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>
diff --git a/block/blk-merge.c b/block/blk-merge.c
index cfcc37c..160035f 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -471,3 +471,40 @@
{
return attempt_merge(q, rq, next);
}
+
+bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
+{
+ if (!rq_mergeable(rq))
+ return false;
+
+ /* don't merge file system requests and discard requests */
+ if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
+ return false;
+
+ /* don't merge discard requests and secure discard requests */
+ if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
+ return false;
+
+ /* different data direction or already started, don't merge */
+ if (bio_data_dir(bio) != rq_data_dir(rq))
+ return false;
+
+ /* must be same device and not a special request */
+ if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
+ return false;
+
+ /* only merge integrity protected bio into ditto rq */
+ if (bio_integrity(bio) != blk_integrity_rq(rq))
+ return false;
+
+ return true;
+}
+
+int blk_try_merge(struct request *rq, struct bio *bio)
+{
+ if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
+ return ELEVATOR_BACK_MERGE;
+ else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
+ return ELEVATOR_FRONT_MERGE;
+ return ELEVATOR_NO_MERGE;
+}