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

Retry all regions (if there was just one region returning -EOPNOTSUPP), for
now, barriers are submitted only for 1-region requests, so it doesn't matter.

In the future, this can be fine-grained to retry only -EOPNOTSUPPed regions.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-io.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-2.6.29-rc1-devel/drivers/md/dm-io.c
===================================================================
--- linux-2.6.29-rc1-devel.orig/drivers/md/dm-io.c	2009-01-22 21:09:28.000000000 +0100
+++ linux-2.6.29-rc1-devel/drivers/md/dm-io.c	2009-01-22 21:09:37.000000000 +0100
@@ -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;