block: don't clear REQ_HIPRI for bio-based drivers

Don't clear REQ_HIPRI for bio-based drivers. Device mapper will need to
see this flag in order to support polling.

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

---
 block/blk-core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/block/blk-core.c
===================================================================
--- linux-2.6.orig/block/blk-core.c	2021-03-02 10:43:28.000000000 +0100
+++ linux-2.6/block/blk-core.c	2021-03-02 10:53:50.000000000 +0100
@@ -836,7 +836,7 @@ static noinline_for_stack bool submit_bi
 		}
 	}
 
-	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
+	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && !bdev->bd_disk->fops->submit_bio)
 		bio->bi_opf &= ~REQ_HIPRI;
 
 	switch (bio_op(bio)) {