code: plan9front

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gefs: make dent cache per-mount

with a global dent cache, directory entries from different
trees can be cached. This almost works, but QID state can
change as the files get modified -- ownership, permissions,
and similar can get changed.

A global mount cache means that changes to a qid may leak
across mount boundaries. Don't do that.

--- a/sys/src/cmd/gefs/dat.h

+++ b/sys/src/cmd/gefs/dat.h

@@ -545,10 +545,6 @@

 	User	*users;

 	int	nusers;

-	/* open directory entries */

-	Lock	dtablk;

-	Dent	*dtab[Ndtab];

-

 	/* slow block io */

 	QLock	blklk[32];

@@ -635,6 +631,10 @@

 	Tree	*root;	/* EBR protected */

 	int	flag;

+

+	/* open directory entries */

+	Lock	dtablk;

+	Dent	*dtab[Ndtab];

 	/* snapshot history */

 	char	minutely[60][128];

--- a/sys/src/cmd/gefs/fs.c

+++ b/sys/src/cmd/gefs/fs.c

@@ -527,7 +527,7 @@

 }

 static Dent*

-getdent(vlong pqid, Xdir *d)

+getdent(Mount *mnt, vlong pqid, Xdir *d)

 {

 	Dent *de;

 	char *e;

@@ -534,8 +534,8 @@

 	u32int h;

 	h = ihash(d->qid.path) % Ndtab;

-	lock(&fs->dtablk);

-	for(de = fs->dtab[h]; de != nil; de = de->next){

+	lock(&mnt->dtablk);

+	for(de = mnt->dtab[h]; de != nil; de = de->next){

 		if(de->qid.path == d->qid.path){

 			ainc(&de->ref);

 			goto Out;

@@ -558,11 +558,11 @@

 	de->k = de->buf;

 	de->nk = e - de->buf;

 	de->name = de->buf + 11;

-	de->next = fs->dtab[h];

-	fs->dtab[h] = de;

+	de->next = mnt->dtab[h];

+	mnt->dtab[h] = de;

 Out:

-	unlock(&fs->dtablk);

+	unlock(&mnt->dtablk);

 	return de;

 }

@@ -674,7 +674,7 @@

 }

 static void

-clunkdent(Dent *de)

+clunkdent(Mount *mnt, Dent *de)

 {

 	Dent *e, **pe;

 	u32int h;

@@ -685,12 +685,12 @@

 		free(de);

 		return;

 	}

-	lock(&fs->dtablk);

+	lock(&mnt->dtablk);

 	if(adec(&de->ref) != 0)

 		goto Out;

 	h = ihash(de->qid.path) % Ndtab;

-	pe = &fs->dtab[h];

-	for(e = fs->dtab[h]; e != nil; e = e->next){

+	pe = &mnt->dtab[h];

+	for(e = mnt->dtab[h]; e != nil; e = e->next){

 		if(e == de)

 			break;

 		pe = &e->next;

@@ -699,7 +699,7 @@

 	*pe = e->next;

 	free(de);

 Out:

-	unlock(&fs->dtablk);

+	unlock(&mnt->dtablk);

 }

 static Fid*

@@ -724,8 +724,8 @@

 {

 	if(adec(&f->ref) != 0)

 		return;

+	clunkdent(f->mnt, f->dent);

 	clunkmount(f->mnt);

-	clunkdent(f->dent);

 	free(f);

 }

@@ -1163,7 +1163,7 @@

 			error(Enosnap);

 		kv2dir(&kv, &d);

 	}

-	de = getdent(-1, &d);

+	de = getdent(mnt, -1, &d);

 	memset(&f, 0, sizeof(Fid));

 	f.fid = NOFID;

 	f.mnt = mnt;

@@ -1190,7 +1190,7 @@

 	poperror();

-Err:	clunkdent(de);

+Err:	clunkdent(mnt, de);

 	clunkmount(mnt);

 }

@@ -1312,15 +1312,15 @@

 			nexterror();

 		}

 		if(up == Qdump)

-			dent = getdent(-1ULL, &d);

+			dent = getdent(mnt, -1ULL, &d);

 		else

-			dent = getdent(up, &d);

+			dent = getdent(mnt, up, &d);

+		clunkdent(f->mnt, f->dent);

 		if(mnt != f->mnt){

 			clunkmount(f->mnt);

 			ainc(&mnt->ref);

 			f->mnt = mnt;

 		}

-		clunkdent(f->dent);

 		f->qpath = r.wqid[i-1].path;

 		f->pqpath = up;

 		f->dent = dent;

@@ -1694,8 +1694,8 @@

 	}

 	upsert(f->mnt, mb, nm);

-	de = getdent(f->qpath, &d);

-	clunkdent(f->dent);

+	de = getdent(f->mnt, f->qpath, &d);

+	clunkdent(f->mnt, f->dent);

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

 	f->pqpath = f->qpath;

 	f->qpath = d.qid.path;

@@ -2616,7 +2616,7 @@

 				am->dent->trunc = 0;

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

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

-				clunkdent(am->dent);

+				clunkdent(am->mnt, am->dent);

 			}

 			clunkmount(am->mnt);

 			poperror();