NFSv4: nfs4_return_incompatible_delegation() should check delegation validity

Ensure that we check that the delegation is valid in
nfs4_return_incompatible_delegation() before we try to return it.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -1796,7 +1796,7 @@ static void nfs4_return_incompatible_delegation(struct inode *inode, fmode_t fmo
 
 	fmode &= FMODE_READ|FMODE_WRITE;
 	rcu_read_lock();
-	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	delegation = nfs4_get_valid_delegation(inode);
 	if (delegation == NULL || (delegation->type & fmode) == fmode) {
 		rcu_read_unlock();
 		return;