consolefs.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

	}
}

int dbmtime;

/*
 *  a request processor (one per Fs)
 */
void
fsrun(void *v)
{
	int n, t;
	Request *r;
	Fid *f;
	Dir *d;
	void **a = v;
	Fs* fs;
	int *pfd;

	fs = a[0];
	pfd = a[1];
	fs->fd = pfd[0];
	for(;;){
		d = dirstat(consoledb);
		if(d != nil && d->mtime != dbmtime){
			dbmtime = d->mtime;
			readdb(fs);
		}
		free(d);
		r = allocreq(fs, messagesize);
		n = read9pmsg(fs->fd, r->buf, messagesize);
		if(n <= 0)
			fatal("unmounted");

		if(convM2S(r->buf, n, &r->f) == 0){
			fprint(2, "can't convert %ux %ux %ux\n", r->buf[0],
				r->buf[1], r->buf[2]);
			free(r);
			continue;
		}


		f = fsgetfid(fs, r->f.fid);
		r->fid = f;
		if(debug)
			fprint(2, "%F path %llux\n", &r->f, f->qid.path);

		t = r->f.type;
		r->f.type++;
		(*fcall[t])(fs, r, f);
	}
}

Fid*
fsgetfid(Fs *fs, int fid)
{
	Fid *f, *nf;

	lock(fs);
	for(f = fs->hash[fid%Nhash]; f; f = f->next){
		if(f->fid == fid){
			f->ref++;
			unlock(fs);
			return f;
		}
	}

	nf = emalloc(sizeof(Fid));
	nf->next = fs->hash[fid%Nhash];
	fs->hash[fid%Nhash] = nf;
	nf->fid = fid;
	nf->ref = 1;
	nf->wp = nf->buf;
	nf->rp = nf->wp;
	unlock(fs);
	return nf;
}

void
fsputfid(Fs *fs, Fid *f)
{
	Fid **l, *nf;

	lock(fs);
	if(--f->ref > 0){
		unlock(fs);
		return;
	}
	for(l = &fs->hash[f->fid%Nhash]; nf = *l; l = &nf->next)
		if(nf == f){
			*l = f->next;
			break;
		}
	unlock(fs);
	free(f->user);
	free(f);
}

void
fsauth(Fs *fs, Request *r, Fid*)
{
	fsreply(fs, r, "consolefs: authentication not required");
}

void
fsversion(Fs *fs, Request *r, Fid*)
{

	if(r->f.msize < 256){
		fsreply(fs, r, "message size too small");
		return;
	}
	messagesize = r->f.msize;
	if(messagesize > 8192+IOHDRSZ)
		messagesize = 8192+IOHDRSZ;
	r->f.msize = messagesize;
	if(strncmp(r->f.version, "9P2000", 6) != 0){
		fsreply(fs, r, "unrecognized 9P version");
		return;
	}
	r->f.version = "9P2000";

	fsreply(fs, r, nil);
}

void
fsflush(Fs *fs, Request *r, Fid *f)
{
	Request *or;

	or = remtag(&f->r, r->f.oldtag);
	if(or != nil){
		fsputfid(fs, or->fid);
		free(or);
	}
	fsreply(fs, r, nil);
}

void
fsattach(Fs *fs, Request *r, Fid *f)
{
	f->qid.type = QTDIR;
	f->qid.path = QID(0, Ttopdir);
	f->qid.vers = 0;

	if(r->f.uname[0])
		f->user = strdup(r->f.uname);
	else
		f->user = strdup("none");

	/* hold down the fid till the clunk */
	f->attached = 1;
	lock(fs);
	f->ref++;
	unlock(fs);

	r->f.qid = f->qid;
	fsreply(fs, r, nil);
}

void
fswalk(Fs *fs, Request *r, Fid *f)
{
	char *name;
	Dir d;
	int i, n, nqid, nwname;
	Qid qid, wqid[MAXWELEM];
	Fid *nf;
	char *err;

	if(f->attached == 0){
		fsreply(fs, r, Enofid);
		return;
	}

	nf = nil;
	if(r->f.fid != r->f.newfid){
		nf = fsgetfid(fs, r->f.newfid);
		nf->attached = f->attached;
		nf->open = f->open;
		nf->qid = f->qid;
		nf->user = strdup(f->user);
		nf->c = f->c;
		nf->wp = nf->buf;
		nf->rp = nf->wp;
		f = nf;
	}

	qid = f->qid;
	err = nil;
	nwname = r->f.nwname;
	nqid = 0;
	if(nwname > 0){
		for(; err == nil && nqid < nwname; nqid++){
			if(nqid >= MAXWELEM){
				err = "too many name elements";
				break;
			}
			name = r->f.wname[nqid];
			if(strcmp(name, "..") == 0)
				qid = parentqid(qid);
			else if(strcmp(name, ".") != 0){
				for(i = 0; ; i++){
					n = fsdirgen(fs, qid, i, &d, nil, 0);
					if(n < 0){
						err = Eexist;
						break;
					}
					if(n > 0 && strcmp(name, d.name) == 0){
						qid = d.qid;
						break;
					}
				}
			}
			wqid[nqid] = qid;
		}
		if(nf != nil && nqid < nwname)
			fsputfid(fs, nf);
		if(nqid == nwname)
			f->qid = qid;
	}

	memmove(r->f.wqid, wqid, nqid*sizeof(Qid));
	r->f.nwqid = nqid;
	fsreply(fs, r, err);
}

int
ingroup(char *user, char *group)
{
	Ndbtuple *t, *nt;
	Ndbs s;

	t = ndbsearch(db, &s, "group", group);
	if(t == nil)
		return 0;
	for(nt = t; nt; nt = nt->entry){
		if(strcmp(nt->attr, "uid") == 0)
		if(strcmp(nt->val, user) == 0)
			break;
	}
	ndbfree(t);
	return nt != nil;
}

int
userok(char *u, char *cname)
{
	Ndbtuple *t, *nt;
	Ndbs s;

	t = ndbsearch(db, &s, "console", cname);
	if(t == nil)
		return 0;

	for(nt = t; nt; nt = nt->entry){
		if(strcmp(nt->attr, "uid") == 0)
		if(strcmp(nt->val, u) == 0)
			break;
		if(strcmp(nt->attr, "gid") == 0)
		if(ingroup(u, nt->val))
			break;
	}
	ndbfree(t);

	return nt != nil;
}

int m2p[] ={
	[OREAD]		4,
	[OWRITE]	2,
	[ORDWR]		6
};

/*
 *  broadcast a message to all listeners
 */
void
bcastmsg(Fs *fs, Console *c, char *msg, int n)
{
	Fid *fl;

	for(fl = c->flist; fl; fl = fl->cnext){
		fromconsole(fl, msg, n);
		fskick(fs, fl);
	}
}

void
fsopen(Fs *fs, Request *r, Fid *f)
{
	int mode;
	Console *c;

	if(f->attached == 0){
		fsreply(fs, r, Enofid);
		return;
	}

	if(f->open){
		fsreply(fs, r, Eisopen);
		return;
	}

	mode = r->f.mode & 3;

	if((QTDIR & f->qid.type) && mode != OREAD){
		fsreply(fs, r, Eperm);
		return;
	}

	switch(TYPE(f->qid)){
	case Qdata:
		c = fs->cons[CONS(f->qid)];
		if(!userok(f->user, c->name)){
			fsreply(fs, r, Eperm);
			return;
		}
		f->rp = f->buf;
		f->wp = f->buf;
		f->c = c;
		lock(c);
		sprint(f->mbuf, "[%s] ", f->user);
		f->bufn = strlen(f->mbuf);
		f->used = 0;
		f->cnext = c->flist;
		c->flist = f;
		bcastmembers(fs, c, "+", f);
		if(c->pid == 0)
			fsreopen(fs, c);
		unlock(c);
		break;
	case Qctl:
		c = fs->cons[CONS(f->qid)];
		if(!userok(f->user, c->name)){
			fsreply(fs, r, Eperm);
			return;
		}
		f->c = c;
		break;
	case Qstat:
		c = fs->cons[CONS(f->qid)];
		if(!userok(f->user, c->name)){
			fsreply(fs, r, Eperm);
			return;
		}
		f->c = c;
		break;
	}

	f->open = 1;
	r->f.iounit = messagesize-IOHDRSZ;
	r->f.qid = f->qid;
	fsreply(fs, r, nil);
}

void
fscreate(Fs *fs, Request *r, Fid*)
{
	fsreply(fs, r, Eperm);
}

void
fsread(Fs *fs, Request *r, Fid *f)
{
	uchar *p, *e;
	int i, m, off;
	vlong offset;
	Dir d;
	char sbuf[ERRMAX];

	if(f->attached == 0){
		fsreply(fs, r, Enofid);
		return;
	}

	if((int)r->f.count < 0){
		fsreply(fs, r, Ebadcount);
		return;
	}

	if(QTDIR & f->qid.type){
		p = r->buf + IOHDRSZ;
		e = p + r->f.count;
		offset = r->f.offset;
		off = 0;
		for(i=0; p<e; i++, off+=m){
			m = fsdirgen(fs, f->qid, i, &d, p, e-p);
			if(m < 0)
				break;
			if(m > BIT16SZ && off >= offset)
				p += m;
		}
		r->f.data = (char*)r->buf + IOHDRSZ;
		r->f.count = (char*)p - r->f.data;
	} else {
		switch(TYPE(f->qid)){
		case Qdata:
			addreq(&f->r, r);
			fskick(fs, f);
			return;
		case Qctl:
			r->f.data = (char*)r->buf+IOHDRSZ;
			r->f.count = 0;
			break;
		case Qstat:
			if(r->f.count > sizeof(sbuf))
				r->f.count = sizeof(sbuf);
			i = pread(f->c->sfd, sbuf, r->f.count, r->f.offset);
			if(i < 0){
				errstr(sbuf, sizeof sbuf);
				fsreply(fs, r, sbuf);
				return;
			}
			r->f.data = sbuf;
			r->f.count = i;
			break;
		default:
			fsreply(fs, r, Eexist);
			return;
		}
	}
	fsreply(fs, r, nil);
}

void
fswrite(Fs *fs, Request *r, Fid *f)
{
	int i, eol = 0;

	if(f->attached == 0){
		fsreply(fs, r, Enofid);
		return;
	}

	if((int)r->f.count < 0){
		fsreply(fs, r, Ebadcount);
		return;
	}

	if(QTDIR & f->qid.type){
		fsreply(fs, r, Eperm);
		return;
	}

	switch(TYPE(f->qid)){
	default:
		fsreply(fs, r, Eperm);
		return;
	case Qctl:
		write(f->c->cfd, r->f.data, r->f.count);
		break;
	case Qdata:
		for(i = 0; i < r->f.count; i++){
			if(r->f.data[i] == '\n'){
				if(f->c->chat && f->used)
					eol = 1;
				if(f->c->cronly)
					r->f.data[i] = '\r';
			}
			else
				f->used = 1;
		}
		if(f->c->chat){
			fskick(fs, f);
			if(!f->used)
				break;
	
			if(f->bufn + r->f.count > Bufsize){
				r->f.count -= (f->bufn + r->f.count) % Bufsize;
				eol = 1;
			}
			strncat(f->mbuf, r->f.data, r->f.count);
			f->bufn += r->f.count;
			if(eol){
				bcastmsg(fs, f->c, f->mbuf, f->bufn);
				sprint(f->mbuf, "[%s] ", f->user);
				f->bufn = strlen(f->mbuf);
				f->used = 0;
			}
		}
		else
			write(f->c->fd, r->f.data, r->f.count);
		break;
	}
	fsreply(fs, r, nil);
}

void
fsclunk(Fs *fs, Request *r, Fid *f)
{
	Fid **l, *fl;
	Request *nr;

	if(f->open && TYPE(f->qid) == Qdata){
		while((nr = remreq(&f->r)) != nil){
			fsputfid(fs, f);
			free(nr);
		}

		lock(f->c);
		for(l = &f->c->flist; *l; l = &fl->cnext){
			fl = *l;
			if(fl == f){
				*l = fl->cnext;
				break;
			}
		}
		bcastmembers(fs, f->c, "-", f);
		if(f->c->ondemand && f->c->flist == nil)
			fsreopen(fs, f->c);
		unlock(f->c);
	}
	fsreply(fs, r, nil);
	fsputfid(fs, f);
}

void
fsremove(Fs *fs, Request *r, Fid*)
{
	fsreply(fs, r, Eperm);
}

void
fsstat(Fs *fs, Request *r, Fid *f)
{
	int i, n;
	Qid q;
	Dir d;

	q = parentqid(f->qid);
	for(i = 0; ; i++){
		r->f.stat = r->buf+IOHDRSZ;
		n = fsdirgen(fs, q, i, &d, r->f.stat, messagesize-IOHDRSZ);
		if(n < 0){
			fsreply(fs, r, Eexist);
			return;
		}
		r->f.nstat = n;
		if(r->f.nstat > BIT16SZ && d.qid.path == f->qid.path)
			break;
	}
	fsreply(fs, r, nil);
}

void
fswstat(Fs *fs, Request *r, Fid*)
{
	fsreply(fs, r, Eperm);
}

void
fsreply(Fs *fs, Request *r, char *err)
{
	int n;
	uchar buf[8192+IOHDRSZ];

	if(err){
		r->f.type = Rerror;
		r->f.ename = err;
	}
	n = convS2M(&r->f, buf, messagesize);
	if(debug)
		fprint(2, "%F path %llux n=%d\n", &r->f, r->fid->qid.path, n);
	fsputfid(fs, r->fid);
	if(write(fs->fd, buf, n) != n)
		fatal("unmounted");
	free(r);
}

/*
 *  called whenever input or a read request has been received
 */
void
fskick(Fs *fs, Fid *f)
{
	Request *r;
	char *p, *rp, *wp, *ep;
	int i;

	lock(f);
	while(f->rp != f->wp){
		r = remreq(&f->r);
		if(r == nil)
			break;
		p = (char*)r->buf;
		rp = f->rp;
		wp = f->wp;
		ep = &f->buf[Bufsize];
		for(i = 0; i < r->f.count && rp != wp; i++){
			*p++ = *rp++;
			if(rp >= ep)
				rp = f->buf;
		}
		f->rp = rp;
		r->f.data = (char*)r->buf;
		r->f.count = p - (char*)r->buf;
		fsreply(fs, r, nil);
	}
	unlock(f);
}

void
usage(void)
{
	fprint(2, "usage: consolefs [-d] [-m mount-point] [-c console-db]\n");
	threadexitsall("usage");
}

void
threadmain(int argc, char **argv)
{
	fmtinstall('F', fcallfmt);

	ARGBEGIN{
	case 'd':
		debug++;
		break;
	case 'c':
		consoledb = ARGF();
		if(consoledb == nil)
			usage();
		break;
	case 'm':
		mntpt = ARGF();
		if(mntpt == nil)
			usage();
		break;
	}ARGEND;

	db = ndbopen(consoledb);
	if(db == nil)
 		fatal("can't open %s: %r", consoledb);

	fsmount(mntpt);
}