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, 4 insertions, 17 deletions

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);