block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions

blk_rq_merge_ok() is the elevator-neutral part of merge eligibility
test.  blk_try_merge() determines merge direction and expects the
caller to have tested elv_rq_merge_ok() previously.

elv_rq_merge_ok() now wraps blk_rq_merge_ok() and then calls
elv_iosched_allow_merge().  elv_try_merge() is removed and the two
callers are updated to call elv_rq_merge_ok() explicitly followed by
blk_try_merge().  While at it, make rq_merge_ok() functions return
bool.

This is to prepare for plug merge update and doesn't introduce any
behavior change.

This is based on Jens' patch to skip elevator_allow_merge_fn() from
plug merge.

Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4F16F3CA.90904@kernel.dk>
Original-patch-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 2 deletions

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c24f3d7fbf1e..d6dfb65c8885 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -122,7 +122,6 @@ extern void elv_dispatch_add_tail(struct request_queue *, struct request *);
 extern void elv_add_request(struct request_queue *, struct request *, int);
 extern void __elv_add_request(struct request_queue *, struct request *, int);
 extern int elv_merge(struct request_queue *, struct request **, struct bio *);
-extern int elv_try_merge(struct request *, struct bio *);
 extern void elv_merge_requests(struct request_queue *, struct request *,
                                struct request *);
 extern void elv_merged_request(struct request_queue *, struct request *, int);
@@ -155,7 +154,7 @@ extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t);
 extern int elevator_init(struct request_queue *, char *);
 extern void elevator_exit(struct elevator_queue *);
 extern int elevator_change(struct request_queue *, const char *);
-extern int elv_rq_merge_ok(struct request *, struct bio *);
+extern bool elv_rq_merge_ok(struct request *, struct bio *);
 
 /*
  * Helper functions.