block: misc cleanups in barrier code

Make the following cleanups in preparation of barrier/flush update.

* blk_do_ordered() declaration is moved from include/linux/blkdev.h to
  block/blk.h.

* blk_do_ordered() now returns pointer to struct request, with %NULL
  meaning "try the next request" and ERR_PTR(-EAGAIN) "try again
  later".  The third case will be dropped with further changes.

* In the initialization of proxy barrier request, data direction is
  already set by init_request_from_bio().  Drop unnecessary explicit
  REQ_WRITE setting and move init_request_from_bio() above REQ_FUA
  flag setting.

* add_request() is collapsed into __make_request().

These changes don't make any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 14 insertions, 18 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index ed0aba5463ab..f1be85ba2bb5 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -110,9 +110,9 @@ static void queue_flush(struct request_queue *q, unsigned which)
         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
 }
 
-static inline bool start_ordered(struct request_queue *q, struct request **rqp)
+static inline struct request *start_ordered(struct request_queue *q,
+                                            struct request *rq)
 {
-        struct request *rq = *rqp;
         unsigned skip = 0;
 
         q->orderr = 0;
@@ -149,11 +149,9 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
 
                 /* initialize proxy request and queue it */
                 blk_rq_init(q, rq);
-                if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
-                        rq->cmd_flags |= REQ_WRITE;
+                init_request_from_bio(rq, q->orig_bar_rq->bio);
                 if (q->ordered & QUEUE_ORDERED_DO_FUA)
                         rq->cmd_flags |= REQ_FUA;
-                init_request_from_bio(rq, q->orig_bar_rq->bio);
                 rq->end_io = bar_end_io;
 
                 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
@@ -171,27 +169,26 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
         else
                 skip |= QUEUE_ORDSEQ_DRAIN;
 
-        *rqp = rq;
-
         /*
          * Complete skipped sequences.  If whole sequence is complete,
-         * return false to tell elevator that this request is gone.
+         * return %NULL to tell elevator that this request is gone.
          */
-        return !blk_ordered_complete_seq(q, skip, 0);
+        if (blk_ordered_complete_seq(q, skip, 0))
+                rq = NULL;
+        return rq;
 }
 
-bool blk_do_ordered(struct request_queue *q, struct request **rqp)
+struct request *blk_do_ordered(struct request_queue *q, struct request *rq)
 {
-        struct request *rq = *rqp;
         const int is_barrier = rq->cmd_type == REQ_TYPE_FS &&
                                 (rq->cmd_flags & REQ_HARDBARRIER);
 
         if (!q->ordseq) {
                 if (!is_barrier)
-                        return true;
+                        return rq;
 
                 if (q->next_ordered != QUEUE_ORDERED_NONE)
-                        return start_ordered(q, rqp);
+                        return start_ordered(q, rq);
                 else {
                         /*
                          * Queue ordering not supported.  Terminate
@@ -199,8 +196,7 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
                          */
                         blk_dequeue_request(rq);
                         __blk_end_request_all(rq, -EOPNOTSUPP);
-                        *rqp = NULL;
-                        return false;
+                        return NULL;
                 }
         }
 
@@ -211,14 +207,14 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
         /* Special requests are not subject to ordering rules. */
         if (rq->cmd_type != REQ_TYPE_FS &&
             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
-                return true;
+                return rq;
 
         /* 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;
+                rq = ERR_PTR(-EAGAIN);
 
-        return true;
+        return rq;
 }
 
 static void bio_end_empty_barrier(struct bio *bio, int err)