9p1.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

	f->lastra = 0;
	if(in->mode & MRCLOSE)
		fmod |= FREMOV;
	f->open = fmod;
	f->addr = addr1;
	f->slot = slot1;
	if(t)
		t->file = f;
	mkqid9p1(&ou->qid, &qid);
	goto out;

badaccess:
	ou->err = Eaccess;
	goto out;

phase:
	ou->err = Ephase;

out:
	if(p)
		putbuf(p);
	if(f)
		qunlock(f);
	ou->fid = in->fid;
}

void
f_read(Chan *cp, Oldfcall *in, Oldfcall *ou)
{
	Iobuf *p, *p1;
	File *f;
	Dentry *d, *d1;
	Tlock *t;
	long addr, offset, tim;
	int nread, count, n, o, slot;

	if(CHAT(cp)) {
		print("c_read %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
		print("	offset = %ld\n", in->offset);
		print("	count = %ld\n", in->count);
	}

	p = 0;
	count = in->count;
	offset = in->offset;
	nread = 0;
	f = filep(cp, in->fid, 0);
	if(!f) {
		ou->err = Efid;
		goto out;
	}
	if(!(f->open & FREAD)) {
		ou->err = Eopen;
		goto out;
	}
	if(count < 0 || count > MAXDAT) {
		ou->err = Ecount;
		goto out;
	}
	if(offset < 0) {
		ou->err = Eoffset;
		goto out;
	}
	p = getbuf(f->fs->dev, f->addr, Bread);
	d = getdir(p, f->slot);
	if(!d || !(d->mode & DALLOC)) {
		ou->err = Ealloc;
		goto out;
	}
	if(ou->err = mkqidcmp(&f->qid, d))
		goto out;
	if(t = f->tlock) {
		tim = time(0);
		if(t->time < tim || t->file != f) {
			ou->err = Ebroken;
			goto out;
		}
		/* renew the lock */
		t->time = tim + TLOCK;
	}
	accessdir(p, d, FREAD);
	if(d->mode & DDIR) {
		addr = 0;
		goto dread;
	}
	if(offset+count > d->size)
		count = d->size - offset;
	while(count > 0) {
		addr = offset / BUFSIZE;
		if(addr == f->lastra+1)
			dbufread(p, d, addr+1);
		f->lastra = addr;
		o = offset % BUFSIZE;
		n = BUFSIZE - o;
		if(n > count)
			n = count;
		p1 = dnodebuf(p, d, addr, 0);
		if(p1) {
			if(checktag(p1, Tfile, QPNONE)) {
				ou->err = Ephase;
				putbuf(p1);
				goto out;
			}
			memmove(ou->data+nread, p1->iobuf+o, n);
			putbuf(p1);
		} else
			memset(ou->data+nread, 0, n);
		count -= n;
		nread += n;
		offset += n;
	}
	goto out;

dread:
	p1 = dnodebuf(p, d, addr, 0);
	if(!p1)
		goto out;
	if(checktag(p1, Tdir, QPNONE)) {
		ou->err = Ephase;
		putbuf(p1);
		goto out;
	}
	n = DIRREC;
	for(slot=0; slot<DIRPERBUF; slot++) {
		d1 = getdir(p1, slot);
		if(!(d1->mode & DALLOC))
			continue;
		if(offset >= n) {
			offset -= n;
			continue;
		}
		if(count < n) {
			putbuf(p1);
			goto out;
		}
		if(convD2M9p1(d1, ou->data+nread) != n)
			print("dirread convD2M\n");
		nread += n;
		count -= n;
	}
	putbuf(p1);
	addr++;
	goto dread;

out:
	count = in->count - nread;
	if(count > 0)
		memset(ou->data+nread, 0, count);
	if(p)
		putbuf(p);
	if(f)
		qunlock(f);
	ou->fid = in->fid;
	ou->count = nread;
	if(CHAT(cp))
		print("	nread = %d\n", nread);
}

void
f_write(Chan *cp, Oldfcall *in, Oldfcall *ou)
{
	Iobuf *p, *p1;
	Dentry *d;
	File *f;
	Tlock *t;
	long offset, addr, tim;
	int count, nwrite, o, n;

	if(CHAT(cp)) {
		print("c_write %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
		print("	offset = %ld\n", in->offset);
		print("	count = %ld\n", in->count);
	}

	offset = in->offset;
	count = in->count;
	nwrite = 0;
	p = 0;
	f = filep(cp, in->fid, 0);
	if(!f) {
		ou->err = Efid;
		goto out;
	}
	if(!(f->open & FWRITE)) {
		ou->err = Eopen;
		goto out;
	}
	if(isro(f->fs->dev) || (cp != cons.chan && writegroup && !ingroup(f->uid, writegroup))) {
		ou->err = Eronly;
		goto out;
	}
	if(count < 0 || count > MAXDAT) {
		ou->err = Ecount;
		goto out;
	}
	if(offset < 0) {
		ou->err = Eoffset;
		goto out;
	}
	p = getbuf(f->fs->dev, f->addr, Bread|Bmod);
	d = getdir(p, f->slot);
	if(!d || !(d->mode & DALLOC)) {
		ou->err = Ealloc;
		goto out;
	}
	if(ou->err = mkqidcmp(&f->qid, d))
		goto out;
	if(t = f->tlock) {
		tim = time(0);
		if(t->time < tim || t->file != f) {
			ou->err = Ebroken;
			goto out;
		}
		/* renew the lock */
		t->time = tim + TLOCK;
	}
	accessdir(p, d, FWRITE);
	if(d->mode & DAPND)
		offset = d->size;
	if(offset+count > d->size)
		d->size = offset+count;
	while(count > 0) {
		addr = offset / BUFSIZE;
		o = offset % BUFSIZE;
		n = BUFSIZE - o;
		if(n > count)
			n = count;
		p1 = dnodebuf(p, d, addr, Tfile);
		if(p1 == 0) {
			ou->err = Efull;
			goto out;
		}
		if(checktag(p1, Tfile, d->qid.path)) {
			putbuf(p1);
			ou->err = Ephase;
			goto out;
		}
		memmove(p1->iobuf+o, in->data+nwrite, n);
		p1->flags |= Bmod;
		putbuf(p1);
		count -= n;
		nwrite += n;
		offset += n;
	}
	if(CHAT(cp))
		print("	nwrite = %d\n", nwrite);

out:
	if(p)
		putbuf(p);
	if(f)
		qunlock(f);
	ou->fid = in->fid;
	ou->count = nwrite;
}

int
doremove(File *f, int iscon)
{
	Iobuf *p, *p1;
	Dentry *d, *d1;
	long addr;
	int slot, err;

	p = 0;
	p1 = 0;
	if(isro(f->fs->dev) || (f->cp != cons.chan && writegroup && !ingroup(f->uid, writegroup))) {
		err = Eronly;
		goto out;
	}
	/*
	 * check on parent directory of file to be deleted
	 */
	if(f->wpath == 0 || f->wpath->addr == f->addr) {
		err = Ephase;
		goto out;
	}
	p1 = getbuf(f->fs->dev, f->wpath->addr, Bread);
	d1 = getdir(p1, f->wpath->slot);
	if(!d1 || checktag(p1, Tdir, QPNONE) || !(d1->mode & DALLOC)) {
		err = Ephase;
		goto out;
	}
	if(!iscon && iaccess(f, d1, DWRITE)) {
		err = Eaccess;
		goto out;
	}
	accessdir(p1, d1, FWRITE);
	putbuf(p1);
	p1 = 0;

	/*
	 * check on file to be deleted
	 */
	p = getbuf(f->fs->dev, f->addr, Bread);
	d = getdir(p, f->slot);
	if(!d || checktag(p, Tdir, QPNONE) || !(d->mode & DALLOC)) {
		err = Ealloc;
		goto out;
	}
	if(err = mkqidcmp(&f->qid, d))
		goto out;

	/*
	 * if deleting a directory, make sure it is empty
	 */
	if((d->mode & DDIR))
	for(addr=0;; addr++) {
		p1 = dnodebuf(p, d, addr, 0);
		if(!p1)
			break;
		if(checktag(p1, Tdir, d->qid.path)) {
			err = Ephase;
			goto out;
		}
		for(slot=0; slot<DIRPERBUF; slot++) {
			d1 = getdir(p1, slot);
			if(!(d1->mode & DALLOC))
				continue;
			err = Eempty;
			goto out;
		}
		putbuf(p1);
	}

	/*
	 * do it
	 */
	dtrunc(p, d);
	memset(d, 0, sizeof(Dentry));
	settag(p, Tdir, QPNONE);

out:
	if(p1)
		putbuf(p1);
	if(p)
		putbuf(p);
	return err;
}

void
f_remove(Chan *cp, Oldfcall *in, Oldfcall *ou)
{
	File *f;

	if(CHAT(cp)) {
		print("c_remove %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
	}

	f = filep(cp, in->fid, 0);
	if(!f) {
		ou->err = Efid;
		goto out;
	}
	ou->err = doremove(f, cp==cons.chan);

out:
	ou->fid = in->fid;
	if(f)
		qunlock(f);
}

void
f_stat(Chan *cp, Oldfcall *in, Oldfcall *ou)
{
	Iobuf *p;
	Dentry *d;
	File *f;

	if(CHAT(cp)) {
		print("c_stat %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
	}

	p = 0;
	memset(ou->stat, 0, sizeof(ou->stat));
	f = filep(cp, in->fid, 0);
	if(!f) {
		ou->err = Efid;
		goto out;
	}
	p = getbuf(f->fs->dev, f->addr, Bread);
	d = getdir(p, f->slot);
	if(!d || checktag(p, Tdir, QPNONE) || !(d->mode & DALLOC)) {
		ou->err = Ealloc;
		goto out;
	}
	if(ou->err = mkqidcmp(&f->qid, d))
		goto out;
	if(d->qid.path == QPROOT)	/* stat of root gives time */
		d->atime = time(0);
	if(convD2M9p1(d, ou->stat) != DIRREC)
		print("stat convD2M\n");

out:
	if(p)
		putbuf(p);
	if(f)
		qunlock(f);
	ou->fid = in->fid;
}

void
f_wstat(Chan *cp, Oldfcall *in, Oldfcall *ou)
{
	Iobuf *p, *p1;
	Dentry *d, *d1, xd;
	File *f;
	int slot;
	long addr;

	if(CHAT(cp)) {
		print("c_wstat %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
	}

	p = 0;
	p1 = 0;
	d1 = 0;
	f = filep(cp, in->fid, 0);
	if(!f) {
		ou->err = Efid;
		goto out;
	}
	if(isro(f->fs->dev) || (cp != cons.chan && writegroup && !ingroup(f->uid, writegroup))) {
		ou->err = Eronly;
		goto out;
	}

	/*
	 * first get parent
	 */
	if(f->wpath) {
		p1 = getbuf(f->fs->dev, f->wpath->addr, Bread);
		d1 = getdir(p1, f->wpath->slot);
		if(!d1 || checktag(p1, Tdir, QPNONE) || !(d1->mode & DALLOC)) {
			ou->err = Ephase;
			goto out;
		}
	}

	p = getbuf(f->fs->dev, f->addr, Bread);
	d = getdir(p, f->slot);
	if(!d || checktag(p, Tdir, QPNONE) || !(d->mode & DALLOC)) {
		ou->err = Ealloc;
		goto out;
	}
	if(ou->err = mkqidcmp(&f->qid, d))
		goto out;

	convM2D9p1(in->stat, &xd);
	if(CHAT(cp)) {
		print("	d.name = %s\n", xd.name);
		print("	d.uid  = %d\n", xd.uid);
		print("	d.gid  = %d\n", xd.gid);
		print("	d.mode = %.4x\n", xd.mode);
	}

	/*
	 * if chown,
	 * must be god
	 */
	while(xd.uid != d->uid) {
		if(wstatallow)			/* set to allow chown during boot */
			break;
		ou->err = Enotu;
		goto out;
	}

	/*
	 * if chgroup,
	 * must be either
	 *	a) owner and in new group
	 *	b) leader of both groups
	 */
	while(xd.gid != d->gid) {
		if(wstatallow || writeallow)		/* set to allow chgrp during boot */
			break;
		if(d->uid == f->uid && ingroup(f->uid, xd.gid))
			break;
		if(leadgroup(f->uid, xd.gid))
			if(leadgroup(f->uid, d->gid))
				break;
		ou->err = Enotg;
		goto out;
	}

	/*
	 * if rename,
	 * must have write permission in parent
	 */
	if(xd.name[0] == 0)
		strncpy(xd.name, d->name, sizeof(xd.name));
	while(strncmp(d->name, xd.name, sizeof(d->name)) != 0) {
		if(checkname(xd.name)) {
			ou->err = Ename;
			goto out;
		}

		if(strcmp(xd.name, ".") == 0 || strcmp(xd.name, "..") == 0) {
			ou->err = Ename;
			goto out;
		}

		/*
		 * drop entry to prevent lock, then
		 * check that destination name is unique,
		 */
		putbuf(p);
		for(addr=0;; addr++) {
			p = dnodebuf(p1, d1, addr, 0);
			if(!p)
				break;
			if(checktag(p, Tdir, d1->qid.path)) {
				putbuf(p);
				continue;
			}
			for(slot=0; slot<DIRPERBUF; slot++) {
				d = getdir(p, slot);
				if(!(d->mode & DALLOC))
					continue;
				if(!strncmp(xd.name, d->name, sizeof(xd.name))) {
					ou->err = Eexist;
					goto out;
				}
			}
			putbuf(p);
		}

		/*
		 * reacquire entry
		 */
		p = getbuf(f->fs->dev, f->addr, Bread);
		d = getdir(p, f->slot);
		if(!d || checktag(p, Tdir, QPNONE) || !(d->mode & DALLOC)) {
			ou->err = Ephase;
			goto out;
		}

		if(wstatallow || writeallow) /* set to allow rename during boot */
			break;
		if(!d1 || iaccess(f, d1, DWRITE)) {
			ou->err = Eaccess;
			goto out;
		}
		break;
	}

	/*
	 * if mode/time, either
	 *	a) owner
	 *	b) leader of either group
	 */
	while(d->mtime != xd.mtime ||
	     ((d->mode^xd.mode) & (DAPND|DLOCK|0777))) {
		if(wstatallow)			/* set to allow chmod during boot */
			break;
		if(d->uid == f->uid)
			break;
		if(leadgroup(f->uid, xd.gid))
			break;
		if(leadgroup(f->uid, d->gid))
			break;
		ou->err = Enotu;
		goto out;
	}
	d->mtime = xd.mtime;
	d->uid = xd.uid;
	d->gid = xd.gid;
	d->mode = (xd.mode & (DAPND|DLOCK|0777)) | (d->mode & (DALLOC|DDIR));

	strncpy(d->name, xd.name, sizeof(d->name));
	if(wstatallow) {
		p->flags |= Bmod;
		if(xd.atime)
			d->atime = xd.atime;
		if(xd.mtime)
			d->mtime = xd.mtime;
	} else
		accessdir(p, d, FWSTAT);

out:
	if(p)
		putbuf(p);
	if(p1)
		putbuf(p1);
	if(f)
		qunlock(f);
	ou->fid = in->fid;
}

void
(*call9p1[MAXSYSCALL])(Chan*, Oldfcall*, Oldfcall*) =
{
	[Tnop9p1]		f_nop,
	[Tosession9p1]	f_session,
	[Tsession9p1]	f_session,
	[Tflush9p1]	f_flush,
	[Toattach9p1]	f_attach,
	[Tattach9p1]	f_attach,
	[Tclone9p1]	f_clone,
	[Twalk9p1]		f_walk,
	[Topen9p1]		f_open,
	[Tcreate9p1]	f_create,
	[Tread9p1]		f_read,
	[Twrite9p1]	f_write,
	[Tclunk9p1]	f_clunk,
	[Tremove9p1]	f_remove,
	[Tstat9p1]		f_stat,
	[Twstat9p1]	f_wstat,
	[Tclwalk9p1]	f_clwalk,
};

static void
send(Chan *c, uchar *buf, int n)
{
	int fd, m;

	fd = c->chan;
	m = write(fd, buf, n);
	if(m == n)
		return;
	panic("write failed");
}

void
error9p1(Chan *c, uchar *buf)
{
	buf[0] = Rnop9p1;
	buf[1] = ~0;
	buf[2] = ~0;

	send(c, buf, 3);
}

void
serve9p1(Chan *chan, uchar *ib, int nib)
{
	int n, t;
	uchar inbuf[MAXMSG+MAXDAT], outbuf[MAXMSG+MAXDAT];
	Oldfcall fi, fo;

	for(;;){
		if(nib){
			memmove(inbuf, ib, nib);
			n = nib;
			nib = 0;
		}else
			n = read(chan->chan, inbuf, sizeof inbuf);
		if(chat)
			print("read msg %d\n", n);
		if(n == 0 && (chan == cons.srvchan || chan == cons.chan))
			continue;
		if(n <= 0)
			return;
		if(convM2S9p1(inbuf, &fi, n) != n){
			error9p1(chan, outbuf);
			continue;
		}

		t = fi.type;
		if(t < 0 || t >= MAXSYSCALL || (t&1) || !call9p1[t]) {
			print("9p1: bad message type\n");
			error9p1(chan, outbuf);
			continue;
		}

		if(CHAT(chan))
			print("9p1: fi %O\n", &fi);

		/*
		 * set up reply message
		 */
		fo.err = 0;
		if(t == Tread9p1)
			fo.data = (char*)outbuf + 8;
	
		/*
		 * call the file system
		 */
		cons.work.count++;
		cons.rate.count += n;

		/*
		 * call the file system
		 */
		rlock(&mainlock);
		rlock(&chan->reflock);
	
		(*call9p1[t])(chan, &fi, &fo);
	
		runlock(&chan->reflock);
		runlock(&mainlock);
	
		fo.type = t+1;
		fo.tag = fi.tag;
	
		if(chat)
			print("9p1: fo %O\n", &fo);

		if(fo.err) {
			strcpy(fo.ename, errstring[fo.err]);
			if(CHAT(cp))
				print("	error: %s\n", fo.ename);
			fo.type = Terror9p1+1;
		}
	
		n = convS2M9p1(&fo, outbuf);
		if(n == 0) {
			print("9p1: bad S2M conversion\n");
			error9p1(chan, outbuf);
			continue;
		}

		cons.rate.count += n;
		send(chan, outbuf, n);
	}
}