Don't hold an extra reference to vnodes. Devfs vnodes are sufficiently

cheap to setup that it doesn't really matter that we recycle device
vnodes at kleenex speed.

Implement first cut try at killing cloned devices when they are
not needed anymore.  For now only the bpf driver is involved in
this experiment.  Cloned devices can set the SI_CHEAPCLONE flag
which allows us to destroy_dev() it when the vcount() drops to zero
and the vnode is reclaimed.  For now it's a requirement that the
driver doesn't keep persistent state from close to (re)open.

Some whitespace changes.

3 files changed, 28 insertions, 24 deletions

diff --git a/sys/fs/devfs/devfs_devs.c b/sys/fs/devfs/devfs_devs.c
index 49854a0..1d5d32b 100644
--- a/sys/fs/devfs/devfs_devs.c
+++ b/sys/fs/devfs/devfs_devs.c
@@ -153,10 +153,10 @@ devfs_attemptoverflow(int insist)
 	bzero(ot, nb);
 	nb = sizeof (int) * n;
 	MALLOC(or, int *, nb, M_DEVFS, insist ? M_WAITOK : M_NOWAIT);
-	if (or == NULL) 
+	if (or == NULL)
 		goto bail;
 	bzero(or, nb);
-	if (!atomic_cmpset_ptr(&devfs_overflow, NULL, ot)) 
+	if (!atomic_cmpset_ptr(&devfs_overflow, NULL, ot))
 		goto bail;
 	devfs_refoverflow = or;
 	devfs_noverflow = n;
@@ -249,10 +249,8 @@ devfs_delete(struct devfs_dirent *dd, struct devfs_dirent *de)
 		FREE(de->de_symlink, M_DEVFS);
 		de->de_symlink = NULL;
 	}
-	if (de->de_vnode) {
+	if (de->de_vnode)
 		de->de_vnode->v_data = NULL;
-		vdrop(de->de_vnode);
-	}
 	TAILQ_REMOVE(&dd->de_dlist, de, de_list);
 	FREE(de, M_DEVFS);
 }
@@ -281,7 +279,7 @@ devfs_populate(struct devfs_mount *dm)
 	struct devfs_dirent *de, **dep;
 	char *q, *s;
 
-	if (dm->dm_generation == devfs_generation) 
+	if (dm->dm_generation == devfs_generation)
 		return (0);
 	lockmgr(&dm->dm_lock, LK_UPGRADE, 0, curproc);
 	if (devfs_noverflow && dm->dm_overflow == NULL) {
@@ -304,10 +302,8 @@ devfs_populate(struct devfs_mount *dm)
 				dd = de->de_dir;
 				*dep = NULL;
 				TAILQ_REMOVE(&dd->de_dlist, de, de_list);
-				if (de->de_vnode) {
+				if (de->de_vnode)
 					de->de_vnode->v_data = NULL;
-					vdrop(de->de_vnode);
-				}
 				FREE(de, M_DEVFS);
 				devfs_dropref(i);
 				continue;
@@ -323,7 +319,7 @@ devfs_populate(struct devfs_mount *dm)
 			for (;;) {
 				for (q = s; *q != '/' && *q != '\0'; q++)
 					continue;
-				if (*q != '/') 
+				if (*q != '/')
 					break;
 				de = devfs_find(dd, s, q - s);
 				if (de == NULL) {
diff --git a/sys/fs/devfs/devfs_vfsops.c b/sys/fs/devfs/devfs_vfsops.c
index 00951ae..0c5d1bb 100644
--- a/sys/fs/devfs/devfs_vfsops.c
+++ b/sys/fs/devfs/devfs_vfsops.c
@@ -133,12 +133,14 @@ devfs_unmount(mp, mntflags, p)
 	fmp = VFSTODEVFS(mp);
 	if (mntflags & MNT_FORCE)
 		flags |= FORCECLOSE;
-	if (rootvp->v_usecount > 1)
+	if (rootvp->v_usecount > 2) {
+		vrele(rootvp);
 		return (EBUSY);
-	devfs_purge(fmp->dm_rootdir);
+	}
 	error = vflush(mp, rootvp, flags);
 	if (error)
 		return (error);
+	devfs_purge(fmp->dm_rootdir);
 	vput(rootvp);
 	vrele(rootvp);
 	vgone(rootvp);
diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
index cb8caff..e3c717e 100644
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -106,7 +106,6 @@ loop:
 	}
 	vp->v_data = de;
 	de->de_vnode = vp;
-	vhold(vp);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	*vpp = vp;
 	return (0);
@@ -148,7 +147,7 @@ devfs_getattr(ap)
 	dev_t dev;
 
 	de = vp->v_data;
-	if (vp->v_type == VDIR) 
+	if (vp->v_type == VDIR)
 		de = de->de_dir;
 	bzero((caddr_t) vap, sizeof(*vap));
 	vattr_null(vap);
@@ -245,7 +244,7 @@ devfs_lookupx(ap)
 			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
 			return (error);
 		}
-		if ((flags & LOCKPARENT) && (flags & ISLASTCN)) 
+		if ((flags & LOCKPARENT) && (flags & ISLASTCN))
 			error = vn_lock(dvp, LK_EXCLUSIVE, p);
 		if (error)
 			vput(*vpp);
@@ -296,13 +295,13 @@ devfs_lookupx(ap)
 	printf("Finished specname: %d \"%s\"\n", i, specname + i);
 #endif
 	cdev = NODEV;
-	EVENTHANDLER_INVOKE(dev_clone, specname + i, 
+	EVENTHANDLER_INVOKE(dev_clone, specname + i,
 	    strlen(specname + i), &cdev);
 #if 0
 	printf("cloned %s -> %p %s\n", specname + i, cdev,
 	    cdev == NODEV ? "NODEV" : cdev->si_name);
 #endif
-	if (cdev == NODEV) 
+	if (cdev == NODEV)
 		goto notfound;
 
 	devfs_populate(dmp);
@@ -431,7 +430,7 @@ devfs_readdir(ap)
 	dd = TAILQ_FIRST(&de->de_dlist);
 	off = 0;
 	while (dd != NULL) {
-		if (dd->de_dirent->d_type == DT_DIR) 
+		if (dd->de_dirent->d_type == DT_DIR)
 			de = dd->de_dir;
 		else
 			de = dd;
@@ -476,14 +475,24 @@ devfs_reclaim(ap)
 {
 	struct vnode *vp = ap->a_vp;
 	struct devfs_dirent *de;
+	int i;
 
 	de = vp->v_data;
+	if (de != NULL)
+		de->de_vnode = NULL;
 	if (de != NULL && de->de_flags & DE_ORPHAN) {
-		if (de->de_symlink) 
+		if (de->de_symlink)
 			FREE(de->de_symlink, M_DEVFS);
-		FREE(de, M_DEVFS);   
+		FREE(de, M_DEVFS);
 	}
 	vp->v_data = NULL;
+	if (vp->v_rdev != NODEV && vp->v_rdev != NULL) {
+		i = vcount(vp);
+		if ((vp->v_rdev->si_flags & SI_CHEAPCLONE) && i == 0) {
+			destroy_dev(vp->v_rdev);
+			printf("Reclaim <%s> %d %d Killed\n", vp->v_rdev->si_name, vp->v_rdev->si_flags, i);
+		}		
+	}
 	return (0);
 }
 
@@ -508,7 +517,6 @@ devfs_remove(ap)
 	if (dep != NULL)
 		*dep = DE_DELETED;
 	de->de_flags |= DE_ORPHAN;
-	vdrop(de->de_vnode);
 	lockmgr(&dmp->dm_lock, LK_RELEASE, 0, curproc);
 	return (0);
 }
@@ -529,8 +537,6 @@ devfs_revoke(ap)
 	struct devfs_dirent *de;
 
 	de = vp->v_data;
-	if (!(de->de_flags & DE_ORPHAN)) 
-		vdrop(de->de_vnode);
 	de->de_vnode = NULL;
 	vop_revoke(ap);
 	return (0);
@@ -565,7 +571,7 @@ devfs_setattr(ap)
 	}
 
 	de = ap->a_vp->v_data;
-	if (ap->a_vp->v_type == VDIR) 
+	if (ap->a_vp->v_type == VDIR)
 		de = de->de_dir;
 
 	error = c = 0;