On Fri, May 18, 2018 at 9:42 PM, 胡海 <hu...@kylinos.cn> wrote:
> Author: huhai <hu...@kylinos.cn>
> Date:   Fri May 18 17:09:56 2018 +0800
>
>     blk-mq: make sure that correct hctx->dispatch_from is set
>
>     When the number of hardware queues is changed, the drivers will call
>     blk_mq_update_nr_hw_queues() to remap hardware queues, and then
>     the ctx mapped on hctx will also change, but the current code forgets to
>     make sure that correct hctx->dispatch_from is set, and hctx->dispatch_from
>     may point to a ctx that does not belong to the current hctx.
>
>     Signed-off-by: huhai <hu...@kylinos.cn>
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 2545081..55d8a3d 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2214,6 +2214,8 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>                 hctx->tags = set->tags[i];
>                 WARN_ON(!hctx->tags);
>
> +               hctx->dispatch_from = NULL;
> +
>                 /*
>                  * Set the map size to the number of mapped software queues.
>                  * This is more accurate and more efficient than looping

Good catch,

Reviewed-by: Ming Lei <ming....@redhat.com>

Thanks,
Ming Lei

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