blocK: Restore barrier support for md and probably other virtual devices.

The next_ordered flag is only meaningful for devices that use __make_request.
So move the test against next_ordered out of generic code and in to
__make_request

Since this test was added, barriers have not worked on md or any
devices that don't use __make_request and so don't bother to set
next_ordered.  (dm explicitly sets something other than
QUEUE_ORDERED_NONE since
  commit 99360b4c18f7675b50d283301d46d755affe75fd
but notes in the comments that it is otherwise meaningless).

Cc: Ken Milmore <ken.milmore@googlemail.com>
Cc: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 02b8713..4b45435 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1170,6 +1170,11 @@ static int __make_request(struct request_queue *q, struct bio *bio)
        const int unplug = bio_unplug(bio);
        int rw_flags;
 
+       if (bio_barrier(bio) && bio_has_data(bio) &&
+           (q->next_ordered == QUEUE_ORDERED_NONE)) {
+               bio_endio(bio, -EOPNOTSUPP);
+               return 0;
+       }
        /*
         * low level driver can indicate that it wants pages above a
         * certain limit bounced to low memory (ie for highmem, or even
@@ -1470,11 +1475,6 @@ static inline void __generic_make_request(struct bio *bio)
                        err = -EOPNOTSUPP;
                        goto end_io;
                }
-               if (bio_barrier(bio) && bio_has_data(bio) &&
-                   (q->next_ordered == QUEUE_ORDERED_NONE)) {
-                       err = -EOPNOTSUPP;
-                       goto end_io;
-               }
 
                ret = q->make_request_fn(q, bio);
        } while (ret);