Re: [PATCH 4/4] tcm_vhost: Convert I/O path to use target_submit_cmd_map_mem

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Oct 02, 2012 at 07:15:47AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
> 
> This patch converts tcm_vhost to use target_submit_cmd_map_mem() for
> I/O submission and mapping of pre-allocated SGL memory from incoming
> virtio-scsi SGL memory -> se_cmd descriptors.
> 
> This includes removing the original open-coded fabric uses of target
> core callers to support transport_generic_map_mem_to_cmd() between
> target_setup_cmd_from_cdb() and transport_handle_cdb_direct() logic.
> 
> It also includes adding a handful of new tcm_vhost_cmnd member +
> assignments in vhost_scsi_allocate_cmd() used from cmwq process
> context I/O submission within tcm_vhost_submission_work()
> 
> Reported-by: Christoph Hellwig <hch@lst.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@gmail.com>
> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> ---
>  drivers/vhost/tcm_vhost.c |   68 +++++++++-----------------------------------
>  drivers/vhost/tcm_vhost.h |    8 +++++
>  2 files changed, 22 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
> index 89dc99b..2ca5f02 100644
> --- a/drivers/vhost/tcm_vhost.c
> +++ b/drivers/vhost/tcm_vhost.c
> @@ -415,10 +415,7 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
>  {
>  	struct tcm_vhost_cmd *tv_cmd;
>  	struct tcm_vhost_nexus *tv_nexus;
> -	struct se_portal_group *se_tpg = &tv_tpg->se_tpg;
>  	struct se_session *se_sess;
> -	struct se_cmd *se_cmd;
> -	int sam_task_attr;
>  
>  	tv_nexus = tv_tpg->tpg_nexus;
>  	if (!tv_nexus) {
> @@ -434,23 +431,11 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
>  	}
>  	INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
>  	tv_cmd->tvc_tag = v_req->tag;
> +	tv_cmd->tvc_task_attr = v_req->task_attr;
> +	tv_cmd->tvc_exp_data_len = exp_data_len;
> +	tv_cmd->tvc_data_direction = data_direction;
> +	tv_cmd->tvc_nexus = tv_nexus;
>  
> -	se_cmd = &tv_cmd->tvc_se_cmd;
> -	/*
> -	 * Locate the SAM Task Attr from virtio_scsi_cmd_req
> -	 */
> -	sam_task_attr = v_req->task_attr;
> -	/*
> -	 * Initialize struct se_cmd descriptor from TCM infrastructure
> -	 */
> -	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, exp_data_len,
> -				data_direction, sam_task_attr,
> -				&tv_cmd->tvc_sense_buf[0]);
> -
> -#if 0	/* FIXME: vhost_scsi_allocate_cmd() BIDI operation */
> -	if (bidi)
> -		se_cmd->se_cmd_flags |= SCF_BIDI;
> -#endif
>  	return tv_cmd;
>  }
>  
> @@ -549,37 +534,10 @@ static void tcm_vhost_submission_work(struct work_struct *work)
>  {
>  	struct tcm_vhost_cmd *tv_cmd =
>  		container_of(work, struct tcm_vhost_cmd, work);
> +	struct tcm_vhost_nexus *tv_nexus;
>  	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
>  	struct scatterlist *sg_ptr, *sg_bidi_ptr = NULL;
>  	int rc, sg_no_bidi = 0;
> -	/*
> -	 * Locate the struct se_lun pointer based on v_req->lun, and
> -	 * attach it to struct se_cmd
> -	 */
> -	rc = transport_lookup_cmd_lun(&tv_cmd->tvc_se_cmd, tv_cmd->tvc_lun);
> -	if (rc < 0) {
> -		pr_err("Failed to look up lun: %d\n", tv_cmd->tvc_lun);
> -		transport_send_check_condition_and_sense(&tv_cmd->tvc_se_cmd,
> -			tv_cmd->tvc_se_cmd.scsi_sense_reason, 0);
> -		transport_generic_free_cmd(se_cmd, 0);
> -		return;
> -	}
> -

IIUC tv_cmd can come from userspace so calling pr_error here
was a bug, it's good that it's fixed now.
And looking at target_submit_cmd_map_mem, it looks that
at least lun lookup error no longer triggers pr_error, right?
If yes it's good.

> -	rc = target_setup_cmd_from_cdb(se_cmd, tv_cmd->tvc_cdb);
> -	if (rc == -ENOMEM) {
> -		transport_send_check_condition_and_sense(se_cmd,
> -				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
> -		transport_generic_free_cmd(se_cmd, 0);
> -		return;
> -	} else if (rc < 0) {
> -		if (se_cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT)
> -			tcm_vhost_queue_status(se_cmd);
> -		else
> -			transport_send_check_condition_and_sense(se_cmd,
> -					se_cmd->scsi_sense_reason, 0);
> -		transport_generic_free_cmd(se_cmd, 0);
> -		return;
> -	}
>  
>  	if (tv_cmd->tvc_sgl_count) {
>  		sg_ptr = tv_cmd->tvc_sgl;
> @@ -597,17 +555,19 @@ static void tcm_vhost_submission_work(struct work_struct *work)
>  	} else {
>  		sg_ptr = NULL;
>  	}
> -
> -	rc = transport_generic_map_mem_to_cmd(se_cmd, sg_ptr,
> -				tv_cmd->tvc_sgl_count, sg_bidi_ptr,
> -				sg_no_bidi);
> +	tv_nexus = tv_cmd->tvc_nexus;
> +
> +	rc = target_submit_cmd_map_mem(se_cmd, tv_nexus->tvn_se_sess,
> +			tv_cmd->tvc_cdb, &tv_cmd->tvc_sense_buf[0],
> +			tv_cmd->tvc_lun, tv_cmd->tvc_exp_data_len,
> +			tv_cmd->tvc_task_attr, tv_cmd->tvc_data_direction,
> +			0, sg_ptr, tv_cmd->tvc_sgl_count,
> +			sg_bidi_ptr, sg_no_bidi);
>  	if (rc < 0) {
>  		transport_send_check_condition_and_sense(se_cmd,
> -				se_cmd->scsi_sense_reason, 0);
> +				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
>  		transport_generic_free_cmd(se_cmd, 0);
> -		return;
>  	}
> -	transport_handle_cdb_direct(se_cmd);
>  }
>  
>  static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
> diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
> index d9e9355..7e87c63 100644
> --- a/drivers/vhost/tcm_vhost.h
> +++ b/drivers/vhost/tcm_vhost.h
> @@ -5,6 +5,12 @@
>  struct tcm_vhost_cmd {
>  	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
>  	int tvc_vq_desc;
> +	/* virtio-scsi initiator task attribute */
> +	int tvc_task_attr;
> +	/* virtio-scsi initiator data direction */
> +	enum dma_data_direction tvc_data_direction;
> +	/* Expected data transfer length from virtio-scsi header */
> +	u32 tvc_exp_data_len;
>  	/* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
>  	u64 tvc_tag;
>  	/* The number of scatterlists associated with this cmd */
> @@ -17,6 +23,8 @@ struct tcm_vhost_cmd {
>  	struct virtio_scsi_cmd_resp __user *tvc_resp;
>  	/* Pointer to vhost_scsi for our device */
>  	struct vhost_scsi *tvc_vhost;
> +	/* Pointer to vhost nexus memory */
> +	struct tcm_vhost_nexus *tvc_nexus;
>  	/* The TCM I/O descriptor that is accessed via container_of() */
>  	struct se_cmd tvc_se_cmd;
>  	/* work item used for cmwq dispatch to tcm_vhost_submission_work() */
> -- 
> 1.7.2.5