Re: [PATCH 1/1] blk-mq: do not reset plug->rq_count before the list is sorted

[Ming Lei]

On Thu, Apr 4, 2019 at 10:54 AM Dongli Zhang <dongli.zhang@xxxxxxxxxx> wrote:
>
> We would never be able to sort the list if we first reset plug->rq_count
> which is used in conditional check later.
>
> Fixes: ce5b009cff19 ("block: improve logic around when to sort a plug list")
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
> ---
>  block/blk-mq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 3ff3d7b..c162718 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1711,11 +1711,12 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
>         unsigned int depth;
>
>         list_splice_init(&plug->mq_list, &list);
> -       plug->rq_count = 0;
>
>         if (plug->rq_count > 2 && plug->multiple_queues)
>                 list_sort(NULL, &list, plug_rq_cmp);
>
> +       plug->rq_count = 0;
> +
>         this_q = NULL;
>         this_hctx = NULL;
>         this_ctx = NULL;
> --
> 2.7.4
>

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>

Thanks,
Ming Lei