[PATCH V2 18/20] block: introduce .last_merge and .hash to blk_mq_ctx

Ming Lei
2017-08-05T06:58:21Z

Prepare for supporting bio merge to sw queue if no
blk-mq io scheduler is taken.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/blk-mq.h | 4 ++++
block/blk.h | 3 +++
block/elevator.c | 22 +++++++++++++++++++---
3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 295fd9dfb01d..3400b01a2e4c 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -18,6 +18,10 @@ struct blk_mq_ctx {
unsigned long rq_dispatched[2];
unsigned long rq_merged;

+ /* bio merge via request hash table */
+ struct request *last_merge;
+ DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
+
/* incremented at completion time */
unsigned long ____cacheline_aligned_in_smp rq_completed[2];

diff --git a/block/blk.h b/block/blk.h
index 313002c2f666..6847c5435cca 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -199,6 +199,9 @@ static inline struct request *rqhash_find(struct hlist_head *hash, sector_t offs
return NULL;
}

+enum elv_merge elv_merge_ctx(struct request_queue *q, struct request **req,
+ struct bio *bio, struct blk_mq_ctx *ctx);
+
void blk_insert_flush(struct request *rq);

static inline struct request *__elv_next_request(struct request_queue *q)
diff --git a/block/elevator.c b/block/elevator.c
index eb56e2709291..cbdbe823d262 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -471,6 +471,13 @@ enum elv_merge elv_merge(struct request_queue *q, struct request **req,
return __elv_merge(q, req, bio, q->elevator->hash, q->last_merge);
}

+enum elv_merge elv_merge_ctx(struct request_queue *q, struct request **req,
+ struct bio *bio, struct blk_mq_ctx *ctx)
+{
+ WARN_ON_ONCE(!q->mq_ops);
+ return __elv_merge(q, req, bio, ctx->hash, ctx->last_merge);
+}
+
/*
* Attempt to do an insertion back merge. Only check for the case where
* we can append 'rq' to an existing request, so we can throw 'rq' away
@@ -516,16 +523,25 @@ void elv_merged_request(struct request_queue *q, struct request *rq,
enum elv_merge type)
{
struct elevator_queue *e = q->elevator;
+ struct hlist_head *hash = e->hash;
+
+ /* we do bio merge on blk-mq sw queue */
+ if (q->mq_ops && !e) {
+ rq->mq_ctx->last_merge = rq;
+ hash = rq->mq_ctx->hash;
+ goto reposition;
+ }
+
+ q->last_merge = rq;

if (e->uses_mq && e->type->ops.mq.request_merged)
e->type->ops.mq.request_merged(q, rq, type);
else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
e->type->ops.sq.elevator_merged_fn(q, rq, type);

+ reposition:
if (type == ELEVATOR_BACK_MERGE)
- elv_rqhash_reposition(q, rq);
-
- q->last_merge = rq;
+ rqhash_reposition(hash, rq);
}

void elv_merge_requests(struct request_queue *q, struct request *rq,
--
2.9.4