Re: [PATCH] scsi: mq queue stall during command requeue

[Bart Van Assche <Bart.VanAssche@sandisk.com>]

On Thu, 2017-01-19 at 15:17 +0100, Hannes Reinecke wrote:
> When we're hitting a busy condition in queuecommand() we need to
> stop the hardware queue before calling blk_mq_delay_queue(); if
> we don't blk_mq_delay_queue() will not do anything and requeue
> will never triggered.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/scsi/scsi_lib.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index e9e1e14..4b1cbc6 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1951,8 +1951,10 @@ static int scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
>  	switch (ret) {
>  	case BLK_MQ_RQ_QUEUE_BUSY:
>  		if (atomic_read(&sdev->device_busy) == 0 &&
> -		    !scsi_device_blocked(sdev))
> +		    !scsi_device_blocked(sdev)) {
> +			blk_mq_stop_hw_queue(hctx);
>  			blk_mq_delay_queue(hctx, SCSI_QUEUE_DELAY);
> +		}
>  		break;
>  	case BLK_MQ_RQ_QUEUE_ERROR:
>  		/*

You may want to add Fixes: 52d7f1b5c2f3 (blk-mq: Avoid that requeueing
starts stopped queues). See also
https://www.spinics.net/lists/linux-block/msg06144.html.

Bart.