[PATCH] nvme: simplify nvme_req_qid()

[PATCH] nvme: simplify nvme_req_qid()

[Minwoo Im]

blk_mq_unique_tag() just makes a unique tag which holds not only the
tag, but also the queue_num of the hctx.  With this unique tag,
blk_mq_unique_tag_to_hwq is nothing but removing the tag from it.

Therefore the qid or the I/O queues can simply be:
	(struct blk_mq_hw_ctx *)->queue_num + 1

Cc: Keith Busch <kbusch at kernel.org>
Cc: Jens Axboe <axboe at fb.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Sagi Grimberg <sagi at grimberg.me>
Signed-off-by: Minwoo Im <minwoo.im.dev at gmail.com>
---
 drivers/nvme/host/nvme.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 26b563f9985b..2e76198f5833 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -126,7 +126,7 @@ static inline u16 nvme_req_qid(struct request *req)
 {
 	if (!req->rq_disk)
 		return 0;
-	return blk_mq_unique_tag_to_hwq(blk_mq_unique_tag(req)) + 1;
+	return req->mq_hctx->queue_num + 1;
 }
 
 /* The below value is the specific amount of delay needed before checking
-- 
2.17.1

[PATCH] nvme: simplify nvme_req_qid()

[Sagi Grimberg]

> blk_mq_unique_tag() just makes a unique tag which holds not only the
> tag, but also the queue_num of the hctx.  With this unique tag,
> blk_mq_unique_tag_to_hwq is nothing but removing the tag from it.
> 
> Therefore the qid or the I/O queues can simply be:
> 	(struct blk_mq_hw_ctx *)->queue_num + 1

This pattern is not unique to nvme, perhaps add a helper for it
in the block layer and modify the callers?

[PATCH] nvme: simplify nvme_req_qid()

[Minwoo Im]

Hi, Sagi.

> > blk_mq_unique_tag() just makes a unique tag which holds not only the
> > tag, but also the queue_num of the hctx.  With this unique tag,
> > blk_mq_unique_tag_to_hwq is nothing but removing the tag from it.
> >
> > Therefore the qid or the I/O queues can simply be:
> > 	(struct blk_mq_hw_ctx *)->queue_num + 1
> 
> This pattern is not unique to nvme, perhaps add a helper for it
> in the block layer and modify the callers?

Sorry, but could you please elaborate a little bit more in detail that
Why the pattern is not unique to nvme ?

Thanks,

[PATCH] nvme: simplify nvme_req_qid()

[Sagi Grimberg]

> Hi, Sagi.
> 
>>> blk_mq_unique_tag() just makes a unique tag which holds not only the
>>> tag, but also the queue_num of the hctx.  With this unique tag,
>>> blk_mq_unique_tag_to_hwq is nothing but removing the tag from it.
>>>
>>> Therefore the qid or the I/O queues can simply be:
>>> 	(struct blk_mq_hw_ctx *)->queue_num + 1
>>
>> This pattern is not unique to nvme, perhaps add a helper for it
>> in the block layer and modify the callers?
> 
> Sorry, but could you please elaborate a little bit more in detail that
> Why the pattern is not unique to nvme ?

This is at least used by smartqpi (although I did remember that more
used to use it...)