shithub: gefs

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fs: properly protect trees with EBR, don't let them change under us

--- a/dat.h

+++ b/dat.h

@@ -603,7 +603,7 @@

 	long	ref;

 	vlong	gen;

 	char	*name;

-	Tree	*root;

+	Tree	*root;	/* EBR protected */

 };

 struct Conn {

--- a/fs.c

+++ b/fs.c

@@ -48,7 +48,7 @@

 	t = nil;

 	for(mnt = fs->mounts; mnt != nil; mnt = mnt->next){

 		if(strcmp(old, mnt->name) == 0){

-			t = mnt->root;

+			t = agetp(&mnt->root);

 			ainc(&t->memref);

 		}

 	}

@@ -241,28 +241,17 @@

 	if(mnt == nil)

 		return Eattach;

-	lock(mnt);

-	r = mnt->root;

-	ainc(&r->memref);

-	unlock(mnt);

-

+	r = agetp(&mnt->root);

 	e = btlookup(r, k, kv, buf, nbuf);

-	closesnap(r);

 	return e;

 }

-int

-frozen(Tree *t)

-{

-	return t->nlbl != 1 || t->nsucc != 0;

-}

-

 static char*

 upsert(Mount *mnt, Msg *m, int nm)

 {

 	char *e;

-	if(frozen(mnt->root))

+	if(mnt->root->nlbl != 1 || mnt->root->nsucc != 0)

 		if((e = updatesnap(&mnt->root, mnt->root, mnt->name)) != nil)

 			return e;

 	return btupsert(mnt->root, m, nm);

@@ -355,10 +344,6 @@

 	PACK64(m->k+1, f->qpath);

 	PACK64(m->k+9, fb);

-

-	if(frozen(f->mnt->root))

-		if(updatesnap(&f->mnt->root, f->mnt->root, f->mnt->name) != nil)

-			return -1;

 	b = newdblk(f->mnt->root, Tdat, f->qpath);

 	if(b == nil)

 		return -1;

@@ -914,6 +899,7 @@

 	char *e, *p, *n, dbuf[Kvmax], kvbuf[Kvmax];

 	Mount *mnt;

 	Dent *de;

+	Tree *t;

 	User *u;

 	Fcall r;

 	Xdir d;

@@ -979,7 +965,8 @@

 		}

 		dk.k = dbuf;

 		dk.nk = p - dbuf;

-		if((e = btlookup(mnt->root, &dk, &kv, kvbuf, sizeof(kvbuf))) != nil){

+		t = agetp(&mnt->root);

+		if((e = btlookup(t, &dk, &kv, kvbuf, sizeof(kvbuf))) != nil){

 			rerror(m, e);

 			goto Out;

 		}

@@ -1215,6 +1202,7 @@

 	Msg mb[3];

 	Xdir n;

 	Dir d;

+	Tree *t;

 	Fid *f;

 	Key k;

 	User *u;

@@ -1240,6 +1228,7 @@

 		goto Out;

 	}

+	t = agetp(&f->mnt->root);

 	n = de->Xdir;

 	n.qid.vers++;

 	p = opbuf+1;

@@ -1263,7 +1252,7 @@

 				rerror(m, Ename);

 				goto Out;

 			}

-			if(walk1(f->mnt->root, f->dent->up, d.name, &old, &oldlen) == 0){

+			if(walk1(t, f->dent->up, d.name, &old, &oldlen) == 0){

 				rerror(m, Eexist);

 				goto Out;

 			}

@@ -1590,20 +1579,22 @@

 candelete(Fid *f)

 {

 	char *e, pfx[Dpfxsz];

+	Tree *t;

 	Scan s;

 	if(f->dent->qid.type == QTFILE)

 		return nil;

+	t = agetp(&f->mnt->root);

 	packdkey(pfx, sizeof(pfx), f->qpath, nil);

 	btnewscan(&s, pfx, sizeof(pfx));

-	if((e = btenter(f->mnt->root, &s)) != nil)

+	if((e = btenter(t, &s)) != nil)

 		goto Out;

-	if((e = btnext(f->mnt->root, &s, &s.kv)) != nil)

+	if((e = btnext(t, &s, &s.kv)) != nil)

 		goto Out;

 	if(!s.done)

 		e = Enempty;

 Out:

-	btexit(f->mnt->root, &s);

+	btexit(t, &s);

 	return e;

 }

@@ -1850,7 +1841,7 @@

 	Scan *s;

 	s = f->scan;

-	t = f->mnt->root;

+	t = agetp(&f->mnt->root);

 	if(s != nil && s->offset != 0 && s->offset != m->offset)

 		return Edscan;

 	if(s == nil || m->offset == 0){

@@ -1979,6 +1970,7 @@

 	char *p, *e;

 	int i, j;

 	Fcall r;

+	Tree *t;

 	Fid *f;

 	if((f = getfid(m->conn, m->fid)) == nil){

@@ -2012,6 +2004,7 @@

 	p = m->data;

 	o = m->offset;

 	c = m->count;

+	t = agetp(&f->mnt->root);

 	for(i = 0; i < nelem(kv)-1 && c != 0; i++){

 		assert(i == 0 || o%Blksz == 0);

 		kv[i].op = Oinsert;

@@ -2022,7 +2015,7 @@

 		n = writeb(f, &kv[i], &bp[i], p, o, c, f->dent->length);

 		if(n == -1){

 			for(j = 0; j < i; j++)

-				freeblk(f->mnt->root, nil, bp[i]);

+				freeblk(t, nil, bp[i]);

 			wunlock(f->dent);

 			fprint(2, "%r");

 			putfid(f);

--- a/load.c

+++ b/load.c

@@ -54,7 +54,7 @@

 void

 loadfs(char *dev)

 {

-	Mount *mnt;

+	Mount *dump;

 	Arena *a;

 	Bptr bp;

 	char *e;

@@ -61,16 +61,15 @@

 	Tree *t;

 	int i, k;

-	if((mnt = mallocz(sizeof(*mnt), 1)) == nil)

+	if((dump = mallocz(sizeof(*dump), 1)) == nil)

 		sysfatal("malloc: %r");

-	if((mnt->name = strdup("dump")) == nil)

+	if((dump->name = strdup("dump")) == nil)

 		sysfatal("malloc: %r");

-	mnt->ref = 1;

-	mnt->root = nil;

-	mnt->gen = -1;

-	mnt->root = &fs->snap;

+	dump->ref = 1;

+	dump->gen = -1;

+	dump->root = &fs->snap;

-	fs->snapmnt = mnt;

+	fs->snapmnt = dump;

 	fs->gotinfo = 0;

 	fs->narena = 1;

 	if((fs->fd = open(dev, ORDWR)) == -1)

--- a/snap.c

+++ b/snap.c

@@ -436,7 +436,7 @@

 		delsnap(o, t->gen, nil);

 	}

 	closesnap(o);

-	*r = t;

+	asetp(r, t);

 	return nil;

 }

@@ -497,7 +497,6 @@

 		abort();

 	f->op = DFtree;

 	f->t = t;

-print("limbo %#p\n", t);

 	ge = agetl(&fs->epoch);

 	f->next = fs->limbo[ge];

 	fs->limbo[ge] = f;