Re: [PATCH 1/3] blk-mq: Cleanup blk_mq_tag_busy() and blk_mq_tag_idle()

From: Jens Axboe
Date: Wed Sep 03 2014 - 16:35:38 EST


On 09/03/2014 02:33 PM, Alexander Gordeev wrote:
> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> ---
> block/blk-mq-tag.c | 4 +---
> block/blk-mq-tag.h | 17 ++++++++---------
> 2 files changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index c1b9242..4953b64 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -58,13 +58,11 @@ static inline void bt_index_atomic_inc(atomic_t *index)
> /*
> * If a previously inactive queue goes active, bump the active user count.
> */
> -bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
> +void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
> {
> if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
> !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
> atomic_inc(&hctx->tags->active_queues);
> -
> - return true;
> }

This is obviously a good idea.

> diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
> index 6206ed1..795ec3f 100644
> --- a/block/blk-mq-tag.h
> +++ b/block/blk-mq-tag.h
> @@ -66,23 +66,22 @@ enum {
> BLK_MQ_TAG_MAX = BLK_MQ_TAG_FAIL - 1,
> };
>
> -extern bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *);
> +extern void __blk_mq_tag_busy(struct blk_mq_hw_ctx *);
> extern void __blk_mq_tag_idle(struct blk_mq_hw_ctx *);
>
> static inline bool blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
> {
> - if (!(hctx->flags & BLK_MQ_F_TAG_SHARED))
> - return false;
> -
> - return __blk_mq_tag_busy(hctx);
> + if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
> + __blk_mq_tag_busy(hctx);
> + return true;
> + }
> + return false;
> }

The normal/fast path here is the flag NOT being set, which is why it was
coded that way to put the fast path inline.

>
> static inline void blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
> {
> - if (!(hctx->flags & BLK_MQ_F_TAG_SHARED))
> - return;
> -
> - __blk_mq_tag_idle(hctx);
> + if (hctx->flags & BLK_MQ_F_TAG_SHARED)
> + __blk_mq_tag_idle(hctx);
> }

Ditto


--
Jens Axboe

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