *d2;
	return 0;
}

enum { DEFB = 8192 };

static int
copy1(int fdf, int fdt, char *from, char *to)
{
	int i, n, rv, pid[Nwork];
	Waitmsg *w;

	n = 0;
	off = 0;
	for(i=0; i<Nwork; i++){
		switch(pid[n] = rfork(RFPROC|RFMEM)){
		case 0:
			notify(failure);
			worker(fdf, fdt, from, to);
		case -1:
			break;
		default:
			n++;
			break;
		}
	}
	if(n == 0){
		fprint(2, "cp: rfork: %r\n");
		return -1;
	}

	rv = 0;
	while((w = wait()) != nil){
		if(w->msg[0]){
			rv = -1;
			for(i=0; i<n; i++)
				if(pid[i] > 0)
					postnote(PNPROC, pid[i], "failure");
		}
		free(w);
	}
	return rv;
}

void
worker(int fdf, int fdt, char *from, char *to)
{
	char buf[DEFB], *bp;
	long len, n;
	vlong o;

	len = sizeof(buf);
	bp = buf;
	o = nextoff();

	while(n = pread(fdf, bp, len, o)){
		if(n < 0){
			fprint(2, "reading %s: %r\n", from);
			_exits("bad");
		}
		if(pwrite(fdt, buf, n, o) != n){
			fprint(2, "writing %s: %r\n", to);
			_exits("bad");
		}
		bp += n;
		o += n;
		len -= n;
		if(len == 0){
			len = sizeof buf;
			bp = buf;
			o = nextoff();
		}
	}
	_exits(nil);
}

vlong
nextoff(void)
{
	vlong o;

	qlock(&lk);
	o = off;
	off += DEFB;
	qunlock(&lk);

	return o;
}

void
failure(void*, char *note)
{
	if(strcmp(note, "failure") == 0)
		_exits(nil);
	noted(NDFLT);
}


static int
opentemp(char *template)
{
	int fd, i;
	char *p;

	p = estrdup(template);
	fd = -1;
	for(i=0; i<10; i++){
		mktemp(p);
		if((fd=create(p, ORDWR|OEXCL|ORCLOSE, 0000)) >= 0)
			break;
		strcpy(p, template);
	}
	if(fd < 0)
		return -1;
	strcpy(template, p);
	free(p);
	return fd;
}

int
copyfile(char *local, char *remote, char *name, Dir *d, int dowstat, int *printerror)
{
	Dir *d0, *d1, *dl;
	Dir nd;
	int rfd, tfd, wfd, didcreate;
	char tmp[32], *p, *safe;
	char err[ERRMAX];

Again:
	*printerror = 0;
	if((rfd = open(remote, OREAD)) < 0)
		return -1;

	d0 = dirfstat(rfd);
	if(d0 == nil){
		close(rfd);
		return -1;
	}
	*printerror = 1;
	if(!tempspool){
		tfd = rfd;
		goto DoCopy;
	}
	strcpy(tmp, "/tmp/replicaXXXXXXXX");
	tfd = opentemp(tmp);
	if(tfd < 0){
		close(rfd);
		free(d0);
		return -1;
	}
	if(copy1(rfd, tfd, remote, tmp) < 0 || (d1 = dirfstat(rfd)) == nil){
		close(rfd);
		close(tfd);
		free(d0);
		return -1;
	}
	close(rfd);
	if(d0->qid.path != d1->qid.path
	|| d0->qid.vers != d1->qid.vers
	|| d0->mtime != d1->mtime
	|| d0->length != d1->length){
		/* file changed underfoot; go around again */
		close(tfd);
		free(d0);
		free(d1);
		goto Again;
	}
	free(d1);
	if(seek(tfd, 0, 0) != 0){
		close(tfd);
		free(d0);
		return -1;
	}

DoCopy:
	/*
	 * clumsy but important hack to do safeinstall-like installs.
	 */
	p = strchr(name, '/');
	if(safeinstall && p && strncmp(p, "/bin/", 5) == 0 && access(local, AEXIST) >= 0){
		/* 
		 * remove bin/_targ
		 */
		safe = emalloc(strlen(local)+2);
		strcpy(safe, local);
		p = strrchr(safe, '/')+1;
		memmove(p+1, p, strlen(p)+1);
		p[0] = '_';
		remove(safe);	/* ignore failure */

		/*
		 * rename bin/targ to bin/_targ
		 */
		nulldir(&nd);
		nd.name = p;
		if(dirwstat(local, &nd) < 0)
			fprint(2, "warning: rename %s to %s: %r\n", local, p);
	}

	didcreate = 0;
	if((dl = dirstat(local)) == nil){
		if((wfd = create(local, OWRITE, 0)) >= 0){
			didcreate = 1;
			goto okay;
		}
		goto err;
	}else{
		if((wfd = open(local, OTRUNC|OWRITE)) >= 0)
			goto okay;
		rerrstr(err, sizeof err);
		if(strstr(err, "permission") == nil)
			goto err;
		nulldir(&nd);
		/*
		 * Assume the person running pull is in the appropriate
		 * groups.  We could set 0666 instead, but I'm worried
		 * about leaving the file world-readable or world-writable
		 * when it shouldn't be.
		 */
		nd.mode = dl->mode | 0660;
		if(nd.mode == dl->mode)
			goto err;
		if(dirwstat(local, &nd) < 0)
			goto err;
		if((wfd = open(local, OTRUNC|OWRITE)) >= 0){
			nd.mode = dl->mode;
			if(dirfwstat(wfd, &nd) < 0)
				fprint(2, "warning: set mode on %s to 0660 to open; cannot set back to %luo: %r\n", local, nd.mode);
			goto okay;
		}
		nd.mode = dl->mode;
		if(dirwstat(local, &nd) < 0)
			fprint(2, "warning: set mode on %s to %luo to open; open failed; cannot set mode back to %luo: %r\n", local, nd.mode|0660, nd.mode);
		goto err;
	}
		
err:
	close(tfd);
	free(d0);
	free(dl);
	return -1;

okay:
	free(dl);
	if(copy1(tfd, wfd, tmp, local) < 0){
		close(tfd);
		close(wfd);
		free(d0);
		return -1;
	}
	close(tfd);
	if(didcreate || dowstat){
		nulldir(&nd);
		nd.mode = d->mode;
		if(dirfwstat(wfd, &nd) < 0)
			fprint(2, "warning: cannot set mode on %s\n", local);
		nulldir(&nd);
		nd.gid = d->gid;
		if(dirfwstat(wfd, &nd) < 0)
			fprint(2, "warning: cannot set gid on %s\n", local);
		if(douid){
			nulldir(&nd);
			nd.uid = d->uid;
			if(dirfwstat(wfd, &nd) < 0)
				fprint(2, "warning: cannot set uid on %s\n", local);
		}
	}
	d->mtime = d0->mtime;
	d->length = d0->length;
	nulldir(&nd);
	nd.mtime = d->mtime;
	if(dirfwstat(wfd, &nd) < 0)
		fprint(2, "warning: cannot set mtime on %s\n", local);
	free(d0);

	close(wfd);
	return 0;
}

/*
 * Applylog might try to overwrite itself.
 * To avoid problems with this, we copy ourselves
 * into /tmp and then re-exec.
 */
char *rmargv0;

static void
rmself(void)
{
	remove(rmargv0);
}

static int
genopentemp(char *template, int mode, int perm)
{
	int fd, i;
	char *p;	

	p = estrdup(template);
	fd = -1;
	for(i=0; i<10; i++){
		mktemp(p);
		if(access(p, 0) < 0 && (fd=create(p, mode, perm)) >= 0)
			break;
		strcpy(p, template);
	}
	if(fd < 0)
		sysfatal("could not create temporary file");

	strcpy(template, p);
	free(p);

	return fd;
}

static void
membogus(char **argv)
{
	int n, fd, wfd;
	char template[50], buf[1024];

	if(strncmp(argv[0], "/tmp/_applylog_", 1+3+1+1+8+1)==0) {
		rmargv0 = argv[0];
		atexit(rmself);
		return;
	}

	if((fd = open(argv[0], OREAD)) < 0)
		return;

	strcpy(template, "/tmp/_applylog_XXXXXX");
	if((wfd = genopentemp(template, OWRITE, 0700)) < 0)
		return;

	while((n = read(fd, buf, sizeof buf)) > 0)
		if(write(wfd, buf, n) != n)
			goto Error;

	if(n != 0)
		goto Error;

	close(fd);
	close(wfd);

	argv[0] = template;
	exec(template, argv);
	fprint(2, "exec error %r\n");

Error:
	close(fd);
	close(wfd);
	remove(template);
	return;
}