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chan: minimize differences with 9front...

--- a/kern/chan.c

+++ b/kern/chan.c

@@ -441,6 +441,12 @@

 		c = nc;

 	}

+	if(c->umh != nil){	//BUG

+		print("cunique umh != nil from %#p\n", getcallerpc(&c));

+		putmhead(c->umh);

+		c->umh = nil;

+	}

+

 	return c;

 }

@@ -512,61 +518,81 @@

 void

 putmhead(Mhead *m)

 {

-	if(m != nil && decref(&m->ref) == 0){

-		assert(m->mount == nil);

-		cclose(m->from);

-		free(m);

-	}

+	if(m == nil)

+		return;

+	if(decref(&m->ref))

+		return;

+	assert(m->mount == nil);

+	cclose(m->from);

+	free(m);

 }

 int

-cmount(Chan **newp, Chan *old, int flag, char *spec)

+cmount(Chan *new, Chan *old, int flag, char *spec)

 {

-	int order, flg;

-	Chan *new;

+	int order;

 	Mhead *m, **l, *mh;

-	Mount *nm, *f, *um, **h;

+	Mount *nm, *f, *um;

 	Pgrp *pg;

-	if(QTDIR & (old->qid.type^(*newp)->qid.type))

-		error(Emount);

-

 	if(old->umh != nil)

-		print("cmount: unexpected umh, caller %#p\n", getcallerpc(&newp));

+		print("cmount: unexpected umh, caller %#p\n", getcallerpc(&new));

+	if(QTDIR & (old->qid.type^new->qid.type))

+		error(Emount);

+

 	order = flag&MORDER;

 	if((old->qid.type&QTDIR) == 0 && order != MREPL)

 		error(Emount);

-	new = *newp;

+	nm = newmount(new, flag, spec);

 	mh = new->umh;

+	if(mh != nil) {

+		rlock(&mh->lock);

+		if(waserror()) {

+			runlock(&mh->lock);

+			mountfree(nm);

+			nexterror();

+		}

+		um = mh->mount;

+		if(um != nil){

+			/*

+			 * Not allowed to bind when the old directory is itself a union. 

+			 * (Maybe it should be allowed, but I don't see what the semantics

+			 * would be.)

+			 *

+			 * We need to check mh->mount->next to tell unions apart from

+			 * simple mount points, so that things like

+			 *	mount -c fd /root

+			 *	bind -c /root /

+			 * work.  

+			 * 

+			 * The check of mount->mflag allows things like

+			 *	mount fd /root

+			 *	bind -c /root /

+			 * 

+			 * This is far more complicated than it should be, but I don't

+			 * see an easier way at the moment.

+			 */

+			if((flag&MCREATE) != 0 && (um->next != nil || (um->mflag&MCREATE) == 0))

+				error(Emount);

-	/*

-	 * Not allowed to bind when the old directory is itself a union. 

-	 * (Maybe it should be allowed, but I don't see what the semantics

-	 * would be.)

-	 *

-	 * We need to check mh->mount->next to tell unions apart from

-	 * simple mount points, so that things like

-	 *	mount -c fd /root

-	 *	bind -c /root /

-	 * work.  

-	 * 

-	 * The check of mount->mflag allows things like

-	 *	mount fd /root

-	 *	bind -c /root /

-	 * 

-	 * This is far more complicated than it should be, but I don't

-	 * see an easier way at the moment.

-	 */

-	if((flag&MCREATE) != 0 && mh != nil && mh->mount != nil

-	&& (mh->mount->next != nil || (mh->mount->mflag&MCREATE) == 0))

-		error(Emount);

+			/*

+			 *  copy a union when binding it onto a directory

+			 */

+			f = nm;

+			for(um = um->next; um != nil; um = um->next){

+				f->next = newmount(um->to, order==MREPL? MAFTER: order, um->spec);

+				f = f->next;

+			}

+		}

+		runlock(&mh->lock);

+		poperror();

+	}

 	pg = up->pgrp;

 	wlock(&pg->ns);

-

 	l = &MOUNTH(pg, old->qid);

 	for(m = *l; m != nil; m = m->hash){

 		if(eqchan(m->from, old, 1))

@@ -573,7 +599,6 @@

 			break;

 		l = &m->hash;

 	}

-

 	if(m == nil){

 		/*

 		 *  nothing mounted here yet.  create a mount

@@ -580,8 +605,6 @@

 		 *  head and add to the hash table.

 		 */

 		m = newmhead(old);

-		*l = m;

-

 		/*

 		 *  if this is a union mount, add the old

 		 *  node to the mount chain.

@@ -588,52 +611,31 @@

 		 */

 		if(order != MREPL)

 			m->mount = newmount(old, 0, nil);

+		*l = m;

 	}

 	wlock(&m->lock);

-	if(waserror()){

-		wunlock(&m->lock);

-		nexterror();

-	}

-	wunlock(&pg->ns);

-

-	nm = newmount(new, flag, spec);

-	if(mh != nil && mh->mount != nil){

-		/*

-		 *  copy a union when binding it onto a directory

-		 */

-		flg = order;

-		if(order == MREPL)

-			flg = MAFTER;

-		h = &nm->next;

-		um = mh->mount;

-		for(um = um->next; um != nil; um = um->next){

-			f = newmount(um->to, flg, um->spec);

-			*h = f;

-			h = &f->next;

-		}

-	}

-

-	if(m->mount != nil && order == MREPL){

-		mountfree(m->mount);

-		m->mount = nil;

-	}

-

-	if(flag & MCREATE)

-		nm->mflag |= MCREATE;

-

-	if(m->mount != nil && order == MAFTER){

-		for(f = m->mount; f->next != nil; f = f->next)

+	um = m->mount;

+	if(um != nil && order == MAFTER){

+		for(f = um; f->next != nil; f = f->next)

 			;

 		f->next = nm;

-	}else{

-		for(f = nm; f->next != nil; f = f->next)

-			;

-		f->next = m->mount;

+		um = nil;

+	} else {

+		if(order != MREPL){

+			for(f = nm; f->next != nil; f = f->next)

+				;

+			f->next = um;

+			um = nil;

+		}

 		m->mount = nm;

 	}

+	order = nm->mountid;

 	wunlock(&m->lock);

-	poperror();

-	return nm->mountid;

+	wunlock(&pg->ns);

+

+	mountfree(um);

+

+	return order;

 }

 void

@@ -736,13 +738,13 @@

 	rlock(&pg->ns);

 	for(m = MOUNTH(pg, qid); m != nil; m = m->hash){

 		if(eqchantdqid(m->from, type, dev, qid, 1)){

-			rlock(&m->lock);

-			runlock(&pg->ns);

 			if(mp != nil)

 				incref(&m->ref);

+			rlock(&m->lock);

 			to = m->mount->to;

 			incref(&to->ref);

 			runlock(&m->lock);

+			runlock(&pg->ns);

 			if(mp != nil){

 				putmhead(*mp);

 				*mp = m;

@@ -957,7 +959,7 @@

 				n = wq->nqid;

 				nc = wq->clone;

 			}else{		/* stopped early, at a mount point */

-				didmount = 1;

+				assert(didmount);

 				if(wq->clone != nil){

 					cclose(wq->clone);

 					wq->clone = nil;

@@ -979,11 +981,6 @@

 	}

 	putmhead(mh);

 	c = cunique(c);

-	if(c->umh != nil){	//BUG

-		print("walk umh\n");

-		putmhead(c->umh);

-		c->umh = nil;

-	}

 	pathclose(c->path);

 	c->path = path;

@@ -1293,8 +1290,13 @@

 		m = nil;

 		if(!nomount)

 			domount(&c, &m, nil);

-		putmhead(c->umh);

+		if(waserror()){

+			putmhead(m);

+			nexterror();

+		}

+		c = cunique(c);

 		c->umh = m;

+		poperror();

 		break;

 	case Aaccess:

@@ -1311,9 +1313,13 @@

 		m = nil;

 		if(!nomount)

 			domount(&c, &m, &path);

-

+		if(waserror()){

+			putmhead(m);

+			nexterror();

+		}

 		/* our own copy to open or remove */

 		c = cunique(c);

+		poperror();

 		/* now it's our copy anyway, we can put the name back */

 		pathclose(c->path);

@@ -1331,16 +1337,17 @@

 		case Aopen:

 		case Acreate:

-			if(c->umh != nil){

-				print("cunique umh Open\n");

-				putmhead(c->umh);

-				c->umh = nil;

-			}

 			/* only save the mount head if it's a multiple element union */

-			if(m != nil && m->mount != nil && m->mount->next != nil)

-				c->umh = m;

-			else

-				putmhead(m);

+			if(m != nil) {

+				rlock(&m->lock);

+				if(m->mount != nil && m->mount->next != nil) {

+					c->umh = m;

+					runlock(&m->lock);

+				} else {

+					runlock(&m->lock);

+					putmhead(m);

+				}

+			}

 			/* save registers else error() in open has wrong value of c saved */

 			saveregisters();

--- a/kern/devmnt.c

+++ b/kern/devmnt.c

@@ -301,6 +301,9 @@

 	Mnt *m;

 	Mntrpc *r;

+	if(ac != nil && ac->mchan != c)

+		error(Ebadusefd);

+

 	m = c->mux;

 	if(m == nil){

 		mntversion(c, nil, 0, 0);

--- a/kern/fns.h

+++ b/kern/fns.h

@@ -25,7 +25,7 @@

 void		closepgrp(Pgrp*);

 void		closergrp(Rgrp*);

 void		cmderror(Cmdbuf*, char*);

-int		cmount(Chan**, Chan*, int, char*);

+int		cmount(Chan*, Chan*, int, char*);

 Block*		concatblock(Block*);

 Block*		copyblock(Block*, int);

 void		cunmount(Chan*, Chan*);

@@ -101,6 +101,7 @@

 Chan*		mntauth(Chan*, char*);

 void		mntdump(void);

 long		mntversion(Chan*, char*, int, int);

+Chan*		mntattach(Chan*, Chan*, char*, int);

 void		mountfree(Mount*);

 void		muxclose(Mnt*);

 Chan*		namec(char*, int, int, ulong);

--- a/kern/sysfile.c

+++ b/kern/sysfile.c

@@ -293,7 +293,7 @@

 }

 static void

-closefd(int fd, int flag)

+fdclose(int fd, int flag)

 {

 	int i;

 	Chan *c;

@@ -325,7 +325,7 @@

 _sysclose(int fd)

 {

 	fdtochan(fd, -1, 0, 0);

-	closefd(fd, 0);

+	fdclose(fd, 0);

 	return 0;

 }

@@ -636,24 +636,23 @@

 	return 0;

 }

-long

-bindmount(int ismount, int fd, int afd, char* arg0, char* arg1, ulong flag, char* spec)

+static int

+bindmount(int ismount, int fd, int afd, char* arg0, char* arg1, int flag, char* spec)

 {

 	int ret;

 	Chan *c0, *c1, *ac, *bc;

-	struct{

-		Chan	*chan;

-		Chan	*authchan;

-		char	*spec;

-		int	flags;

-	}bogus;

 	if((flag&~MMASK) || (flag&MORDER)==(MBEFORE|MAFTER))

 		error(Ebadarg);

-	bogus.flags = flag & MCACHE;

-

 	if(ismount){

+		validaddr((uintptr)spec, 1, 0);

+		spec = validnamedup(spec, 1);

+		if(waserror()){

+			free(spec);

+			nexterror();

+		}

+

 		if(up->pgrp->noattach)

 			error(Enoattach);

@@ -660,7 +659,7 @@

 		ac = nil;

 		bc = fdtochan(fd, ORDWR, 0, 1);

 		if(waserror()) {

-			if(ac)

+			if(ac != nil)

 				cclose(ac);

 			cclose(bc);

 			nexterror();

@@ -669,26 +668,14 @@

 		if(afd >= 0)

 			ac = fdtochan(afd, ORDWR, 0, 1);

-		bogus.chan = bc;

-		bogus.authchan = ac;

-

-		validaddr((ulong)spec, 1, 0);

-		bogus.spec = spec;

-		if(waserror())

-			error(Ebadspec);

-		validname(spec, 1);

-		poperror();

-

-		ret = devno('M', 0);

-		c0 = devtab[ret]->attach((char*)&bogus);

-

-		poperror();

-		if(ac)

+		c0 = mntattach(bc, ac, spec, flag&MCACHE);

+		poperror();	/* ac bc */

+		if(ac != nil)

 			cclose(ac);

 		cclose(bc);

 	}else{

-		bogus.spec = 0;

-		validaddr((ulong)arg0, 1, 0);

+		spec = nil;

+		validaddr((uintptr)arg0, 1, 0);

 		c0 = namec(arg0, Abind, 0, 0);

 	}

@@ -697,7 +684,7 @@

 		nexterror();

 	}

-	validaddr((ulong)arg1, 1, 0);

+	validaddr((uintptr)arg1, 1, 0);

 	c1 = namec(arg1, Amount, 0, 0);

 	if(waserror()){

 		cclose(c1);

@@ -704,15 +691,17 @@

 		nexterror();

 	}

-	ret = cmount(&c0, c1, flag, bogus.spec);

+	ret = cmount(c0, c1, flag, spec);

 	poperror();

 	cclose(c1);

 	poperror();

 	cclose(c0);

-	if(ismount)

-		closefd(fd, 0);

-

+	if(ismount){

+		fdclose(fd, 0);

+		poperror();

+		free(spec);

+	}

 	return ret;

 }