shithub: gefs

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fs: fix locking and length around file truncation

--- a/dat.h

+++ b/dat.h

@@ -620,9 +620,11 @@

 	Xdir;

 	Dent	*next;

 	QLock	trunclk;

+	Rendez	truncrz;

 	vlong	up;

 	long	ref;

 	char	gone;

+	char	trunc;

 	char	buf[Maxent];

 };

--- a/fs.c

+++ b/fs.c

@@ -396,13 +396,14 @@

 static void

 truncwait(Dent *de, int id)

 {

-	if(canqlock(&de->trunclk))

-		return;

-	epochend(id);

 	qunlock(&fs->mutlk);

 	qlock(&de->trunclk);

-	qlock(&fs->mutlk);

+	epochend(id);

+	while(de->trunc)

+		rsleep(&de->truncrz);

 	epochstart(id);

+	qunlock(&de->trunclk);

+	qlock(&fs->mutlk);

 }

 static int

@@ -509,6 +510,7 @@

 	de->up = pqid;

 	de->qid = d->qid;

 	de->length = d->length;

+	de->truncrz.l = &de->trunclk;

 	if((e = packdkey(de->buf, sizeof(de->buf), pqid, d->name)) == nil){

 		free(de);

@@ -1301,7 +1303,7 @@

 {

 	char rnbuf[Kvmax], opbuf[Kvmax], upbuf[Upksz];

 	char *p, strs[65535];

-	int op, nm, rename, truncate;

+	int op, nm, rename;

 	vlong oldlen;

 	Qid old;

 	Fcall r;

@@ -1316,7 +1318,6 @@

 	*ao = nil;

 	rename = 0;

-	truncate = 0;

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

 		rerror(m, Enofid);

 		return;

@@ -1367,6 +1368,9 @@

 			if(d.length < de->length){

 				if((*ao = malloc(sizeof(Amsg))) == nil)

 					error(Enomem);

+				qlock(&de->trunclk);

+				de->trunc = 1;

+				qunlock(&de->trunclk);

 				aincl(&de->ref, 1);

 				aincl(&f->mnt->ref, 1);

 				(*ao)->op = AOclear;

@@ -1375,7 +1379,6 @@

 				(*ao)->off = d.length;

 				(*ao)->length = f->dent->length;

 				(*ao)->dent = de;

-				truncate = 1;

 			}

 			de->length = d.length;

 			n.length = d.length;

@@ -1501,9 +1504,7 @@

 	respond(m, &r);

 	poperror();

-Err:	if(!truncate)

-		qunlock(&de->trunclk);

-	wunlock(de);

+Err:	wunlock(de);

 	putfid(f);

 }

@@ -1719,7 +1720,7 @@

 	r.type = Rremove;

 	respond(m, &r);

 	poperror();

-Err:	qunlock(&f->dent->trunclk);

+Err:

 	wunlock(f->dent);

 	putfid(f);

 	return;

@@ -1747,6 +1748,8 @@

 		putfid(f);

 		return;

 	}

+	if(m->mode & OTRUNC)

+		truncwait(f->dent, id);

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

 	if((f->qpath & Qdump) != 0){

 		filldumpdir(&d);

@@ -1781,8 +1784,27 @@

 	}

 	f->mode = mode2bits(m->mode);

 	if(m->mode & OTRUNC){

-		truncwait(f->dent, id);

 		wlock(f->dent);

+

+		if(waserror()){

+			wunlock(f->dent);

+			free(*ao);

+			*ao = nil;

+			nexterror();

+		}

+		*ao = emalloc(sizeof(Amsg), 1);

+		qlock(&f->dent->trunclk);

+		f->dent->trunc = 1;

+		qunlock(&f->dent->trunclk);

+		aincl(&f->dent->ref, 1);

+		aincl(&f->mnt->ref, 1);

+		(*ao)->op = AOclear;

+		(*ao)->mnt = f->mnt;

+		(*ao)->qpath = f->qpath;

+		(*ao)->off = 0;

+		(*ao)->length = f->dent->length;

+		(*ao)->dent = f->dent;

+

 		f->dent->muid = f->uid;

 		f->dent->qid.vers++;

 		f->dent->length = 0;

@@ -1796,21 +1818,8 @@

 		mb.nk = f->dent->nk;

 		mb.v = buf;

 		mb.nv = p - buf;

-		if(waserror()){

-			qunlock(&f->dent->trunclk);

-			wunlock(f->dent);

-			nexterror();

-		}

-		*ao = emalloc(sizeof(Amsg), 1);

-		aincl(&f->mnt->ref, 1);

-		(*ao)->op = AOclear;

-		(*ao)->mnt = f->mnt;

-		(*ao)->qpath = f->qpath;

-		(*ao)->off = 0;

-		(*ao)->length = f->dent->length;

-		(*ao)->dent = nil;

+

 		upsert(f->mnt, &mb, 1);

-		qunlock(&f->dent->trunclk);

 		wunlock(f->dent);

 		poperror();

 	}

@@ -2024,7 +2033,6 @@

 	wlock(f->dent);

 	if(waserror()){

 		rerror(m, errmsg());

-		qunlock(&f->dent->trunclk);

 		wunlock(f->dent);

 		putfid(f);

 		return;

@@ -2091,7 +2099,6 @@

 Out:

 	poperror();

  	respond(m, &r);

-	qunlock(&f->dent->trunclk);

 	wunlock(f->dent);

 	putfid(f);	

 }

@@ -2435,6 +2442,8 @@

 				ainc(&fs->rdonly);

 				break;

 			}

+			if(am->dent != nil)

+				qlock(&am->dent->trunclk);

 			for(off = am->off; off < am->length; off += Blksz){

 				qlock(&fs->mutlk);

 				if(waserror()){

@@ -2457,6 +2466,8 @@

 				poperror();

 			}

 			if(am->dent != nil){

+				am->dent->trunc = 0;

+				rwakeup(&am->dent->truncrz);

 				qunlock(&am->dent->trunclk);

 				clunkdent(am->dent);

 			}