File system locking fixups, mostly from NetBSD:

- cache_lookup
        move common code from various fs's here
        always return with vnode and parent locked
        adjust return codes
- PDIRUNLOCK - new flag set if lookup couldn't lock parent vnode
- kernfs and procfs
        lock vnode in get_root
        don't unlock (again) in kernfs_freevp
        fix memory leak in procfs

From tedu@stanford.edu
deraadt@ and various other ok

2 files changed, 41 insertions, 24 deletions

diff --git a/sys/miscfs/kernfs/kernfs_vfsops.c b/sys/miscfs/kernfs/kernfs_vfsops.c
index 68ded75d74b..561c2c4e904 100644
--- a/sys/miscfs/kernfs/kernfs_vfsops.c
+++ b/sys/miscfs/kernfs/kernfs_vfsops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kernfs_vfsops.c,v 1.19 2002/10/12 02:03:46 krw Exp $	*/
+/*	$OpenBSD: kernfs_vfsops.c,v 1.20 2003/01/31 17:37:50 art Exp $	*/
 /*	$NetBSD: kernfs_vfsops.c,v 1.26 1996/04/22 01:42:27 christos Exp $	*/
 
 /*
@@ -102,7 +102,10 @@ kernfs_mount(mp, path, data, ndp, p)
 	struct nameidata *ndp;
 	struct proc *p;
 {
+	int error = 0;
 	size_t size;
+	struct vnode *rvp;
+	struct kern_target *kt;
 
 #ifdef KERNFS_DIAGNOSTIC
 	printf("kernfs_mount(mp = %p)\n", mp);
@@ -114,7 +117,17 @@ kernfs_mount(mp, path, data, ndp, p)
 	if (mp->mnt_flag & MNT_UPDATE)
 		return (EOPNOTSUPP);
 
+	kt = kernfs_findtarget(".", 1);
+	error = kernfs_allocvp(kt, mp, &rvp);
+	if (error)
+		return (error);
+
+	rvp->v_type = VDIR;
+	rvp->v_flag |= VROOT;
+
 	mp->mnt_flag |= MNT_LOCAL;
+	mp->mnt_data = (qaddr_t)rvp;
+	vrele(rvp);
 	vfs_getnewfsid(mp);
 
 	(void) copyinstr(path, mp->mnt_stat.f_mntonname, MNAMELEN - 1, &size);
@@ -158,8 +171,12 @@ kernfs_unmount(mp, mntflags, p)
 #ifdef KERNFS_DIAGNOSTIC
 	printf("kernfs_unmount: calling vflush\n");
 #endif
-	if ((error = vflush(mp, 0, flags)) != 0)
+
+	if ((error = vflush(mp, 0, flags)) != 0) {
 		return (error);
+	}
+
+	mp->mnt_data = 0;
 
 	return (0);
 }
@@ -169,24 +186,16 @@ kernfs_root(mp, vpp)
 	struct mount *mp;
 	struct vnode **vpp;
 {
-	struct kern_target *kt;
-	int error;
+	struct vnode *vp = (struct vnode *)mp->mnt_data;
 
 #ifdef KERNFS_DIAGNOSTIC
 	printf("kernfs_root(mp = %p)\n", mp);
 #endif
-	kt = kernfs_findtarget(".", 1);
-	/* this should never happen */
-	if (kt == NULL) 
-		panic("kernfs_root: findtarget returned NULL");
-	
-	error = kernfs_allocvp(kt, mp, vpp);
-	/* this should never happen */
-	if (error) 
-		panic("kernfs_root: couldn't find root");
-
-	return(0);
-	
+
+	vget(vp, LK_EXCLUSIVE | LK_RETRY, curproc);
+	*vpp = vp;
+
+	return (0);
 }
 
 int
diff --git a/sys/miscfs/kernfs/kernfs_vnops.c b/sys/miscfs/kernfs/kernfs_vnops.c
index 269c0842653..3db0fadc84e 100644
--- a/sys/miscfs/kernfs/kernfs_vnops.c
+++ b/sys/miscfs/kernfs/kernfs_vnops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kernfs_vnops.c,v 1.28 2002/10/12 02:03:46 krw Exp $	*/
+/*	$OpenBSD: kernfs_vnops.c,v 1.29 2003/01/31 17:37:50 art Exp $	*/
 /*	$NetBSD: kernfs_vnops.c,v 1.43 1996/03/16 23:52:47 christos Exp $	*/
 
 /*
@@ -287,7 +287,6 @@ kernfs_freevp(vp, p)
 	struct kernfs_node *kf = VTOKERN(vp);
 
 	TAILQ_REMOVE(&kfshead, kf, list);
-	VOP_UNLOCK(vp, 0, p);
 	FREE(vp->v_data, M_TEMP);
 	vp->v_data = 0;
 	return(0);
@@ -487,15 +486,16 @@ kernfs_lookup(v)
 	struct proc *p = cnp->cn_proc;
 	struct kern_target *kt;
 	struct vnode *vp;
-	int error;
+	int error, wantpunlock;
 
 #ifdef KERNFS_DIAGNOSTIC
 	printf("kernfs_lookup(%p)\n", ap);
 	printf("kernfs_lookup(dp = %p, vpp = %p, cnp = %p)\n", dvp, vpp, ap->a_cnp);
 	printf("kernfs_lookup(%s)\n", pname);
 #endif
-	VOP_UNLOCK(dvp, 0, p);
+
 	*vpp = NULLVP;
+	cnp->cn_flags &= ~PDIRUNLOCK;
 
 	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
 		return (EROFS);
@@ -503,14 +503,14 @@ kernfs_lookup(v)
 	if (cnp->cn_namelen == 1 && *pname == '.') { 
 		*vpp = dvp;
 		VREF(dvp);
-		vn_lock(dvp, LK_SHARED | LK_RETRY, p);
 		return (0);
 	}
 
+	wantpunlock = (~cnp->cn_flags & (LOCKPARENT | ISLASTCN));
+
 	kt = kernfs_findtarget(pname, cnp->cn_namelen);
 	if (kt == NULL) {
 		/* not found */
-		vn_lock(dvp, LK_SHARED | LK_RETRY, p);
 		return(cnp->cn_nameiop == LOOKUP ? ENOENT : EROFS);
 	}
 
@@ -524,17 +524,25 @@ kernfs_lookup(v)
 		*vpp = vp;
 		if (vget(vp, LK_EXCLUSIVE, p)) 
 			goto loop;
+		if (wantpunlock) {
+			VOP_UNLOCK(dvp, 0, p);
+			cnp->cn_flags |= PDIRUNLOCK;
+		}
 		return(0);
 	}
 
 
 	if ((error = kernfs_allocvp(kt, dvp->v_mount, vpp)) != 0) {
-		vn_lock(dvp, LK_SHARED | LK_RETRY, p);
 		return(error);
 	}
 
 	vn_lock(*vpp, LK_SHARED | LK_RETRY, p);
-	return(error);
+
+	if (wantpunlock) {
+		VOP_UNLOCK(dvp, 0, p);
+		cnp->cn_flags |= PDIRUNLOCK;
+	}
+	return (0);
 }
 		
 /*ARGSUSED*/