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>

3 files changed, 23 insertions, 37 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)
diff --git a/block/blk-core.c b/block/blk-core.c
index f06354183b29..f8d37a8e2c55 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1037,22 +1037,6 @@ void blk_insert_request(struct request_queue *q, struct request *rq,
 }
 EXPORT_SYMBOL(blk_insert_request);
 
-/*
- * add-request adds a request to the linked list.
- * queue lock is held and interrupts disabled, as we muck with the
- * request queue list.
- */
-static inline void add_request(struct request_queue *q, struct request *req)
-{
-        drive_stat_acct(req, 1);
-
-        /*
-         * elevator indicated where it wants this request to be
-         * inserted at elevator_merge time
-         */
-        __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
-}
-
 static void part_round_stats_single(int cpu, struct hd_struct *part,
                                     unsigned long now)
 {
@@ -1316,7 +1300,10 @@ get_rq:
                 req->cpu = blk_cpu_to_group(smp_processor_id());
         if (queue_should_plug(q) && elv_queue_empty(q))
                 blk_plug_device(q);
-        add_request(q, req);
+
+        /* insert the request into the elevator */
+        drive_stat_acct(req, 1);
+        __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
 out:
         if (unplug || !queue_should_plug(q))
                 __generic_unplug_device(q);
diff --git a/block/blk.h b/block/blk.h
index 6e7dc87141e4..874eb4ea8093 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -51,6 +51,8 @@ static inline void blk_clear_rq_complete(struct request *rq)
  */
 #define ELV_ON_HASH(rq)         (!hlist_unhashed(&(rq)->hash))
 
+struct request *blk_do_ordered(struct request_queue *q, struct request *rq);
+
 static inline struct request *__elv_next_request(struct request_queue *q)
 {
         struct request *rq;
@@ -58,8 +60,9 @@ static inline struct request *__elv_next_request(struct request_queue *q)
         while (1) {
                 while (!list_empty(&q->queue_head)) {
                         rq = list_entry_rq(q->queue_head.next);
-                        if (blk_do_ordered(q, &rq))
-                                return rq;
+                        rq = blk_do_ordered(q, rq);
+                        if (rq)
+                                return !IS_ERR(rq) ? rq : NULL;
                 }
 
                 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))