NFS: Ensure that we always drop inodes that have been marked as stale

There is no need to cache stale inodes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 117183b..2faae14 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -107,6 +107,12 @@
 	return ino;
 }
 
+int nfs_drop_inode(struct inode *inode)
+{
+	return NFS_STALE(inode) || generic_drop_inode(inode);
+}
+EXPORT_SYMBOL_GPL(nfs_drop_inode);
+
 void nfs_clear_inode(struct inode *inode)
 {
 	/*