Re: [PATCH v3 05/26] scsi: core: Add scsi_{get,put}_internal_cmd() helpers

[John Garry <john.g.garry@oracle.com>]

On 27/08/2025 01:06, Bart Van Assche wrote:
> From: Hannes Reinecke <hare@suse.de>
> 
> Add helper functions to allow LLDDs to allocate and free internal commands.
> 
> Cc: John Garry <john.g.garry@oracle.com>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> [ bvanassche: changed the 'nowait' argument into a 'flags' argument /
>    added scsi_get_internal_cmd_hctx(). See also
>    https://lore.kernel.org/linux-scsi/20211125151048.103910-3-hare@suse.de/ ]
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

did you consider reusing/refactoring scsi_execute_cmd() here? I'm just 
wondering if it is possible.

> ---
>   drivers/scsi/scsi_lib.c    | 80 ++++++++++++++++++++++++++++++++++++++
>   include/scsi/scsi_cmnd.h   |  2 +
>   include/scsi/scsi_device.h |  7 ++++
>   3 files changed, 89 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 2d81fd837d47..c988e6f8194b 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1247,6 +1247,18 @@ struct request *scsi_alloc_request(struct request_queue *q, blk_opf_t opf,
>   }
>   EXPORT_SYMBOL_GPL(scsi_alloc_request);
>   
> +struct request *scsi_alloc_request_hctx(struct request_queue *q, blk_opf_t opf,
> +			blk_mq_req_flags_t flags, unsigned int hctx_idx)
> +{
> +	struct request *rq;
> +
> +	rq = blk_mq_alloc_request_hctx(q, opf, flags, hctx_idx);
> +	if (!IS_ERR(rq))
> +		scsi_initialize_rq(rq);
> +	return rq;
> +}
> +EXPORT_SYMBOL_GPL(scsi_alloc_request_hctx);
> +
>   /*
>    * Only called when the request isn't completed by SCSI, and not freed by
>    * SCSI
> @@ -2139,6 +2151,74 @@ void scsi_mq_free_tags(struct kref *kref)
>   	complete(&shost->tagset_freed);
>   }
>   
> +/**
> + * scsi_get_internal_cmd() - Allocate an internal SCSI command.
> + * @sdev: SCSI device from which to allocate the command
> + * @data_direction: Data direction for the allocated command
> + * @flags: request allocation flags, e.g. BLK_MQ_REQ_RESERVED or
> + *	BLK_MQ_REQ_NOWAIT.
> + *
> + * Allocates a SCSI command for internal LLDD use.
> + */
> +struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
> +					enum dma_data_direction data_direction,
> +					blk_mq_req_flags_t flags)
> +{
> +	enum req_op op = data_direction == DMA_TO_DEVICE ? REQ_OP_DRV_OUT :
> +							   REQ_OP_DRV_IN;
> +	struct scsi_cmnd *scmd;
> +	struct request *rq;
> +
> +	rq = scsi_alloc_request(sdev->request_queue, op, flags);
> +	if (IS_ERR(rq))
> +		return NULL;
> +	scmd = blk_mq_rq_to_pdu(rq);
> +	scmd->device = sdev;
> +
> +	return scmd;
> +}
> +EXPORT_SYMBOL_GPL(scsi_get_internal_cmd);
> +
> +/**
> + * scsi_get_internal_cmd_hctx() - Allocate an internal SCSI command from a given
> + *	hardware queue.
> + * @sdev: SCSI device from which to allocate the command
> + * @data_direction: Data direction for the allocated command
> + * @flags: request allocation flags, e.g. BLK_MQ_REQ_RESERVED or
> + *	BLK_MQ_REQ_NOWAIT.
> + * @hctx_idx: Hardware queue index.
> + *
> + * Allocates a SCSI command for internal LLDD use.
> + */
> +struct scsi_cmnd *scsi_get_internal_cmd_hctx(struct scsi_device *sdev,
> +			enum dma_data_direction data_direction,
> +			blk_mq_req_flags_t flags, unsigned int hctx_idx)
> +{
> +	enum req_op op = data_direction == DMA_TO_DEVICE ? REQ_OP_DRV_OUT :