- Fix nullfs vnode reference leak in nullfs_reclaim_lowervp(). The

  null_hashget() obtains the reference on the nullfs vnode, which must
  be dropped.

- Fix a wart which existed from the introduction of the nullfs
  caching, do not unlock lower vnode in the nullfs_reclaim_lowervp().
  It should be innocent, but now it is also formally safe.  Inform the
  nullfs_reclaim() about this using the NULLV_NOUNLOCK flag set on
  nullfs inode.

- Add a callback to the upper filesystems for the lower vnode
  unlinking. When inactivating a nullfs vnode, check if the lower
  vnode was unlinked, indicated by nullfs flag NULLV_DROP or VV_NOSYNC
  on the lower vnode, and reclaim upper vnode if so.  This allows
  nullfs to purge cached vnodes for the unlinked lower vnode, avoiding
  excessive caching.

Reported by:	G??ran L??wkrantz <goran.lowkrantz@ismobile.com>
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

1 files changed, 14 insertions, 5 deletions

diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c
index f59865f..6ff15ee 100644
--- a/sys/fs/nullfs/null_vnops.c
+++ b/sys/fs/nullfs/null_vnops.c
@@ -692,18 +692,24 @@ null_unlock(struct vop_unlock_args *ap)
 static int
 null_inactive(struct vop_inactive_args *ap __unused)
 {
-	struct vnode *vp;
+	struct vnode *vp, *lvp;
+	struct null_node *xp;
 	struct mount *mp;
 	struct null_mount *xmp;
 
 	vp = ap->a_vp;
+	xp = VTONULL(vp);
+	lvp = NULLVPTOLOWERVP(vp);
 	mp = vp->v_mount;
 	xmp = MOUNTTONULLMOUNT(mp);
-	if ((xmp->nullm_flags & NULLM_CACHE) == 0) {
+	if ((xmp->nullm_flags & NULLM_CACHE) == 0 ||
+	    (xp->null_flags & NULLV_DROP) != 0 ||
+	    (lvp->v_vflag & VV_NOSYNC) != 0) {
 		/*
 		 * If this is the last reference and caching of the
-		 * nullfs vnodes is not enabled, then free up the
-		 * vnode so as not to tie up the lower vnodes.
+		 * nullfs vnodes is not enabled, or the lower vnode is
+		 * deleted, then free up the vnode so as not to tie up
+		 * the lower vnodes.
 		 */
 		vp->v_object = NULL;
 		vrecycle(vp);
@@ -748,7 +754,10 @@ null_reclaim(struct vop_reclaim_args *ap)
 	 */
 	if (vp->v_writecount > 0)
 		VOP_ADD_WRITECOUNT(lowervp, -1);
-	vput(lowervp);
+	if ((xp->null_flags & NULLV_NOUNLOCK) != 0)
+		vunref(lowervp);
+	else
+		vput(lowervp);
 	free(xp, M_NULLFSNODE);
 
 	return (0);