[PATCH -next] blk-mq: fix tag_get wait task can't be awakened

[QiuLaibin]

ping...

On 2021/9/16 22:10, qiulaibin wrote:
> When multiple hctx share one tagset. The wake_batch is calculated during initialization by queue_depth. But when multiple hctx share one tagset. The queue depth assigned to each user may be smaller than wakup_batch. This may cause the waiting queue to fail to wakup and leads to Hang.
>
> Fix this by recalculating wake_batch when inc or dec active_queues.
>
> Fixes: 0d2602ca30e41 ("blk-mq: improve support for shared tags maps")
> Signed-off-by: Laibin Qiu <qiulaibin@xxxxxxxxxx>
> ---
>   block/blk-mq-tag.c      | 44 +++++++++++++++++++++++++++++++++++++++--
>   include/linux/sbitmap.h |  8 ++++++++
>   lib/sbitmap.c           |  3 ++-
>   3 files changed, 52 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 86f87346232a..d02f5ac0004c 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -16,6 +16,27 @@
>   #include "blk-mq-sched.h"
>   #include "blk-mq-tag.h"
>   
> +static void bt_update_wake_batch(struct sbitmap_queue *bt, unsigned int
> +users) {
> +	unsigned int depth;
> +
> +	depth = max((bt->sb.depth + users - 1) / users, 4U);
> +	sbitmap_queue_update_wake_batch(bt, depth); }
> +
> +/*
> + * Recalculate wakeup batch when tag is shared by hctx.
> + */
> +static void blk_mq_update_wake_batch(struct sbitmap_queue *bitmap_tags,
> +		struct sbitmap_queue *breserved_tags, unsigned int users) {
> +	if (!users)
> +		return;
> +
> +	bt_update_wake_batch(bitmap_tags, users);
> +	bt_update_wake_batch(breserved_tags, users); }
> +
>   /*
>    * If a previously inactive queue goes active, bump the active user count.
>    * We need to do this before try to allocate driver tag, then even if fail @@ -24,17 +45,29 @@
>    */
>   bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)  {
> +	unsigned int users;
> +
>   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>   		struct request_queue *q = hctx->queue;
>   		struct blk_mq_tag_set *set = q->tag_set;
>   
>   		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
> -		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
> +		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags)) {
>   			atomic_inc(&set->active_queues_shared_sbitmap);
> +
> +			users = atomic_read(&set->active_queues_shared_sbitmap);
> +			blk_mq_update_wake_batch(&set->__bitmap_tags,
> +					&set->__breserved_tags, users);
> +		}
>   	} else {
>   		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
> -		    !test_and_set_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);
> +
> +			users = atomic_read(&hctx->tags->active_queues);
> +			blk_mq_update_wake_batch(&hctx->tags->__bitmap_tags,
> +					&hctx->tags->__breserved_tags, users);
> +		}
>   	}
>   
>   	return true;
> @@ -59,16 +92,23 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
>   	struct blk_mq_tags *tags = hctx->tags;
>   	struct request_queue *q = hctx->queue;
>   	struct blk_mq_tag_set *set = q->tag_set;
> +	unsigned int users;
>   
>   	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>   		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
>   					&q->queue_flags))
>   			return;
>   		atomic_dec(&set->active_queues_shared_sbitmap);
> +		users = atomic_read(&set->active_queues_shared_sbitmap);
> +		blk_mq_update_wake_batch(&set->__bitmap_tags,
> +				&set->__breserved_tags, users);
>   	} else {
>   		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
>   			return;
>   		atomic_dec(&tags->active_queues);
> +		users = atomic_read(&tags->active_queues);
> +		blk_mq_update_wake_batch(&tags->__bitmap_tags,
> +				&tags->__breserved_tags, users);
>   	}
>   
>   	blk_mq_tag_wakeup_all(tags, false);
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 2713e689ad66..d49e4f054bfe 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -406,6 +406,14 @@ static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
>   	sbitmap_free(&sbq->sb);
>   }
>   
> +/**
> + * sbitmap_queue_update_wake_batch() - Recalucate wake batch.
> + * @sbq: Bitmap queue.
> + * @depth: New number of queue depth.
> + */
> +void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> +				     unsigned int depth);
> +
>   /**
>    * sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
>    * @sbq: Bitmap queue to resize.
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c index b25db9be938a..bbe1d663763f 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -457,7 +457,7 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,  }  EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
>   
> -static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
> +void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
>   					    unsigned int depth)
>   {
>   	unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth); @@ -475,6 +475,7 @@ static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
>   			atomic_set(&sbq->ws[i].wait_cnt, 1);
>   	}
>   }
> +EXPORT_SYMBOL_GPL(sbitmap_queue_update_wake_batch);
>   
>   void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)  {
> --
> 2.22.0
>
> .