- 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, 4 insertions, 0 deletions

diff --git a/sys/fs/nullfs/null.h b/sys/fs/nullfs/null.h
index 4f37020d6da5..0972dfc409c3 100644
--- a/sys/fs/nullfs/null.h
+++ b/sys/fs/nullfs/null.h
@@ -53,8 +53,12 @@ struct null_node {
 	LIST_ENTRY(null_node)	null_hash;	/* Hash list */
 	struct vnode	        *null_lowervp;	/* VREFed once */
 	struct vnode		*null_vnode;	/* Back pointer */
+	u_int			null_flags;
 };
 
+#define	NULLV_NOUNLOCK	0x0001
+#define	NULLV_DROP	0x0002
+
 #define	MOUNTTONULLMOUNT(mp) ((struct null_mount *)((mp)->mnt_data))
 #define	VTONULL(vp) ((struct null_node *)(vp)->v_data)
 #define	NULLTOV(xp) ((xp)->null_vnode)