From: Mikulas Patocka <mpatocka@redhat.com>

If -EOPNOTSUPP was returned and the request was a barrier request, retry it
without barrier.

Retry all regions for now. Barriers are submitted only for one-region requests,
so it doesn't matter.  (In the future, retries can be limited to the actual
regions that failed.)

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

---
drivers/md/dm-io.c |    6 ++++++
 drivers/md/dm-io.c |    6 ++++++
 1 file changed, 6 insertions(+)
Index: linux-2.6.30/drivers/md/dm-io.c
===================================================================
--- linux-2.6.30.orig/drivers/md/dm-io.c
+++ linux-2.6.30/drivers/md/dm-io.c
@@ -364,6 +364,7 @@ static int sync_io(struct dm_io_client *
 		return -EIO;
 	}
 
+retry:
 	io.error_bits = 0;
 	io.eopnotsupp_bits = 0;
 	atomic_set(&io.count, 1); /* see dispatch_io() */
@@ -382,6 +383,11 @@ static int sync_io(struct dm_io_client *
 	}
 	set_current_state(TASK_RUNNING);
 
+	if (io.eopnotsupp_bits && (rw & (1 << BIO_RW_BARRIER))) {
+		rw &= ~(1 << BIO_RW_BARRIER);
+		goto retry;
+	}
+
 	if (error_bits)
 		*error_bits = io.error_bits;