block: inherit CPU completion on bio->rq and rq->rq merges

Somewhat incomplete, as we do allow merges of requests and bios
that have different completion CPUs given. This is done on the
assumption that a larger IO is still more beneficial than CPU
locality.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 6 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 5484838f46e..b9a252cae4d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1134,6 +1134,8 @@ static int __make_request(struct request_queue *q, struct bio *bio)
                 req->biotail = bio;
                 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
                 req->ioprio = ioprio_best(req->ioprio, prio);
+                if (!blk_rq_cpu_valid(req))
+                        req->cpu = bio->bi_comp_cpu;
                 drive_stat_acct(req, 0);
                 if (!attempt_back_merge(q, req))
                         elv_merged_request(q, req, el_ret);
@@ -1161,6 +1163,8 @@ static int __make_request(struct request_queue *q, struct bio *bio)
                 req->sector = req->hard_sector = bio->bi_sector;
                 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
                 req->ioprio = ioprio_best(req->ioprio, prio);
+                if (!blk_rq_cpu_valid(req))
+                        req->cpu = bio->bi_comp_cpu;
                 drive_stat_acct(req, 0);
                 if (!attempt_front_merge(q, req))
                         elv_merged_request(q, req, el_ret);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index c77196d5589..908d3e11ac5 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -400,6 +400,8 @@ static int attempt_merge(struct request_queue *q, struct request *req,
         }
 
         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
+        if (blk_rq_cpu_valid(next))
+                req->cpu = next->cpu;
 
         __blk_put_request(q, next);
         return 1;