pnfs: Increase the refcount when LAYOUTGET fails the first time

The layout will be set unusable if LAYOUTGET fails. Is it reasonable to
increase the refcount iff LAYOUTGET fails the first time?

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org [>= 3.7]

fs/nfs/pnfs.c

@@ -254,7 +254,7 @@ static void
 pnfs_layout_set_fail_bit(struct pnfs_layout_hdr *lo, int fail_bit)
 {
 	lo->plh_retry_timestamp = jiffies;
-	if (test_and_set_bit(fail_bit, &lo->plh_flags))
+	if (!test_and_set_bit(fail_bit, &lo->plh_flags))
 		atomic_inc(&lo->plh_refcount);
 }