Re: [PATCH 1/3] blk-mq: use right tag offset after wait

[Ming Lei <ming.lei@redhat.com>]

On Mon, Nov 30, 2020 at 01:36:25AM +0000, Pavel Begunkov wrote:
> blk_mq_get_tag() selects tag_offset in the beginning and doesn't update
> it even though the tag set it may have changed hw queue during waiting.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  block/blk-mq-tag.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index 9c92053e704d..dbbf11edf9a6 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -101,10 +101,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
>  			return BLK_MQ_NO_TAG;
>  		}
>  		bt = tags->breserved_tags;
> -		tag_offset = 0;
>  	} else {
>  		bt = tags->bitmap_tags;
> -		tag_offset = tags->nr_reserved_tags;
>  	}
>  
>  	tag = __blk_mq_get_tag(data, bt);
> @@ -167,6 +165,11 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
>  	sbitmap_finish_wait(bt, ws, &wait);
>  
>  found_tag:
> +	if (data->flags & BLK_MQ_REQ_RESERVED)
> +		tag_offset = 0;
> +	else
> +		tag_offset = tags->nr_reserved_tags;
> +

So far, the tag offset is tag-set wide, and 'tag_offset' is same for all tags,
looks no need to add the extra check.


thanks,
Ming