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>

3 files changed, 7 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 5484838f46e7..b9a252cae4df 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 c77196d55899..908d3e11ac52 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;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 93204bf7b297..12df8efeef19 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -545,6 +545,7 @@ enum {
 #define blk_pm_request(rq)      \
         (blk_pm_suspend_request(rq) || blk_pm_resume_request(rq))
 
+#define blk_rq_cpu_valid(rq)    ((rq)->cpu != -1)
 #define blk_sorted_rq(rq)       ((rq)->cmd_flags & REQ_SORTED)
 #define blk_barrier_rq(rq)      ((rq)->cmd_flags & REQ_HARDBARRIER)
 #define blk_fua_rq(rq)          ((rq)->cmd_flags & REQ_FUA)