[PATCH V3 3/8] blk-mq: introduce 'start_tag' field to 'struct blk_mq_tags'

Ming Lei
2018-02-27T10:07:45Z

This patch introduces 'start_tag' field to 'struct blk_mq_tags' so that
host wide tagset can be supported easily in the following patches by
partitioning host wide tags into multiple hw queues.

No function change.

Cc: Hannes Reinecke <hare@suse.de>
Cc: Arun Easi <arun.easi@cavium.com>
Cc: Omar Sandoval <osandov@fb.com>,
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
Cc: James Bottomley <james.bottomley@hansenpartnership.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Don Brace <don.brace@microsemi.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Peter Rivera <peter.rivera@broadcom.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/blk-mq-tag.c | 3 ++-
block/blk-mq-tag.h | 6 ++++--
block/blk-mq.c | 7 ++++---
3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 336dde07b230..5014d7343ea9 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -179,12 +179,13 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
finish_wait(&ws->wait, &wait);

found_tag:
- return tag + tag_offset;
+ return tag + tag_offset + tags->start_tag;
}

void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
struct blk_mq_ctx *ctx, unsigned int tag)
{
+ tag -= tags->start_tag;
if (!blk_mq_tag_is_reserved(tags, tag)) {
const int real_tag = tag - tags->nr_reserved_tags;

diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 61deab0b5a5a..1d629920db69 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -13,6 +13,8 @@ struct blk_mq_tags {

atomic_t active_queues;

+ unsigned int start_tag;
+
struct sbitmap_queue bitmap_tags;
struct sbitmap_queue breserved_tags;

@@ -78,13 +80,13 @@ static inline void blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
static inline void blk_mq_tag_set_rq(struct blk_mq_hw_ctx *hctx,
unsigned int tag, struct request *rq)
{
- hctx->tags->rqs[tag] = rq;
+ hctx->tags->rqs[tag - hctx->tags->start_tag] = rq;
}

static inline bool blk_mq_tag_is_reserved(struct blk_mq_tags *tags,
unsigned int tag)
{
- return tag < tags->nr_reserved_tags;
+ return (tag - tags->start_tag) < tags->nr_reserved_tags;
}

#endif
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 357492712b0e..5ea11d087f7b 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -270,7 +270,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
unsigned int tag, unsigned int op)
{
struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
- struct request *rq = tags->static_rqs[tag];
+ struct request *rq = tags->static_rqs[tag - tags->start_tag];
req_flags_t rq_flags = 0;

if (data->flags & BLK_MQ_REQ_INTERNAL) {
@@ -283,7 +283,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
}
rq->tag = tag;
rq->internal_tag = -1;
- data->hctx->tags->rqs[rq->tag] = rq;
+ data->hctx->tags->rqs[rq->tag - tags->start_tag] = rq;
}

/* csd/requeue_work/fifo_time is initialized before use */
@@ -801,6 +801,7 @@ EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);

struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
+ tag -= tags->start_tag;
if (tag < tags->nr_tags) {
prefetch(tags->rqs[tag]);
return tags->rqs[tag];
@@ -1076,7 +1077,7 @@ bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx,
rq->rq_flags |= RQF_MQ_INFLIGHT;
atomic_inc(&data.hctx->nr_active);
}
- data.hctx->tags->rqs[rq->tag] = rq;
+ data.hctx->tags->rqs[rq->tag - data.hctx->tags->start_tag] = rq;
}

done:
--
2.9.5