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

	Dentry *d, *d1;
	Tlock *t;
	Off addr, offset;
	Timet 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 = %lld\n", (Wideoff)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 = toytime();
		if(t->time < tim || t->file != f) {
			ou->err = Ebroken;
			goto out;
		}
		/* renew the lock */
		t->time = tim + TLOCK;
	}
	accessdir(p, d, FREAD, f->uid);
	if(d->mode & DDIR) {
		addr = 0;
		goto dread;
	}

	/* XXXX terrible hack to get at raw data XXXX */
	if(rawreadok && strncmp(d->name, "--raw--", 7) == 0) {
		Device *dev;
		Devsize boff, bsize;

		dev = p->dev;
		putbuf(p);
		p = 0;

		boff = number(d->name + 7, 0, 10) * 100000;
		if(boff < 0)
			boff = 0;
		if(boff > devsize(dev))
			boff = devsize(dev);
		bsize = devsize(dev) - boff;

		if(offset+count >= 100000*RBUFSIZE)
			count = 100000*RBUFSIZE - offset;

		if((offset+count)/RBUFSIZE >= bsize) {
			/* will not overflow */
			count = bsize*RBUFSIZE - offset;
		}

		while(count > 0) {
			addr = offset / RBUFSIZE;
			addr += boff;
			o = offset % RBUFSIZE;
			n = RBUFSIZE - o;
			if(n > count)
				n = count;

			p1 = getbuf(dev, addr, Bread);
			if(p1) {
				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;
	}

	if(offset+count > d->size)
		count = d->size - offset;
	while(count > 0) {
		if(p == 0) {
			p = getbuf(f->fs->dev, f->addr, Bread);
			d = getdir(p, f->slot);
			if(!d || !(d->mode & DALLOC)) {
				ou->err = Ealloc;
				goto out;
			}
		}
		addr = offset / BUFSIZE;
		f->lastra = dbufread(p, d, addr, f->lastra, f->uid);
		o = offset % BUFSIZE;
		n = BUFSIZE - o;
		if(n > count)
			n = count;
		p1 = dnodebuf1(p, d, addr, 0, f->uid);
		p = 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:
	for (;;) {
		if(p == 0) {
			p = getbuf(f->fs->dev, f->addr, Bread);
			d = getdir(p, f->slot);
			if(!d || !(d->mode & DALLOC)) {
				ou->err = Ealloc;
				goto out;
			}
		}
		p1 = dnodebuf1(p, d, addr, 0, f->uid);
		p = 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("9p1: dirread convD2M1990\n");
			nread += n;
			count -= n;
		}
		putbuf(p1);
		addr++;
	}
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);
}

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

	if(CHAT(cp)) {
		print("c_write %d\n", cp->chan);
		print("	fid = %d\n", in->fid);
		print("	offset = %lld\n", (Wideoff)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(f->fs->dev->type == Devro) {
		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 = toytime();
		if(t->time < tim || t->file != f) {
			ou->err = Ebroken;
			goto out;
		}
		/* renew the lock */
		t->time = tim + TLOCK;
	}
	accessdir(p, d, FWRITE, f->uid);
	if(d->mode & DAPND)
		offset = d->size;
	if(offset+count > d->size)
		d->size = offset+count;
	while(count > 0) {
		if(p == 0) {
			p = getbuf(f->fs->dev, f->addr, Bread|Bmod);
			d = getdir(p, f->slot);
			if(!d || !(d->mode & DALLOC)) {
				ou->err = Ealloc;
				goto out;
			}
		}
		addr = offset / BUFSIZE;
		o = offset % BUFSIZE;
		n = BUFSIZE - o;
		if(n > count)
			n = count;
		qpath = d->qid.path;
		p1 = dnodebuf1(p, d, addr, Tfile, f->uid);
		p = 0;
		if(p1 == 0) {
			ou->err = Efull;
			goto out;
		}
		if(checktag(p1, Tfile, qpath)) {
			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 wok)
{
	Iobuf *p, *p1;
	Dentry *d, *d1;
	Off addr;
	int slot, err;

	p = 0;
	p1 = 0;
	if(f->fs->dev->type == Devro) {
		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(iaccess(f, d1, DWRITE) && !wok) {
		err = Eaccess;
		goto out;
	}
	accessdir(p1, d1, FWRITE, f->uid);
	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, f->uid);
		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, f->uid);
	memset(d, 0, sizeof(Dentry));
	settag(p, Tdir, QPNONE);

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

static int
doclunk(File* f, int remove, int wok)
{
	Tlock *t;
	int err;

	err = 0;
	if(t = f->tlock) {
		if(t->file == f)
			t->time = 0;	/* free the lock */
		f->tlock = 0;
	}
	if(remove)
		err = doremove(f, wok);
	f->open = 0;
	freewp(f->wpath);
	freefp(f);

	return err;
}

static void
f_clunk(Chan *cp, Fcall *in, Fcall *ou)
{
	File *f;

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

	f = filep(cp, in->fid, 0);
	if(!f)
		ou->err = Efid;
	else {
		doclunk(f, f->open & FREMOV, 0);
		qunlock(f);
	}
	ou->fid = in->fid;
}

static void
f_remove(Chan *cp, Fcall *in, Fcall *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;
	else {
		ou->err = doclunk(f, 1, cp==cons.chan);
		qunlock(f);
	}
	ou->fid = in->fid;
}

static void
f_stat(Chan *cp, Fcall *in, Fcall *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();
	if(convD2M9p1(d, ou->stat) != DIRREC)
		print("9p1: stat convD2M\n");

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

static void
f_wstat(Chan *cp, Fcall *in, Fcall *ou)
{
	Iobuf *p, *p1;
	Dentry *d, *d1, xd;
	File *f;
	int slot;
	Off 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(f->fs->dev->type == Devro) {
		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 = %o\n", xd.mode);
	}

	/*
	 * if user none,
	 * cant do anything
	 */
	if(f->uid == 0) {
		ou->err = Eaccess;
		goto out;
	}

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

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

	/*
	 * if rename,
	 * must have write permission in parent
	 */
	if (strncmp(d->name, xd.name, sizeof(d->name)) != 0) {
		if (checkname(xd.name) || !d1 ||
		    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, f->uid);
			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 */
		    (!d1 || iaccess(f, d1, DWRITE))) {
			ou->err = Eaccess;
			goto out;
		}
	}

	/*
	 * if mode/time, either
	 *	a) owner
	 *	b) leader of either group
	 */
	if (d->mtime != xd.mtime ||
	    ((d->mode^xd.mode) & (DAPND|DLOCK|0777)))
		if (!wstatallow &&	/* set to allow chmod during boot */
		    d->uid != f->uid &&
		    !leadgroup(f->uid, xd.gid) &&
		    !leadgroup(f->uid, d->gid)) {
			ou->err = Ewstatu;
			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));
	accessdir(p, d, FREAD, f->uid);

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

static void
f_clwalk(Chan *cp, Fcall *in, Fcall *ou)
{
	int er, fid;

	if(CHAT(cp))
		print("c_clwalk macro\n");

	f_clone(cp, in, ou);		/* sets tag, fid */
	if(ou->err)
		return;
	fid = in->fid;
	in->fid = in->newfid;
	f_walk(cp, in, ou);		/* sets tag, fid, qid */
	er = ou->err;
	if(er == Eentry) {
		/*
		 * if error is "no entry"
		 * return non error and fid
		 */
		ou->err = 0;
		f_clunk(cp, in, ou);	/* sets tag, fid */
		ou->err = 0;
		ou->fid = fid;
		if(CHAT(cp))
			print("	error: %s\n", errstr9p[er]);
	} else if(er) {
		/*
		 * if any other error
		 * return an error
		 */
		ou->err = 0;
		f_clunk(cp, in, ou);	/* sets tag, fid */
		ou->err = er;
	}
	/*
	 * non error
	 * return newfid
	 */
}

void
(*call9p1[MAXSYSCALL])(Chan*, Fcall*, Fcall*) =
{
	[Tnop]		f_nop,
	[Tosession]	f_session,
	[Tsession]	f_session,
	[Tflush]	f_flush,
	[Toattach]	f_attach,
	[Tattach]	f_attach,
	[Tclone]	f_clone,
	[Twalk]		f_walk,
	[Topen]		f_open,
	[Tcreate]	f_create,
	[Tread]		f_read,
	[Twrite]	f_write,
	[Tclunk]	f_clunk,
	[Tremove]	f_remove,
	[Tstat]		f_stat,
	[Twstat]	f_wstat,
	[Tclwalk]	f_clwalk,
};

int
error9p1(Chan* cp, Msgbuf* mb)
{
	Msgbuf *mb1;

	print("type=%d count=%d\n", mb->data[0], mb->count);
	print(" %.2x %.2x %.2x %.2x\n",
		mb->data[1]&0xff, mb->data[2]&0xff,
		mb->data[3]&0xff, mb->data[4]&0xff);
	print(" %.2x %.2x %.2x %.2x\n",
		mb->data[5]&0xff, mb->data[6]&0xff,
		mb->data[7]&0xff, mb->data[8]&0xff);
	print(" %.2x %.2x %.2x %.2x\n",
		mb->data[9]&0xff, mb->data[10]&0xff,
		mb->data[11]&0xff, mb->data[12]&0xff);

	mb1 = mballoc(3, cp, Mbreply4);
	mb1->data[0] = Rnop;	/* your nop was ok */
	mb1->data[1] = ~0;
	mb1->data[2] = ~0;
	mb1->count = 3;
	mb1->param = mb->param;
	send(cp->reply, mb1);

	return 1;
}

int
serve9p1(Msgbuf* mb)
{
	int t, n;
	Chan *cp;
	Msgbuf *mb1;
	Fcall fi, fo;

	cp = mb->chan;
	if(convM2S9p1(mb->data, &fi, mb->count) == 0){
		if(cp->protocol == nil)
			return 0;
		print("9p1: bad M2S conversion\n");
		return error9p1(cp, mb);
	}

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

	/*
	 * allocate reply message
	 */
	if(t == Tread) {
		mb1 = mballoc(MAXMSG+MAXDAT, cp, Mbreply2);
		fo.data = (char*)(mb1->data + 8);
	} else
		mb1 = mballoc(MAXMSG, cp, Mbreply3);

	/*
	 * call the file system
	 */
	cons.work[0].count++;
	cons.work[1].count++;
	cons.work[2].count++;
	cp->work.count++;
	cons.rate[0].count += mb->count;
	cons.rate[1].count += mb->count;
	cons.rate[2].count += mb->count;
	cp->rate.count += mb->count;
	fo.err = 0;

	(*call9p1[t])(cp, &fi, &fo);

	fo.type = t+1;
	fo.tag = fi.tag;

	if(fo.err) {
		if(cons.flags&errorflag)
			print("	type %d: error: %s\n", t,
				errstr9p[fo.err]);
		if(CHAT(cp))
			print("	error: %s\n", errstr9p[fo.err]);
		fo.type = Rerror;
		strncpy(fo.ename, errstr9p[fo.err], sizeof(fo.ename));
	}

	n = convS2M9p1(&fo, mb1->data);
	if(n == 0) {
		print("9p1: bad S2M conversion\n");
		mbfree(mb1);
		return error9p1(cp, mb);
	}
	mb1->count = n;
	mb1->param = mb->param;
	cons.rate[0].count += n;
	cons.rate[1].count += n;
	cons.rate[2].count += n;
	cp->rate.count += n;
	send(cp->reply, mb1);

	return 1;
}