block: kill QUEUE_ORDERED_BY_TAG

Nobody is making meaningful use of ORDERED_BY_TAG now and queue
draining for barrier requests will be removed soon which will render
the advantage of tag ordering moot.  Kill ORDERED_BY_TAG.  The
following users are affected.

* brd: converted to ORDERED_DRAIN.
* virtio_blk: ORDERED_TAG path was already marked deprecated.  Removed.
* xen-blkfront: ORDERED_TAG case dropped.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 7 insertions, 28 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index f0faefca032f..c807e9ca3a68 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -26,10 +26,7 @@ int blk_queue_ordered(struct request_queue *q, unsigned ordered)
         if (ordered != QUEUE_ORDERED_NONE &&
             ordered != QUEUE_ORDERED_DRAIN &&
             ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
-            ordered != QUEUE_ORDERED_DRAIN_FUA &&
-            ordered != QUEUE_ORDERED_TAG &&
-            ordered != QUEUE_ORDERED_TAG_FLUSH &&
-            ordered != QUEUE_ORDERED_TAG_FUA) {
+            ordered != QUEUE_ORDERED_DRAIN_FUA) {
                 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
                 return -EINVAL;
         }
@@ -155,21 +152,9 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
          * For an empty barrier, there's no actual BAR request, which
          * in turn makes POSTFLUSH unnecessary.  Mask them off.
          */
-        if (!blk_rq_sectors(rq)) {
+        if (!blk_rq_sectors(rq))
                 q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
                                 QUEUE_ORDERED_DO_POSTFLUSH);
-                /*
-                 * Empty barrier on a write-through device w/ ordered
-                 * tag has no command to issue and without any command
-                 * to issue, ordering by tag can't be used.  Drain
-                 * instead.
-                 */
-                if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
-                    !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
-                        q->ordered &= ~QUEUE_ORDERED_BY_TAG;
-                        q->ordered |= QUEUE_ORDERED_BY_DRAIN;
-                }
-        }
 
         /* stash away the original request */
         blk_dequeue_request(rq);
@@ -210,7 +195,7 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
         } else
                 skip |= QUEUE_ORDSEQ_PREFLUSH;
 
-        if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
+        if (queue_in_flight(q))
                 rq = NULL;
         else
                 skip |= QUEUE_ORDSEQ_DRAIN;
@@ -257,16 +242,10 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
                 return true;
 
-        if (q->ordered & QUEUE_ORDERED_BY_TAG) {
-                /* Ordered by tag.  Blocking the next barrier is enough. */
-                if (is_barrier && rq != &q->bar_rq)
-                        *rqp = NULL;
-        } else {
-                /* Ordered by draining.  Wait for turn. */
-                WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
-                if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
-                        *rqp = NULL;
-        }
+        /* Ordered by draining.  Wait for turn. */
+        WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
+        if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
+                *rqp = NULL;
 
         return true;
 }