block: optionally merge discontiguous discard bios into a single request

[mirror_ubuntu-artful-kernel.git] / block / blk-merge.c

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6cbd90ad5f903379b501545868da1528a8dea6b3..2afa262425d102e5c1500912f3b6d77525754566 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -803,7 +803,10 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 
 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 {
-       if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
+       if (req_op(rq) == REQ_OP_DISCARD &&
+           queue_max_discard_segments(rq->q) > 1)
+               return ELEVATOR_DISCARD_MERGE;
+       else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
                return ELEVATOR_BACK_MERGE;
        else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
                return ELEVATOR_FRONT_MERGE;